193 articles found
Laser-induced breakdown spectroscopy; Stand-off analysis; Solid aerosol detection; Steelshop atmosphere; Continuous casting line; Sampling rate;INDUCED BREAKDOWN SPECTROSCOPY; AEROSOL-PARTICLES; INTEGRATED IRON; AIR; TEMPERATURE; EMISSIONS; OXIDATION; ALUMINUM; SURFACES; ALLOYS
The analytical possibilities of laser induced breakdown spectroscopy (LIBS) to carry out in-situ and real-time detection and compositional characterization of aerosols in the atmosphere of a steelmaking factory, have been evaluated. To this aim, a compact and versatile dual-pulse LIBS analyzer, able to sample at distances up to eight meters, has been designed to work in these hostile industrial environments. Due to the discrete nature of the particulate matter, the particle sampling rate was less than 2.5% and 6% for single-and double-pulse regimes, respectively. An efficient statistical procedure, based on the calculation of standard deviations, is used to qualitatively characterize the elemental composition of the aerosol. Then, a conditional analysis based on the limit of detection, is employed to assess the elemental sampling rate. This experimental methodology has been used to evaluate the influence on the aerosol formed of the oxycutting process in a continuous casting machine producing steel slabs, revealing a strong presence of elements derived from the casting powder used in the production. Moreover, chromium, present in the steel cast, is detected in aerosol suspension in the steel shop. An increase in the concentration of particulate matter was expected when oxycutting was on. Single-pulse and dualpulse excitation modes are also evaluated.
Zhundong coal; Sodium; Alkali metal; Sorbent additives; LIBS;INDUCED BREAKDOWN SPECTROSCOPY; FIXED-BED REACTOR; ATOMIC SODIUM; BROWN-COAL; ALKALI REMOVAL; COMBUSTION; PYROLYSIS; SORBENTS; GASIFICATION; TEMPERATURE
The retention performance of 5 different sorbent additives, including 2 pure additives, i.e., silica and alumina, and 3 typical natural mineral additives, i.e., kaolin, mica and pyrophyllite, on the release of sodium during the combustion of Zhundong coal is investigated via a combination of online multi-point Laser-Induced Breakdown Spectroscopy (LIBS) technique and offline measurements including inductively coupled plasma atomic emission spectrometer (ICP-AES), X-ray diffraction, and ash fusion temperatures (AFTs). The online and offline measurement results for the sodium release of Zhundong coal/additives mixtures are compared and verified with each other. Ternary phase diagram simulations are performed to further substantiate the impact of different additives on liquidus temperatures of Zhundong coal ash. All the five sorbent additives show a significant sodium retention effect, while alumina and kaolin are better additives considering the effects on AFTs.
LIBS; Karats of gold; Elemental composition; Plasma parameters; LA-TOF-mass spectrometry;ELEMENTAL ANALYSIS; OSCILLATOR-STRENGTHS; INDUCED PLASMA; ALLOYS; TRANSITIONS; LIFETIMES; LITHIUM; SAMPLES; LINES
Laser induced breakdown spectroscopy (LIBS) coupled with a laser ablation time of flight mass spectrometer (LA-TOF-MS) has been developed for discrimination/analysis of the precious gold alloys cartage. Five gold alloys of Karats 18K, 19K, 20K, 22K and 24K having certified composition of gold as 75, 79, 85, 93 and 99.99% were tested and their precise elemental compositions were determined using the laser produced plasma technique. The plasma was generated by focusing beam of a Nd:YAG laser on the target in air and its time integrated emission spectra were registered in the range 250-870 nm. The calibration free LIBS technique (CF-LIBS) was used for the quantitative determination of the constituent elements present in different Karats of gold. Elemental compositions of these gold alloys were also determined using a Laser Ablation time of flight mass spectrometer (LA-TOF-MS). The LIBS limit of detection was calculated from the calibration curves for copper, silver and gold. Results of CF-LIBS and LA-TOF-MS are in excellent agreement with the certified values. It is demonstrated that LIBS coupled with LA-TOF-MS is an efficient technique that can be used to analyze any precious alloys in a fraction of a second.
Raw materials; Particles; Raman; Infrared; Spectroscopy; Laser-induced breakdown spectroscopy (LIBS);
Raw materials need to be of a certain quality with respect to physical and chemical composition. They also need to have no contaminants in the form of particles because these could get into the product or indicate the raw materials are not pure enough to make a good quality product. When particles are found, it is important to identify their chemical and elemental composition to correct any process errors that can cause them and to have acceptable quality of the final product. Sources of materials can be the environment, process equipment and processing, and packaging. Microscope versions of Raman spectroscopy, laser-induced breakdown spectroscopy (LIBS), and IR spectroscopy are excellent tools for identifying particles in materials because they are fast and accurate techniques needing minimal sample preparation that can provide chemical composition as well as images that can be used for identification. The micro analysis capabilities allow for easy analysis of different portions of samples so that multiple components can be identified and sample preparation can be reduced or eliminated. The complementarity of the techniques provides the advantage of identifying various chemical components, as well as elemental and image analyses. The sources of materials were seen to be the environment, process equipment and processing, and packaging.
CF-LIBS; internal reference self-absorption correction (IRSAC); brass; quantitative analysis; plasma parameters; energy dispersive x-ray spectroscopy (EDX); laser ablation time-of-flight mass spectrometry (LA-TOF-MS);INDUCED BREAKDOWN SPECTROSCOPY; CALIBRATION-FREE; ELEMENTAL ANALYSIS; PLASMA TEMPERATURE; PARAMETERS; ACCURACY
We present a quantitative analysis of a brass alloy using laser induced breakdown spectroscopy, energy dispersive x-ray spectroscopy (EDX) and laserablation time-of-flight mass spectrometry (LA-TOF-MS). The emission lines of copper (Cu I) and zinc (Zn I), and the constituent elements of the brass alloy were used to calculate the plasma parameters. The plasma temperature was calculated from the Boltzmann plot as (10 000 +/- 1000) K and the electron number density was determined as (2.0 +/- 0.5) x 10(17) cm(-3) from the Stark-broadened Cu I line as well as using the Saha-Boltzmann equation. The elemental composition was deduced using these techniques: the Boltzmann plot method (70% Cu and 30% Zn), internal reference self-absorption correction (63.36% Cu and 36.64% Zn), EDX (61.75% Cu and 38.25% Zn), and LA-TOF (62% Cu and 38% Zn), whereas, the certified composition is (62% Cu and 38% Zn). It was observed that the internal reference self-absorption correction method yields analytical results comparable to that of EDX and LA-TOF-MS.
Kumar, G. A. ; Nayak, R. ; Patil, A. ; Shameem, K. M. M. ; Tamboli, M. M. ; Unnikrishnan, V. K.
rare earth elements; absorption; fluorescence; laser-induced breakdown spectroscopy (LIBS);INDUCED BREAKDOWN SPECTROSCOPY; OPTICAL-PROPERTIES; QUANTITATIVE-ANALYSIS; WHITE-LIGHT; DY3+ IONS; LUMINESCENCE; LIBS; YB3+
In this work, rare earth-doped phosphate glasses were synthesized and characterized using three different spectroscopic techniques. The absorption spectra of the prepared praseodymium (Pr) and samarium (Sm) doped glasses, recorded by a UV-VIS-NIR spectrophotometer, show the characteristic absorption bands of these elements. To confirm this inference, laser-induced fluorescence spectra of Pr and Sm were obtained at a laser excitation of 442 nm. Their emission bands are reported here. The elemental analysis of these samples was carried out using a laser-induced breakdown spectroscopy (LIBS) system. Characteristic emission lines of Pr and Sm have been identified and reported by the recorded LIBS spectra of glass samples. Results prove that using these three complimentary spectroscopic techniques (absorption, fluorescence and LIBS), we can meaningfully characterize rare earth-doped glass samples.
Hrdlička, A. ; Kaiser, J. ; Klus, J. ; Novotný, J. ; Novotný, K. ; Prochazka, D. ; Škarková, P. ; Vrábel, J.
Multivariate data analysis (MVDA) is getting popular across the spectroscopic community. To assess accurate results, the obtained data should be preprocessed prior to utilization of any MVDA algorithm. The process of data normalization or “internal standardization” is widely used across a broad range of applications. In this manuscript we investigate the utilization of Laser-Induced Breakdown Spectroscopy (LIBS) coupled with MVDA. However, many articles regarding the use of MVDA on data from LIBS do not provide any information about the data pretreatment. This work describes the impact of LIBS data normalization approaches on MVDA classification accuracy. Also, the impact of classical data preprocessing (mean centering and scaling) exploiting the prior utilization of MVDA was studied. This issue was investigated exploiting simple soft independent modelling of class analogies algorithm. The findings were generalized for three sample matrices (steel, Al alloys, and sedimentary ores). Furthermore, the selection of an appropriate normalization algorithm is not trivial since the spectrum of each sample matrix is composed of a different number of elements and corresponding elemental lines.
Kaiser, J. ; Mikysek, P. ; Novotný, J. ; Novotný, K. ; Pořízka, P. ; Prochazka, D. ; Slobodník, M.
Laser-Induced Breakdown Spectroscopy; Uranium ore; Elements distribution; Self-organizing maps;
This paper presents a novel approach for processing the spectral information obtained from high-resolution elemental mapping performed by means of Laser-Induced Breakdown Spectroscopy. The proposed methodology is aimed at the description of possible elemental associations within a heterogeneous sample. High-resolution elemental mapping provides a large number of measurements. Moreover, typical laser-induced plasma spectrum consists of several thousands of spectral variables. Analysis of heterogeneous samples, where valuable information is hidden in a limited fraction of sample mass, requires special treatment. The sample under study is a sandstone-hosted uranium ore that shows irregular distribution of ore elements such as zirconium, titanium, uranium and niobium. Presented processing methodology shows the way to reduce the dimensionality of data and retain the spectral information by utilizing self-organizing maps (SOM). The spectral information from SOM is processed further to detect either simultaneous or isolated presence of elements. Conclusions suggested by SOM are in good agreement with geological studies of mineralization phases performed at the deposit. Even deeper investigation of the SOM results enables discrimination of interesting measurements and reveals new possibilities in the visualization of chemical mapping information. Suggested approach improves the description of elemental associations in mineral phases, which is crucial for the mining industry.
Čelko, L. ; Hrdlička, A. ; Kaiser, J. ; Novotný, K. ; Pořízka, P. ; Prochazka, D. ; Remešová, M. ; Škarková, P.
Laser-Induced Breakdown Spectroscopy; Silver nanoparticles; Low pressure conditions; Sensitivity improvement;
In this work we studied the effect of vacuum (low pressure) conditions on the behavior of laser-induced plasma (LIP) created on a sample surface covered with silver nanoparticles (Ag-NPs), i.e. Nanoparticles-Enhanced Laser-Induced Breakdown Spectroscopy (NELIBS) experiment in a vacuum. The focus was put on the step by step optimization of the measurement parameters, such as energy of the laser pulse, temporally resolved detection, ambient pressure, and different content of Ag-NPs applied on the sample surface. The measurement parameters were optimized in order to achieve the greatest enhancement represented as the signal-to-noise ratio (SNR) of NELIBS signal to the SNR of LIBS signal. The presence of NPs involved in the ablation process enhances LIP intensity; hence the improvement in the analytical sensitivity was yielded. A leaded brass standard was analyzed with the emphasis on the signal enhancement of Pb traces. We gained enhancement by a factor of four. Although the low pressure had no significant influence on the LIP signal enhancement compared to that under ambient conditions, the SNR values were noticeably improved with the implementation of the NPs.
Heitz, J. ; Jasik, J. ; Lackner, J. ; Parigger, C. G. ; Pedarnig, J. D. ; Spendelhofer, W. ; Veis, P.
Laser-induced breakdown spectroscopy; LIBS; Polyethylene; Rubber from tire production; Molecular emission spectroscopy; Rotational-vibrational analysis;
INDUCED BREAKDOWN SPECTROSCOPY; FEMTOSECOND LASER; NANOSECOND; DYNAMICS
Besides Raman spectroscopy, laser induced breakdown spectroscopy (LIBS) can provide standoff detection of trace chemicals at longer distances by applying filamentation techniques and using femtosecond rather than nanosecond pulses.
Laser-induced breakdown spectroscopy; tissue ablation; soft tissue; classification; principal component analysis; k nearest neighbors; confusion matrix; pork;BIOMEDICAL APPLICATIONS
Classification of pork soft tissues, including skin, fat, loin, tenderloin and ham muscles, was achieved using combination of laser-induced breakdownspectroscopy, principal component analysis and k nearest neighbors classification.
Capacitor; Tantalum; LIBS; Multipulse; Nd:YAG laser;INDUCED BREAKDOWN SPECTROSCOPY; ABLATION; LIBS
In this paper a method for cleaning tantalum capacitors terminals, using the technique of selective ablation by pulsed laser is proposed. Such ablation is studied by the LIBS technique to characterize capacitors and determine the resin composition and possible contaminants adhered. In addition, OCT measurements are performed to recreate the damage done to the samples.
Liquid lithium corrosion; Corroded layer; Depth profiling; LIBS; Refined grains enhanced;INDUCED PLASMA; QUANTITATIVE-ANALYSIS; SURFACE-TOPOGRAPHY; MASS-SPECTROMETRY; EUTECTIC PB-17LI; ABLATION; BEHAVIOR; SAMPLES; HELIUM; CURVES
Liquid metal lithium cause severe corrosion on the surface of metal structure material that used in the blanket and first wall of fusion device. Fast and accurate compositional depth profile measurement for the boundary layer of the corroded specimen will reveal the clues for the understanding and evaluation of the liquid lithium corrosion process as well as the involved corrosion mechanism. In this work, the feasibility of laser-induced breakdown spectroscopy for the compositional depth profile analysis of type 316 stainless steel which was corroded by liquid lithium in certain conditions was demonstrated. High sensitivity of LIBS was revealed especially for the corrosion medium Li in addition to the matrix elements of Fe, Cr, Ni and Mn by the spectral analysis of the plasma emission. Compositional depth profile analysis for the concerned elements which related to corrosion was carried out on the surface of the corroded specimen. Based on the verified local thermodynamic equilibrium shot-by-shot along the depth profile, the matrix effect was evaluated as negligible by the extracted physical parameter of the plasmas generated by each laser pulse in the longitudinal depth profile. In addition, the emission line intensity ratios were introduced to further reduce the impact on the emission line intensity variations arise from the strong inhomogeneities on the corroded surface. Compositional depth profiles for the matrix elements of Fe, Cr, Ni, Mn and the corrosion medium Li were constructed with their measured relative emission line intensities. The distribution and correlations of the concerned elements in depth profile may indicate the clues to the complicated process of composition diffusion and mass transfer. The results obtained demonstrate the potentiality of LIBS as an effective technique to perform spectrochemical measurement in the research fields of liquid metal lithium corrosion. 2017 Elsevier B.V. All rights reserved.
Ferri, J. M.
Halloysite nanotubes; Lumen enlargement; Acid treatment; Catalysis; LIBS;CLAY NANOTUBES; TREATED HALLOYSITE; CONTROLLED-RELEASE; CARBON NANOTUBES; NANOCOMPOSITES; ADSORPTION; LUMEN; SEPARATION; OXIDATION; DELIVERY
Halloysite nanotubes are a type of naturally occurring inorganic nanotubes that are characterized by a different composition between their external and internal walls. The internal walls are mainly composed of alumina whilst external walls are composed of silica. This particular structure offers a dual surface chemistry that allows different selective surface treatments which can be focused on increasing the lumen, increasing porosity, etc. In this work, HNTs were chemically treated with different acids , for 72 h at a constant temperature of 50 degrees C. As per the obtained results, the treatment with sulphuric acid is highly aggressive and the particular shape of HNTs is almost lost, with a remarkable increase in porosity. The BET surface area increases from 52.9 up to 132.4 m g with sulphuric acid treatment, thus showing an interesting potential in the field of catalysis. On the other hand, the treatment with acetic acid led to milder effects with a noticeable increase in the lumen diameter that changed from 13.8 nm up to 18.4 nm which the subsequent increase in the loading capacity by 77.8%. The aluminium content was measured by X-ray fluorescence and laser induced breakdown spectroscopy . The final results using two systems, suggest a good correlation between the acid strength and the aluminium reduction. Consequently, is possible to conclude that new applications for HNTs can be derived from selective etching with acids. Sulphuric acid widens the potential of HNTs in the field of catalysis while weak acids such as acetic and acrylic acids give a controlled and homogeneous lumen increase with the corresponding increase in the loading capacity.
MACHINE REGRESSION-MODEL; CONVEX-OPTIMIZATION; COEFFICIENTS; LIBS
In quantitative laser-induced breakdown spectroscopy analysis, spectral signals are usually represented by the linear combination of characteristic peaks with useful spectral information and unwanted noise components. All of the existing regression analysis methods are related to a spectral data matrix, which is composed of certified samples with different spectral intensity. Therefore, spectral data matrix processing is critical for quantitative LIBS analysis. A prevalent assumption when constructing a matrix approximation is that the partially observed matrix is of low-rank. Moreover, the low-rank structure always reflects the useful information and is regarded as a powerful data preprocessing method. In this paper, a novel and quantitative LIBS analysis method based on a sparse low-rank matrix approximation via convex optimization is proposed. Based on the sparsity of the spectral signals, we present a convex objective function consisting of a data-fidelity term and two parameterized penalty terms. To improve the accuracy of the quantitative analysis, a new non-convex and non-separable penalty based on the Moreau envelope is proposed. Then, the alternating direction method of multipliers algorithm was utilized to solve the optimization problem. The proposed method was applied to the quantitative analysis of 23 high alloy steel samples. Both of the performances of the Partial Least Squares and Support Vector Machine regression models are improved by using the low-rank matrix approximation scheme, which proves the effectiveness of the proposed method.
INDUCED BREAKDOWN SPECTROSCOPY; SUPPORT VECTOR MACHINES; PARTIAL LEAST-SQUARES; DISCRIMINANT-ANALYSIS; SUBSET-SELECTION; LASER; CLASSIFICATION; SAMPLES; IDENTIFICATION; ALGORITHM
In recent years, LIBS quantitative analysis based on multivariate regression has received considerable attention, and variable selection is critical for improving accuracy of multivariate regression analysis of LIBS. In the present study, sequential backward selection combined with random forest was proposed to improve detection accuracy of sulfur and phosphorus in steel. First, LIBS spectrum line of S and P was identified by the NIST database. Second, input variables for RF calibration model were selected and optimized by SBS, and RF model parameters and m) were optimized by out-of-bag estimation. Finally, optimized input variables and model parameters were employed to build an SBS-RF calibration model for quantitative analysis of P and S in steel. Results showed that the SBS-RF model provided good predictions for S and P compared with those provided by the univariate method, PLS model and traditional RF model. Thus, LIBS coupled with SBS-RF is an effective method for quality supervision and control of steel products.
Laser induced breakdown spectroscopy; Lanthanides; Quantitative analysis;RARE-EARTH-ELEMENTS; PLASMA-MASS SPECTROMETRY; NEUTRON-ACTIVATION ANALYSIS; QUANTITATIVE-ANALYSIS; AQUEOUS-SOLUTION; LIBS LIMIT; WASTE SALT; SAMPLES; OXIDE; WATER
Quantitative analysis of Pr, Nd, Ce, La and Sm were carried out simultaneously in LiF-KCl matrix using laser induced breakdown spectroscopic technique. Two non-interfering analytical emission lines have been identified for each lanthanide and using the internal standard method, the calibration curve is constructed from 0.3 to 5% for Pr, Nd, Ce and La and from 0.3 to 3% for Sm. Both the emission lines showed good regression coefficient ) ranging from 0.9953 to 0.9996. The analytical capability of this method is studied through the correlation uncertainty of measured values with its known value in synthetic samples containing all the lanthanides in equal amount . Low value of correlation uncertainty confirms that LIBS has a great potential for quantitative analysis of lanthanides in LiF-KCl matrix.
Laser-induced breakdown spectrometry; X-ray fluorescence spectrometry; Chromium; Surface layer; Steel sheets;DEPTH PROFILE ANALYSIS; GALVANIZED STEEL; COATED STEEL; ABLATION; SPECTROSCOPY; COPPER
A method was proposed for the determination of Cr in a thin surface nanolayer deposited on top of a micrometrical Zn-based anticorrosive coating of steel sheets using laser-induced breakdown spectrometry . Optimization of the LIBS parameters was performed with respect to the statistical parameters of regression, these being the coefficient of determination , akaike information criterion and mean-squared prediction error. These were calculated for curves describing the relationship between the Cr surface concentration and the intensity of LIBS signal. The most critical parameter of analysis appears to be the focal spot diameter. When its value was 200 mu m and corresponding energy density had value of 413.8 J/cm, the intensity-concentration relationship revealed a negative slope. This phenomenon was caused by the difference in total ablated volume for samples with a different content of Cr in the surface layer. This phenomenon was not observed for higher values of the focal spot diameter and lower values of fluence ). A range of calibration obtained under optimal conditions was 11-21 mg/m and the limit of detection was 0.7 mg/m. The recovery values calculated from the results of the proposed LIBS method and the standard ED XRF method ranged from 99.2 to 101%.
INDUCED BREAKDOWN SPECTROMETRY; INDUCED PLASMA SPECTROMETRY; JEWELRY INDUSTRY; SPECTROSCOPY; METALS; STEEL
In this study, galvanic coatings of Cu and Ni, typically applied in industrial standard routines, were investigated. Ablation experiments were carried out using the first two harmonic wavelengths of a pulsed Nd: YAG laser and the resulting plasma spectra were analysed using a linear Pearson correlation method. For both wavelengths the absorption/ablation behaviour as well as laser-induced breakdown spectroscopy (LIBS) depth profiles were studied varying laserfluences between 4.3-17.2 J/cm(2) at 532 nm and 2.9-11.7 J/cm(2) at 1064 nm. The LIBS-stratigrams were compared with energy-dispersive X-ray spectroscopy of cross-sections. The ablation rates were calculated and compared to theoretical values originating from a thermal ablation model. Generally, higher ablation rates were obtained with 532 nm light for both materials. The light-plasma interaction is suggested as possible cause of the lower ablation rates in the infrared regime. Neither clear evidence of the pure thermal ablation, nor correlation with optical properties of investigated materials was obtained.
SPECTRUM STANDARDIZATION; QUANTITATIVE-ANALYSIS; LIBS; NORMALIZATION; SIGNAL; MODEL
The uncertainty of collected spectral data is one of the most important issues for the application of laser-induced breakdown spectroscopy (LIBS) quantitative analysis. The fluctuation of the target surface simultaneously affects both the focus depth of the laser beam and the relative collection position, either of which may lead to severe fluctuation of the spectral signal. Thus, in this study, for detecting and reducing the fluctuation, an imaging system was deployed to monitor the plasma, and a mathematical model was also built based on both spectral signal and positional information. An ICCD camera was used to record the image of the plasma so as to detect the plasma and acquire positional information. Furthermore, the relationship between plasma position and specific spectral line intensity was obtained by the fitting function. Five aluminium alloy samples were employed to validate the reliability of the proposed method. As a result, the average RSDs of the samples (with a position fluctuation range of about 2 mm) in different spectral lines (Si 288.15 nm, Fe 273.95 nm, Cu 324.75 nm, Mn 259.37 nm and Mg 280.27 nm) were reduced from 34.57%, 38.86%, 31.05%, 39.74%, and 36.91% (without normalization) to 4.63%, 6.84%, 5.64%, 7.64%, and 4.83% (with the combination method presented in this paper), respectively; the determination coefficients (R-2) reached 0.996, 0.999, 0.989, 0.999, and 0.9999, respectively. These results prove that the proposed method can both improve measurement reliability and guarantee measurement accuracy.
Deng, L. M. ; Guo, L. B. ; Li, J. M. ; Li, K. H. ; Li, X. Y. ; Lu, Y. F. ; Yang X. Y. ; Zeng, X. Y. ; Zhu, Z. H.
QUANTITATIVE-ANALYSIS; CARBON CONTENT; LIBS; TEMPERATURE; TRANSFORM; PLASMAS; LINES
To minimize the impact of spectral interference on laser-induced breakdown spectroscopy (LIBS) quantitative analyses, an algorithm based on wavelet transform was developed for simultaneous correction of spectral interference and continuum background. The root-mean-square error of calibration (RMSEC) of the univariate regression model for the element of interest was applied to determine the wavelet function, decomposition level, and scaling factor alpha. When the interference-free analytical lines of the elements of interest cannot be directly obtained from the measured spectra, they can be extracted from the spectra with the developed method for quantitative analysis. This method was applied for LIBS analyses of chromium (Cr), silicon (Si), titanium (Ti), and manganese (Mn) with continuum backgrounds and spectral interference in low alloy steel samples. The root-mean-square errors of cross-validation (RMSECV) of elements Cr, Si, Ti, and Mn were 0.0295, 0.0140, 0.0183, and 0.0558 wt%, respectively. The results demonstrated that the developed algorithm contributed to accuracy improvement for LIBS quantitative analyses with the presence of spectral interference.
Laser-induced plasma; Equivalence ratio; Plasma emission; Spray flame;LASER-INDUCED BREAKDOWN; EQUIVALENCE RATIO MEASUREMENT; TO-AIR RATIO; INDUCED SPARK; GAS-DENSITY; SPECTROSCOPY; METHANE; MIXTURE; PRESSURE; IGNITION
A portable device composed of photodiodes and bandpass filters was developed to measure local fuel concentration in a liquid hydrocarbon-fueled spray flame. The plasma emission spectra in and around the flame were selectively captured using such simplified device or plug instead of using a laboratory standard laser-induced breakdown spectroscopy (LIES) system consisting of an ICCD and a spectrometer. The hydrogen (656 nm) and oxygen (777 nm) atomic lines were selected to determine the fuel concentration in atmospheric pressure. The WO signal intensity ratio was found to be a strong function of the fuel concentration, and thus a calibration curve for the concentration measurements was established and validated using conventional LIES. The proposed scheme to measure the local equivalence ratio of spray flames using a bundled layout of multiple LIES plugs alongside the combustor wall may offer simple and highly robust diagnostics, especially under the harsh combustion conditions within air breathing engines. (C) 2017 Elsevier Ltd. All rights reserved.
MINERALS; ELEMENTS; SAMPLES; WATER; PB
On-stream analysis of the element content in ore slurry has important significance in the control of the flotation process and full use of raw materials. Therefore, techniques that can monitor the chemistry in slurries online are required. Laser-induced breakdown spectroscopy (LIBS) is one of the potential approaches to online measurements due to its capability of in situ and real-time analysis. However, using LIBS for on-stream analysis of slurries is challenging due to the issues such as surface ripples, sample splashing, sedimentation, etc. To address these problems, we developed a slurry circulation system. The effects of slurry flow rate on LIBS spectra were investigated to achieve the optimal detecting surface for better repeatability of LIBS. The coefficient of determination R-2 of the calibration curve for Fe element is 0.982, and the limit of detection of Fe element was estimated to be 0.075 wt. % under the optimized experimental parameters. The results show that this slurry circulation system is applicable to the on-stream slurry analysis. (C) 2017 Optical Society of America
INDUCED BREAKDOWN SPECTROSCOPY; STAINLESS-STEEL; PROPAGATION; REMOVAL; MEDIA
High Energy Lasers (HELs) used for defense applications require operational distances ranging from few hundred meters to several kilometers. As the distance increases, the incident beam properties and, consequently, the anticipated effect delivered to the sample become less predictable. Therefore, the direct observation of the event induced by the laser can become an asset. In this paper, we propose a novel spectroscopic method that analyses in real time the spectral components present in the flames produced during the interaction of a HEL with a metallic piece at a long distance. This method was used on aluminum and carbon steel samples placed 200 m away from the laser system. It was discovered that the aluminum and iron oxides created as a by-product of the HEL reaction with the samples emitted clear fingerprint signatures that could be detected remotely using a spectroscopic receiver placed beside the HEL beam director. The real-time assessment of the laser-induced effect can be achieved by monitoring the temporal evolution of the oxide signatures, hence providing information to the operator about the reaction and the nature of the sample illuminated.
RARE-EARTH-ELEMENTS; COLLOIDS; LIQUIDS
In this paper, we report the use of laser induced breakdown spectroscopy (LIBS) to detect dissolved Eu and Yb in bulk aqueous solutions. Ten strong emission lines of Eu and one strong emission line of Yb were identified in the underwater LIBS spectra obtained by using Czerny-Turner spectrometer within the wavelength range of 375-515 nm, Temporal evolution of plasma and the effect of laser pulse energy on the spectral emission were studied. Calibration curves using the concentration range from 500 to 10,000 ppm were developed and limits of detection for Eu and Yb were estimated to be 209 and 156 ppm, respectively. (C) 2017 Elsevier B.V. All rights reserved.
Libs; Soil analysis; Practical powder sample holder; Quantitative powder analysis;ATOMIC EMISSION-SPECTROMETRY; SPECTROCHEMICAL ANALYSIS; PLASMA; LIBS; ABLATION; MATRIX; METALS; PB
A practical alternative of sample preparation technique is proposed for direct powder analysis using laser-induced breakdown spectroscopy (LIBS) instead of the commonly adopted treatment of pelletizing the powder. The resulted pellet is known to suffer from reduced sensitivity of emission. Besides, it may also give rise to interfering effect from the binder emission. We introduce in this report a more practical technique of using a subtarget supported micro mesh (SSMM) powder sample holder. The LIBS spectrum of standard soil powder measured with 13 mJ 1064 nm Nd:YAG laser in 0.65 kPa ambient air is shown to exhibit the sharp emission lines of all the major elements in the sample. A comparison with the emission spectra measured from the pelletized powder, the spectrum obtained using the SSMM sample holder shows distinctly superior spectral quality marked by the absence of matrix effect found in pelletized powder samples, and the much stronger intensity due to the more effective shock wave plasma induced thermal excitation process produced by the hard subtarget in the sample holder. Repeating the measurement on a number of the standard soil samples of various Pb contents is shown to yield a linear calibration line with practically zero intercept and a detection limit of less than 10 ppm. We have thus demonstrated the viability of the proposed powder sample holder for the development of practical and quantitative powder analysis in the field. (C) 2017 Elsevier B.V. All rights reserved.
Fan, Z. W. ; Li, X. ; Lian, F. Q. ; Lin, W. R. ; Liu, Y. ; Mo, Z. Q. ; Nie, S. Z. ; Wang, P. ; Xiao, H. ; Zhang, H. B. ; Zhong, Q. X.
LIBS instrument design; Liquid steel analysis; On-line process monitoring; Vacuum alloys production; Laser-induced breakdownspectroscopy;LIBS; STEEL
Laser-induced breakdown spectroscopy (LIBS) utilizing an echelle spectrograph-ICCD system is employed for online analysis of elements concentration in a vacuum induction melting workshop. Active temperature stabilization of echelle spectrometer is implemented specially for industrial environment applications. The measurement precision is further improved by monitoring laser parameters, such as pulse energy, spatial and temporal profiles, in real time, and post-selecting laser pulses with specific pulse energies. Experimental results show that major components of nickel-based alloys are stable, and can be well detected. By using internal standard method, calibration curves for chromium and aluminum are obtained for quantitative determination, with determination coefficient (relative standard deviation) to be 0.9559 (<22%) and 0.9723 (<2.8%), respectively. (C) 2017 Elsevier B.V. All rights reserved.
Magnetic field; Lithium plasma; Excited state; Recombination cross-section; Libs;INDUCED BREAKDOWN SPECTROSCOPY; OPTICAL-EMISSION SPECTROSCOPY
In this paper, the effect of magnetic field (1.1 T) on the atomic and ionic spectral emission of a laser produced lithium plasma at low pressure has been investigated. The experimental results indicate that magnetic field enhances the intensities of Li I spectral lines but reduces the Li II spectral lines intensities. In this study, two narrowband filters were placed before the ICCD camera to observe the evolution feature of Li II spectral line (548.39 nm, 2p(3)P(2,1,0)-> 2s(3)S(1)) and Li I spectral line (610.30 nm, 3d(2)P(3/2,5/2) -> 2p(2)P(1/2,3/2)), respectively. The plasma dynamic images show that with the magnetic field, the number density of luminous Li atoms is higher, while the number density of luminous Li ions is lower in comparison to the field-free case. The reduced Li II spectral intensities indicate that the quenching rate of Li ions in the excited state is greater than that without the magnetic field. The enhanced impact frequency of recombination indicates that magnetic field increases the recombination process of electron and Li ions. All of these observations strongly suggest that magnetic confinement increases the recombination process of the electrons with Li ions in the plasma, which results in the decrease in the intensity of Li II line. The results are useful for applying laser-induced breakdown spectroscopy (LIBS) to in-situ diagnose the processes of lithium wall conditioning in EAST tokamak. (C) 2017 Elsevier B.V. All rights reserved.
Laser-induced breakdown spectroscopy; Plastic; Partial least squares; Classification;IDENTIFICATION; LIBS; DISCRIMINATION; POLYMERS
The traditional ways of waste plastics processing mainly use the burning landfill, which lead to environmental pollution and the waste of resources. Waste plastic recycling is very important on the circulation economy and the sustainable development. The traditional instruments have some shortcomings in plastic classification, such as lower precision, higher cost, the influence of the sample color and a serious threat to operating personnel's health. Laser inducedbreakdown spectroscopy has many advantages, such as simultaneous multielement detection of elements, free from sample preparation, rapid and real-time analysis, slight damages to sample and no impact on the sample color. The method of Chemometrics combined with LIBS technique is applied to the plastic, which improves the accuracy of plastic classification. But at present, the classification has many problems, such as more parameters and the poor universality. Using on a self built LIBS instrument, we can study the laser energy, delay time, integration time and the angle of the optical fiber, which can achieve a better experiment condition. With the experimental platform, we analyze the 2 200 sample points and choose the partial least squares to analyze the spectral data. In order to achieve the correlation between the sample label and the data, we discuss the better ratio of the training set and validation set. The experimental results show that replacing the interference spectra, classification accuracy of all 11 plastic is increased to 100%, while the validation set's accuracy is only 99.8% and the test set is 99.09% without replacing the interference spectra. It can be seen that the laser induced breakdown spectroscopy combined with partial least squares method can be successfully used for the plastic sample classification.
Laser-induced breakdown spectroscopy; X-ray fluorescence; Reflectance spectroscopy; Data fusion; Mineral interpretation; Partial least squares;INDUCED BREAKDOWN SPECTROSCOPY; QUANTITATIVE MINERALOGY; RAMAN-SPECTROSCOPY; WESTERN-AUSTRALIA; WAVELENGTH; DEPOSIT
This article is extension of the earlier work (Khajehzadeh et al., 2016), where quantitative mineralogical information of slurry samples was achieved using an on-stream LIES analyzer. Despite the great advances in the analytical methods and laser-based measurement techniques, the industrial developers are still demanding novel ideas enabling differentiation between minerals having similar elemental contents such as hematite and magnetite or silicon-bearing minerals such as quartz and other mixed silica minerals since they have different flotation properties. The available analytical techniques for LIES spectral analysis (including the earlier work of this research) could not distinguish between such minerals with identical elemental contents. This work at first presents data fusion of LIES and reflectance spectroscopy and then discusses the data fusion of reflectance spectroscopy and X-ray fluorescence (XRF) measurement techniques operating on the same slurry samples. The results will show that such data integrations enable on-stream and quantitative identification of slurry mineral contents specially for hematite, magnetite, quartz and ferrorichterite which are important minerals in iron ore beneficiation.
SPATIAL CONFINEMENT; BEAM GEOMETRY; SPECTROSCOPY; IMPROVEMENT; EXPOSURE
The inevitable problems in laser induced breakdown spectroscopy are matrix effect and statistical fluctuation of the spectral signal, which can be partly avoided by utilizing a proper confined unit. The dependences of spectral signal enhancement on relative permittivity were studied by varying materials to confine the plasma, which include polytetrafluoroethylene( PTFE), nylon/dacron, silicagel, and nitrile-butadiene rubber (NBR) with the relative permittivity 2.2, similar to 3.3, 3.6, 8 similar to 13, 15 similar to 22. We found that higher relative permittivity rings induce stronger enhancement ability, which restricts the energy dissipation of plasma better and due to the reflected electromagnetic wave from the wall of different materials, the electromagnetic field of plasma can be well confined and makes the distribution of plasma more orderly. The spectral intensities of the characteristic lines Si I 243.5 nm and Si I 263.1 nm increased approximately 2 times with relative permittivity values from 2.2 to similar to 20. The size dependent enhancement of PTFE was further checked and the maximum gain was realized by using a confinement ring with a diameter size of 5 mm and a height of 3 mm (D5mmH3mm), and the rings with D2mmH1mm and D3mmH2mm also show higher enhancement factor. In view of peak shift, peak lost and accidental peaks in the obtained spectra were properly treated in data progressing; the spectral fluctuation decreased drastically for various materials with different relative permittivities as confined units, which means the core of plasma is stabilized, attributing to the confinement effect. Furthermore, the quantitative analysis in coal shows wonderful results-the prediction fitting coefficient R-2 reaches 0.98 for ash and 0.99 for both volatile and carbon. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
laser-induced breakdown spectroscopy; ageing layer depth; silicone polymer surface;SPECTROMETRY; LIBS
Silicone rubber composite materials have been widely used in high voltage transmission lines for anti-pollution flashover. The aging surface of silicone rubber materials decreases service properties, causing loss of the anti-pollution ability. In this paper, as an analysis method requiring no sample preparation that is able to be conducted on site and suitable for nearly all types of materials, laser-induced breakdown spectroscopy (LIBS) was used for the analysis of newly prepared and aging (out of service) silicone rubber composites. With scanning electron microscopy (SEM) and hydrophobicity test, LIBS was proven to be nearly non-destructive for silicone rubber. Under the same LIBS testing parameters, a linear relationship was observed between ablation depth and laserpulses number. With the emission spectra, all types of elements and their distribution in samples along the depth direction from the surface to the inner part were acquired and verified with EDS results. This research showed that LIBS was suitable to detect the aging layer depth and element distribution of the silicone rubber surface.
Amdaoud, M. ; Clavaguera, S. ; Dewalle, P. ; Fauvet, V. ; Gensdarmes, F. ; Golanski, L. ; Guiot, A. ; Motellier, S. ; Ouf, F. X. ; Pontreau, S. ; Quere, C. ; Roynette, A. ; Tabarant, M.
INDUCED PLASMA SPECTROSCOPY; HEAVY-METAL AEROSOLS; X-RAY-FLUORESCENCE; PARTICULATE MATTER; ELEMENTAL COMPOSITION; NANOMATERIALS; WORKPLACES; APPRAISAL; RELEASE; COBALT
Exposure assessment is a key step in the evaluation of the risk induced by the handling of engineered nanomaterials. It is a very complex task, because several properties of nanoparticles are assumed to have an effect on their hazards. For exposure monitoring at the workplace, real-time onsite measurements are commonly implemented to measure the particles size and number density, whereas the sampled material is subsequently analysed by electron microscopy. A complementary approach would consist in doing onsite chemical analysis of the filter samples, in order to routinely monitor a potential chronic exposure. Laser-induced breakdown spectroscopy (LIBS) has distinctive advantages for this purpose. Therefore, this work aims at evaluating the performances of LIBS to assess the exposure to airborne carbon nanotubes (CNTs) at the workplace. As carbon is a ubiquitous element in the environment, our strategy was to target metal impurities in CNTs, aluminum and iron in our case. Then, we proceeded in three steps. First, we optimized the choice of the filter type to get the lowest detection limit for both elements. Secondly, this filter was used to quantitatively measure deposited CNTs. Eventually, we conducted an onsite measurement campaign in an industrial CNT production plant to evaluate the exposure in a real situation. We demonstrated that we could reach a detection limit for CNTs compliant with the current NIOSH recommendation of 1 mu g m(-3), and that the detected CNTs during the onsite campaign in areas accessible to workers were at an extremely low concentration, several orders of magnitude lower than this recommendation.
INDUCED BREAKDOWN SPECTROSCOPY; SPECTRUM STANDARDIZATION METHOD; PARTIAL LEAST-SQUARES; MICROCHIP LASER; CARBON ANALYSIS; MN; SPECTROMETRY; CONFINEMENT; IMPROVEMENT; REGRESSION
Laser-induced breakdown spectroscopy (LIBS) was named a future superstar. Nevertheless, in the last couple of years, several commercial instruments of LIBS and its different variants have become available on a limited scale due to the confinement of quantitative analysis. In this paper, quantitative analysis of various steel samples using a specially designed handheld mu-LIBS instrument and dominant factor based partial-least squares (PLS) regression with spectral standardization is presented. Average absolute measurement errors of 0.019, 0.039, 0.013 and 0.001% for the elements of Si, Cr, Mn and Ni, respectively, were achieved. The average relative standard deviation (RSD) for these elements was less than 5%. A linear calibration response was obtained for C which is difficult to achieve using traditional PLS and for Cu whose concentration in the samples is very low. The results are better than the results of previous LIBS studies using mu J lasers or portable handheld devices, comparable to those obtained using conventional benchtop LIBS systems and better than those of commercial handheld XRF instruments. The present work presents the best results for steel analysis using portable LIBS systems so far and shows the feasibility of the technology for real industrial applications.
INDEPENDENT COMPONENT ANALYSIS; SUPPORT VECTOR MACHINES; NEURAL-NETWORK WNN; QUANTITATIVE-ANALYSIS; RANDOM FOREST; FLY-ASH; WAVELET-TRANSFORM; UNBURNED CARBON; SIGNAL; MODEL
The classification and identification of coal ash contributes to recycling and reuse of metallurgical waste. This work explores the combination of the laser-induced breakdown spectroscopy (LIBS) technique and independent component analysis-wavelet neural network (ICA-WNN) for the classification analysis of coal ash. A series of coal ash samples were compressed into pellets and prepared for LIBS measurements. At first, principal component analysis (PCA) was used to identify and remove abnormal spectra in order to optimize the training set for the WNN model. And then, ICA was employed to select and optimize input variables for the WNN model. The classification of coal ash was carried out by using the WNN model with optimized model parameters (the number of hidden neurons (NHN), the number of iterations (NI), the learning rate (LR) and the momentum) and input variables optimized by ICA. Under the optimized WNN model parameters, the coal ash samples for test sets were identified and classified by using WNN and artificial neural network (ANN) models, and the WNN model shows a better classification performance. It was confirmed that the LIBS technique coupled with the WNN method is a promising approach to achieve the online analysis and process control of the coal industry.
Guo, L. B. ; Hao, Z. Q. ; Li, J. M. ; Li, X. ; Li, X. Y. ; Lu, Y. F. ; Tang, S. S. ; Yang, P. ; Yang, X. Y. ; Yi, R. X. ; Zeng, X. Y.
IN-SITU; LIBS; STEELS; CLASSIFICATION; EXPLORATION; ELEMENTS; SPECTRA; SAMPLES; SOIL; MN
Stand-off laser-induced breakdown spectroscopy (ST-LIBS) has attracted increasing attention as a valuable method for the remote analysis of materials. In this work, a multi-collector (MC) system combining low cost small lenses imitating the structure and shape of an artificial optical compound eye (AOCE) is presented to enhance the spectral intensity of ST-LIBS. The volume of the MC system is one eighteenth smaller than that of a telescope system and the number of collectors can be flexibly changed according to the requirements. The mechanisms of spectral enhancement are also discussed. In order to illustrate the performance of the MC system, the spectral intensities and the limits of detection (LoDs) of Mn and Cr elements acquired by the telescope system and the MC system were compared at a distance of 2 meters. The results showed that the spectral intensity acquired from the MC system was enhanced by 2.2 times, and the LoDs of Mn and Cr were decreased to 294 mu g g(-1) and 49 mu g g(-1). These results indicate that the MC system has great potential in providing a portable, flexible and effective collection method for remote detection.
RARE-EARTH-ELEMENTS; SPACE EXPLORATION; IRON OBJECTS; STEEL WORKS; ICP-MS; LIBS; SPECTROMETRY; UNIVARIATE; SAMPLES; CURVES
Laser-induced breakdown spectroscopy (LIBS) was used for the analysis of charcoal blast furnace slags. Plasma was generated by an application of a 1064 nm wavelength Nd:YAG laser beam to the surface of pellets created from the slags. The presence of Al, Ca, Fe, K, Mg, Mn, and Si was determined by identifying their characteristic spectral signatures. Multivariate analysis was performed for the quantification of these elements. The predicted LIBS results were found in agreement with the inductively coupled plasma optical emission spectrometry analysis. The limit of detection for Al, Ca, Fe, K, Mg, Mn, and Si was calculated to be 0.10%, 0.22%, 0.02%, 0.01%, 0.01%, 0.005%, and 0.18%, respectively. (C) 2017 Optical Society of America
Laminar premixed methane-air flame; Laser-induced breakdown spectroscopy; Flames structure; Radial distribution;BURNING COAL PARTICLE; POLARIZATION SPECTROSCOPY; ANALYTICAL TOOL; ATOMIC SODIUM; JET FLAME; SPECTROMETRY; OH; TEMPERATURE; SPARK; RATIO
Laser-induced breakdown spectroscopy was evaluated for the analysis of the structure of laminar premixed methane-air flames. Firstly, breakdown threshold pulse energy and plasma energy in different areas of the flame were measured simultaneously, and an approximate linear relation between them was detected. Secondly, a new approach was proposed to qualitatively characterize the flame temperature distributions based on the plasma energy distributions. Finally, combination of the spatial analysis of the spectrum intensity, plasma energy and equivalence ratio, the laminar premixed flames structure was investigated deeply, including the distribution of the flame temperature, the width and distribution of different flame region (e.g. premixed combustion regions, high temperature regions.),as well as the location of the flame front. (C) 2017 Elsevier B.V. All rights reserved.
Laser-induced breakdown spectroscopy (LIBS); Signal enhancement; Microwave assisted; Imaging;SPECTROSCOPY LIBS; PLASMA; ENHANCEMENT; DISCHARGE
This study reports a sensitive spectroscopic method for quantitative elemental detection by manipulating the temporal and spatial parameters of laser-inducedplasma. The method was tested for indium detection in solid samples, in which laser ablation was used to generate a tiny plasma. The lifetime of the laser-induced plasma can be extended to hundreds of microseconds using microwave injection to remobilize the electrons. In this novel method, temporal integrated signal of indium emission was significantly enhanced. Meanwhile, the projected detectable area of the excited indium atoms was also significantly improved using an interference-, instead of diffraction-, based technique, achieved by directly imaging microwave-enhanced plasma through a novel narrow-bandpass filter, exactly centered at the indium emission line. Quantitative laser-induce breakdown spectroscopy was also recorded simultaneously with the new imaging method. The intensities recorded from both methods exhibit very good mutual linear relationship. The detection intensity was improved to 14-folds because of the combined improvements in the plasma lifetime and the area of detection. Crown Copyright (C) 2017 Published by Elsevier B.V. All rights reserved.
LIBS; Thin films; Thickness;
A new laser-induced breakdown spectroscopy (LIES) technique is proposed to measure the thickness of films thinner than the ablation rate. The film thickness dependence of the signal intensity is used as a calibration curve. It is demonstrated that calibration curves are successfully made for thin W films and (Fe, Cr, Ni) mixed-material films produced in a magnetron sputtering device. (C) 2017 Elsevier B.V. All rights reserved.
LIBS; Cigarette brands; Elemental composition; Plasma parameters; LA-TOF-mass spectrometry;TOBACCO; CRYSTAL; SAMPLES; PLASMA
We present qualitative and quantitative analysis of the trace elements present in different brands of tobacco available in Pakistan using laser inducedbreakdown spectroscopy (LIBS) and Laser ablation Time of Flight Mass Spectrometer (LA-TOFMS). The compositional analysis using the calibration free LIBS technique is based on the observed emission spectra of the laser produced plasma plume whereas the elemental composition analysis using IA-TOFMS is based on the mass spectra of the ions produced by laser ablation. The optical emission spectra of these samples contain spectral lines of calcium, magnesium, sodium, potassium, silicon, strontium, barium, lithium and aluminum with varying intensities. The corresponding mass spectra of the elements were detected in LA-TOF-MS with their composition concentration. The analysis of different brands of cigarettes demonstrates that LIBS coupled with a LA-TOF-MS is a powerful technique for the elemental analysis of the trace elements in any solid sample. (C) 2017 Elsevier B.V. All rights reserved.
Femtosecond laser ablation; Laser induced breakdown spectroscopy (LIBS); Spectrochemical imaging; YBa2Cu3O7 (YBCO); Thin film;OPTICAL-EMISSION SPECTROMETRY; MASS-SPECTROMETRY; ABLATION; SURFACE; SAMPLES; LIBS; PULSES; IDENTIFICATION; METALS; DAMAGE
We investigate femtosecond laser-induced breakdown-spectroscopy (fs-LIBS) for the spectrochemical imaging of thin films with high spatial resolution. Chemical images are obtained by recording LIBS spectra at each site of 2D raster-scans across the samples employing one fs-laser pulse per site. The diffraction images of the Echelle spectrometer are binned to reduce the read-out time of the intensified CCD detector and to increase the stability of the emission signals against peak drifts in the echellograms. For copper thin films on glass the intensities of Cu I emission lines and the size of ablation craters vary non-monotonously with the film thickness h(Cu) = 5-500 nm. The emission efficiency, defined as the Cu I line intensity per ablated volume, strongly decreases for films thicker than the optical penetration depth. The Na I line intensity from glass increases exponentially with decreasing Cu film thickness. For yttrium barium copper oxide (YBCO) thin films on MgO various atomic and molecular emission lines of the laser-induced plasma are measured (film thickness h(YBCO) = 200-1000 nm). The obtained element (Y, Ba, Cu, Mg) and molecular (Y-O) fs-LIBS images match the structure of the micro-patterned YBCO films very well. The achieved lateral resolution delta r = 6 mu m is among the best values reported for spectrochemical LIBS imaging. (C) 2017 Elsevier B.V. All rights reserved.
LIBS; Steel analysis; Material identification; Rolling mill; Production control;QUANTITATIVE-ANALYSIS; HIGH-TEMPERATURE; SAMPLES; SPECTROMETRY; LIBS
Laser-induced breakdown spectroscopy (LIBS) is applied for the elemental analysis of steel blooms in a rolling mill. The 2-3 tons steel blooms with superficial scale are transported in a sequence on a roller table to successive processing steps. Laser ablation of the scale and the analysis of the subsurface bulk steel is carried out using the same laser in <50 s during scheduled stop times of the roller table. Up to 14 elements such as Ni, Cr, and Mo are measured for several hundreds of blooms of low and high alloy steel during routine production. The comparison of the measured with the nominal compositions, results in root mean square errors of prediction in the range of 0.01-0.2 m.-%. The rolling sequence is clearly reflected by the LIBS measurement of the individual blooms demonstrating the feasibility for material identification. Identification rates are estimated from computer simulations by permutation of the LIBS measured values and the reference values from the rolling sequence. (C) 2017 The Authors. Published by Elsevier B.V.
BUILDING EXPERT-SYSTEMS; FUEL PROPERTIES; SPECTROSCOPY; MODEL
A quiet but interesting trend has been occurring in material analysis, coincident with the rise of artificial intelligence (Al) and so-called ""deep"" machine learning methods. Astute spectroscopists have always known that there is more information in the spectra that they obtain than simply the molecular or atomic peaks that are directly measured. Particularly with methods such as infrared, Raman, and laser-induced breakdown spectroscopy (LIBS), the spectral background contains a wealth of information about the sample, and analytical combinations of the peaks can provide material properties. Traditionally, such analytical combinations of peaks were performed explicitly by analysts, but now information about material properties embedded in the spectra can be derived implicitly by Al and machine learning algorithms. This column introduces these ideas and touches on recent results indicative of what more may be coming in this direction.
Laser-induced breakdown spectroscopy; Proximate analysis of coal; Spectral fitting; Support vector machine;LIBS; SYSTEM
Online accurate proximate analysis of coal is vitally important to the optimization of industrial production and reduction in coal consumption. However, due to the ""matrix effect"" caused by the complex and diverse coal species in China, the measurement accuracy needs to be improved by using laser-inducedbreakdown spectroscopy (LIBS). In our experiment, both the spectral pretreatment method and the calibration model for the conversion of laser induced coal plasma spectra to the coal proximate analysis results were optimized. Experimental results showed that, compared with the traditional method, the proposed single or multiple-peak Lorentzian spectral fitting for spectral line intensity calculation reduced the mean RSD from 12. 1% to 9. 7%. For kernel function parameters optimization, the mean absolute error (MAE) of the particle swarm optimization (PSO) was smaller than that of the grid parameter (Grid) and the genetic algorithm (GA). The root mean square error (RMSEP) of support vector machine (SVM) regression model based on PSO parameter optimization was less than that of partial least squares regression (PLS). By combining the single- or multiple-peak Lorentzian spectral fitting method with the PSO based SVM for regression modeling, the average absolute errors (AAE) of predicted proximate analysis results were certified to be: 1. 37% for coal ash content of 16%similar to 30%, 1. 77% for coal ash content of 30% or more, 0. 65 MJ . kg(-1) for calorific value of 9 similar to 24 MJ . kg(-1), 1. 09% for volatile matter of 20% or less, and 1. 02% for volatile matter of 20% or more.
Laser-induced breakdown spectroscopy (LIBS); laser ablation; stability; monitoring;NEUTRON-ACTIVATION ANALYSIS; SPECTROMETRY; SULFUR; LIBS; ENVIRONMENT; FLUORINE; AEROSOLS; CHLORINE; CONCRETE; COAL
Mastering the change of cement raw materials composition in real time has important significance to timely adjusting the proportion of raw materials and improving the quality of cement products. As a result, a greater need for online chemical sensors is evolving. Laser-induced breakdown spectroscopy (LIBS) possesses many of the characteristics required for such online chemical sensing, and is a promising technique for field measurements in harsh industrial environments. In this work, we developed a LIBS device for online cement raw materials quality monitoring in the way of ejecting gas-powder mixture, and enhanced the measurement stability through approaches including powder concentration of the ejected gas-powder stream stabilization, pulsed laser power stabilization, and optical efficiency enhancement.
IN-SITU ANALYSIS; AEROSOL-PARTICLES; ALUMINUM-ALLOY; STEEL; SPECTROMETRY; CLEANLINESS; ABLATION; EMISSIONS; MELT
In order for metals to meet the demand for critical applications in the automotive, aerospace, and defense industries, tight control over the composition and cleanliness of the metal must be achieved. The use of laser-induced breakdown spectroscopy (LIBS) for applications in metal processing has generated significant interest for its ability to perform quick analyses in situ. The fundamentals of LIBS, current techniques for deployment on molten metal, demonstrated capabilities, and possible avenues for development are reviewed and discussed.
LIBS stratigraphy; Galvanic coatings; Ablation rate; Plasma shielding; Light-plasma interaction; Depth profiling;INDUCED BREAKDOWN SPECTROMETRY; ION-BEAM ANALYSIS; PULSED-LASER DEPOSITION; REDUCED PRESSURE; JEWELRY INDUSTRY; PURE METALS; ABLATION; SPECTROSCOPY; FILMS; THICKNESS
Laser-induced depth profiling was applied to the investigation of galvanised steel sheets as a typical modern multi-layer coating system for environmental corrosion protection. The samples were ablated stepwise by the use of two different wavelengths of a frequency-converted Nd:YAG-laser, 266nm and 532nm, with a pulse duration of tau = 4ns at fluences ranging from F=50 to 250 J cm(-2). The emission light of the resulting plasma was analysed as a function of both penetration depth and elemental spectrum in terms of linear correlation analysis. Elemental depth profiles were calculated and compared to EDX-cross sections of the cut sample. A proven mathematical algorithm designed for the reconstruction of layer structures from distorted emission traces caused by the Gaussian ablation profile can even resolve thin intermediate layers in terms of depth and thickness. The obtained results were compared to a purely thermally controlled ablation model. Thereby light-plasma coupling is suggested to be a possible cause of deviations in the ablation behaviour of Al. The average ablation rate h as a function of fluence F for Ni ranges from 1 to 3.5 mu m/pulse for lambda = 266nm as well as for lambda =532nm. In contrast, the range of h for Al differs from 2 to 4 mu m/pulse for lambda = 532 nm and 4 to 8 mu m/pulse for lambda = 266 nm in the exact same fluence range on the exact same sample. (C) 2016 Elsevier B.V. All rights reserved.
LIBS; Femtosecond; Organic solar cell; Selective ablation; Depth profiling;DEPTH-RESOLVED ANALYSIS; SELECTIVE ABLATION; SOLAR-CELLS; SPECTROMETRY; LIBS; ABSORPTION; COATINGS; SPECTRA; SAMPLES; PULSES
The potential of laser induced breakdown spectroscopy (LIBS) as a non-contact probe, for characterizing organic photovoltaic devices during selective laserscribing, was investigated. Samples from organic solar cells were studied, which consisted of several layers of materials including a top electrode (Al, Mg or Mo), organic layer, bottom electrode (indium tin oxide), silicon nitride barrier layer and substrate layer situated from the top consecutively. The thickness of individual layers varies from 115 to 250 nm. LIBS measurements were performed by use of a 40 femtosecond Ti:Sapphire laser operated at very low pulse energy (<10 micro-joule) to ensure a fine depth-profiling of the very thin layers. Probing a fixed spot on the sample with successive laser pulses, produced plasma emission spectra corresponding to individual laser ablation events. This enabled discrimination of the different layers on the basis of characteristic spectral lines reflecting key elemental constituents of each layer in the organic solar cell structure, demonstrating the potential of LIBS for fast, non-contact characterization of organic photovoltaic coatings. (C) 2016 The Author(s). Published by Elsevier B.V.
SUPPORT VECTOR MACHINES; ELEMENTAL ANALYSIS; IRON-ORES; CLASSIFICATION; SPECTROMETRY; SAMPLES; PLASMA; INDUSTRY; ALLOYS; MODEL
The basicity of sintered ore, which is related to the melting point of the sinter, is vital to ore mining and blastfurnace smelting. Laser-induced breakdownspectroscopy (LIBS) with random forest regression (RFR) has been applied for measuring the basicity of sintered ore, which can be defined by the concentrations of oxides: CaO, SiO2, Al2O3 and MgO. In this work, thirty sintered ore samples are used, of which twenty samples are used for the calibration set to construct the random forest regression (RFR) calibration model for the above-mentioned oxides and ten samples are used for the test set. The characteristic lines of the main components in the sintered ore are identified using the National Institute of Standards and Technology (NIST) database. Two model parameters (the number of decision trees -ntree and the number of random variables - m(try)) of the RFR were optimized by out-of-bag (OOB) error estimation for improving the predictive accuracy of the RFR model. The RFR model was applied to sample measurements and the results were compared with partial least squares regression (PLSR) models. The RFR model has shown better predictive capabilities than the PLSR model. In order to verify the stability of the RFR model, fifty measurements were made and the relative standard deviation (RSD) of the data is between 0.27% and 0.59%. Therefore, LIBS combined with RFR could be a promising method for realtime online, rapid analysis in mining and mineral processing industries.
Bunkin, F. ; Filichkina, V. A. ; Filippov, M. N. ; Grishin, M. Y. ; Pershin, S. M. ; Sdvizhenskii, P. A. ; Stavertiy, A. Y. ; Tretyakov, R. S.
Wear resistant coatings; Tungsten carbide; Elemental profiling; Laser induced breakdown spectroscopy; Energy dispersive X-ray spectroscopy; Laser cladded coating;TUNGSTEN CARBIDE; MICROSTRUCTURAL CHARACTERIZATION; COMPOSITE COATINGS; ABLATION; STEEL; LIBS; WEAR; EXCITATION; PLASMA; PULSES
Multilayer tungsten carbide wear resistant coatings were analyzed by laser induced breakdown spectroscopy (LIBS) and energy dispersive X-ray (EDX) spectroscopy. Coaxial laser cladding technique was utilized to produce tungsten carbide coating deposited on low alloy steel substrate with additional inconel 625 interlayer. EDX and LIBS techniques were used for elemental profiling of major components (Ni, W, C, Fe, etc.) in the coating. A good correlation between EDX and LIBS data was observed while LIBS provided additional information on light element distribution (carbon). A non-uniform distribution of tungsten carbide grains along coating depth was detected by both LIBS and EDX. In contrast, horizontal elemental profiling showed a uniform tungsten carbide particles distribution. Depth elemental profiling by layer by-layer LIBS analysis was demonstrated to be an effective method for studying tungsten carbide grains distribution in wear resistant coating without any sample preparation. (C) 2017 Published by Elsevier B.V.
POLISHING-INDUCED CONTAMINATION; INDUCED DAMAGE THRESHOLD; X-RAY REFLECTION; REFRACTIVE-INDEX; ROUGHNESS; OPTICS; GLASS; MITIGATION; CRACKS; ELLIPSOMETRY
We report on investigations of the spatial variations of contamination, roughness, and index of refraction of classically manufactured polished fused silica surfaces. Therefore, laser-induced breakdown spectroscopy was used to probe surface and subsurface impurities via the detection of aluminum. Measurements at different positions on the surface of the cylindrical fused silica windows evidenced an almost contamination-free center region, whereas a relatively large contamination area was found close to the edge. In-depth measurements verify the presence of aluminum atoms in the bulk until a depth of several tens of microns for the edge region. In addition, atomic force microscopic measurements show that the surface roughness is larger in the center region compared to the edge. Further, the index of refraction increases from the center region towards the edge as measured via ellipsometry. The results indicate a nonuniform impact of the grinding, lapping, and polishing tools on the surface. The findings turn out to be of specific interest for different applications, particularly for the realization of large-scale high-performance coatings. (C) 2017 Optical Society of America
INDUCED BREAKDOWN SPECTROSCOPY; EMISSION-SPECTROSCOPY; MOLECULAR-EMISSION; ABLATION; AIR; CARBON; ALO; TEMPERATURE; GENERATION; CHEMISTRY
Experimental investigations into the characteristics of laser-induced plasmas indicate that LIBS provides a relatively inexpensive and easily replicable laboratory technique to isolate and measure reactions germane to understanding aspects of high-explosive detonations under controlled conditions. Spectral signatures and derived physical parameters following laser ablation of aluminum, graphite and laser-sparked air are examined as they relate to those observed following detonation of high explosives and as they relate to shocked air. Laser-induced breakdown spectroscopy (LIBS) reliably correlates reactions involving atomic Al and aluminum monoxide (AlO) with respect to both emission spectra and temperatures, as compared to small-and large-scale high-explosive detonations. Atomic Al and AlO resulting from laser ablation and a cited small-scale study, decay within similar to 10(-5) s, roughly 100 times faster than the Al and AlO decay rates (similar to 10(-3) s) observed following the large-scale detonation of an Al-encased explosive. Temperatures and species produced in laser-sparked air are compared to those produced with laser ablated graphite in air. With graphite present, CN is dominant relative to N-2(+). In studies where the height of the ablating laser's focus was altered relative to the surface of the graphite substrate, CN concentration was found to decrease with laser focus below the graphite surface, indicating that laser intensity is a critical factor in the production of CN, via reactive nitrogen. (C) 2017 Author(s).
LIBS quantitative analysis; reduction of matrix effect; internal standard calibration; normalization; correction of self-absorption;PART II; SAMPLES; PARAMETERS
A procedure for matrix effect reduction is proposed to enhance the precision of quantitative analysis of metal alloys using laser-induced breakdownspectroscopy (LIBS). This procedure is based on a number of successive steps in order to correct the signal fluctuations caused by plasma interaction and the matrix effect. The first step is the selection of optimum parameter settings of the detection system, such as laser power, delay time, and focal distance. The second step is the estimation of the absolute or relative values of impurities on the basis of the internal standard calibration. The third step is the analysis of the metal basis of the alloy used as an internal standard, which requires spectrum averaging, whole integral spectrum normalization, and self-absorption correction. Three sets of metal-based alloys (aluminum, steel, and copper) are used in this investigation as reference standards for calibration and validation. Successive improvements of the quality of calibration curves are observed during the proposed procedure.
Wear elements in engine oil; Indirect ablation laser induced breakdown spectroscopy; Matrix effect; Calibration curves;LUBRICATING OILS; CRUDE-OIL; QUANTITATIVE-DETERMINATION; MASS-SPECTROMETRY; METALS
Engine oil plays an important role in the engine operation. Elements composition and concentration in engine oil will be changed as the engine operates, which can lead to the deterioration of engine oil, and the engine thereby will be worse. A rapid and effective detection approach for oil performance, therefore, is proposed to prevent further deterioration. Indirect ablation laser induced breakdown spectroscopy (IA-LIES) is a new technology introduced specially for oil samples, which focuses on the indirect ablation of oil samples by metallic plasma with high temperature, improving the detection sensitivity and stability. In this paper, the matrix effect on calibration curves of analytical elements (Mg, Fe and Ni) in different oils was investigated. The results show that the matrix effect is quite small and reasonably negligible. A universal calibration curve can be established for analytical metals in different types of oil, and the linear fitting coefficients are all superior to 0. 99. We used the universal calibration curves to determine the concentrations of Mg, Fe and Ni in mixed oils. The IA-LIES results show a good agreement between the measured and known values. The IA-LIBS is further improved and can promote the detection of engine oil performance, which has important scientific significance for the diagnosis of engine wear.
Cama-Moncunill, X. ; Casado-Gavalda, M. P. ; Cullen, P. J. ; Dixit, Y. ; Markiewicz-Keszycka, M. ; Sullivan, C.
LIBS; Trace-element premixes; Univariate analysis; Multivariate analysis; PLS;SPECTROCHEMICAL ANALYSIS; LIBS; ADULTERATION; COPPER; MILK; BEEF
Infant formula is a human milk substitute generally based upon fortified cow milk components. In order to mimic the composition of breast milk, trace elements such as copper, iron and zinc are usually added in a single operation using a premix. The correct-addition of premixes must be verified to ensure that the target levels in infant formulae are achieved. In this study, a laser-induced breakdown spectroscopy (LIBS) system was assessed as a fast validation tool for trace element premixes. LIBS is a promising emission spectroscopic technique for elemental analysis, which offers real-time analyses, little to no sample preparation and ease of use. LIBS was employed for copper and iron determinations of premix samples ranging approximately from 0 to 120 mg/kg Cu/1640 mg/kg Fe. LIES spectra are affected by several parameters, hindering subsequent quantitative analyses. This work aimed at testing three matrix-matched calibration approaches (simple-linear regression, multi-linear regression and partial least squares regression (PLS)) as means for precision and accuracy enhancement of LIBS quantitative analysis. All calibration models were first developed using a training set and then validated with an independent test set. PLS yielded the best results. For instance, the PLS model for copper provided a coefficient of determination (R-2) of 0.995 and a root mean square error of prediction (RMSEP) of 14 mg/kg. Furthermore, LIBS was employed to penetrate through the samples by repetitively measuring the same spot. Consequently, LIBS spectra can be obtained as a function of sample layers. This information was used to explore whether measuring deeper into the sample could reduce possible surface-contaminant effects and provide better quantifications. (C) 2017 Elsevier B.V. All rights reserved.
GRADIENT-INDEX MICROLENSES; INTRAOCULAR LENSES; CONTACT-LENSES; POLY(METHYL METHACRYLATE); INDUCEDBREAKDOWN; FUSED-SILICA; WAVE-GUIDES; IN-VIVO; POLYMERS; INTERFEROMETRY
We describe the treatment of new hydrogels with nine different chemical compositions by femtosecond laser writing. The phase change induced in the wavefront when passing through the written areas was measured in all of these materials. The induced phase change is negative, which is attributed to the higher presence of water in the written regions and confirmed via Raman spectroscopy. The largest induced change in a single layer at 100 mm/s was -3.69 waves at 543 nm. These results show a strong dependence of the phase change on the concentration of some components and their molar ratio. We propose that some components are essential for the nonlinear energy absorption (""dopants""), while other components (""quenchers"") are essential in redirecting the absorbed energy to cause chemical reactions that profoundly change the polymer structure. (C) 2017 Optical Society of America
Deguchi, Y. ; Chong, D. T. ; Ikutomo, A. ; Liu, J. P. ; Liu, R. W. ; Shiou, F. J. ; Yan, J. J. ; Zhang, Z. Z.
Long pulse; dual-pulse laser-induced breakdown spectroscopy; DP-LIBS; enhancement; plasma temperature stabilization; underwater measurement;CO2-LASER PULSE; AMBIENT GAS; ABLATION; ENHANCEMENT; PRESSURES; FEASIBILITY; MAGNESIUM; DISCHARGE; SPECTRUM; LIQUIDS
Collinear long and short dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) was employed to clarify the emission characteristics from laser-inducedplasma. The plasma was sustained and became stable by the long pulse-width laser with the pulse width of 60s under free running (FR) conditions as an external energy source. Comparing the measurement results of stainless steel in air using single-pulse LIBS (SP-LIBS) and DP-LIBS, the emission intensity was markedly enhanced using DP-LIBS. The temperature of plasma induced by DP-LIBS was maintained at a higher temperature under different gate delay time and short pulse-width laser power conditions compared with those measured using short SP-LIBS. Moreover, the variation rates of plasma temperatures measured using DP-LIBS were also lower. The superior detection ability was verified by the measurement of aluminum sample in water. The spectra were clearly detected using DP-LIBS, whereas it cannot be identified using SP-LIBS of short and long pulse widths. The effects of gate delay time and short pulse-width laser power were also discussed. These results demonstrate the feasibility and enhanced detection ability of the proposed collinear long and short DP-LIBS method.
INDUCED BREAKDOWN SPECTROSCOPY; LASER-INDUCED FLUORESCENCE; EXCITED ATOMIC FLUORESCENCE; ELEMENTAL ANALYSIS; ABLATION; LIBS; SPECTROMETRY; MECHANISM; METALS; WASTE
Coupling laser-induced fluorescence to laser ablation can reduce detection limits relative to LIBS. The wing of the broadband similar to 193.3 nm emission from unmodified argon fluoride lasers can excite arsenic fluorescence via its 193.76 nm ground state transition for a simple fluorescence scheme. We present argon fluoride-excited laser-ablation laser-excited atomic fluorescence (LA-LEAF) measurements in steel and copper under argon and helium atmospheres. Because the ArF laser saturates the absorption transition and the steel samples show substantial nonspecific iron fluorescence, it is necessary to optimize the laser energy in addition to interpulse delay. LODs are slightly lower under helium (1.0 ppm in steel, 0.15 ppm in copper). These detection limits represent a modest improvement over previous LODs with LIBS, but suggest potential for improvement with line narrowing of the ArF laser.
Hedwig, R. ; Jobiliong, E. ; Kagawa, K. ; Karnadi, I. ; Kurniawan, K. H. ; Lie, T. J. ; Lie, Z. S. ; Pardede, M. ; Suliyanti, M. M. ; Suyanto, H. ; Tjia, M. O. ; Wihardjo, E.
DUAL-PULSE LIBS; INDUCED PLASMA; ABLATION EFFICIENCY; SENSITIVE ANALYSIS; HELIUM PLASMA; FEMTOSECOND; ENHANCEMENT; NANOSECOND; MICROANALYSIS; DEUTERIUM
A time-resolved spectroscopic study is performed by using 125-500 micro-Joule (mu J) ps laser focused directly without the aid of microscope on a Cu plate sample in a variety of low-pressure ambient gases including air, helium and argon. It is shown that the ultrashort mu J laser-induced low-pressure plasma in Ar ambient gas exhibits the typical characteristics of shock wave plasma responsible for the thermal excitation and sharp emission of the analyte atoms. It is found that the highest signal to background (S/B) ratio of about 100 is achieved in 1.3 kPa argon ambient gas and detected with optical multichannel analyzer (OMA) gate delay of 1 ns and gate width of 50 mu s. The emission spectra obtained from pure Zn sample show the effective suppression of the ionic emission with ablation energy around and below 500 mu J. The experimental setup is successfully applied to Cr analysis with low detection limit in steel. In particular, its application to C analysis in steel is demonstrated to resolve the long standing problem of overlapping contributions from the neutral and ionic Fe emission. It is further found that an element of high excitation energy such as fluorine (F) can be clearly detected from a non metal teflon sample. Further, its application to alluminum sample containing various concentrations of Mg, Ca, Fe, and Si impurity elements clearly displays the existence of linear calibration lines promising for quantitative analyses in certain dynamical ranges. Finally, in view of the tiny crater sizes of less than 10 mu m diameter created by the very low ps laserenergy, this technique is promising for micrometer resolution mapping of elemental distribution on the sample surface and its depth profiling. (C) 2017 The Japan Society of Applied Physics
URANIUM; LIBS; FLUORESCENCE; SPECTROMETRY; MATRICES; SAMPLES; SYSTEM; PULSE; UF6
A hand-held device for laser-induced breakdown spectroscopy has been investigated for the determination of uranyl fluoride surface contamination. This research demonstrates the ability to successfully detect uranium on surfaces when using a low resolving power (lambda/Delta lambda = 4000) spectrograph, with a 5 mJ energy per 1 ns pulsed laser radiation, available as a commercially packaged hand-held system. Sand/uranyl fluoride mixtures are prepared to simulate residue likely encountered during decontamination efforts at facilities that handle uranium hexafluoride. Detection limits are described for four uranium lines with one revealing the capability to detect uranium at a level of 250 parts per million. Advantages of the studied compact device include that location specific information can be obtained on-site to augment contamination identification. (c) 2017 Optical Society of America
Dong, L. ; Hou, J. J. ; Hou, Z. Y. ; Jia, S. T. ; Ma, W. G. ; Wang, Z. ; Yang, G. Y. ; Yin, W. B. ; Zhang, L.
QUANTITATIVE-ANALYSIS; PARAMETERS; SAMPLES; LIBS
A calibration method based on homogeneous material for correcting laser-induced breakdown spectroscopy (LIBS) measurement-error bias in the case of dust pollution under laboratory conditions is proposed. The measured plasma spectra of the sample can be corrected by measuring the spectral integral of the homogeneous material. Thus, we can effectively minimize the dust pollution effect on LIBS and guarantee its precision. Results show that the mean absolute errors of CaO, MgO, Fe2O3, Al2O3, and SiO2 in cement samples are decreased notably from 1.02%, 0.06%, 0.15%, 0.57%, and 0.80% to 0.41%, 0.02%, 0.04%, 0.35%, and 0.39%, respectively. Combination of this calibration method with the traditional optical dustproof methods will significantly extend the LIBS equipment maintenance cycle and make preliminary preparations for the next practical industrial application. (C) 2017 Optical Society of America
Grishin, M. Y. ; Cheverikin, V. V. ; Peshin, M. ; Sdvizhenskii, P. A. ; Stavertiy, A. Y. ; Taksanc, M. V. ; Tretyakov, R. S.
HIGH-SPATIAL-RESOLUTION; STEEL-INDUSTRY; CHEMICAL MAPS; SPECTROMETRY; PLASMA; IDENTIFICATION; LIBS; MICROANALYSIS; CONVERTERS; SAMPLES
Three-dimensional multi-elemental mapping of composite wear-resistant coatings by laser-induced breakdown spectroscopy has been demonstrated for the first time, to the best of our knowledge. Individual clads of 1560 nickel alloy reinforced with tungsten carbide were synthesized by a co-axial laser cladding technique. Electron energy dispersive x-ray spectroscopy revealed elemental maps for major elements (W, Ni, Co, Cr, Fe) but failed to measure silicon and carbon. Laser-induced breakdown spectroscopy was utilized for elemental mapping of carbon and all other elements of interest. It was demonstrated that three-dimensional elemental profiling for a few tens of micrometers requires substantial laser spot overlapping during the scanning procedure in order to achieve good accuracy of depth measurements. Elemental maps for nickel, iron, chromium, silicon, tungsten, and carbon were quantified for 900 mu m x 900 mu m x 45 mu m volume with 30 mu m lateral and 4 mu m depth resolution in the case of tungsten carbide particles in nickel alloy. (C) 2017 Optical Society of America
Lead-free ferroelectrics; Cation vacancies; Laser-induced breakdown spectroscopy; Dielectric measurements;INDUCED BREAKDOWN SPECTROSCOPY; FREE PIEZOELECTRIC CERAMICS; SODIUM-POTASSIUM NIOBATE; ELECTRICAL-PROPERTIES; (K0.5NA0.5)NBO3 CERAMICS; NA0.5K0.5NBO3 CERAMICS; PHASE-TRANSITIONS; MICROSTRUCTURE; TEMPERATURE; PZT
The formation of cation vacancies can be useful for electro-chemical devices. In this regard, an understanding of vacancy formation is an important subject for enhancing current electrochemical devices and for developing next generation energy devices. In this work, we chose the well-known lead-free ferroelectric (K0.5Na0.5)NbO3 (KNN) as a model system to understand both the formation of cation vacancies and the relationship between cation vacancies and the physical properties. We studied sintering-duration dependence of the dielectric properties and the cation contents of KNN ceramics at the temperatures near the melting point of KNN. The difference in sintering duration led to a drastic change in the dielectric property, as well as to the creation of cation vacancies. Interestingly, we observed unequal evaporation of cations during the sintering process, which was confirmed by the data obtained from laser-inducedbreakdown spectroscopy. In addition, we found more drastic changes in the imaginary dielectric constant, which were likely due to a decrease in ionic conducting species, such as K and Na, in KNN.
laser-induced breakdown spectroscopy; eutectic glass; bioactive materials;FLOATING-ZONE TECHNIQUE; WOLLASTONITE-TRICALCIUM PHOSPHATE; EUTECTIC GLASS-CERAMICS; ND3+ IONS; WAVE-GUIDES; IN-VIVO; BIOCERAMICS; COMPOSITE; STRESSES; GROWTH
Laser-induced breakdown spectroscopy (LIBS) is applied to characterize the formation of porous hydroxyapatite layers on the surface of 0.8CaSiO(3)-0.2Ca(3)(PO4)(2) biocompatible eutectic glass immersed in simulated body fluid (SBF). Compositional and structural characterization analyses were also conducted by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and micro-Raman spectroscopy.
laser-induced breakdown spectroscopy; borate fusion; bauxite; sample preparation; matrix-match; pellet;PLASMA-MASS SPECTROMETRY; ELEMENTAL ANALYSES; LIBS; SAMPLES; GEOCHEMISTRY; FUSION
Due to matrix interference and sample particle size effects, some of the most important and difficult issues in laser-induced breakdown spectroscopy (LIBS) analysis are the calibration and quantitative measurement of a complex matrix. This study proposes the use of borate fusion as an alternative sample preparation procedure for the quantitative measurement of Al, Fe, Si and Ti in bauxite by LIBS. Analytical calibration curves were made using bauxite certified reference materials (CRM), and the precision and accuracy of the methods were evaluated by analysing an additional bauxite CRM, using two different approaches: pressed powder pellets and fused glass beads. The borate fusion method was the most suitable sample preparation technique, since particle size effects and matrix interference could be minimised, obtaining better linearity on the analytical calibration curves (r(2)), and more accurate and more precise results for bauxite analysis.
Polyacrylate polymer; Fourier transform infrared photoacoustic spectroscopy; Laser-induced breakdown spectroscopy; Principal component analysis;FILM FORMATION; FERTILIZER; LATEX; IDENTIFICATION; COMPLEXES
Polyacrylate polymer (PA) has been widely applied in coating products for decades. Recently, it has been used in controlled-release fertilizers. Nano Fe-III-tannic acid modified PA (PA-Fe) provides a better nutrient controlled release performance than conventional PA. In this work, a preliminary database of molecular and elemental information about the polymer was obtained using FTIR-PAS (Fourier transform infrared photoacoustic spectroscopy) and LIBS (laser-induced breakdown spectroscopy), respectively. The PA-Fe polymer contained more hydrophobic groups (-CH3) and fewer hydrophilic groups (-COOR, -COOH) than PA. More elements were detected for PA-Fe than PA. LIBS was useful to identify and classify PA and PA-Fe samples using principal component analysis. The combination of spectroscopic results and a film formation process model explained the lower nutrient release rate of PA-Fe. These results showed the strong analytical capabilities of FTIR-PAS combined with LIBS for identifying and characterizing modified PA.
Laser induced breakdown spectroscopy; Food analysis; Review; Sample preparation; Food fraud;INDUCED BREAKDOWN SPECTROSCOPY; SELF-ABSORPTION COEFFICIENTS; INDUCED PLASMA SPECTROSCOPY; ELEMENTAL ANALYSIS; EMISSION-LINES; LASER-ABLATION; SURFACE; MILK; CLASSIFICATION; ADULTERATION
Food is the main source of different elements which are essential, trace and fundamental for human diet and health. The type and level of elements in foods indicates whether it's toxic or not. Therefore, determination of elements and their amounts is crucial for food safety and quality. In order to fulfill the increasing demand on multi-elemental information for product monitoring, rapid and sensitive analytical techniques which are capable of detecting major and trace elements with good precision and accuracy are required. In this review, the most recent literature about the use of LIBS for the analysis of food and capabilities and limitations of LIBS on foods have been reported. This review provides comprehensive overview of the applications on food quality and fraud monitoring of several foods, sampling techniques and some limitations of LIBS. Furthermore, it provides a critical outlook on the developments to analyze food matrices with proper sample preparations. (C) 2017 Elsevier B.V. All rights reserved.
LIBS; Ash analysis; Wheat flour; PLS;LIBS
Ash content is an important quality control parameter in milling industry. Measurement of ash content is routinely performed using standard ash analysis method in which the sample is burned at 500-600 degrees C for 5-6 h. However, this method is not convenient for industrial applications, and thus, rapid and reliable methods are needed to be developed. The aim of this study was to develop a new method for ash analysis to be used in wheat milling fractions by using laser induced breakdown spectroscopy (LIBS). LIBS is an optic based multi-elemental, spectroscopic method which can analyze high number of samples in a considerably short time. In the study, wheat flour, whole wheat meal and semolina samples with different ash contents were analyzed using LIBS, and the spectra were evaluated with partial least squares (PLS) method. The results were correlated with the ones taken from standard ash analysis method. Calibration graph showed good linearity with the ash content between 0.48 and 2.44%, and 0.997 coefficient of determination (R-2). Limit of detection for ash analysis was calculated as 0.11%. The results indicated that LIBS is a promising and reliable method with high sensitivity for routine ash analysis in milling industry. (C) 2017 Elsevier Ltd. All rights reserved.
Hu, X. Y. ; Chen, X. ; Chen, X. J. ; Jiang, J. ; Shi, Y. J. ; Ye, P. C. ; Yuan, L. M. ; Yuan, M. S. ; Zhu, D. H.
toxic heavy metal; laser-induced breakdown spectroscopy (LIBS); Tegillarca granosa; discrimination analysis; wavelet transform algorithm (WTA);INFRARED-SPECTROSCOPY; CULTURAL-HERITAGE; TRACE-METALS; LABEO-ROHITA; IDENTIFICATION; LIBS; CADMIUM; SAMPLES; MODEL; ZINC
Tegillarca granosa samples contaminated artificially by three kinds of toxic heavy metals including zinc (Zn), cadmium (Cd), and lead (Pb) were attempted to be distinguished using laser-induced breakdown spectroscopy (LIBS) technology and pattern recognition methods in this study. The measured spectra were firstly processed by a wavelet transform algorithm (WTA), then the generated characteristic information was subsequently expressed by an information gain algorithm (IGA). As a result, 30 variables obtained were used as input variables for three classifiers: partial least square discriminant analysis (PLS-DA), support vector machine (SVM), and random forest (RF), among which the RF model exhibited the best performance, with 93.3% discrimination accuracy among those classifiers. Besides, the extracted characteristic information was used to reconstruct the original spectra by inverse WTA, and the corresponding attribution of the reconstructed spectra was then discussed. This work indicates that the healthy shellfish samples of Tegillarca granosa could be distinguished from the toxic heavy-metal-contaminated ones by pattern recognition analysis combined with LIBS technology, which only requires minimal pretreatments.
Guo, L. B. ; Li, X. Y. ; Luo, Y. F. ; Yang, X. Y. ; Yi, R. X. ; Zeng, X. Y. ; Zhao, N. ; Zhou, R. ; Zhu, Z. H.
VACUUM-ULTRAVIOLET; INDUCED PLASMA; SPECTROMETRY; OPTIMIZATION; COAL; IMPROVEMENTS; ABSORPTION
Carbon is a key element for steel properties but (a) hard to be determined by laser-induced breakdown spectroscopy (LIBS). Utilizing the combination of carbon in analytes and nitrogen in ambient gas to generate carbon nitrogen (CN) radicals, LIBS assisted with laser-induced radical fluorescence (LIBS-LIRF) was proposed to resonantly excite radicals instead of atoms in plasmas. The CN radicals in the B-2 Sigma-A(2)II band were stimulated by a 421.60 nm laserwavelength and emitted 388.34 nm fluorescence. The results show that the spectral intensity of the CN radicals was enhanced by 2 orders of magnitude using LIBS-LIRF. Then carbon content in steels was accurately and sensitively determined without spectral interference. The limits of detection (LoDs) were 0.039 and 0.013 wt % in air and nitrogen gas, respectively. The limits of quantification (LoQs) were 0.130 and 0.043 wt % in air and nitrogen gas, respectively. This work demonstrated the feasibility of LIES to realize reliable carbon determination in steel industry.
Devismes, D. ; Feugier, A. ; Maurelli, J. ; Moncayo, S. ; Motto-Ros, V. ; Pelascini, F. ; Sasseville, C. ; Surma, F.
INDUCED PLASMA SPECTROSCOPY; ATOMIC EMISSION-SPECTROMETRY; VACUUM-ULTRAVIOLET; SULFUR; STEEL; NANOPARTICLES; CALIBRATION; SAMPLES; RATIOS; SYSTEM
This work introduces a new approach to perform LIBS elemental imaging in the vacuum ultraviolet (VUV) wavelength range by using an argon purged probe coupled to a compact spectrometer. In spite of several important elements for geological and industrial applications such as S, P, As, B, C, or Zn presenting strong lines in the VUV range, the need for using specific optics and working under oxygen-free conditions has limited the extension of LIBS systems available for such a range. Herein, we present an adaptation of our LIBS imaging instrumentation to access the VUV while operating under ambient conditions. The proposed detection system is based on an optical probe directly coupled to a Maya2000Pro compact spectrometer (Ocean Optics), all purged with argon. The technical design along with a detailed evaluation of the VUV probe is addressed. The possibility of using this VUV probe for LIBS imaging is also investigated by studying a Canadian mine core sample with special emphasis on the detection of sulfur. In addition to sulfur, more than 15 elements including P, As, C, Ca, Si, Mo, B, and Zn have also been detected. Elemental images covering sample surfaces in the range of cm(2) with a micrometric spatial resolution (10 mu m) are presented. A detection limit of 0.2 wt% for sulfur is demonstrated in a single shot configuration. These results open new perspectives for both conventional LIBS and LIBS-based imaging in various application fields.
Calibration-free laser-induced breakdown spectroscopy; CF-LIBS; self-absorption; Saha-Boltzmann; Stark broadening; standard reference line;QUANTITATIVE ELEMENTAL ANALYSIS; INDUCED PLASMA SPECTROSCOPY; SELF-ABSORPTION; SPECTRAL-LINES; TEMPERATURE; ACCURACY; ALUMINUM
In this work, calibration-free laser-induced breakdown spectroscopy (CF-LIBS) is used to analyze a certified stainless steel sample. Due to self-absorption of the spectral lines from the major element Fe and the sparse lines of trace elements, it is usually not easy to construct the Boltzmann plots of all species. A standard reference line method is proposed here to solve this difficulty under the assumption of local thermodynamic equilibrium so that the same temperature value for all elements present into the plasma can be considered. Based on the concentration and rich spectral lines of Fe, the Stark broadening of Fe(I) 381.584nm and Saha-Boltzmann plots of this element are used to calculate the electron density and the plasma temperature, respectively. In order to determine the plasma temperature accurately, which is seriously affected by self-absorption, a pre-selection procedure for eliminating those spectral lines with strong self-absorption is employed. Then, one spectral line of each element is selected to calculate its corresponding concentration. The results from the standard reference lines with and without self-absorption of Fe are compared. This method allows us to measure trace element content and effectively avoid the adverse effects due to self-absorption.
Armstrong, M. R. ; Azer, M. ; Crowhurst, J. C. ; Curreli, D. ; Finko, M. S. ; Isselhardt, B. H. ; Koroglu, B. ; Radousky, H. B. ; Rose, T. P. ; Savina, M. R. ; Siekhaus, W. J. ; Zaug, J. M.
INDUCED BREAKDOWN SPECTROSCOPY; MOLECULAR ISOTOPIC SPECTROMETRY; URANIUM MONOXIDE; INDUCED PLASMAS; SPECTRA; UO; COMPUTATION; STATES; ORE
We have measured vibronic emission spectra of an oxide of uranium formed after laser ablation of the metal in gaseous oxygen. Specifically, we have measured the time-dependent relative intensity of a band located at approximately 593.6 nm in O-16(2). This band grew in intensity relative to neighboring atomic features as a function time in an oxygen environment but was relatively invariant with time in argon. In addition, we have measured the spectral shift of this band in an O-18(2) atmosphere. Based on this shift, and by comparison with earlier results obtained from free-jet expansion and laser excitation, we can confirm that the oxide in question is UO, consistent with recent reports based on laser ablation in O-16(2) only. Published by AIP Publishing.
Du, M. ; Guo, L. B. ; Hao, Z. Q. ; Li, J. M. ; Li, X. Y. ; Liu, J. G. ; Lu, Y. F. ; Shen, M. ; Yi, R. X. ; Zeng, X. Y.
Laser-induced breakdown spectroscopy; Characteristic spectral lines of non-metallic elements; Support vector machine; Plastics identification;ARTIFICIAL NEURAL-NETWORKS; INDUCED PLASMA; EMISSION; POLYMERS
Laser-induced breakdown spectroscopy (LIPS) combined with support vector machine (SVM) was adopted to identify 20 kinds of different colored industrial plastics from different manufacturers in open air. The experimental parameters of spectral acquisition were optimized firstly. 100 spectra recorded under optimum conditions were randomly and equally divided into training set and test set. 6 non-metallic characteristic spectral lines were used to avoid the interference with metallic lines. And the training time of SVM model was reduced. The results show that 996 of 1000 test spectra were identified correctly and the average classification accuracy is reached to 99.6%. The classification efficiency is improved with 6 non-metallic characteristic spectral lines. The research demonstrates that, when fewer of major non-metallic characteristic spectral lines are used, laser-induced breakdown spectroscopy technique with support vector machine can identify more kinds of plastics with high accuracy and efficiency.
SILICON-WAFERS; CRYSTAL-GROWTH; SOLAR-CELL; AEROSOLS; ABLATION; CU(IN,GA)SE-2; TRANSISTORS; CAPACITANCE; THICKNESS; RESIDUES
The current Largest market share and continually growing industry of the semiconductor manufacturing sector in the US demands rapid and cost-effective quality control and characterization of thin film semiconducting materials. To this end, we demonstrate Laser Induced Breakdown Spectroscopy (LIBS) as a facile and effective analytical tool for rapid process-Line characterization of metal-oxide semiconductor (MOS) transistors and capacitors. Specifically, we carry out quantitative LIBS analysis on siLicon oxide (Si02) thin-films of various thicknesses grown by high-temperature moisture-free oxidation on industrial-grade Si wafers. The stoichiometric ratios of oxygen to siLicon ([O]/[Si]) in various SiO2 films are measured by LIBS anaLyses using an internal calibration technique. The results are verified against benchmark anaLyses based on oxide Layer thicknesses and Laser-induced crater profile topographies from eLLipsometry, scanning electron microscopy (SEM), atomic force microscopy (AFM), and profflometry measurements. The stoichiometric ratios of [O]/[Si] calculated from thickness and profflometry measurements are used to compare with our direct LIBS measurements. Our results indicate good agreement between the LIBS and profibmetry calculation results, demonstrating the future capability of LIBS for thin film characterization during their industrial processing.
MATRIX CONVERSION; QUANTITATIVE-ANALYSIS; AQUEOUS-SOLUTIONS; METAL DETECTION; HEAVY-METALS; SPECTROMETRY; LIBS; MICROEXTRACTION; PLASMA; MEMBRANE
Laser-induced breakdown spectroscopy (LIBS) is a simple, fast, and direct technique for the elemental analysis of various samples. However, the practical application of this method in direct liquid analysis is limited due to its inherent disadvantages including surface ripples and extinction of emitted intensity. Applicable treatments of liquids always involve complicated procedures or additional instruments, which is disadvantageous to its analytical performance. In this study, we proposed a novel method for the LIBS analysis of liquid samples via a hydrogel-based solidification technique. In this new method, aqueous solution is directly poured into sodium polyacrylate resins. Owing to the high hydroscopicity of sodium polyacrylate resins, the resins quickly form a hydrogel and immediately solidify the liquid samples. After this, the LIBS analysis is directly performed. To estimate the analytical performance of this proposed method, calibration curves were established and limits of detection for Al, Cu, and Cr were obtained. The limits of detection (CODs) for the emission lines of Al(I) 308.21 nm, Cu(I) 324.75 nm, and Cr(I) 425.43 nm were 0.460 mu g mL(-1), 4.69 mu g mL(-1), and 4.44 mu g mL(-1), respectively. According to the obtained results, this proposed method demonstrates its better analytical performance in terms of CODs at the ppm level and requires shorter processing time as compared to other analytical methods based on the LIBS technique for liquid sample analysis. Especially, the short pretreatment of samples and simple auxiliary equipment make this hydrogel-based solidification method bring LIBS out of the laboratory for the direct analysis of environmental liquid samples. The feasibility and potential of this novel method have also been discussed for special analytical applications in slurry samples.
Laser-induced breakdown spectroscopy (LIBS); Magnetic properties; Uniaxial anisotropy;INDUCED BREAKDOWN SPECTROSCOPY; LASER-PRODUCED PLASMA; OPTICAL-EMISSION; SAMPLE TEMPERATURE; ALLOYS
Laser-induced breakdown spectroscopy (LIBS) has been investigated as a potential analytical tool for better understanding the role of sample temperature and magnetization on the optical emission of laser-induced plasma for NdFeB sample. The mechanism of optical emission by increasing of sample temperature (T (s) ) and plasma confinement including shock wave in the presence of magnetic field is discussed. The heated samples show a significant decrease in magnetic properties, especially the coercivity and saturation of magnetization. The coercivity and saturation of magnetization of NdFeB were 15000 Oe and 95 emu/g, respectively. The intensity of emission lines decreased with an increase in T (s) for NdFeB sample. The coercivity and saturation of magnetization of samples was monotonically decreased and caused to decrease in LIBS signal intensities.
LIBS; Quantification; Elemental imaging; Elemental profile; Heterogeneous catalyst; Palladium;X-RAY-FLUORESCENCE; FLIGHT MASS-SPECTROMETRY; HIGH-SPEED; GEOLOGICAL SAMPLES; HIGH-RESOLUTION; TRACE-ELEMENTS; CONVERTERS; METALS; MICROANALYSIS; MICROPROBE
Currently, the use of catalysis is widespread in almost all industrial processes; its use improves productivity, synthesis yields and waste treatment as well as decreases energy costs. The increasingly stringent requirements, in terms of reaction selectivity and environmental standards, impose progressively increasing accuracy and control of operations. Meanwhile, the development of characterization techniques has been challenging, and the techniques often require equipment with high complexity. In this paper, we demonstrate a novel elemental approach for performing quantitative space-resolved analysis with ppm-scale quantification limits and mu m-scale resolution. This approach, based on laser-induced breakdown spectroscopy (LIBS), is distinguished by its simplicity, all-optical design, and speed of operation. This work analyzes palladium-based porous alumina catalysts, which are commonly used in the selective hydrogenation process, using the LIBS method. We report an exhaustive study of the quantification capability of LIBS and its ability to perform imaging measurements over a large dynamic range, typically from a few ppm to wt. These results offer new (i)nsight into the use of LIBS-based imaging in the industry and paves the way for innumerable applications. (C) 2017 Elsevier B.V. All rights reserved.
De Giacomo, A. ; Dell'Aglio, M. ; Fortes, F. J. ; Gaudiuso, R. ; Laserna, J. J. ; Santagata, A.
Laser-induced breakdown spectroscopy; Deep Sea; Double pulse; Cavitation bubble; High pressure;BULK AQUEOUS-SOLUTIONS; ELEMENTAL ANALYSIS; SINGLE-PULSE; SHOCK-WAVES; LIQUIDS; LIBS; EXCITATION; INTENSITY; ABLATION; INSIGHTS
There is a growing interest in the development of sensors use in exploration of the deep ocean. Techniques for the chemical analysis of submerged solids are of special interest, as they show promise for subsea mining applications where a rapid sorting of materials found in the sea bottom would improve efficiency. Laser-Induced Breakdown Spectroscopy (LIBS) has demonstrated potential for this application thanks to its unique capability of providing the atomic composition of submerged solids. Here we present a study on the parameters that affect the spectral response of metallic targets in an oceanic pressure environment. Following laser excitation of the solid, the plasma persistence and the cavitation bubble size are considerably reduced as the hydrostatic pressure increases. These effects are of particular concern in dual pulse excitation as reported here, where a careful choice of the interpulse timing is required. Shadowgraphic images of the plasma demonstrate that cavitation bubbles are formed early after the plasma onset and that the effect of hydrostatic pressure is negligible during the early stage of plasma expansion. Contrarily to what is observed at atmospheric pressure, emission spectra observed at high pressures are characterized by self-absorbed atomic lines on continuum radiation resulting from strong radiative recombination in the electron-rich confined environment. This effect is much less evident with ionic lines due to the much higher energy of the levels involved and ionization energy of ions, as well as to the lower extent of absorption effects occurring in the inner part of the plasma, where ionized species are more abundant. As a result of the smaller shorter-lived cavitation bubble, the LIBS intensity enhancement resulting from dual pulse excitation is reduced when the applied pressure increases. (C) 2017 Elsevier B.V. All rights reserved.
Cama-Moncunill, R. ; Cama-Moncunill, X. ; Cullen, P. J. ; Dixit, Y. ; Geulen, D. ; Markiewicz-Keszycka, M. ; Sullivan, C.
LIBS; Beef; Offal; Copper; PLSR; Chemometrics;MOTION CONDITIONS; TRACE-ELEMENTS; MEAT; SPECTROMETRY; LIBS; CLASSIFICATION; PREDICTION; SAMPLES
Laser induced breakdown spectroscopy (LIBS) is an emerging technique in the field of food analysis which provides various advantages such as minimal sample preparation, chemical free, rapid detection, provision of spatial information and portability. In this study, LIBS was employed for quantitative analysis of copper content in minced beef samples spiked with beef liver over three independent batches. Copper content was determined with graphite furnace atomic absorption spectroscopy (GFAAS) in order to obtain reference values for modelling. Partial least square regression (PLSR) was performed to build a calibration and validation model. A calibration model with a high R-cv(2) of 0.85 and a RMSECV of 43.5 ppm was obtained, confirming a good fit for the model. The validation model showed a good prediction accuracy with a high R-p(2) of 0.85 and RMSEP of 36.8 ppm. Moreover, on a further study to evaluate the spatial capabilities, LIBS was able to successfully map copper content within a pellet, indicating the suitability of LIBS to provide spatial information and therefore potential use on heterogeneous samples. Overall, it can be concluded that LIBS combined with chemometrics demonstrates potential as a quality monitoring tool for the meat processing industry.
INDUCED BREAKDOWN SPECTROSCOPY; QUANTITATIVE-ANALYSIS; STEEL SAMPLES; CLASSIFICATION; PLASMA; RECOGNITION; TEMPERATURE; EXPLOSIVES; MODELS; SOILS
Laser induced breakdown spectroscopy with chemometric methods has been employed for sorting zamak alloy (zinc based alloy) samples. Plasma plumes were created on the sample surface using 50 mJ Nd:YAG laser pulses at its fundamental wavelength (lambda = 1064 nm). Six types of zinc alloy samples with different elemental compositions have been used to perform the LIBS measurements under optimized experimental conditions. On the obtained LIBS data three different chemometric classification models were applied, namely K Nearest Neighbor (KNN), Support Vector Machine (SVM) and Artificial Neural Networks (ANN). The effect of the input database choice and its normalization on the classification model efficiency has been investigated and found to play a crucial role. It was found that KNN, SVM and ANNs permit an appropriate classification of different zinc alloys using LIBS spectra and the best results were obtained from the largest input database. The effect of data normalization has been discussed for each model. The obtained results demonstrate the feasibility of using chemometric methods associated with the LIBS technique as an industrial tool for in situ zamak sorting.
TRACE-METAL ANALYSIS; AQUEOUS-SOLUTION; MATRIX CONVERSION; HEAVY-METALS; LIBS; MEMBRANE; WATER; SPECTROMETRY; DEPOSITION; ADSORBENT
A highly concentrated, ring-shaped phase conversion (RSPC) method was developed for liquid sample analysis using the laser-induced breakdownspectroscopy (LIBS) technique. In this work, test samples were prepared by mixing the metal particles with polyvinyl alcohol (PVA) supporter in liquid phase. With heat, the PVA solution solidified inside a modified glass petri dish, forming a metal-enriched polymer ring film. Distinguished from other traditional liquid-to-solid conversing methods, the proposed new method takes advantage of enhanced homogeneity for the target elements inside the ring film. The modified glass petri dish was used to control the ring-shaped concentration. Due to the specially designed circular groove at the bottom of this dish, where the PVA solution and liquid sample mixture accumulated, the target elements were concentrated in this small ring, which is beneficial for enhancing and stabilizing the plasma signals compared to the direct liquid sample analysis using LIBS. The limits of detection for Ag, Cu, Cr, and Ba obtained with the RSPC-LIBS technology were 0.098 mu g . mL(-1), 0.18 mu g . mL(-1), 0.83 mu g . mL(-1), and 0.046 mu g . mL(-1), respectively, which provided greater improvement than the direct bulk liquid analysis using LIBS. (C) 2017 Optical Society of America
All solid state batteries; Solid electrolytes; Li7La3Zr2O12; Garnet;AL-SUBSTITUTED LI7LA3ZR2O12; ELECTROCHEMICAL PROPERTIES; DOPED LI7LA3ZR2O12; CRYSTAL-CHEMISTRY; STABILITY; TEMPERATURE; MICROSTRUCTURE; STABILIZATION; SPECTROSCOPY; CONDUCTION
Al-substituted Li7La3Zr2O12 samples processed under argon show enhanced Li-ion transport and interfacial properties in symmetrical cells with lithium electrodes, compared to those prepared in air. In particular, the samples prepared under argon have higher ionic conductivities and lower interfacial impedances in symmetrical lithium cells, and show better DC cycling characteristics. The electronic conductivities are also somewhat higher. Pellets subjected to thermal treatment under the two types of atmospheres have different colors but exhibit similar microstructures. X-ray diffraction experiments suggest that there are slight structural differences between the two types of samples, but few dissimilarities were observed in elemental composition, distribution of ions, oxidation states, or bond lengths using laser-induced breakdown spectroscopy (LIBS), x-ray photoelectron spectroscopy (XPS), and extended x-ray absorption fine structure spectroscopy (EXAFS) to analyze the materials. Additionally, there was no evidence that La or Zr were reduced during the processing under Ar. Possible explanations for the improved electrochemical properties of the sample prepared under Ar compared to the one prepared in air include differences in grain boundary chemistries and conductivities and/or a small concentration of oxygen vacancies in the former.
INDUCED PLASMA SPECTROSCOPY; SELF-ABSORPTION; ACCURACY
The quantitative analysis of the standard aluminum-silicon alloy has been performed using calibration free laser induced breakdown spectroscopy (CF-LIBS). The plasma was produced using the fundamental harmonic (1064 nm) of the Nd: YAG laser and the emission spectra were recorded at 3.5 mu s detector gate delay. The qualitative analysis of the emission spectra confirms the presence of Mg, Al, Si, Ti, Mn, Fe, Ni, Cu, Zn, Sn, and Pb in the alloy. The background subtracted and self-absorption corrected emission spectra were used for the estimation of plasma temperature as 10 100 +/- 300 K. The plasma temperature and self-absorption corrected emission lines of each element have been used for the determination of concentration of each species present in the alloy. The use of corrected emission intensities and accurate evaluation of plasma temperature yield reliable quantitative analysis up to a maximum 2.2% deviation from reference sample concentration. Published by AIP Publishing.
INDUCED BREAKDOWN SPECTROSCOPY; INDUCTIVELY-COUPLED PLASMA; MOLECULAR ISOTOPIC SPECTROMETRY; FLIGHT MASS-SPECTROMETRY; LA-ICP-MS; DEPTH PROFILE; LIBS; SAMPLES; STEEL
Laser ablation has become a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser-ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution, reduced risk of contamination or sample loss, analysis of very small samples not separable for solution analysis, and determination of spatial distributions of elemental composition. This short review describes the most common approaches-laser-induced breakdown spectroscopy (LIBS) and laser-ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS)-and provides an introduction to laser-ablation molecular isotopic spectrometry (LAMIS).
Detonation nanodiamond, DND; Transmission electron microscopy, TEM; Electron energy loss spectroscopy, EELS; Energy-dispersive spectrometry, EDS; Fast Fourier transform, FFT; High-angle annular dark-field, HAADF; X-ray photoelectron spectroscopy, XPS; Diffraction, lattice spacing, desorption gas chromatography - mass spectrometry, D-GC-MS; Laser induced breakdown spectroscopy, LIBS; Fourier transform infrared spectroscopy, FTIR;ULTRADISPERSE-DIAMOND; SURFACE; CARBON; TRANSITION; ADSORPTION; STABILITY; GRAPHENE; POWDER; VAPOR
Unexpected variations in the purity and structure of commercial detonation nanodiamonds (DNDs) is an ongoing issue. Unfortunately, influences of these variations and how they affect DND behaviors are seldom addressed. This work investigates nominally homologous commercial DNDs sold by a single vendor under the same item number but different lots. Paraffin wax and surfactant were discovered as the major organic contaminants in the DND samples along with metallic impurities. The relative quantities of these contaminants were correlated to discrepancies in the structure and crystallinity of DNDs. The DNDs containing more contaminants possessed thicker shells surrounding the diamond cores; the diamond crystallinity was observed to quickly disappear, on the order of several minutes, when exposed to 200 kV electron beam. On the other hand, those DNDs carrying fewer impurities exhibited a stable diamond structure. The differences in metallic impurities were attributed to variations in the DND purification treatments, and did not appear to affect a morphological change under the electron beam. The present work demonstrates the negative effects of impurities in commercial DNDs on the content and stability of diamond carbons. The results also have implications on possible factors that must be considered when using commercial DNDs for advanced applications.
NONLINEAR OPTICS; FILAMENTATION; AIR; OPERATION; PULSES; WATER; GAS
We extend the detection range of laser-induced breakdown spectroscopy by combining high-intensity femtosecond laser pulses with high-energy nanosecond - CO2 laser pulses. The femtosecond laser pulses ionize the molecules and generate filament in air. The free electrons generated in the self-confined plasma channel by the femtosecond laser serve as the seed electrons which cause efficient avalanche ionization in the nanosecond - CO2 laser field. We show that the detection distance has been extended by three times with the assistance of femtosecond laser filamentation.
INDUCED BREAKDOWN SPECTROSCOPY; SINGLY IONIZED ALUMINUM; DUAL PULSE EXCITATION; EXPANSION DYNAMICS; ELEMENTAL ANALYSIS; ABLATION PLUME; GENERATION; EMISSION; UNDERWATER; LIQUID
We report on the findings of double-pulse studies performed on an aluminium target submerged in water using Nd: YAG laser pulses. Shadowgraphy measurements were performed to examine the dynamic behaviour of the cavitation bubble that eventually forms some considerable time post-plasma ignition. These measurements were used to inform subsequent investigations designed to probe the bubble environment. The results of time-resolved imaging from within the cavitation bubble following irradiation by a second laser pulse reveal the full dynamic evolution of a plasma formed in such an environment. Rapid displacement of the plasma plume in a direction normal to the target surface followed by a diffusive outwards expansion is observed and a qualitative model is proposed to explain the observed behaviour. Line profiles of several ionic and atomic species were observed within the irradiated cavitation bubble. Electron densities were determined using the Stark broadening of the Al II line at 466.3 nm and electron temperatures inferred using the ratio of the Al II (466.3 nm) and Al I (396.15 nm) lines. Evidence of self-reversal of neutral emission lines was observed at times corresponding to growth and collapse phases of the cavitation bubble suggesting high population density for ground state atoms during these times.
INDUCED PLASMA SPECTROMETRY; IN-SITU ANALYSIS; HIGH-TEMPERATURE; ELEMENTAL ANALYSIS; GRADE TRANSITION; MOLECULAR BANDS; REAL-TIME; MOLD; LIBS; SAMPLES
Among the several controlling routines utilized in the steelmaking process, analytical operations during continuous casting are especially demanding due to the extreme environment of steel plants and the crude conditions of the steel surface at the exit of the casting system. This report presents how dual-pulse laser-induced breakdown spectroscopy (LIBS) can be used for the real-time monitoring of continuous casting sequences in a steel plant and the operations needed for detecting the separation between grades of close chemical compositions. Diverse dual-pulse laser conditions have been tested in order to improve the LIBS system performance. Apart from the scale layer formed by the oxidation of steel by the surrounding air, the presence of residues of mould powder on the steel surface tends to complicate the LIBS analysis as elements present in the powder such as manganese interfere with the steel components. LIBS data processing by discriminant function analysis has been demonstrated to be beneficial for the identification of steel transitions. Changes in steel composition as low as 0.20 percentage points Cr in a stainless steel sample containing above 17% of this element are detected by corresponding changes in Wilks' lambda values from 1.0 to 0.75 during the transition. Changes in the concentration of nickel are of minor relevance as its concentration on the steel surface at the time of continuous casting is depleted. For steel concentrations differing to a larger extent, differentiation of steel grades is straight, involving changes in Wilks' lambda values from 1 to below 0.1.
Laser induced breakdown spectroscopy (LIBS); Laser wavelength; Plasma time evolution; Plasma shielding effect; Coal;INDUCED BREAKDOWN SPECTROSCOPY; ELEMENTAL ANALYSIS; DEPENDENCE; PARAMETERS
In face of the complicated and changeable coal in Chinese power stations, the on-line measurement of coal elemental composition is extremely significant in terms of enhancing the safety and efficiency of boilers as well as lowering the waste emission during operation. In this work, laser induced breakdownspectroscopy (LIBS) was applied to coal quality measurement. Laser wavelength was changed as 355, 532 and 1 064 nm to investigate the influence on coal LIBS features, including plasma time evolution and the spectral lines intensity-time characteristics of different elements. Energy threshold for shielding effect was also tested to verify how it varies with laser wavelengths. Additionally, coal LIBS spectrum was analyzed under different laser wavelengths. It has been proven by experiments that higher intensity of coal LIBS spectrum and energy threshold can be easily achieved when using laser of 532 nm, making it a fantastic energy source for coal LIBS tests. Results of these experiments serve to guide the industrial application of LIBS technology in the field of coal quality measurement.
LIBS; SIMFUEL; AHWR; Argon; Nuclear;INDUCED PLASMAS; URANIUM; THORIUM; LIBS; SPECTROMETRY; EMISSION; GLASS
Advanced Heavy Water Reactor (AHWR) grade (Th-U)O-2 fuel sample and Simulated High Burn-Up Nuclear Fuels (SIMFUEL) samples mimicking the 28 and 43 GWd/Fe irradiated burn-up fuel were studied using laser-induced breakdown spectroscopy (LIBS) setup in a simulated hot-cell environment from a distance of >1.5 m. Resolution of <38 pm has been used to record the complex spectra of the SIMFUEL samples. By using spectrum comparison and database matching >60 emission lines of fission products was identified. Among them only a few emission lines were found to generate calibration curves. The study demonstrates the possibility to investigate impurities at concentrations around hundreds of ppm, rapidly at atmospheric pressure without any sample preparation. The results of Ba and Mo showed the advantage of LIBS analysis over traditional methods involving sample dissolution, which introduces possible elemental loss. Limits of detections (LOD) under Ar atmosphere shows significant improvement, which is shown to be due to the formation of stable plasma. (C) 2017 Elsevier B.V. All rights reserved.
LIBS; Mobile LIBS; Chemometrics; PLS-R; Building materials;CONCRETE STRUCTURES; CALIBRATION; REGRESSION; TUTORIAL; LIMIT
For the damage assessment of reinforced concrete structures the quantified ingress profiles of harmful species like chlorides, sulfates and alkali need to be determined. In order to provide on-site analysis of concrete a fast and reliable method is necessary. Low transition probabilities as well as the high ionization energies for chlorine and sulfur in the near-infrared range makes the detection of CI I and S I in low concentrations a difficult task. For the on-site analysis a mobile LIBS-system (lambda = 1064 nm, E-pulse <= 3 mJ, tau = 1.5 ns) with an automated scanner has been developed at BAM. Weak chlorine and sulfur signal intensities do not allow classical univariate analysis for process data derived from the mobile system. In order to improve the analytical performance multivariate analysis like PLS-R will be presented in this work. A comparison to standard univariate analysis will be carried out and results covering important parameters like detection and quantification limits (LOD, LOQ) as well as processing variances will be discussed (Allegrini and Olivieri, 2014 ; Ostra et al., 2008 ). It will be shown that for the first time a low cost mobile system is capable of providing reproducible chlorine and sulfur analysis on concrete by using a low sensitive system in combination with multivariate evaluation. (C) 2017 Elsevier B.V. All rights reserved.
LITHIUM-ION BATTERIES; INDUCED BREAKDOWN SPECTROSCOPY; TEMPERATURE HEAT-CAPACITY; TRANSPORT-PROPERTIES; INSERTION MATERIAL; COBALT OXIDE; LICOO2; LICO1/3NI1/3MN1/3O2; ELECTRODES; CONDUCTIVITY
Thermal behaviour and thermophysical properties of two typical cathodes for lithium- ion batteries were studied in dependence of temperature. The cathode materials are composite thick films containing a mixture of 90 wt% LiMeO2 active material (with Me = Co or Me = Ni + Mn + Co, respectively) and additives (binder and carbon black), deposited on aluminium current collector foils. The thermal conductivity of each cathode type and their corresponding composite layers were determined up to 573 K from the measured thermal diffusivity, the specific heat capacity and the estimated density based on metallographic methods and structural investigations. In addition, the impact of lithiation degree x in LixMeO2 on the transport properties of cathode samples was also investigated. The quantitative determination and the homogeneity of Li content on the surface and within the bulk of the samples were validated by laserinduced breakdown spectrometry. The results presented here explain at cell component level, i.e. cathode material, the thermal runaway behaviour of lithium-ion batteries in a combined approach of application oriented and fundamental research. Therefore, these data are significant for improving the simulation studies of their thermal management, in which the bulk properties are assumed, as a common approach, temperature and lithiation degree independent.
INDUCTIVELY-COUPLED PLASMA; ATOMIC-ABSORPTION-SPECTROMETRY; COMPOSITE FILM ELECTRODES; RAY-FLUORESCENCE ANALYSIS; HEXAVALENT CHROMIUM; WASTE-WATER; ELECTROCHEMICAL DETECTION; MATRIX CONVERSION; OXIDE COMPOSITES; METAL DETECTION
Traditional laser-induced breakdown spectroscopy (LIES) always fails to directly detect target in aqueous solution due to rapid quenching of emitted light and adsorption of pulse energy by surrounding water. A method is proposed for the in situ underwater LIES analysis of Cr(VI) in aqueous solution freed from the common problems mentioned above by combining a gas-assisted localized liquid discharge apparatus with electrosorption for the first time. In this approach, the introduction of the gas assisted localized liquid discharge apparatus provides an instantaneous gaseous environment for underwater LIES measurement (that is, the transfer of sampling matrix is not needed from aqueous solution to dry state). The preconcentration of Cr(VI) is achieved by electrosorption with a positive potential applied around adsorbents, which can promote the adsorption of Cr(VI) and inhibit that of the coexisting cations leading to a good anti interference. Amino groups functionalized chitosan-modified graphene oxide (CS-GO) is utilized for Cr(VI) enrichment, which can be protonated to form NH3+ in acidic condition promoting the adsorption toward Cr(VI) by electrostatic attraction. The highest detection sensitivity of 5.15 counts mu g(-1) L toward Cr(VI) is found for the optimized electrosorption potential (E-Es = 1.5 V) and electrosorption time (t(Es) = 600 s) without interference from coexisting metal ions. A corresponding limit of detection (LOD) of 12.3 mu g L-1 (3 sigma method) is achieved, which is amazingly improved by 2 or even 3 orders of magnitude compared to the previous reports of LIES.
INDUCED BREAKDOWN SPECTROSCOPY; BORON ISOTOPIC RATIO; ABLATION PLASMAS; EMISSION FEATURES; INFRARED-SPECTRA; ENERGY-LEVELS; LIBS; NANOSECOND; SPECTROMETRY; PERFORMANCE
We report on the observation of uranium monoxide (UO) emission following fs laser ablation (LA) of a uranium metal sample. The formation and evolution of the molecular emission is studied under various ambient air pressures. Observation of UO emission spectra at a rarefied residual air pressure of similar to 1 Torr indicates that the UO molecule is readily formed in the expanding plasma with trace concentrations of oxygen present within the vacuum chamber. The persistence of the UO emission exceeded that of the atomic emission; however, the molecular emission was delayed in time compared to the atomic emission due to the necessary cooling and expansion of the plasma before the UO molecules can form. (C) 2017 Optical Society of America
laser ablation in liquid; silver NPs; laser induced plasma; shockwave; bubble dynamics; water jet; thin water layer; bubble near a free surface;FREE-SURFACE; CAVITATION BUBBLES; LIQUID-JET; WAVE; NANOPARTICLES; COLLAPSE; GENERATION; BREAKDOWN; EROSION; YIELD
In this paper, emission spectroscopy and fast imaging surveys during pulsed laser ablation in liquid (PLAL) for nanoparticles (NPs) production have been used, in order to provide further details about the process involved and the potentialities offered by a wire-shaped sample ablated in a flowing water jet. This kind of set-up has been explored because the laser ablation efficiency in water increases when a thin water layer and a wire-shaped target are used. In order to understand the physical processes causing the increasing ablation efficiency, both the laser-induced plasma and bubble dynamics generated in a flowing liquid jet have been analysed. The plasma parameters and the bubble behaviour in such a system have been compared with those observed in conventional PLAL experiments, where either a bulk or a wire-shaped target is immersed in bulk water. From the data presented here it is evidenced that the plasma and shockwave induced during the breakdown process can play a direct role in the ablation efficiency variation observed. With regard to the cavitation bubbles evolving near a free surface (the interface between water and air) it should be noted that these have to be treated with caution as a consequence of the strong influence played in these circumstances by the boundary of the water jet during its expansion dynamics. The effects due to the size of the liquid layer, the presence of the water/air interface, the liquid characteristics, the target shape, the plasma evolution and the bubble dynamics together with their outcomes on the NPs' production, are presented and discussed.
Laser matter interaction; Microstructures and defects; Confinement geometry target; Glass transmission; Free electron density;FEMTOSECOND LASER; TRANSPARENT SOLIDS; INDUCED PLASMA; SHOCK-WAVES; LINES; ABLATION; SURFACE; TEMPERATURE; DIAGNOSTICS; DEPENDENCE
Confinement geometry target assemblies are very important in the study of laser shocked materials. The shock pressure in confinement geometry depends on incident laser intensity and has main limitation of dielectric breakdown of transparent materials used for confinement. This makes study of damage mechanism induced by laser pulses in dielectric materials necessary. We investigated the front and rear surface damage threshold of borosilicate glass (dielectric material) and their dependency on laser parameters. The induced damage width, geometries and microstructure changes are analyzed with optical microscope, scanning electron microscope and Raman spectroscopy. The results show that at low energies symmetrical damages are found and these damage width increases nonlinearly with laser intensity. The emitted optical spectrum during the process of breakdown is also investigated and is used for the characterization of emitted plasma such as plasma temperature and free electron density. Optical emission lines from Si I, Si II and Si III ions are used for temperature and density estimations. The plasma temperature and density are measured as similar to 0.94 eV and 10(16)-10(17) cm(-3) respectively. All results are found consistent with the earlier, published results and are used in designing the confinement geometry targets for laser shock experiments. (C) 2017 Published by Elsevier B.V.
laser-induced breakdown spectrometry; chlorine; plants; concrete;SPECTROSCOPY
We consider collinear and orthogonal beam-convergence configurations in double-pulse laser-induced breakdown spectrometry (LIBS, also known as laser-spark emission spectrometry) for chlorine determination in plants and concrete from the Cl I 837.59 nm line. We have observed that the signal-to-noise ratio is not much lower for the orthogonal configuration due to spatial instability in the second breakdown. At the same time, suppression of interfering molecular bands in this configuration lets us improve the sensitivity of LIBS for chlorine determination in plant material.
INDUCED BREAKDOWN SPECTROSCOPY; HIGH-TEMPERATURE; PARTICLES
A new route for directly measuring the fly ash unburned carbon in a gas solid flow by laser-induced breakdown spectroscopy (LIBS) was proposed. A homemade gas-solid flow generation system was developed to simulate the gas solid flow in the duct of a coal-fired plant. For improving the measurement performance, the emission characteristics of the laser induced plasma, the influence of the fly ash mass flow rate, and the correlation between the unburned carbon content and the carbon emission intensity were studied in detail. The SNR of the Si spectral line at 288.15 nm was selected as the index for false spectra identification because the distribution of Si is not related to the particle size. The results highlight the change of the plasma shape and volume with fluctuations of the gas solid flow because of the uneven distribution of the fly ash particle size and number in the laser focal spot. The mass flow rate of the fly ash affected the false hit rate, while it did not affect the intensity of the analyte lines. The regression coefficients (R-2) between the normalized intensity of C 247.86 nm and the unburned carbon content improved from 0.93 to 0.98 when the false spectra were rejected. The good agreement between the normalized intensity of C 247.86 nm and the unburned carbon content indicates that LIBS can be developed as a promising tool for directly measuring the fly ash unburned carbon in a gas-solid flow.
CHEMCAM; MISSION; UNIT
The SuperCam remote sensing instrument suite under development for the National Aeronautics and Space Administration's (NASA) Mars 2020 rover performs laser-induced breakdown spectroscopy (LIBS), remote Raman spectroscopy, visible and infrared (VISIR) reflectance spectroscopy, acoustic sensing, and high-resolution color imaging. The instrument builds on the successful architecture of the ChemCam instrument, which provides LIBS and panchromatic images on the Curiosity rover, adding remote Raman spectroscopy by frequency doubling the laser and using a gated intensified detector to obtain Raman signals at distances to 12 m. To the visible reflectance spectroscopy used by ChemCam, an acousto-optic tunable filter (AOTF)-based IR spectrometer is added to cover the 1.3-2.6 mu m range that contains important mineral signatures. A complementary metal-oxide semiconductor (CMOS) detector provides color (Bayer filter) images at a pixel resolution of 19 mu rad and an optical resolution of 30 mu rad. Sounds are recorded via a Knowles Electret microphone, which is the same one that was included but not used on two earlier missions. The acoustic signals of the LIBS plasmas will provide information on the hardness of the targets, while other sounds (wind, rover sounds) will also be recorded. The laser, telescope, IR spectrometer, and camera reside on the rover's mast and, are provided by the Centre national d'etudes spatiales (CNES), while the LIBS, Raman, and VIS spectrometers and data processing unit are built by Los Alamos National Laboratory (LANL) and reside in the rover body. A calibration target assembly provided by the University of Valladolid, Spain, resides on the back of the rover. The overall mass of the instrument suite is 10.7 kg.
Beck, P. ; Buch, A. ; Coll. P. ; Cousin, A. ; Gasnault, O. ; Jaber, M. ; Lasne, J. ; Maurice, S. ; Meslin, P. Y. ; Rapin, W. ; Szopa, C. P. P.
INDUCED PLASMA SPECTROSCOPY; CHEMCAM INSTRUMENT SUITE; VACUUM-ULTRAVIOLET; QUANTITATIVE-ANALYSIS; GALE CRATER; RADIATION CONDITIONS; STEEL ANALYSIS; SURFACE; MOLECULES; ROVER
Organic matter has been continuously delivered by meteorites and comets to Mars since its formation, and possibly formed in situ by abiogenic and/or biogenic processes, This organic matter may be preserved from the harsh oxidizing environment of Mars in specific locations. Together with water, organic molecules are necessary to the emergence of life as we know it. Since the first martian landers, scientists have been searching for organics and until today, only one positive detection has been made by a Gas Chromatography Mass Spectrometer (GCMS) instrument onboard the Curiosity rover. In this article we investigate a complementary approach to guide the search for organic matter using ChemCam, the first Laser-Induced Breakdown Spectroscopy (LIBS) instrument on Mars. This experimental study focuses on the analysis of carbon and nitrogen LIBS signatures in organoclay samples and allows the determination of the critical level (L-c) and limit of detection (LoD) of these elements with LIBS under Mars-like conditions, giving new insights into the search of organic matter on Mars. (C) 2017 Elsevier B.V. All rights reserved.
Di Rocco, H. O. ; Garcia, F. A. ; Legnaioli, S. ; Lorenzetti, G. ; Miguel, R. E. ; Palleschi, V. ; Pardini, L.
Laser-induced breakdown spectroscopy; LIBS; Waste sand; Plasma characterization;SELF-ABSORPTION COEFFICIENTS; INDUCED PLASMA; EMISSION-LINES; NEUTRAL ATOM; LIBS; EMPHASIS; PROFILE; ALLOYS; MATRIX
Laser-induced breakdown spectroscopy (LIBS) was applied for quantitative analysis of the elemental composition of waste molding and core sands produced from industry as part of the casting process. To perform the analysis, waste foundry sands (WFS) were collected from metalcasting foundries and prepared in the form of solid pellets with the addition of polyvinyl alcohol as binder. The measurements were carried out using the Mobile double pulse instrument for LIBS analysis (Mod)). The spectral analysis was carried out with the calibration free approach (CF-LIBS). Metal elements commonly found in WFS including Al, Ba, Fe, Li, Mg, Mn, Pb, Ti, Zr, and Zn, were detected and quantified. The metal concentrations for WFS were compared with virgin sand to assess the influence of the casting material as well as the binders used in the foundries to reclaim the sands. The results demonstrated the feasibility of LIBS method as an alternative or complementary technique for the chemical characterization of WFS. (c) 2017 Elsevier B.V. All rights reserved.
LIBS; Solution; Zirconium; Fukushima Dai-chi decommissioning; Ultra-thin liquid jet;WATER-BASED LIQUIDS; QUANTITATIVE-ANALYSIS; METALLIC TRACES; SPECTROMETRY; SINGLE; CHROMIUM; PLASMA; SPECIATION; SODIUM; DEBRIS
In the context of the Fukushima Dai-ichi Nuclear Power Plant (F1-NPP) decommissioning process, laser-induced breakdown spectroscopy (LIBS) has many advantages. The purpose of the present work is to demonstrate the on-line monitoring capability of the LIBS coupled with the ultra-thin liquid jet sampling method. The study focuses on zirconium in aqueous solution, considering that it is a major element in the F1-NPP fuel debris that has been subject to only a few LIBS studies in the past. The methodology of data acquisition and processing are described. In particular, two regions of interest with many high intensity zirconium lines have been observed around 350 nm in the case of the ionic lines and 478 nm in the case of atomic lines. The best analytical conditions for zirconium are different depending on the analysis of ionic lines or atomic lines. A low LOD of about 4 mg L-1 could be obtained, showing that LIBS coupled with the ultra-thin liquid jet sampling technique is a promising alternative for more complex solutions found in the F1-NPP, namely mixtures containing zirconium. (C) 2017 Elsevier B.V. All rights reserved.
INDUCED PLASMA; LIGHT-BEAMS; AIR; WATER; PARTICLES; VAPORIZATION; CONSTITUENTS; SPECTROMETRY; CLOUDS
Nanosecond laser-induced breakdown spectroscopy has been examined for the analysis of suspended matter in a free stream of air. The real-time monitoring of this scenario poses major challenges for an accurate categorization due to its changing characteristics such as composition, size, and density of particles. The effects of particle size and matrix in the optical emission responses registered from such scenarios have been evaluated. Distant (10 m) plasmas of saline solutions, containing either NaCl or Na2SO4 at different concentrations, have been induced by nanosecond laser pulses at a wavelength of 1064 nm. The effects of the droplet size and its concentration on differences in the laser-induced breakdown probability, the intensity of the characteristic lines, and the plasma emission continuum have been discussed. The quantification of sodium in distant water droplets has been proved. However, an initial knowledge on the average droplet size is required. The average droplet size could be determined from the slope of H I and O I lines versus the continuum plasma emission, which is only weakly influenced by the salt content in the droplets. (C) 2017 Optical Society of America.
Transparent ceramics are important optical materials with applications in street lighting, high-strength windows, electro-and magneto-optical isolators, high-power laser gain media and radiation detectors. Their fabrication most often relies on powder densification techniques carried out at high temperatures, sometimes promoted by sintering additives. Here, we describe the application of laser-induced breakdown spectroscopy (LIBS) for following the concentration levels of silica used as a sintering agent in the fabrication of yttrium aluminum garnet (YAG) transparent ceramics. The sensitivity limit of our protocol reaches a few tens of ppm of silica in YAG ceramic samples, showing that LIBS can be implemented reliably for the rapid assessment of sintering additives in advanced ceramic processing. (C) 2017 Optical Society of America
Bankapur, A. ; George, S. D. ; Choudhari, K. S. ; Kartha, V. B. ; Kulkarni, S. D. ; Santhosh, C. ; Unnikrishnan, V. K.
Laser ablation; Raman spectroscopy; Chemometrics; Complementarity; Polymers;INDUCED BREAKDOWN SPECTROSCOPY; INDUCED PLASMA SPECTROSCOPY; ARTIFICIAL NEURAL-NETWORKS; POLYMER IDENTIFICATION; CLASSIFICATION; MICROSCOPY; PIGMENTS; SPECTRA; COPPER; NIR
Classification of plastics is of great importance in the recycling industry as the littering of plastic wastes increases day by day as a result of its extensive use. In this paper, we demonstrate the efficacy of a combined laser-induced breakdown spectroscopy (LIBS)-Raman system for the rapid identification and classification of post-consumer plastics. The atomic information and molecular information of polyethylene terephthalate, polyethylene, polypropylene, and polystyrene were studied using plasma emission spectra and scattered signal obtained in the LIBS and Raman technique, respectively. The collected spectral features of the samples were analyzed using statistical tools (principal component analysis, Mahalanobis distance) to categorize the plastics. The analyses of the data clearly show that elemental information and molecular information obtained from these techniques are efficient for classification of plastics. In addition, the molecular information collected via Raman spectroscopy exhibits clearly distinct features for the transparent plastics (100% discrimination), whereas the LIBS technique shows better spectral feature differences for the colored samples. The study shows that the information obtained from these complementary techniques allows the complete classification of the plastic samples, irrespective of the color or additives. This work further throws some light on the fact that the potential limitations of any of these techniques for sample identification can be overcome by the complementarity of these two techniques.
Laser-induced breakdown spectrometry; Polymers recycling; E-waste; Chemometrics;ELECTRONIC EQUIPMENT WEEE; MASS-SPECTROMETRY; PLASTICS; LIBS; INFORMATION; FRACTIONS; EFFICIENT
In the recycling of polymer e-waste, there is a pressing need for rapid measurement technologies for the simple identification and classification of these materials. The goal of this work was to instantly identify e-waste polymers by laser-induced breakdown spectrometry (LIBS). The studied polymers were acrylonitrile-butadiene-styrene (ABS), polystyrene (PS), polyethylene (PE), polycarbonate (PC), polypropylene (PP), and polyamide (PA). Emission lines were selected for C (247), H (656), N (742 + 744 + 747), and 0 (777), as well as the molecular band of C2 (516), and the ratios of the emission lines and molecular band were utilized. Classification models, k-nearest neighbors (KNN) and soft independent modeling of class analogy (SIMCA), were used to rank the polymers. Both constructed models gave satisfactory results for the validation samples, with average accuracies of 98% for KNN and 92% for SIMCA. These results prove the predictive analytical capabilities of the LIBS technique for plastic identification and classification. (C) 2017 Elsevier Ltd. All rights reserved.
Process monitoring; Plasma temperature; Blast-wave theory; Laser microdrilling; Ablation;SHOCK-WAVE; ABLATION; DEPTH
In this work, self-mixing interferometry (SMI) was used to monitor the optical path difference induced by the ablation plasma and plume. The paper develops the analytical relationships to explain the fringe appearance in the SMI during laser microdrilling. The monitoring principle was tested under a large experimental campaign of laser microdrilling on TiAlN ceramic coating with a low-ns green fibre laser. Key process parameters namely pulse energy, number and repetition rate were varied. The effect of side gas on the SMI signal characteristic was analysed. Laser induced breakdown spectroscopy (LIBS) was used to identify the plasma temperature and electron number density. The SMI signals were correlated to the plume size and its evolution as a function of process parameters, as well as electron number density estimated by spectroscopy. In addition to proving the validity of the proposed new method, the results show insights to the micromachining of the ceramic material with low ns pulses.
SURFACES; WATER; LIBS; SERS; IMPROVEMENT; ABLATION; SAMPLES; SENSOR; FLUIDS
In this study, we developed a substrate to enhance the sensitivity of LIBS by 5 orders of magnitude. Using a combination of field enhancement due to the metal nanoparticles in the substrate, the aggregate effect of super-hydrophobic interfaces and magnetic confinement, we performed a quantitative measurement of copper in solution with concentrations on the ppt level. We also demonstrated that the substrate improves quantitative measurements by providing an opportunity for internal standardization.
INDUCED BREAKDOWN SPECTROSCOPY; SATURATION VAPOR-PRESSURE; INDUCED INCANDESCENCE; SI-I; NANOSECOND; RADIATION; SURFACE
The temporal luminescence behavior of silicon atoms during and after laser-heating of gas-borne silicon nanoparticles was investigated. Silicon nanoparticles were formed in the exhaust stream of a microwave plasma reactor at 100 mbar. The observed prompt atomic line intensities correspond with thermal excitation of the evaporated species. A prompt signal at 251.61 and 288.15 nm originating from the 3s(2)3p(2) -> 3s(2)3p4s transitions showed a lifetime of 16 ns that matches the documented excited-state lifetime for the respective transitions. A secondary delayed signal contribution with similar peak intensities was observed commencing approximately 100-300 ns after the laser pulse and persisting for hundreds of nanoseconds. This signal contribution is attributed to electron impact excitation or recombination after electron impact ionization of the silicon evaporated as a consequence of the laser heating of the plasma leading to non-thermal population of electronically excited silicon. The observations support a nanoparticle evaporation model that can be used to recover nanoparticle sizes from timeresolved LII data. (C) 2017 Optical Society of America
Laser Induced Breakdown Spectroscopy (LIBS); Transversely excited atmospheric carbondioxide (TEA CO2) laser; Aluminum alloys; Qualitative analysis; Quantitative analysis;INDUCED GAS PLASMA; SPECTROCHEMICAL ANALYSIS; QUANTITATIVE-ANALYSIS; OPTICAL-EMISSION; LIBS; SAMPLES; PULSES; SPECTROMETRY; METALS; AIR
The applicability of nanosecond infrared Transversely Excited Atmospheric (TEA) CO2 laser induced plasma for spectrochemical analysis of aluminum alloys was investigated. The plasma was generated by focusing a pulsed TEA CO2 laser that emits at 10.6 mu m on the Al target in ambient air at atmospheric pressure. The temporal profile of the laser pulse is composed of a 100 ns peak followed by a slowly decaying tail of about 2 mu s. The output pulse energy was approximately 160 mJ, thus the peak output power was estimated to be around 1.6 MW. Time-Integrated Space-Resolved Laser Induced BreakdownSpectroscopy (TISR-LIBS) was employed to obtain the emission spectra. The maximum intensity of emission, with sharp and well resolved spectral lines that were almost free of the background continuum, was obtained from plasma region 2 mm from the target surface. Linear calibration curves for Mg, Cr, Cu and Fe were obtained using aluminum alloy spectrochemical standards. The limits of detection for the investigated elements were in the 2-73 ppm range. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) was used as a reference technique to estimate the accuracy of LIBS determination by use of control samples with known compositions. Comparison of the obtained results with those available in the literature confirms that LIBS system based on TEA CO2 laser, in combination with TISR spectral measurements, can be successfully applied to qualitative and quantitative determinations of minor elements in aluminum based alloys. (C) 2017 Elsevier B.V. All rights reserved.
ARRAY DETECTION SYSTEM; ENERGETIC MATERIALS; SENSOR TECHNOLOGY; LIBS; SPECTRA; AIR; FEMTOSECOND; WAVELENGTHS; TIME
In this work, comparative long-wave infrared (LWIR) laser-induced breakdown spectroscopy (LIBS) emission studies of two excitation sources: conventional 1.064 mu m and eye-safe laser wavelength at 1.574 mu m were performed to analyze several widely-used inorganic energetic materials such as ammonium and potassium compounds as well as the organic liquid chemical warfare agent simulant, dimethyl methylphosphate (DMMP). LWIR LIBS emissions generated by both excitation sources were examined using three different detection systems: a single element liquid nitrogen cooled Mercury Cadmium Telluride (MCT) detector, an MCT linear array detection system with multi-channel preamplifiers + integrators, and an MCT linear array detection system with readout integrated circuit. It was observed that LWIR LIBS studies using an eye-safe pump laser generally reproduced atomic and molecular IR LIBS spectra as previously observed under 1.064 mu m laser excitation. (C) 2017 Optical Society of America
PRE-ABLATION SPARK; ORTHOGONAL BEAM GEOMETRY; INDUCED PLASMAS; CONFIGURATION; SPECTROMETRY; EMISSION; MATRICES; SINGLE; LIBS
Two Q-switched Nd: YAG lasers at 1064-nm wavelength have been employed to detect the trace elements in microalloy steel samples by single-pulse and reheating double-pulse laser-induced breakdown spectroscopy. It is found that the emission lines intensities of the trace elements were significantly enhanced by reheating double-pulse scheme. Furthermore, the extent of the enhancement of the line intensity was related to the excitation energy level of the emission line. Then, the emission enhancement was explained by the investigation of the spatial resolution of the plasma temperatures. The results have shown that the enhancement mechanism can be attributed to the greater and hotter plasma generated by the re-excitation of the reheating laser pulse in double-pulse scheme. Finally, calibration plots were constructed for Mn, Cr, and Cu using a set of certified microalloy steel samples. The detection limits of the trace elements were calculated for the reheating double-pulse scheme and compared to those of single-pulse scheme. It has been shown that the detection limits of the trace elements were improved by a factor of 1.81-3.46 when the reheating double-pulse scheme was used.
LIBS; Gunshot residues; Distance estimation; Forensic analysis; Imaging;INDUCED BREAKDOWN SPECTROSCOPY; FIRING DISTANCE; IMAGE-ANALYSIS; FABRICS; SHOOTER; HANDS; DARK
The study of gunshot residue (GSR) patterns can assist in the reconstruction of shooting incidences. Currently, there is a real need of methods capable of furnishing simultaneous elemental analysis with higher specificity for the GSR pattern visualization. Laser-Induced Breakdown Spectroscopy (LIBS) provides a multi-elemental analysis of the sample, requiring very small amounts of material and no sample preparation. Due to these advantages, this study aims at exploring the potential of LIBS imaging for the visualization of GSR patterns. After the spectral characterization of individual GSR particles, the distribution of Pb, Sb and Ba over clothing targets, shot from different distances, were measured in laser raster mode. In particular, an array of spots evenly spaced at 800 mm, using a stage displacement velocity of 4 mm/s and a laser frequency of 5 Hz was employed (e.g. an area of 130 x 165 mm(2) was measured in less than 3 h). A LIBS set-up based on the simultaneous use of two spectrographs with iCCD cameras and a motorized stage was used. This set-up allows obtaining information from two different wavelength regions (258-289 and 446-463 nm) from the same laser induced plasma, enabling the simultaneous detection of the three characteristic elements (Pb, Sb, and Ba) of GSR particles from conventional ammunitions. The ability to visualize the 2D distribution GSR pattern by LIBS may have an important application in the forensic field, especially for the ballistics area. (C) 2017 Elsevier B.V. All rights reserved.
Clegg, S. M. ; Cousin, A. ; Delapp, D. ; Dyar, M. D. ; Ehlmann, B. L. ; Forni, O. ; Gasnault, O. ; Lasue, J. ; Maurice, S. ; McInroy, R. E. ; Schroder, S. ; Thomas, N. H. ; Wiens, R. C.
LIBS spectroscopy; carbon; chlorine; sulfur; salts; Mars Science Laboratory;INDUCED BREAKDOWN SPECTROSCOPY; GALE CRATER; INSTRUMENT SUITE; MARS; MINERALOGY; CHEMISTRY; FEATURES; VEINS; ROCK; UNIT
Ancient environmental conditions on Mars can be probed through the identification of minerals on its surface, including water-deposited salts and cements dispersed in the pore space of sedimentary rocks. Laser-induced breakdown spectroscopy (LIBS) analyses by the Martian rover Curiosity's ChemCam instrument can indicate salts, and ChemCam surveys aid in identifying and selecting sites for further, detailed in situ analyses. We performed laboratory LIBS experiments under simulated Mars conditions with a ChemCam-like instrument on a series of mixtures containing increasing concentrations of salt in a basaltic background to investigate the potential for identifying and quantifying chloride, carbonate, and sulfate salts found only in small amounts, dispersed in bulk rock with ChemCam, rather than concentrated in veins. Data indicate that the presence of emission lines from the basalt matrix limited the number of Cl, C, and S emission lines found to be useful for quantitative analysis; nevertheless, several lines with intensities sensitive to salt concentration were identified. Detection limits for the elements based on individual emission lines ranged from similar to 20wt % carbonate (2wt % C), similar to 5-30wt % sulfate (1-8wt % S), and similar to 5-10wt % chloride (3-6wt % Cl) depending on the basaltic matrix and/or salt cation. Absolute quantification of Cl, C, and S in the samples via univariate analysis depends on the cation-anion pairing in the salt but appears relatively independent of matrices tested, following normalization. These results are promising for tracking relative changes in the salt content of bulk rock on the Martian surface with ChemCam.
Gunshot residue; laser-induced breakdown spectroscopy; LIBS; evidence preservation; scanning electron microscopy energy dispersive X-ray spectroscopy; SEM-EDX;HANDS; AMMUNITION; SHOOTER
This study investigated the use of laser-induced breakdown spectroscopy (LIBS) and scanning electron microscopy energy dispersive X-ray spectroscopy(SEM-EDX) as means of characterizing gunshot residue (GSR) originating from commercially available lead-free rounds. Data from two experiments are presented in this work. One experiment focused on identifying prominent analytical markers present in lead-free GSR by LIBS while the other applied SEM-EDX to determine the degree of evidence preservation after LIBS analysis. Samples of GSR were collected via tape-lift method from the hands of volunteer shooters and instrumental analyses were conducted in triplicate. As a result, the lead-free ammunition analyzed in this work generated GSRs comprising primarily Ba, Al, Si, and/or K. Trace amounts of Ti, Fe, and S were also apparent in some compositions. Through SEM-EDX analysis, a spheroidal geometry consistent with traditional lead-containing GSR was observed. Additionally, it was determined that evidence is preserved after LIBS analysis which supports the implementation of LIBS as a rapid preliminary screening method followed by confirmatory testing via SEM-EDX on the preserved evidence.
Laser-induced breakdown spectroscopy; LIBS; long-wave infrared spectra; explosives;ARRAY DETECTION SYSTEM; ENERGETIC MATERIALS; SPECTRA; PHASE; ACID; HMX
Thin solid films made of high nitro (NO2)/nitrate (NO3) content explosives were deposited on sand-blasted aluminum substrates and then studied using a mercury-cadmium-telluride (MCT) linear array detection system that is capable of rapidly capturing a broad spectrum of atomic and molecular laser-inducedbreakdown spectroscopy (LIBS) emissions in the long-wave infrared region (LWIR; similar to 5.6-10 mm). Despite the similarities of their chemical compositions and structures, thin films of three commonly used explosives (RDX, HMX, and PETN) studied in this work can be rapidly identified in the ambient air by their molecular LIBS emission signatures in the LWIR region. A preliminary assessment of the detection limit for a thin film of RDX on aluminum appears to be much lower than 60 mg/cm(2). This LWIR LIBS setup is capable of rapidly probing and charactering samples without the need for elaborate sample preparation and also offers the possibility of a simultaneous ultraviolet visible and LWIR LIBS measurement.
SITE QUANTITATIVE-ANALYSIS; LIBS SPECTRA; POWER-PLANTS; ASH CONTENT; WELL LOGS; VALUE GCV; CALIBRATION; PREDICTION; MODEL; PERFORMANCE
Online measurement for the gross calorific Value (GCV) of coal is important in the coal Utilization industry. This paper proposed a rapid GCV determination method that combined a laser-induced breakdown spectroscopy (LIBS) technique with artificial neural networks (ANNs) and genetic algorithm (GA). Input variables were selected according to the physical mechanism and mathematical significance to improve the prediction of the ANN. GA was applied to determine an,optirnal architecture for the network instead of a trial and error method. As a result, the mean standard deviatiori (MSD) of the GCV for four prediction set samples is,0.38 MJ/kg in 50 trials (repetitions of training the ANN with the same; input data but different random initial weights and biases), proving that the ANN model is able to provide high modeling repeatability in the GCV analysis. The mean absolute error (MAE) of the GCV for the prediction set is 039 MJ/kg. The result meets the requirements (0.8 MI/kg) for coal online analyses using the neutron activation method in the Chinese national standard (GB/T 29161-2012).
Micro-algal consortia; Pulse amplitude modulated chlorophyll fluorescence (PAM); Scanning electron microscopy (SEM); Laser inducedbreakdown spectroscopy (LIBS); Atomic absorption spectroscopy (AAS);SYNECHOCYSTIS PCC 6803; BIOMASS; BIODIVERSITY; ACCUMULATION; DIVERSITY; PLANTS; CYANOBACTERIA; CARBOHYDRATE; BIOSORPTION; MECHANISMS
A set of experiments was conducted to provide significant insights of micro-algal consortia regarding chromium adsorption. Four monocultures; Scenedesmus dimorphus, Chlorella sp., Oscillatoria sp., and Lyngbya sp., and their synthetic consortia were evaluated initially for chromium bio-adsorption at four different regimes of hexavalent chromium i.e. 0.5, 1.0, 3.0 and 5.0 ppm. Based on findings, only 1.0 and 5.0 ppm were considered for future experiments. Consequently, three different types of monoculture and consortia cells namely; live cells, heat-killed cells, and pre-treated cells were prepared to enhance their adsorption potential. Maximal adsorption of 112% was obtained at the dose of 1.0 ppm with 0.1% SDS pre-treated consortia cells over live consortia cells. In support, atomic absorption spectroscopy, laser induced breakdown spectroscopy, pulse amplitude modulated chlorophyll fluorescence, and scanning electron microscopy were performed to assess the structural and functional changes within consortia and their utilization in mitigation of elevated chromium levels.
Laser-induced breakdown spectroscopy; Microscope optics; Mn; Quantitative analysis;SPECTROMETRY; SAMPLES; LIBS
Manganese in the low alloy steel was analyzed quantitatively using micro-laser-induced breakdown spectroscopy. The spatial resolution of 20 mu m and the single pulse limit of detection of 0. 10% were obtained. The calibration curve of Mn was established with basic calibration method, with determination coefficient (R-2) of 0. 97. The average relative error of Mn concentration prediction on 7 samples is 12. 91%, and the root-mean-square error of cross-validation (RMSECV) is 0. 11%. The R2 reaches 0. 99 when using internal calibration method, as well as the average relative error of Mn concentration prediction on 7 samples and RMSECV were decreased to 7. 25% and 0. 07%, respectively. These results show that MicroLIBS technique is an effective approach for material surfaces quantitative microanalysis.
INDUCED BREAKDOWN SPECTROSCOPY; ELEMENTAL ANALYSIS; SPECTRUM STANDARDIZATION; UNBURNED CARBON; FLY-ASH; SAMPLES; SPECTROMETRY; PELLETS; MODEL; PLANT
Quantitative analysis of elements by laser-induced breakdown spectroscopy (LIBS) is significantly affected by matrix effects in coal. Coal powder was mixed with the KBr binder and pressed into pellets to reduce matrix effects. Four groups of mixed-pressed pellet samples were prepared from nine different coal types and different percentages of the KBr binder (KBr accounts for 0 wt%, 30 wt%, 60 wt%, and 90 wt%, respectively). To optimize the percentages of the KBr binder in the mixed-pressed pellets, the influence of KBr binder on laser-induced plasma was investigated in detail. The results indicate that the plasma excitation temperature decreases with increase of the KBr binder concentration. The difference of the excitation temperature between the nine different coal samples was minimal when KBr accounts for 60 wt% in the mixed-pressed pellets. The relative standard deviation of the excitation temperature is 4.26%. The matrix changes from coal to KBr when the percentages of KBr are higher than 60 wt%, which was confirmed by scanning electron microscopy images of the ablated crater. Finally, Si and K were individually chosen as the internal calibration element to construct the calibration curves of carbon. Better results were obtained when Si I 288.16 nm was used as the internal standard. The correlation coefficients R-2 of the four groups of mixed-pressed pellet samples are 0.835, 0.893, 0.983, and 0.903, respectively. Hence, the appropriate percentage of binders needs to be carefully confirmed to reduce matrix effects in quantitative analysis of coal by LIBS.
Laser induced breakdown spectroscopy (LIBS); 3D chemical maps; Brass oxidation; Dealloying/dezincification;INDUCED PLASMA SPECTROMETRY; CHEMICAL MAPS; ALLOYS; DEZINCIFICATION
The dealloying phenomenon, also called demetalification, is a; consequence of a corrosion problem found in binary alloys where an enrichment of one of the two main elements of the alloy is produced at the expense of the leaching of the other element. In the present work, the ability of laser induced breakdownspectroscopy (LIBS) for the detection and characterization of dealloying films formed on metal has been tested. For this purpose, specific areas of brass specimens have been subjected to a chemical attack of the surface in order to produce a selective leaching of zinc or dezincification. For the lateral and in-depth characterization of the dealloyed areas by LIES, depth profiles, 2D and 3D maps have been generated from the treated samples and from a reference non-treated sample. The differences in the maps and depth profiles between the corroded and non-corroded regions have allowed to reveal the localization and extension of the dealloying process along the brass sample surface and to estimate the thickness of the dezincification layers, demonstrating the capability of LIBS technique for the characterization of dealloying phenomena. (C) 2016 Published by Elsevier B.V.
Laser-induced breakdown spectroscopy; Stress corrosion cracking; Chlorine; Alkali elements;ATMOSPHERE
Chlorine can play an important role in the process of stress corrosion cracking of dry cask storage canisters for used nuclear fuel, which are frequently located in marine environments. It is of significant interest to determine the surface concentration of chlorine on the stainless steel canister surface, but measurements are often limited by difficult access and challenging conditions, such as high temperature and high radiation fields. Laser-induced breakdown spectroscopy(LIBS) could enable chlorine concentration measurements while meeting the other constraints of this application, but suffers from high excitation energy of chlorine and the interference of the atomic emission lines of iron, thus limiting the sensitivity of detection, especially when LIBS has to be delivered over an optical fiber. We demonstrate that chlorine surface concentrations in the range of 0.5-100 mg/m(2) can be inferred by the detection and quantification of sodium contained in chlorine salts if the speciation and neutralization of salts are not of major concern, whereas minor components of sea salt such as magnesium and potassium are less attractive as surrogates for chlorine due to the lower sensitivity of LIBS for their detection and quantification. The limit of detection, measurement accuracy, and other features and limitations of this surrogate measurement approach are discussed. (C) 2017 Elsevier B.V. All rights reserved.
Laser-induced breakdown spectroscopy; LIBS; Solid aerosols; Single particle analysis; Optical catapulting; Optical trapping; Atomization efficiency; Photon yield;RADIATION PRESSURE; AEROSOL-PARTICLES; AIR-POLLUTION; BLACK CARBON; SIMULATION; LEVITATION; HEALTH; LIBS
Laser-induced breakdown spectroscopy (LIBS) was employed for investigating the influence of particle size on the dissociation efficiency and the absolute production of photons per mass unit of airborne solid graphite spheres under single-particle regime. Particles of average diameter of 400 nm were probed and compared with 2 pm particles. Samples were first catapulted into aerosol form and then secluded in an optical trap set by a 532 nm laser. Trap stability was quantified before subjecting particles to LIBS analysis. Fine alignment of the different lines comprising the optical catapulting-optical trapping-laser-inducedbreakdown spectroscopy instrument and tuning of excitation parameters conditioning the LIBS signal such as fluence and acquisition delay are described in detail with the ultimate goal of acquiring clear spectroscopic data on masses as low as 75 fg. The atomization efficiency and the photon yield increase as the particle size becomes smaller. Time-resolved plasma imaging studies were conducted to elucidate the mechanisms leading to particle disintegration and excitation. (C) 2017 Elsevier B.V. All rights reserved.
PLASMA-MASS SPECTROMETRY; ICP-MS; EMISSION-SPECTROMETRY; PRECONCENTRATION; SAMPLES; ROCKS; SOIL; CHROMATOGRAPHY; SEPARATION; THORIUM
Univariate and multivariate analyses of six rare earth elements [cerium (Ce), europium (Eu), gadolinium (Gd), neodymium (Nd), samarium (Sm), and yttrium (Y)] have been performed using data from laser-induced breakdown spectroscopy (LIBS). Binary mixtures of oxide forms of each rare earth element in an Al2O3 matrix with their concentrations varying from 1% to 10% by weight in powder form were used as working samples for univariate analysis. For multivariate analysis, complex mixtures of oxides of all these six rare earth elements and Al2O3 in powder form, where the concentration of each element oxide was varied from 1% to 50% by weight one by one, were used to record LIBS spectra. Optimum values of gate delay, gate width, and laser energy were used to get spectra from these samples and spectra were used to develop calibration models. The limits of detection for Ce, Eu, Gd, Nd, Sm, and Y were calculated to be 0.098%, 0.052%, 0.077%, 0.047%, 0.250%, and 0.036%, respectively, from the calibration curves. (C) 2017 Optical Society of America
Guo, L. B. ; Hao, Z. Q. ; Li, X. Y. ; Lu, Y. F. ; Tang, S. S. ; Yi, R. X. ; Zeng, X. Y. ; Zhao, N. ; Zhou, R.
QUANTITATIVE-ANALYSIS; INSTRUMENT; ABSORPTION; PLASMA; COBALT; LEAD; SOIL; AIR
Spatially selective excitation was proposed to improve excitation efficiency in laser-induced breakdown spectroscopy combined with laser-inducedfluorescence (LIBS-LIF). Taking chromium (Cr) and nickel (Ni) elements in steels as examples, it was discovered that the optimal excitation locations were the center of the plasmas for the matrix of the iron (Fe) element but the periphery for Cr and Ni elements. By focusing an excitation laser at the optimal locations, not only excitation efficiency but also the analytical accuracy and sensitivity of quantitative LIBS-LIF were better than those with excitation at the plasma center in conventional LIBS-LIF. This study provides an effective way to improve LIBS-LIF analytical performance. (C) 2017 Optical Society of America
BULK AQUEOUS-SOLUTIONS; SINGLE-PULSE; ELEMENTAL ANALYSIS; OPTICAL-BREAKDOWN; OCEANIC PRESSURES; PLASMA FORMATION; WATER; LIQUIDS; NANOSECOND; PARAMETERS
Axial focusing arrangement effects on collinear dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) in a bulk solution were investigated by spectra and fast images. By properly defocusing the second laser pulse beyond the first laser formed bubble (LFB), brighter and larger plasmas could be produced due to higher breakdown efficiency and higher expansion efficiency. It is attributed to a distinct mechanism of underwater DP-LIBS that the plasma mostly forms at the bubble-water interface and then expands into the gaseous LFB. The results show that optimization of the axial focusing arrangement in underwater collinear DP-LIBS enables significant emission enhancements with relatively low laser energies. Published by AIP Publishing.
Fresnel Zone Plates; Femtosecond; Laser Direct-Write;PHOTON-SIEVE
With an advantage in photonic integration and device miniaturization, fabrication of micron sized diffractive optical elements has gained attention due to their low volume, light weight and flexible design. We discuss the fabrication of phase zone plates in soda-lime and borosilicate glass using a femtosecond laser, and its characterization. Our technique of fabrication involves a one-step laser direct writing process in comparison to the popular photolithography based micro-structuring. In this work, the femtosecond laser oscillator system is used to successfully fabricate phase zone plate structures at low energies and high repetition rate. In addition to this, a laser induced breakdown spectroscopy (LIBS) study was done to confirm the consistency of glass obtained from different manufacturers through its composition.
CF-LIBS; CuNi alloy; Electron density; LA-TOFMS; LIBS; Plasma temperature; Quantitative analysis;LASER-INDUCED BREAKDOWN; QUANTITATIVE ELEMENTAL ANALYSIS; INDUCED PLASMA; SPECTROSCOPY; SPECTROMETRY; EMISSION
LASER induced breakdown spectroscopy (LIBS) has been used for the quantitative analysis of Cu-Ni alloy of known composition (75% Cu, 25% Ni) using the one line calibration free-LIBS (OLCF-LIBS), self-calibration-LIBS (SC-LIBS), calibration free LIBS (CF-LIBS), time of flight-mass spectroscopy (TOF-MS), energy dispersive X-ray spectroscopy (EDX) and X-ray fluorescence spectroscopy (XRF). For the LIBS-based studies, the plasma was generated by focusing the beam of a Q-switched Nd:YAG laser (532 nm, pulse energy about 200 mJ, 5 ns pulse duration) while the sample was placed in air at an atmospheric pressure. Plasma temperature about (9500 +/- 300) K was calculated by the Boltzmann plot method using the neutral lines of Cu and Ni whereas the electron number density was calculated (2.0 +/- 0.5) x 10(16) cm(-3) from the Stark broadening of an isolated Cu line as well as using the relative intensities of the neutral and singly ionized optically thin lines in the Saha-Boltzmann equation. The elemental compositions determined by different LIBS methods and standard techniques are; OLCF-LIBS (69% Cu and 31% Ni), SC-LIBS (72% Cu and 28% Ni), CF-LIBS (74% Cu and 26% Ni), TOF (74% Cu and 26% Ni), EDX (75% Cu and 24.5% Ni), XRF (73% Cu and 24.7% Ni), and LA-TOF (74% Cu and 26% Ni). It is demonstrated that the CF-LIBS method gives compositions comparable with that determined by LA-TOF, EDX, or XRF, which is also in agreement with the certified reported composition.
Akram, M. ; Amin, S. ; Bashir, S. ; Dawood, A. A. M. ; Hayat, A. ; Mahmood, K. ; Murtaza, F. ; Zaheer, A.
Laser-induced breakdown spectroscopy; Electron temperature; Number density; Magnetic confinement; Surface structuring;X-RAY-EMISSION; OPTICAL-EMISSION; ELECTRON-DENSITY; CARBON PLASMA; AMBIENT GAS; ABLATION; PLUME; TEMPERATURE; CONFINEMENT; PARAMETERS
The effect of the transverse magnetic field on laser-induced breakdown spectroscopy and surface modifications of germanium (Ge) has been investigated at various fluences. Ge targets were exposed to Nd: YAG laser pulses (1064 nm, 10 ns, 1 Hz) at different fluences ranging from 3 to 25.6 J/cm(2) to generate Ge plasma under argon environment at a pressure of 50 Torr. The magnetic field of strength 0.45 Tesla perpendicular to the direction of plasma expansion was employed by using two permanent magnets. The emission spectra of laser-induced Ge plasma was detected by the laser-induced breakdown spectroscopysystem. The electron temperature and number density of Ge plasma are evaluated by using the Boltzmann plot and stark broadening methods, respectively. The variations in emission intensity, electron temperature (T-e), and number density (n(e)) of Germanium plasma are explored at various fluences, with and without employment of the magnetic field. It is observed that the magnetic field is responsible for significant enhancement of both excitation temperature and number density at all fluences. It is revealed that an excitation temperature increases from T-e,T-max,T-without B = 16,190 to T-e,T-max,T-with B = 20,123 K. Similarly, the two times enhancement in the electron density is observed from n(e,max,without B) = 2 x 10(18) to n(e,max,with B) = 4 x 10(18) cm(-3). The overall enhancement in Ge plasma parameters in the presence of the magnetic field is attributed to the Joule heating effect and adiabatic compression. With increasing fluence both plasma parameters increase and achieve their maxima at a fluence of 12.8 J/cm(2) and then decrease. In order to correlate the plasma parameters with surface modification, scanning electron microscope analysis of irradiated Ge was performed. Droplets and cones are formed for both cases. However, the growth of ridges and distinctness of features is more pronounced in case of the absence of the magnetic field; whereas surface structures become more diffusive in the presence of the magnetic field.
METHANE-AIR FLAMES; DIFFUSION FLAMES; CH-ASTERISK; OH-ASTERISK; SOOT; DIAGNOSTICS; EMISSION; FRACTION; MIXTURE; ETHANE
Real-time monitoring of the local equivalence ratio is of primary importance for combustion efficiency improvement. Chemiluminescence and laser-inducedbreakdown spectroscopy (LIBS) measurements can be powerful tools for sensing the equivalence ratio. Radicals, such as OH*, CH*, and C-2*, are formed within the flame front, and consequently, the related chemiluminescence emission can be considered as a marker to follow the evolution of combustion processes. From LIBS measurements, the ratio of two characteristic spectral lines of fuel (H) and oxidizer (0) is related to the equivalence ratio. In this work, LIBS measurements have been carried out in premixed flames of known equivalence ratio for calibration purposes. Then, the application to non-premixed flames has been performed to evaluate the local equivalence ratio. Chemiluminescence emission spectra have also been collected, and the values of OH*, CH*, and C-2* have been properly evaluated, taking into account the contribution of CO2* broad band emission. A methane co-flow diffusion flame has been investigated along the centerline as well as at three cross sections, and the local equivalence ratio profiles obtained by LIBS have been compared to CH* chemiluminescence profiles. Finally, the experimental data obtained were compared to the results of a detailed chemical kinetic model.
ECHELLE SPECTROMETER; ELEMENTAL ANALYSIS; INDUCED PLASMA; LIBS LIMIT; ALLOYS; SALT; AIR
Laser-induced breakdown spectroscopy (LIBS) was applied to inspect trace substances on aluminum alloy surfaces. Silicone oil, which is often used as a release agent, was employed as the adhered substance. Nanosecond laser pulses at UV wavelengths (KrF laser, lambda = 248 nm) were employed for the LIBS measurements. Although the absorption of silicone oil at 248 nm was negligible, the Si emission of surface-adhered silicone oil was detected. The intensity ratio of the Si emission at 288 nm to the Al emission at 309 nm increased with increasing surface concentrations in the range 1-35 mu g cm(-2), and a linear dependence on the silicone oil surface concentration was observed at low surface concentrations (<5.0 mu g cm(-2)). The limit of detection was evaluated to be 1.18 mu g cm(-2).
Barthalay, N. ; Lebbou, K. ; Li, H. ; Motto-Ros, V. ; Pezzani, C. ; Silvestre, M. ; Trichard, F.
Ti-doped sapphire; Titanium distribution; Kyropoulos; Czochralski; LIBS measurement;SAPPHIRE LASER; CRYSTALS; TI-AL2O3
The titanium distributions in Ti-doped sapphires grown by Czochralski and Kyropoulos techniques were evaluated using Laser-Induced BreakdownSpectroscopy (LIBS) and luminescence characterizations. Distinctly different radial profiles of Ti4+ distribution were observed in the as grown Ti: Al2O3 crystals. The TO4+ distribution in the crystal grown by Kyropoulos technique was analyzed as a function of the specific of the growth technique, the conclusion is significant for Ti: sapphire on laser-application. Kyropoulos technique presents an advantage to reduce the proportion of Ti4+ in Ti: sapphire comparing to Czochralski technique. (C)2016 Elsevier B.V. All rights reserved
Fang, L. ; Gu, Y. H. ; Jia, Y. ; Liu, J. G. ; Liu, W. Q. ; Ma, M. J. ; Meng, D. S. ; Yu, Y. ; Zhao, N. J.
Laser-induced breakdown spectroscopy(LIBS); Electrode enrichment; Limit of detection; Heavy metal in water;INDUCED BREAKDOWN SPECTROSCOPY
In order to improve the detection sensitivity of laser-induced breakdown spectroscopy (LIES) and lower the limit of the detection of elements, LIBS combined with Aluminum electrode enrichment method is adopted to analyze heavy metals such as Pb, Cdand Ni in the water. The relationship between the characteristic spectral intensity and the key parameters-voltage of electrode method is discussed, the spectral intensity increases first and then decreases with the increase of voltage. The spectral intensity reaches-the maximum value when the enrichment voltage is 1.2 V while the optimal enrichment voltage value is 1.2 V. The stability of characteristic spectral lines of heavy metals is studied, and the relative standard deviation(RSD) of spectral intensity of Pb, Cd and Ni is 5.98%, 4.25 % and 5.27% respectively, the result shows that the spectral line obtained by this method has high stability. A series of samples in the range of 0 similar to 0.13mg.L-1 are prepared and quantitatively analyzed, the limit of detection of Pb, Cd and Ni is obtained 1.2, 3.1 and 1.7 ppb respectively. The above result shows that LTBS combined with aluminum electrode enrichment method can effectively improve the stability of characteristic spectral lines and lower the limit of detection of Pb,Cd and Ni. This research also provides a method to further improve detection sensitivity of LIES and analysis ability of heavy metal in the water.
Laser Induced Breakdown Spectroscopy (LIBS); Intermetallic nanoalloys; Nanocomposites Calibration-free; Quantitative analysis;OXYGEN REDUCTION REACTION; PLASMA-MASS SPECTROMETRY; BIFUNCTIONAL ELECTROCATALYSTS; OXIDE NANOPARTICLES; EVOLUTION REACTIONS; ABLATION SYNTHESIS; CATALYTIC-ACTIVITY; AEROSOL-PARTICLES; ALLOY; COBALT
Intermetallic nanoalloys (NAs) and nanocomposites (NCs) have increasingly gained prominence as efficient catalytic materials in electrochemical energy conversion and storage systems. But their morphology and chemical compositions play critical role in tuning their catalytic activities, and precious metal contents. While advanced microscopy techniques facilitate morphological characterizations, traditional chemical characterizations are either qualitative or extremely involved. In this study, we apply Laser Induced Breakdown Spectroscopy (LIBS) for quantitative compositional analysis of NAs and NCs synthesized with varied elemental ratios by our in-house built pulsed laser ablation technique. Specifically, elemental ratios of binary PtNi, PdCo (NAs) and PtCo (NCs) of different compositions are determined from LIBS measurements employing an internal calibration scheme using the bulk matrix species as internal standards. Morphology and qualitative elemental compositions of the aforesaid NAs and NCs are confirmed from Transmission Electron Microscopy (TEM) images and Energy Dispersive X-ray Spectroscopy (EDX) measurements. LIBS experiments are carried out in ambient conditions with the NA and NC samples drop cast on silicon wafers after centrifugation to increase their concentrations. The technique does not call for cumbersome sample preparations including acid digestions and external calibration standards commonly required in Inductively Coupled Plasma -Optical Emission Spectroscopy (ICP-OES) techniques. Yet the quantitative LIBS results are in good agreement with the results from ICP-OES measurements. Our results indicate the feasibility of using LIBS in future for rapid and in situ quantitative chemical characterizations of wide classes of synthesized NM and NCs.
Mahdieh, M. H.
Double pulse laser ablation; Laser induced phase explosion; Plasma expansion; Pre plasma formation; Single pulse laser ablation; Water interaction ambient;INDUCED BREAKDOWN SPECTROSCOPY; PHASE-EXPLOSION; NANOSECOND; METALS; PLASMA; ENHANCEMENT; THRESHOLDS
In this paper, single pulse and double pulse laser ablation of an aluminum target in two interaction ambient was investigated experimentally. The interaction was performed by nanosecond Nd:YAG laser beam in air and four depths (i.e. 9, 13, 17, and 21 mm) of distilled water ambient. The irradiation was carried out in single and collinear double pulse configurations in both air and liquid ambient. Crater geometry (depth and diameter) was measured by an optical microscope. The results indicated that the crater geometry strongly depends on both single pulse and double pulse configurations and interaction ambient. In single pulse regime, the crater diameter is higher for all water depths compared to that of air. However, the crater depth, depend on water depth, is higher or lower than the crater depth in air. In double pulse laser ablation, there are greater values for both crater diameters and crater depths in the water. (C) 2016 Elsevier B.V. All rights reserved.
Double-pulse laser ablation; Molecular dynamics; Hydrodynamics; Crater depth; Plume reheating;INDUCED BREAKDOWN SPECTROSCOPY; SIGNAL ENHANCEMENT; MOLECULAR-DYNAMICS; METAL TARGETS; SPALLATION; SINGLE
We elaborated two numerical methods, two-temperature hydrodynamics and hybrid two-temperature molecular dynamics, which take into account basic mechanisms of a metal target response to ultra short laser irradiation. The model used for the description of the electronic subsystem is identical for both approaches, while the ionic part is defined by an equation of state in hydrodynamics and by an interatomic potential in molecular dynamics. Since the phase diagram of the equation of state and corresponding potential match reasonably well, the dynamics of laser ablation obtained by both methods is quite similar. This correspondence can be considered as a first step towards the development of a self consistent combined model. Two important processes are highlighted in simulations of double-pulse ablation: (1) the crater depth decrease as a result of recoil flux formation in the nascent plume when the delay between the pulses increases; (2) the plume reheating by the second pulse that gives rise to two three-fold growth of the electron temperature with the delay varying from 0 to 200 ps. (C) 2016 Published by Elsevier B.V.
IMPROVEMENT; CHEMOMETRICS; SPECTROMETRY; CONFINEMENT; CALIBRATION; SELECTION; PLASMA; LIBS; SOIL
In this work, a genetic algorithm (GA) was employed to select the intensity ratios of the spectral lines belonging to the target and domain matrix elements, then these selected line-intensity ratios were taken as inputs to construct an analysis model based on an artificial neural network (ANN) to analyze the elements copper (Cu) and vanadium (V) in steel samples. The results revealed that the root mean square errors of prediction (RMSEPs) for the elements Cu and V can reach 0.0040 wt. % and 0.0039 wt. %, respectively. Compared to 0.0190 wt. % and 0.0201 wt. % of the conventional internal calibration approach, the reduction rates of the RMSEP values reached 78.9% and 80.6%, respectively. These results indicate that the GA combining ANN can excellently execute the quantitative analysis in laser-induced breakdown spectroscopy for steel samples and further improve analytical accuracy. (C) 2017 Optical Society of America
VICTORIAN BROWN-COAL; FIXED-BED REACTOR; ASH DEPOSITION; ALKALI REMOVAL; ATOMIC SODIUM; SORBENTS; GASIFICATION; TEMPERATURE; MECHANISMS; CORROSION
Zhundong coal represents a large portion of China's future energy supply, because of the large reserve capacity. Although Zhungdong coal has low ash and good ignition characteristics, it also contains large amounts of sodium, which can foul and corrode heat-transfer surfaces. For economically viable use of Zhundong coal or other high-alkali coals, the alkali release must be mitigated prior to or within the burner. This can be done either by washing the coal,, using sorbents to trap the sodium, or a combination of these methods. Additive influence on the release of sodium over the entire coal combustion process was measured using a calibrated laser-induced breakdown spectroscopy (LIBS) technique. The additives used were alumina, silica, and five mineral sorbents comprising blends of silica, alumina, and various other inorganic compounds; different coal/sorbent ratios were assessed (1%, 3%, and 5% additive, by weight). During the three stages of sample coal combustion, it was found that the first stage, devolatilization, releases only similar to 1.2% of the total sodium; the char combustion stage releases similar to 28% of the total sodium; and the ash stage releases the vast majority of sodium (similar to 70%). The peak instantaneous release rate occurs during the char combustion stage. The sodium retention efficiency for all of the sorbents tested was lowest during the devolatilization stage and there was no appreciable change to the duration of the stage. Sodium retention efficiency was greatest in the ash stage, primarily due to the sheer amount of sodium released during this stage. The ash stage was effectively shortened, in proportion to the retention efficiency of the sorbent. The sodium release during the char combustion stage showed an obvious difference in profile for the various types of sorbent tested. Alumina was the least effective in reducing sodium release and retained the characteristic shape of sodium release from raw coal during this stage. Silica and sepiolite demonstrated similar sodium release profiles, which were markedly different than the sodium release profiles of either alumina or aluminosilicate mineral samples. Time-resolved sodium retention plots show an enhancement in the sodium retention by alumina during the char burnout. The addition of sodium sorbent to the coal extended the duration of the char burnout stage, which may indicate that the reduction of available sodium reduces the alkali catalysis of the char decomposition.
BISMUTH TANTALATE CERAMICS; QUANTITATIVE-ANALYSIS; TRANSPARENT CERAMICS; OPTICAL-PROPERTIES; THIN-FILMS; MICROSTRUCTURE; FABRICATION; ABSORPTION
Strict control of composition is of paramount importance for the reproducible fabrication of advanced ceramics. In particular, the preparation of high-grade transparent ceramics of definite line-compounds requires that the ratio of major constitutive elements be quantified with a precision better than a fraction of a mole percent to prevent the precipitation of secondary phases and the scattering of light. Such a requirement poses difficult challenges to most analytical methods, especially when applied to nearly-stoichiometric insulating phases. In this work, we show that laser-induced breakdown spectroscopy (LIBS) is a well-suited technique for the assessment of non-stoichiometry in yttrium aluminum garnet (YAG) ceramics and that the aluminum to yttrium ratio can be determined with a resolution of 0.3 mol %, well within the phase boundaries of YAG. (C) 2017 Optical Society of America
NMR; LIBS; Surface relaxivity; Paramagnetic impurities; Porous media;NUCLEAR MAGNETIC-RELAXATION; POROUS-MEDIA WETTABILITY; TO-VOLUME RATIO; SEDIMENTARY-ROCKS; NMR RELAXOMETRY; PROTON NMR; PORE SIZES; DIFFUSION; VALIDATION; REGRESSION
Nuclear magnetic resonance (NMR) relaxometry is a common technique used to assess the pore size of fluid-filled porous materials in a wide variety of fields. However, the NMR signal itself only provides a relative distribution of pore size. To calculate an absolute pore size distribution from the NMR data, the material's surface relaxivity needs to be known. Here, a method is presented using laser-induced breakdown spectroscopy (LIBS) to evaluate surface relaxivity in sandstones. NMR transverse and longitudinal relaxation was measured on a set of sandstone samples and the surface relaxivity was calculated from the pore size distribution determined with MICP measurements. Using multivariate analysis, it was determined that the LIBS data can predict with good accuracy the longitudinal (R-2 similar to 0.84) and transverse (R-2 similar to 0.79) surface relaxivity. Analysis of the regression coefficients shows significant influence from several elements. Some of these are elements previously established to have an effect on surface relaxivity, such as iron and manganese, while others are not commonly associated with surface relaxivity, such as cobalt and titanium. Furthermore, LIBS provides advantages compared to current methods to calibrate surface relaxivity in terms of speed, portability, and sample size requirements. While this paper focuses on geological samples, the method could potentially be expanded to other types of porous materials. (C) 2016 Elsevier Inc. All rights reserved.
Davydov, M. A. ; Grishin, M. Y. ; Pershin, S. M. ; Sdvizhenskii, P. A. ; Stavertiy, A. Y. ; Tretyakov, R. S.
laser ablation; laser induced breakdown spectroscopy; picosecond pulse train ablation;ND-YAG LASER; QUANTITATIVE-ANALYSIS; Q-SWITCH; ABLATION; PLASMA; SAMPLES; STEEL; GENERATION
Picosecond pulse train and nanosecond pulse were compared for laser ablation and laser induced breakdown spectroscopy (LIBS) measurements. A detailed study revealed that the picosecond pulse train ablation improved the quality of laser craters (symmetric crater walls and the absence of large redeposited droplets), which was explained by a smaller heat affected zone and suppression of melt splash. Greater plasma dimensions and brighter plasma emission were observed by gated imaging for picosecond pulse train compared to nanosecond pulse ablation. Increased intensity of atomic and ionic lines in gated and time integrated spectra provided better signal-to-noise ratio for picosecond pulse train sampling. Higher temperature and electron density were detected during first microsecond for the plasma induced by the picosecond pulse train. Improved shot-to-shot reproducibility for atomic/ionic line intensity in the case of picosecond pulse train LIBS was explained by more effective atomization of target material in plasma and better quality of laser craters. Improved precision and limits of detections were determined for picosecond pulse train LIBS due to better reproducibility of laser sampling and increased signal-to-noise ratio.