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; 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.

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

ELECTROLYTE FUEL-CELL; DEPTH-RESOLVED ANALYSIS; CATHODE ELECTRODE; LAYER ELECTRODES; INDUCED PLASMA; REACTION-RATES; SPECTROMETRY; LIBS; CHINA

Pt and Nafion are materials widely used in electrochemical devices including PEM fuel cells, flow batteries, electrolyzers, and electrochemical sensors. In PEM fuel cells, the catalyst layer consists of multiple materials including catalyst Platinum (Pt) or Pt-based alloys, carbon, and ionomer (usually Nafion). Laserinduced breakdown spectroscopy (LIBS) is a promising analytical tool for probing the elemental composition in a sample, offering advantages of fast, in-situ, and online analysis, minimal sample preparation requirement, and the capability of spontaneous multi-element analysis. In this paper, we present a study of probing the Pt and Nafion loadings in their mixtures with graphite carbon, respectively, using LIBS technology. Pt-carbon and Nafion-carbon samples of various material loading are prepared for the LIBS testing. Plasma plume and shadowgraphic images are presented to show plasma and associated shockwave evolution. It takes a few milliseconds for spectrum collection per laser shot. Each sample analysis contains 49 shots in the present study and takes less than 1 minute. The results show LIBS is capable of probing the Pt and Nafion loadings in the mixtures. The method is useful in rapid analysis of catalyst layer composition and examination of material loss due to degradation. (c) 2017 The Electrochemical Society. All rights reserved.