基于黑体辐射提高自由定标激光诱导击穿光谱(CF-LIBS)定量精度的方法

Method of Improving Quantitative Accuracy of CF-LIBS Based on Black Body Radiation

自由定标激光诱导击穿光谱(Calibration-Free LIBS,CF-LIBS)技术是定量分析行业发展的主要趋势之一。该技术可直接基于局部热力学平衡等离子体模型,通过LIBS光谱数据和谱线参数计算出等离子体参数和各元素含量。且无需使用标准样品建立定标曲线,该技术不受基体效应的影响,非常适合实时、在线和多元素同时分析。但由光学厚而引起的自吸收效应是影响定量分析的重要因素。通过对比实验光谱数据与黑体辐射强度,研究等离子体温度,提高光学系统收集效率,抑制自吸收效应对CF-LIBS定量结果的影响。经过黑体辐射校正后,基体元素Fe的测定含量从88.700%提升到94.575%,相对误差(RE)从8.072%降低到1.984%。微量元素Cr、Mo和V的测定含量分别从0.635%、0.096%和0.023%降低至0.698%、0.143%和0.022%,相对误差(RE)从13.723%、45.455%和21.053%降低至5.163%、18.75%和15.789%。整体的平均绝对误差(MAE)从1.994%降低至0.497%。玻尔兹曼图拟合回归曲线有了更高的线性度。拟合系数R 2分别从0.95531、0.82966、0.45217和0.54493提升至0.99620、0.99231、0.99882和0.97269。结果表明,相较于传统的CF-LIBS,经过黑体辐射参考校正自吸收(BRR-SAC)后,合金样品中的各元素定量准确度均有明显提高,为抑制自吸收效应提高CF-LIBS定量精度研究提供了理论指导。

The Calibration-Free LIBS(CF-LIBS)technique,which stands for laser-induced breakdown spectroscopy with calibration-free capability,is one of the main trends in the development of quantitative analysis industry.This technology can calculate plasma parameters and element contents directly based on the local thermodynamic equilibrium plasma model,using LIBS spectral data and spectral line parameters.Moreover,since there is no need to establish a calibration curve using standard samples,this technology is not affected by matrix effects and is therefore suitable for real-time,online,and simultaneous multi-element analysis.The self-absorption effect caused by optical thickness is an important factor that affects quantitative analysis.This study aims to investigate plasma temperature,improve the collection efficiency of the optical system,and suppress the influence of self-absorption effect on the quantitative results of CF-LIBS by comparing experimental spectral data with black body radiation intensity.After blackbody radiation correction,the measured content of matrix element Fe increased from 88.700%to 94.575%,with a relative error(RE)reduced from 8.072%to 1.984%.The measured contents of trace elements Cr,Mo,and V decreased from 0.635%,0.096%and 0.023%to 0.698%,0.143%and 0.022%,respectively,with relative errors(RE)reduced from 13.723%,45.455%and 21.053%to 5.163%,18.75%and 15.789%,respectively.The overall mean absolute error(MAE)decreased from 1.994%to 0.497%.The Boltzmann plot fitting regression curves exhibited higher linearity.The fitting coefficients R 2 increased from 0.95531,0.82966,0.45217 and 0.54493 to 0.99620,0.99231,0.99882 and 0.97269,respectively.The results indicated that compared to traditional CF-LIBS,the quantitative accuracy of elemental analysis in alloy samples was significantly improved after blackbody radiation referenced self-absorption correction(BRR-SAC).This study provides theoretical guidance for enhancing the quantitative precision of CF-LIBS by suppressing the self-absorption effect.