共线DP-LIBS低碳合金钢中碳元素定量分析

碳元素是决定合金钢性能的重要元素之一。为了提高低碳合金钢中碳元素的检测灵敏度，在氩气氛围中利用共线双脉冲激光诱导击穿光谱(DP-LIBS)合金钢样品中的碳元素进行了检测。首先，使用高速相机采集双脉冲实验条件下的等离子体图像，研究等离子体形貌随脉冲间隔时间变化的演化规律，结合双脉冲条件下获得的光谱信息，确立碳元素的最佳脉冲间隔时间为1 900 ns。其次，研究了氩气吹扫条件和氩气气室条件对碳元素光谱信号强度的影响。氩气气室能够有效屏蔽空气中二氧化碳的影响，从而提高合金钢中碳元素分析的准确性。最后，采用内标法对合金钢样品中的碳元素进行定量分析。与单脉冲得到的结果相比，双脉冲实验条件下，碳元素定标曲线的R2由0.983提升至0.991，检测限由206 μg·g-1提高至110 μg·g-1，共线DP-LIBS技术使合金钢中碳元素检测限提高了1.87倍。恰当的脉冲间隔时间能够有效的提高共线DP-LIBS光谱特性和设备的检测灵敏度，同时双脉冲的二次激发效果可以进一步有效的减弱实验条件波动带来的影响，使定标模型具有更好的线性相关性。

Quantitative Analysis of Carbon in Low-Carbon Alloy Steel by Collinear DP-LIBS

Carbon (C) is one of the key elements for alloy steel properties. In this paper, we used collinear double pulse laser induced breakdown spectroscopy to detect C in alloy steel samples under argon atmosphere in order to improve the sensitivity of detection of C content in low-carbon alloy steels. Firstly, the plasma images produced by Double pulse Laser Induced Breakdown Spectroscopy (DP-LIBS) were collected by high-speed camera to study the evolution of plasma morphology with inter-pulse delay time, then combining the spectral information obtained under double pulse to establish the optimal inter-pulse delay time which was 1900 ns for carbon. In addition，the influence of argon purge and argon chamber condition on the C spectral signal intensity was studied. Between these two situations, the argon chamber can effectively shield the effect from carbon dioxide in the air, and consequently improve the analysis accuracy of C content in alloy steel. Finally, we used the internal standard method to quantify the concentration of C in alloy steel samples. Compared with the results obtained by single pulse, the R2 of calibration curve for C element increased from 0.983 to 0.991 by double pulse, and the limit of detection (LOD) decreased from 206 to 110 μg·g-1. The collinear DP-LIBS improved the limit of detection of C content in alloy steel by 1.87 times. The results show that the appropriate inter-pulse delay time can effectively improve the collinear DP-LIBS spectral quality and instrument’s sensitivity. At the same time, the secondary excitation effect of double pulse can further effectively reduce influence of the fluctuation of experimental condition, and make the calibration model possesses better linear correlation.