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激光诱导击穿光谱(LIBS)技术应用于颗粒流的直接测量是实现固体物料特性在线监测的有效途径之一。以不同粒径的高纯石英砂为研究对象,利用高精度的连续给粉机产生稳定连续的石英砂颗粒流。脉冲激光在大气环境下分别激发5组不同粒径的石英砂颗粒流,研究LIBS直接测量颗粒流时的粒径效应及其修正方法。研究结果表明,在相同粒径下质量流量小范围波动对激光等离子体光谱强度没有显著影响,而粒径波动则会引起光谱强度的较强变化,光谱强度随着粒径的减小而增强。通过分析各粒径的颗粒流在不同光谱信号探测延迟时间下的光谱特性,发现在2~4μs的延迟时间区间内,粒径效应较弱。在此优化延时基础上,将颗粒流直接激发时同步产生的N谱线作为石英砂组分谱线的内标时,可以进一步减弱粒径效应,从而获得可以表征颗粒流基体特性的修正光谱强度。在N元素的各条特征谱线中,343.76nm谱线的修正效果最佳。
The application of laser induced breakdown spectroscopy (LIBS) technology to the direct measurement of particle flow is one of the effective ways to realize on-line monitoring of solid material properties. With different particle size of high purity quartz sand as the object of study, the use of high-precision continuous feeder to produce a steady and continuous flow of quartz sand particles. Pulsed laser excited five groups of quartz sand particles with different particle sizes under atmospheric environment respectively, and studied the particle size effect when LIBS measured particle flow directly and its correction method. The results show that the small-scale fluctuations of mass flow have no significant effect on the spectral intensity of laser plasma at the same particle size, while the fluctuation of particle size causes a strong change of spectral intensity. The spectral intensity increases with the decrease of particle size. By analyzing the spectral characteristics of the particle flow at different detection delay time, we found that the particle size effect is weak in the delay time of 2 ~ 4μs. On the basis of this optimization delay, the particle size effect can be further reduced by using the N line generated synchronously when the particle flow is directly excited as the internal standard of the quartz sand component spectral line, so as to obtain a modified spectrum that can characterize the particle flow matrix characteristics strength. In the N element of each characteristic line, 343.76nm line correction effect best.