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2~4 μs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, 343.76 nm谱线的修正效果最佳。

Laser-induced breakdown spectroscopy (LIBS) is one of the effective ways to achieve online monitoring of solid material characteristics by detecting the particle flow directly. We investigated the different particle sizes of high purity quartz sand, whose stable flow was produced by high precision continuous powder feeding machine. 5 groups of quartz sand flow samples with different particle sizes were then ablated by a pulse laser directly to test the particle size effect and its modified method. The results show that slight fluctuation of mass flow has no obvious effect on the spectral intensity, while the fluctuation of particle size has significant impact on the spectral intensity. The spectral intensity increases with the decrease of particle size. By analyzing the time characteristics of Si spectral line intensity of each particle size, it is found that the effect of particle size is weak during the 2-4 μs delay time. Besides, the directly, synchronously excited and generated N spectral lines were used as an internal standard of silica spectrum, which may further weaken the effect of particle size, thereby obtaining the corrected spectral intensity which can characterize the particle flow. In this experiment, the correction effect of 343.76 nm line is best.