激光粒度测试结果影响因素分析

Analysis of influencing factors on laser particle size measurement

针对目前市面上激光粒度仪品牌、型号众多,但激光粒度测试结果差异较大的现象,以清华大学研制的球形石英粉标准样品为测试样品,使用不同厂家的激光粒度仪,通过激光散射法,对比不同复折射率下的检测结果,探究激光粒度测试结果的影响因素。研究发现,针对同种样品、不同厂家的激光粒度仪检测结果偏差较大。折射率与吸收率对粒度检测结果有较大影响,折射率的影响比吸收率的影响大,但随着吸收率增大可以逐渐抵消折射率的变化给粒度检测结果带来的波动,使检测结果趋于稳定。通过寻找拟合残差与粒度检测结果之间的变化规律,发现残差值越小,理论散射光强与实际检测光强的偏差越小,检测结果越趋于一个较稳定的值,但对比发现目前激光粒度测试用户根据残差值判断待测样品折射率的方法并没有可靠的依据。通过比较不同样品的最小残差值,发现同种样品的不同粒度区间对应的折射率与吸收率不同,从而证明粒度检测行业内以每种物质固定的折射率和吸收率来进行粒度测试的方法缺乏实际依据。

In view of the numerous brands and models of laser particle size analyzer that have large discrepancies in laser particle size measuring results, the spherical quartz powder standard sample developed by the Tsinghua University is taken as the test sample which is tested with laser particle size analyzers from different manufacturers by means of laser scattering method so as to compare the measuring results with different complex refractive index and explore the influential factors of laser particle size test results. According to the research findings, against same type of sample, there are discrepancies in measuring results obtained by laser particle size analyzers made by different manufacturers. The particle size measuring results are greatly affected by the refractive index and absorption rate. The refractive index is more influential to the measurement. However, with the increase of the absorption rate, the fluctuation of testing results caused by the changes of refractive index can be gradually neutralized, making the measuring results tend to be stable. By seeking for the varying pattern between the fitting residual error and particle size measuring results, it is noted that the smaller the residual value are, the smaller the deviation between the theoretical scattering light intensity and the actual detection light intensity are, and the resultstend to he a more stable value. However, it is also found lhrough comparison that the method of measuring lhe refractive index of the sample to be tested according to the residual value is not reliable. By comparing the minimun residual values of different samples, the refractive index and ahsorption rate of different particle sizes of the same sample are found to be different. Thus, it is proved that the method of particle size measurement based on the refractive index and absorption rate of each material is lack of practical basis in the area of particle size measurement.