Transient bimodal effects in the in-line particle size measurement during milling of solid state materials

For the processing or synthesis of solid state materials, ball milling has proven to be an effective method. However, due to the continuous agitation, the process is not suited for in-situ measurement techniques. In this work, a system for the in-line particle size measurement during milling has been developed and tested. The results show that milling of a sample with a certain mean particle size results in the production of a bimodal size distribution before a final product with the smaller particle size is produced. Moreover, a much faster than expected reduction in size was achieved, whose time evolution could otherwise only be followed by wasteful and time-consuming specimen analysis in intervals. In conclusion, in-line particle size measurement during milling is a promising technique to optimize the processing time or obtain a product powder in a certain condition. • A setup to measure the particle size of solid state powder materials during milling was designed, built and successfully tested • The particle size during milling showed an unexpected evolution from a monomodal to a transient bi-modal distribution density • A solution for the return of analyzed powder to the mill was explored