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We started for 30 minutes in isopropyl alcohol (IPA). Afterwards, we checked the present fineness by optical microscopy. Majority of sample use to be ground smaller as 10 µm.
We exchanged the grinding balls against 100 µm Ø after 30 minutes and processed grinding for a total of 90 minutes.
By checking the fineness after 60 and 90 minutes, there was only a minor improvement. A longer grinding time is still possible, but we are guessing that only by adding of grinding agents, a significant improvement can be possible.
On separate pages, you will find the particle size distribution after a total grinding time of 60 minutes with standard Mie parameters for silica (meas. no. 67790 with d50 < 115 nm). Because the proper Mie parameters for your kind of sample are not given, we recalculate the present result with different refractive indices (1,8; 2,1 ; 2,3), it has shown that the main particle fraction has been ground to about 30 nm - 300 nm.
A more precise distribution can be recalculated if proper Mie parameters for your kind of sample can be provided.
We aborted the grinding process after a total grinding time of 90 minutes.
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