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With about 100 g of sample, the bowl will be filled to the maximum.
After the first 2 minutes of dry grinding, the sample started sticking lightly to the bowls wall. It was still easy to remove, so dry grinding has been proceeded. After a total dry grinding time of 10 minutes, sticking became stronger.
This uses to happen after the majority of particles reached a fineness of < 20-30 µm. Interacting forces between fine ground particles will become bigger as their own g-force. Therefore, particles will stick to each other and become compressed by the used grinding balls. These clusters of particles also contain bigger particles which will not be ground any further.
By using anti-sticking agents, sticking can be delayed a little, but a final fineness of < 10µm is not expected to be achieved.
To improve the grinding result, a grinding in suspension is required. For this, see the following grinding trail.
Attached to this report, you will find the particle size distribution of the original sample, after 5 minutes of dry grinding and after 10 minutes of dry grinding. All measurements have been performed with our Laser Particle Sizer ANALYSETTE 22 NanoTec plus.
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