FRITSCH PULVERISETTE 7 classic line - Manual (Page 33)

6.4.3 Reverse mode
n Useful for mechanical alloying.
n Improvement of the homogeneity of the sample during mixing.
A low to medium speed is recommended for mixing (dry or
wet).
6.4.4 Number and size of the balls
Pre-grind course, hard material with large balls:
Reduced percentage of fine material!
Many small balls increase the percentage of fine material during
extended running time.
6.4.5 Weight of the balls (type of material)
A higher mass (specific weight) of the grinding balls accelerates grinding.
(see table in Ä Chapter 6.1 ‘Choice of grinding bowls and grinding balls’
on page 28).
6.4.6 Dry grinding
Below a particle size of approx. 20 µm, the surface forces prevail. The
grinding stock begins to stick.
Additional dry comminution can be achieved by adding surface-active
substances to the material to be ground.
Examples (maximum amount to be added in mass%)
n Stearic acid 2-3%
n Aerosil (fine-particle silicic acid) 0.5 - 2%
n Quartz sand ~ 2%
n Glass powder ~ 2%
n Glycol (Ethylene glycol) ~ 0.1 - 0.5 % ( ≙ 5 - 25 droplets)
n Triethanolamine ~ 0.1 - 0.5 %
Using the device
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