Intensive grinding of powders in an electro-magneto-mechanical mill

The paper presents the results of high-energy grinding in the electro-magneto-mechanical (EMM) mill. Ground powder is treated in a very specific and intensive way owing to several field forces operating simultaneously in the EMM mill. The grinding power in the centre of the millʹs working chamber is in the order of 2 MW/m3, which is much more than in ordinary mills. Therefore, the grinding time is very short, i.e., several tens of seconds. The self-disintegrated Fe–Al–Si powders of 155 μm on average undergo size reduction to 8 μm after 120 s. Over 25% of the total weight get the size of less than 1.3 μm. Very hard materials, such as SiC and B4C reduce their grain size over 30 times after 120 s of grinding in the EMM mill. The results of the grinding of Fe2O3 powder are even better. In ball mills, vibration and planetary mills, similar results can be achieved after a period several hundreds times longer. The treatment of Fe–Al–Si powder presented here is intended as the preparation procedure for sintering, plasma spraying or laser surface alloying.