BALL-MILLING CONDITIONS OF A VERY SMALL AMOUNT OF LARGE PARTICLES IN SILICON-NITRIDE POWDER

The effect of ball milling conditions on pulverization of the very sma ll amount of large particles in silicon nitride powder was examined. I n this paper, the wet sieve analysis and X-ray sedimentation method we re used to measure the content of large particles in the ground powder which influence important properties of sintered ceramics such as fra cture strength. As a result, it was made clear that the wet sieve anal ysis would be a reliable method to measure the content of just a few l arge particles in the ground powder. By applying this analysis to the ball-mill grinding of silicon nitride powder, it was found that the pr ocessing conditions required to grind the large particles were differe nt from those to obtain high specific surface area as well as small av erage size of particles. This is because the impact force exerted onto the particles by the media balls is more effective on grinding large particles.