High-packing silicon nitride powder and method for making

摘要

High-packing silicon nitride powder is prepared by reacting metallic silicon powder having a mean particle size of 1 to 10 mu m and a purity of at least 99% directly with nitrogen for forming silicon nitride powder, milling the silicon nitride powder in a dry attritor until the tap density exceeds 0.9 g/cm3 and the content of particles having an aspect ratio of up to 3 exceeds 95% by weight, and further milling the silicon nitride powder in a wet attritor for finely dividing coarse particles having a particle size of at least 2 mu m. The silicon nitride powder has a tap density of at least 0.9 g/cm3 and a mean particle size of 0.4 to 0.6 mu m and contains at least 95% by weight of particles having an aspect ratio of up to 3 and up to 5% by weight of coarse particles having a particle size of at least 2 mu m. The powder is moldable into a high density compact, from which a sintered part having improved dimensional precision and strength is obtained.