Effects of Ball-Milling Time on the Properties of Low Purity β-Phase Silicon Nitride Powder and the Hot-Pressed Body

Abstract

Y2O3-doped low purity β-Si3N4 powder was ball-milled for 6 to 100h. The effects of ball-milling time on the properties of the powder and the hot-pressed body were investigated. As increasing ball-milling time, average particle size and crystallite size decreased and the amount of SiO2, carbon, some metallic impurities and lattice strain increased for the ball-milled powder. The increase of SiO2 was ascribed to the mechanochemical reaction of H2O contained in the milling fluid with newly formed powder surfaces. The source of carbon was both the milling fluid and the container. The increase of Al and Mg was explained by the wear of milling balls. Sintering behavior and microstructure of the sintered bodies were influenced by the powder properties modified by different ball-milling time. Mechanical properties were strongly dependent on their microstructures.