Mechanochemical effects for some Al₂O₃ powders of dry grinding

Abstract

Three kinds of Al₂O₃ powders, i.e. two kinds of low-soda Al₂O₃ with average particle sizes of 3.9 and 0.6 μm and an electrofused Al₂O₃ with an average particle size of 21.8 μm, were ground for up to 300 h in a dry vibration ball mill. Variations in particle-size distribution, specific surface area, crystallite size, lattice strain, effective temperature factor and lattice constant were examined against milling time. The mechanism of grinding was found to differ between low-soda Al₂O₃ and electrofused Al₂O₃. The mechanochemical effects on these Al₂O₃ powders occurred in the order decrease of crystallite size → increase of effective temperature factor → increase of lattice strain. The length of the a-axis was clearly increased by a prolonged grinding. The difference in the ground state of three specimens was attributed to differences in the physical state of particles originating from the preparation methods, and also to particle size.