Sintering of bimodal alumina powder mixtures with a nanocrystalline component

Packing characteristics and sintering behavior of the bimodal mixtures of n anocrystalline (75 nm) and conventional (1 mu m) alumina powders were inves tigated. Green density of the pure nanocrystalline compact was lower than t hat of the pure coarse particles. Increase in the packing density was obser ved at 70% coarse particle composition. The powders shrinkage characteristi cs were determined by dilatometry. The cold pressed compacts were sintered within the temperature range of 1300 degrees C to 1600 degrees C. The green density followed the packing rules giving rise to higher packings in the b imodal compacts. At temperatures below 1400 degrees C, the relative density kept this pattern. Above 1400 degrees C, this advantageous densification w as lost. The changes in densification of the compacts versus powder composi tion and sintering temperature were discussed with respect to phase transit ion and sintering in the compacts. (C) 1999 Acta Metallurgica Inc.