Abstract
An alum-derived Al2O3 powder and aluminum hydroxide one were calcined at 1280°C for 2 h in flowing 02. Both the resultant powders had similar primary particles in size ( ?? 0.2 μm). The latter had smaller aggregates (<3μm) than the former (<5 μm), but was nonsinterable. This nonsinterable behavior was explained from the hard aggregates and from the appreciable contribution of the surface diffusion of atoms toward the sintering of this powder. The porous aggregates of the alum-derived Al2O3 powder, having randomly arranged primary particles, that is, very dispersed pore sizes were easily disintegrated not only by ball-milling but also by pressing at 200 MPa, and the narrow dispersion of small pores (0.05-0.073 μm) in the green compact was considered to be one of origins for the sinterable behavior of this powder.
