SINTERING KINETIC OF AN AGGLOMERATED POWD ER - ALUMINUM NITRIDE

During sintering agglomerated powders generate an interagglomerate por osity, larger in size than the one between the elementary grains. This porosity involves a new approach for the description of the rearrange ment and diffusion steps. The mean relative density is not sufficient to describe such a microstructure. Two new variables, the relative int eragglomerate density (rho e) and intraagglomerate density (rho i) are substituted to the mean relative density. The kinetic studies in this work were considered at a given microstructure (rho i, rho e) rather than a fixed density (rho). After the rearrangement step, sintering ki netics are described by means of a sintering map, i.e. interagglomerat e density versus intraagglomerate density. This map leads to the defin ition of optimal sintering trajectories in order to eliminate large po res before the small ones. Optimal conditions for temperature and gran ulometry are deduced. This analysis was confirmed by an experimental w ork on an agglomerated aluminium nitride powder.