Intermediate Stage Densification in Vacuum Hot Pressing of Alumina

摘要

An analysis was made of the densification kinetics preceding the final stage densification of alumina hot pressed in vacuum between 1150 and 1350C and between 2000 and 6000 psi. The analysis suggests a diffusional creep mechanism, possibly consistent with a Narbarro-Herring vacancy model. The measured activation energy, 116 kcal/mole, agrees with the activation energy for the final stage of densification and for the self-diffusion of aluminum ions in alumina. It is conjectured that the pore structure (i.e., open or closed) determines the stage of densification and further that pore structure has a profound effect on the apparent diffusion coefficients. (Author)