Initial Sintering of Alumina and Hematite

Abstract

Experimental measurements of the rate of shrinkage of pressed Al 2 O 3 compacts, the neck growth between single‐crystal Al 2 O 3 spheres and plates, and the effect of particle size on neck growth between single‐crystal Al 2 O 3 spheres and plates are mutually consistent with the bulk diffusion sintering model. Tbe temperature dependence of the rate of shrinkage and neck growth in Al 2 O 3 is characterized by an activation energy of 165 kcal. per mole. Apparent diffusion coefficients and temperature dependence calculated from the shrinkage of pressed compacts of Fe 2 O 3 agree with measured diffusion coefficients for the diffusion of Fe in Fe 2 O 3 .