SINTERING AND GRAIN-GROWTH RATES OF 2 SPHERES WITH DIFFERENT RADII

Rate equations for sintering and grain growth have been proposed on the two-sphere model that simulates shrinkage processes during heating of a ceramic powder compact. In the model it was assumed that total excess energy associated with surfaces and grain boundary drives mass transport in sintering and grain growth. The rate equations formulated here show that sintering and grain growth are activated by the same kinds of driving force and processes. They show quantitatively that the sintering rate increases with a decrease in grain boundary energy and with a decrease in the grain size difference. It is found also that the grain growth of a larger grain is much slower than a smaller grain and that the growth rate of a smaller grain is accelerated remarkably when its grain size becomes smaller compared with a lager grain.