KINETICS AND MECHANISM OF A SINTERING PROCESS FOR MACROPOROUS ALUMINACERAMICS BY EXTRUSION

The paper describes an evaluation of kinetic parameters for sintering from the analysis of stepwise isothermal dilatometry data for the pore -forming process of macroporous alpha-Al2O3 ceramics fabricated by ext rusion, The experimental results demonstrated that isothermal shrinkag e data for the sintering process can fit the following rate equation: dY/dt = nK(T)Y(1 - Y)[(1 - Y)/Y](1/n), where Y is the fraction of volu me shrinkage, Kinetic parameters, i.e., the average exponent n and the activation energy E for the pore-forming process, were calculated to be 0.232 and 415.5 kJ/mol, respectively, in the temperature range of 1 200-1400 degrees C, The results also show the equivalence between isot hermal sintering and stepwise sintering in alumina. In the latter case the temperature is increased in steps over a period of time, The equi valence is derived from understanding how the sintering rate changes w ith porosity. The sintering mechanism in different temperature ranges is discussed, with reference to microstructure development. The bend s trengths of porous ceramics with different porosities are also present ed.