Abstract
Sintering of alumina is affected by the property of raw material, additives, atmosphere, etc. In this paper, the rate and the activation energy of sintering of alumina containing MgO, Co3O4, TiO2 and MnO2 by 2 or 5 wt.% were examined in the temperature range from 1400 to 1650°C.
The relation between the extent of sintering (P) and time (t) can be described by the following equation: P=Ktn where K is the rate constant for sintering and n is the time exponent depending on temperature and specimens with different additives. A recent work on sintering of alumina has reported that n was a constant of the value 0.4 unrelated to temperature. However, n from this experiment was not constant but small at low temperatures and with rising temperature increased up to a maximum point and then decreased. The value was smaller than 0.4, and 0.2-0.29 at the maximum point though varied by the additives. The velues of n obtained were as follows:
The self-diffusion coefficient was calculated from the measurement of shrinkage using a Kingery's equation for diffusion sintering, from which the activation energy (Q) for sintering was obtained by Arrhenius plotting. The results were as follows:
