Sintering kinetics of porous ceramics from natural diatomite

The sintering kinetics of the porous ceramics from natural diatomite is investigated by means of stepwise isothermal dilatometry (SID) accompanied with XRD, scanning electron microscope (SEM), and porosity measurement. We find that the isothermal shrinkage data from SID could be well analyzed to get kinetic parameters according to the empirical rate equation developed by Makipirtti-Meng, dY/dt = nk(T)Y(1 - Y)(Y/1 - Y)(1/n) where Y is the fractional volume shrinkage during sintering process and n a dimensionless exponent. The apparent activation energy Delta E values obtained for 850 degrees-1000 degrees C and 1050 degrees-1150 degrees C are 911.8 and 610.5 kJ/mol, respectively. Correspondingly, the exponent n values for the two temperature ranges are also much different and can be served to reveal the morphology changing during the sintering process, which is well consistent with the SEM observation.