Onset sintering-coarsening-coalescence kinetics of calcite powders

An onset sintering-coarsening-coalescence (SCC) event based on a significant decrease of specific surface area relative to the dry pressed samples after isothermal firing in the 450-600 °C range in air was determined by N2 adsorption-desorption hysteresis isotherm for submicron-sized calcite powders. The apparent activation energy for such a rapid SCC event was estimated as 57.5 ± 1.0 kJ/mol based on the time for 50% reduction of specific surface area without appreciable phase change of calcite. The minimum temperature to activate the SCC process, as of concern to industrial CaCO3 applications and natural limestone formation, is 317 °C based on the extrapolation of steady specific surface area reduction rates to null.