Influence of Anisotropy and Water Vapor on the Solid‐State Reaction of CaO and Beta Quartz

The kinetics of the solid‐state reaction of CaO and β‐quartz were studied between 1000° and 1200°C in wet and dry N 2 . Parabolic kinetics were observed in all cases; Ca 2 SiO 4 was the only reaction product. The reaction was faster on the basal plane of the β‐quartz than on the prism plane, and although moisture enhanced the reaction rates on both planes, the enhancement of the basal‐plane reaction was significantly higher. Activation energies and results of marker experiments indicated that Ca 2+ diffusion in the product was rate‐controlling and that α‐Ca 2 SiO 4 possibly formed on the basal plane of the β‐quartz and α'‐Ca 2 SiO 4 on the prism plane. A model for the observed kinetic enhancement in the presence of moisture is proposed on the basis of creation of interstitial Ca 2+ sites in the products.