CaO-β Quartz Reaction at Moderate Temperatures

Abstract

<p> An investigation is reported on the kinetics of Ca0-β quartz solid state reaction on basal and prism planes of β-quartz at temperatures in the range between 1000 degrees Celsius and 1200 degrees Celsius. Excess lime present in all the samples ensured ensured the formation of c2s (dicalcium silicate) only. The thickness of the c2s product layer was measured on a Zeiss camera microscope Ultraphot II. The line scans for the distribution of Ca and Si across the reaction layer were obtained on the electron microprobe analyser. The kinetics of the reaction on basal and prism planes of a-quartz in wet and dry nitrogen atmospheres in the temperature range considered was studied by measuring the thickness of c2s as a function of time of reaction. </p> <p> The CaO-β quartz reaction was found to be anisotropic, the basal plane reaction being faster than the .Prism plane reaction. The reaction on both basal and prism planes in the temperature range between l000°C and 1200°C was found to be enhanced in the presence of moisture. The enhancement due to the presence of moisture was found to be more on the basal plane reaction than on the prism plane reaction. This appears to be due to the fact that different polymorphs of c2s with different sensitivities to the presence of moisture are produced on different crystallographic planes of a-quartz considered. The activation energies for the reaction on basal plane and prism plane were found to be about 53 kcal/mole and 63 kcal/mole respectively. They have good agreement with the activation energies of 55 kcal/mole and 65 kcal/mole for Ca diffusion in a-c2s and a-c2s respectively as reported by Lindner. </p>