The initial sintering of alkaline earth oxides in water vapor and hydrogen gas.

概要

論文の詳細を見る
The initial sintering (crystallite growth and surface-area diminution) of freely dispersed powders was studied. For MgO in H2O vapor, the sintering rate at 1073 K was directly proportional to the water-vapor pressure, PH2O, in the range of 27–2700 Pa, and the apparent activation energy, E, for the sintering was 137 kJ mol−1. These facts lead to the conclusion that, in this system, the surface migration of O2− caused by the repetition of the adsorp-tion-desorption cycle of the H2O molecule is rate-determining step for the sintering. For CaO in H2O vapor, the rate-determining step appears to be migration on and/or near the surface of a cation vacancy produced by the H2O adsorption, judging upon the facts that the sintering rate at 873 K was proportional to PH2O0.34 in the range of 11–1600 Pa and that E was 79.4 kJ mol−1. For MgO in H2 gas, the sintering rate at 1123 K was approximately proportional to the hydrogen pressure in the range of 3.3–66.5 kPa and E was 310 kJ mol−1, indicating that the sintering in H2 was caused by H2O vapor formed upon the desorption of the surface hydroxyl groups which had been produced by a heterolytic dissociative adsorption of H2.
公益社団法人日本化学会の論文