2001 年 50 巻 9 号 p. 1007-1012
The effect of curing temperature on hardening of α-alumina slurry including ρ-alumina was investigated by X-ray diffraction (XRD), thermal analysis (DTA) and scanning electron microscopy (SEM). From the experimental results, it was clarified that the penetration resistance rapidly increased as the curing temperature increased. It was thought that the hardening of the slurry was progressed with following two stages. At the first stage, alumina particles were mainly coagulated by the neutralization effect of polynuclear hydroxo-aluminum ion which was produced by the dissolution of ρ-alumina. At the second stage, alumina particles were bound to each other with the pseudoboehmite which was produced by the hydration reaction of ρ-alumina. The logarithmic time required to reach the same penetration resistance increased almost linearly with an increase of the reciprocal curing temperature, after the correction for the delay time which was caused by heating from the initial temperature (280K) to the curing temperatures (318-363K). The apparent activation energy for the hardening was approximately 79kJ/mol. This value was nearly equal to the apparent activation energy for the dissolution of aluminum anodic oxide film. This suggested that the dissolution of ρ-alumina was the rate-controlling step of the hardening.