Ceを添加したγ-Al₂O₃の熱安定性

抄録

The thermal stability of Ce added γ-Al₂O₃ was investigated in the temperature range up to 1200°C. The addition of Ce prevented the phase trasition of γ-Al₂O₃ to α-Al₂O₃ and improved the thermal stability of alumina at 1200°C. The surface area after being heated at 1200°C for 5 hours was 40 m²/g for 1 mol % Ce added alumina and 12 m²/g for pure alumina. The activation energy of the phase trasition had a constant value, about 580kJ/mol, regardless of the Ce addition. The isothermal transformation data at 1250°C were represented by the kinetic equation, X=1-exp{-K(t-t₀)ⁿ}, where X is the fraction transformed, K is the rate constant, t is the time and n is the dimensionless time exponent. The sintering of alumina at 1000°C was due to the change of γ-Al₂O₃ to θ-Al₂O₃ with the volume diffusion and was not influenced by the Ce addition. The state of the added Ce was examined with electron spin resonance method using Gd as a probe, and was characterized by the fine CeO₂ on alumina surface.