Ceを添加したγ-Al2O3の熱安定性

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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.
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