碱土金属修饰Al2O3的表面热稳定性

采用浸渍法,添加不同碱土金属元素对γ-Al2O3进行改性.通过BET、XRD等手段,研究考察了在1 373 K空气中,经不同时间处理γ-Al2O3的相变和烧结情况,比较了各样品烧结后比表面积的差异.结果表明,碱土金属的引入（尤其是Sr、Ca）有效地抑制了氧化铝比表面积的损失和α相变.并对Al2O3的烧结动力学进行了研究探讨,研究表明,铝酸盐的生成并不是稳定氧化铝的根本原因,碱土金属的高温稳定作用主要是分散态的碱土金属氧化物抑制氧化铝焙烧过程中最初1 h内的烧结和α相变引起的比表面积损失.

Surface Aea Stabiligyt of AI2O3 Moddified by Alialine Earths

The thermal stabilization mechanism of Al2O3 modified by alkaline earths using impregnation method with various contents and calculation time was studied by BET surface area and powder X-ray diffraction.It was found that the addition of alkaline earths increased the surface area of Al2O3 and retarded the transforming into α phase.The stabilization effect was enhanced with the increase of the alkaline earths contents,whereas,the overabundance weakened the stabilization effect.Among the alkaline earths,strontium and calcium are the most effective promoters for inhibiting the reduction of surface area of Al2O3 sintered in air at 1 373K for 10 h.The study of the kinetics behavior of Al2O3 at 1 373K indicated that the stabilization of Al2O3 due to strontium and calcium was mainly attributed to that the alkaline earths played the retarding role of the sintering and α phase transformation within initial 1h during the calcination process.It was the dispersed oxide of alkaline earths but not aluminate that resulted in the stabilization of Al2O3 at high temperature.