碱土金属修饰Al_2O_3的表面热稳定性

Surface Area Stability of Al_2O_3 Modified by Alkaline Earths

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1373K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1h内的烧结和α相变引起的比表面积损失.

The thermal stabilization mechanis m of Al 2 O 3 modified by alkaline earths using im pregnation method with various contents and calculati on time was studied by BET surface are a and powder X-ray diffraction.It wa s found that the addition of alkaline e arths increased the surface area of A l 2 O 3 and retarded the transforming intoαphase.The stabilization effect was enhanced with the increase of the alk aline earths contents,whereas,the over-abundance weakened the stabilization effect.Among the alkaline earths,strontium and calcium are the most effec-tive promoters for inhibiting the re duction of surface area of Al 2 O 3 sintered in air at 1373K for 10h.The s tudy of the kinetics behavior of Al 2 O 3 at 1373K indicated that the stabiliz ation of Al 2 O 3 due to strontium and calcium was mainly attributed to that the alkaline earths played the retarding role o f the sintering andαphase transformation within initial 1h during the calcination process.It was the dispersed ox ide of alkaline earths but not alumin ate that resulted in the stabilization of Al 2 O 3 at high temperature.