The evolution of microstructure in nonhydrolytic alumina xerogels

The effect of drying, aging and thermal treatment of alumina xerogels prepa red by the nonhydrolytic route was investigated using SAXS, BET and HR-SEM techniques. The microstructure of the fresh xerogels prepared under differe nt procedures varied drastically, ranging from aerogel-like mass fractals t o narrow pore size distribution materials. By variation of the drying condi tions the N-2-BET surface area was varied from an immeasurable low level up to 600 m(2)/g. The initial microstructure has a significant influence on t he xerogel behaviour during the post-drying heating stage. The ability to p roduce aerogel-like mass fractal materials from the nonhydrolytic systems i s discussed. Finally, a brief theoretical treatment of the drying process o f mass fractals is presented as well.