Evolution of microstructure in nonhydrolytic alumina xerogels

The effect of drying, aging and thermal treatment of alumina xerogels prepared by the nonhydrolytic route was investigated using SAXS, BET and HR-SEM techniques. The microstructure of the fresh xerogels prepared under different procedures varied drastically, ranging from aerogel-like mass fractals to narrow pore size distribution materials. By variation of the drying conditions the N₂-BET surface area was varied from an immeasurable low level up to 600 m²/g. The initial microstructure has a significant influence on the xerogel behaviour during the post-drying heating stage. The ability to produce aerogel-like mass fractal materials from the nonhydrolytic systems is discussed. Finally, a brief theoretical treatment of the drying process of mass fractals is presented as well.