Thermal evolution of thin boehmite films

Using transmission electron microscopy, electron diffraction and resistance change measurements, the process of thermal evolution of thin boehmite ( alpha -Al sub 2 O sub 3 x H sub 2 O) films was studied. It has been shown that the crystal lattice of boehmite decomposes at a temperature of 670K, with simultaneous partial dehydration. Above 875K crystallization of gamma -Al sub 2 O sub 3 occurs and the morphology of the film changes from fibrous to granular. Annealing of gamma -Al sub 2 O sub 3 at 1300K results in its transformation into delta -Al sub 2 O sub 3 . At temperatures of 1475-1575K the transformation of delta -Al sub 2 O sub 3 into alpha -Al sub 2 O sub 3 was observed. Depending on the temperature of annealing, thin alpha -Al sub 2 O sub 3 films were composed of fine crystals or of large ( mu m) corundum crystals. The method of producing various aluminas in the form of thin films presented makes investigation of the structure transitions in aluminium oxides by means of transmission electron microscopy possible, and such films can be also used as supports for transmission electron microscopy studies of the model metal-oxide supported catalysts. 13 ref.--AA