Abstract
The forming and thermal stability of a coat layer was investigated through a simple suspension-dipping procedure of aqueous La-modified γ-Al2O3 suspension. The effect of La on the stabilization of surface area for powder, and the morphology of coat layers, which are heated at elevated temperatures, were examined by X-ray diffraction, nitrogen adsorption and scanning electron microscopy. The La-addition stabilized the metastable phases of Al2O3 at temperatures up to 1200'C, and induced the increase of phase-transformation temperature to α-Al2O3. The surface area of pure Al2O3 layer decreased after heat treatment at 900-1200°C. Several factors for controlling the formation of a coat layer from La-modified γ-Al2O3 suspension were discussed. A fabricated La-modified alumina layer was stable to realize high surface area as well as homogeneous shape without large cracks after heat treatment under heating condition at 1100°C in air.
