Structure characterization of alumina-silica coatings prepared on polyimide substrate by sol-gel

摘要

Alumina-silica coatings were prepared on polyimide substrate by sol-gel method using aluminium isopropoxide and tetraethyl orthosilicate as the precursors. The molar ratios of Si/Al were designed as 1:3, 1:1 and 3:1. The surface morphology and structure of as-deposited coatings were investigated by various complementary analysis techniques. The results indicate that all silica-alumina coatings show a smooth and dense surface and have a thickness of ~400 nm. After treatment at 230℃, the alumina-silica coatings are a diphase structure of AlOOH and amorphous silica, the same as the corresponding gel powders. Moreover, after calcination at 550℃, the alumina-silica gel powders still remain a diphase structure, but AlOOH transforms into γ-Al_2O_3. The Si content has no obvious effect on the phase structure. However, increasing the Si/ Al ratio in the as deposited coatings causes the binding energies of Si 2p, Al 2p and 0 1s peaks to shift to higher energy.