Synthesis of γ-alumina coating by Combustion Chemical Vapour Deposition (C-CVD)

Abstract

Alumina coatings have been deposited on mild steel, stainless steel (ANSI-304), and silicon (100) using Combustion-Chemical Vapor Deposition (C-CVD) technique. Volatile and easy to prepare aluminum acetylacetonate (Al(acac)₃), dissolved in ethanol (0.001 to 0.01 M), was used as a precursor. A premixed diffusion type flame was used as the energy source. The temperature of the flame was controlled by adjusting fuel to oxidant ratio such that the precursor vaporized in the flame without undergoing decomposition. The flame containing the precursor vapor was directed onto the substrate at a glancing angle of 45° for obtaining uniform coating over large surface area. Adherent coatings were obtained on mild steel and silicon; where as the coatings on stainless steel were not very adherent. SEM examination of the microstructure yielded an estimation of cluster size of 400-800 nm. The critical load for coating failure evaluated using an automated scratch-adhesion tester were 5.5 N, 9 N and 12 N on stainless steel (SS), mild steel (MS) and silicon (Si), respectively.