Optimisation of processing parameters on formation of silica coating on nickel substrates by sol–gel processing

Abstract

A silica coating was deposited on the nickel substrate by the sol–gel process, and the structure and composition were evaluated. The sols were made from several acid catalysts, including HNO₃–HCl, CH₃COOH, HCl, a base catalyst (NH₄OH, NH₃) and two step catalysts such as CH₃COOH–NH₃. To produce adherent silica coatings on nickel, various additives such as surfactants, viscous additives and drying control chemical additives were introduced to the system, and appropriate drying and firing cycles were applied after dipping in solution. The structure and uniformity of the coatings were examined by SEM. Coating compositions were studied by glow discharge optical spectroscopy and EDAX microanalysis. The results indicate that a uniform coating of silica can be produced on a nickel substrate by optimising the composition of the sol and the process variables.