| 摘要 |
A method of manufacturing an alumina film comprises the steps of forming a porous alumina frame 5-20 m thick on one side of an aluminium foil by anodic oxidation, forming an alumina film on the same side of the foil by anodic oxidation of the foil enclosed by said frame such that the film and the frame are integral, and then removing the remaining metallic aluminium with the aid of a reagent which dissolves aluminium but does not appreciably attack the alumina. The porous alumina frame may be formed using an oxalic acid or sulphuric acid electrolyte and the alumina film, which may be about 0.1 m thick, may be formed using a 4% aqueous solution of tartaric acid or a 6% aqueous solution of boric acid containing 1.5% sodium borate. The reagent used to dissolve the metallic aluminium may be a mixture of hydrofluoric and nitric acids or a mixture of chromic and phosphoric acids. The film may be formed with two concentric annular frames, the outer being later cut away. A vopour deposited layer, e.g. of PbO may be formed upon the alumina film. |
