Permeable anodic alumina film

摘要

A permeable anodic alumina film is described in which amorphous anodic alumina is in the form of a thin layer of film (3) and is initially in communication with the alumina substrate (1) and has an array of blind pores (5) or holes opening into one surface of the thin layer (3). The alumina substrate (1) is removed from the alumina layer by electrochemical treatment which opens the blind pores (5) of the amorphous anodic alumina thereby forming an amorphous permeable film (16) with open pores (6), which are of substantially the same diameter, extending from one side of the film to the other side. In another aspect the electrochemical treatment causes cracks or micropores (9) to form within and extending through the barrier layer (7) and which provide communication between the bottom of the bores and the far side of the barrier layer. This results in the alumina substrate layer becoming detached. The alumina permeable film may be heated to convert the alumina permeable film to the crystalline alumina permeable film.