NEW AND MODIFIED ANODIC ALUMINA MEMBRANES .1. THERMOTREATMENT OF ANODIC ALUMINA MEMBRANES

Polycrystalline anodic alumina membranes have been prepared by control led calcination. Phase transformations, porosity changes and conversio n of electrolyte impurities incorporated into the anodic alumina latti ce were studied as functions of the calcination temperature (up to 120 0 degrees C). A comparative IR investigation of hydroxyl cover of the polycrystalline anodic alumina membranes and pure gamma- and delta-alu mina was carried out. Amorphous anodic alumina films calcined at tempe ratures up to 800 degrees C with a barrier layer in place (thickness o f barrier layer ranged from 5 to 90 nm) were prepared and the permeabi lities measured, It is hypothesised that the thin layer of relatively pure and dense alumina of the anodic alumina cell prevents migration o f ions, water or small molecules through the barrier layer as well as between the adjacent cells.