Various anodizing conditions and follow-up processes have been investigated to obtain films that have fine pores and are transparent in the infrared region One of the most successful minimizations of pore diameter was achieved by a combination of reducing the voltage in the process of forming a film in oxalic acid, and sealing the film with humidity. This film has fine pores at the section near the barrier layer, pore diameter was estimated at 1nm by measuring the dependence of gas permeability on the molecular diameter of different gases The pores are so fine that the separation factor for...