POROUS ALUMINA FREE-STANDING FILM, ALUMINA SOL AND METHODS FOR PRODUCING SAME

摘要

Disclosed is a porous alumina free-standing film which has sufficient strength for use as a free-standing film as well as flexibility and high transparency.  Also disclosed are an alumina sol obtained by dispersing fibrous or needle-like boehmite particles in a solution and having high storage stability, and a method for producing the alumina sol.  The porous alumina free-standing film is an assembly of fibrous or needle-like alumina hydrate or alumina particles having an average breadth of 1-10 nm, an average aspect ratio (length/breadth) of 30-5,000 and an average length of 100-10,000 nm.  The porous alumina free-standing film has orientation, a pore distribution with a pore diameter (dpeak) of 0.5-20 nm, flexibility, high transparency, and an ability of emitting light when excited by ultraviolet light.  The alumina sol has Na, K and SO4 contents of 0-1 ppm and orientation upon particle assembly, and emits light when fired at 250-900°C and then excited by ultraviolet light.  Also disclosed are a method for producing the porous alumina free-standing film and a method for producing the alumina sol.