Fabrication of transparent self-supporting alumina films by homogeneous precipitation process

This paper reports fabrication of transparent self-supporting alumina films by using homogeneous precipitation and peptization processes. White precipitate of aluminum hydroxide was prepared with a homogeneous precipitation method using aluminum nitrate and urea in aqueous solution. The obtained aluminum hydroxide precipitate was peptized by using acetic acid at room temperature, which resulted in production of a transparent alumina sol. The alumina sol was transformed to an alumina gel film by drying the sol at room temperature. The alumina film was amorphous or fine crystallites even after annealed at a temperature as high as 500 degrees C, and was crystallized to gamma-Al2O3 at 900 degrees C. (C) 2013 The Ceramic Society of Japan. All rights reserved.