日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

Boehmite nanomaterials can be produced in various forms by hydrothermal synthesis. Under appropriate conditions, nanofibers with aspect ratios exceeding 1000 can be produced, and their dispersions are industrially available. Boehmite nanofibers can be used as a raw material to fabricate various three-dimensional structures. For example, adding a base or phosphoric acid to a boehmite nanofiber dispersion results in gelation within a few minutes. Drying this gel yields a characteristic porous material (aerogel) with ultralow bulk density and high visible light transmittance. This fibrous porous material has a skeletal structure with almost no necks and thus exhibits higher mechanical strength than granular skeletal aerogels reported for silica and other materials. Macroporous materials formed by compositing boehmite nanofibers with polymers have high handling and processing properties despite their light weight. By changing the type of polymer used, functions such as liquid repellency and flame resistance can be added. This paper describes the physical properties of boehmite nanofibers, various porous materials obtained by sol-gel reaction, and their applicability.