alumina fiber is a high-strength ceramic material with good chemical resistance and thermal stability. It can be used as an insulating material in a wide range of applications such as aerospace & defense, automobile and high-strength refractory systems. It is also an excellent choice for metal matrix composites. It can replace other materials in applications such as fire insulation, noise absorption and battery separators because it is lighter, has superior mechanical properties and lowers thermal expansion.
Alumina is an excellent refractory material and can resist the erosion of molten metals and non-oxide materials at temperatures up to 1800degC, and maintains high purity even in reducing atmospheres. It has low electric conductivity, high strength, extreme hardness (9 on the Mohs scale) and a low coefficient of thermal expansion. It is suitable for use in abrasive environments and is easily machined.
The present invention relates to the preparation of alumina fibres in which at least part of the alumina is dispersed in the form of catalyst materials, preferably in its eta or alpha forms. The alumina can be present in the form of a solid or as a solution in water or other liquids. The fibres may be used as filler; reinforcement for resins, metals and ceramics; filters; or as catalyst supports or fibrous catalysts.
It is found that by combining the use of ammonia or a basic amine in conjunction with hydrothermal treatment, alumina fibres are obtained having a mean BET surface area after calcination and a smaller mean crystalline size than is otherwise obtainable. This method is a simple and economical process, which can be applied to a broad variety of alumina precursors.