Processing, structure and properties of ceramic fibers

Ceramic fibers are small-dimension filament or thread composed of a ceramic material, usually alumina and silica, used in lightweight units for electrical, thermal, and sound insulation.

Ceramic fibers are also mostly used as refractory fibers in uses over 1000 °C and are characterized by a polycrystalline structure rather than amorphous. Refractory ceramic fibers are mostly used for thermal insulation at high temperatures and to make special composites. They are very expensive fibers because only a small quantity is produced and they are used in particular fields such as aerospace.

Ceramic fibre is manufactured with different qualities depending on the production method: the spun and the blown fibre. A spun fibre yields the strongest, but also the most expensive product. In most fields of application the two types of fibre function in the same way, and therefore the spun fibre is the most commonly used type.

Another commonly used type of ceramic fibre is blankets that are manufactured by placing the spun fibre on a conveyor belt. The belt speed and the thickness of the fibre layer determine the two most important quality parameters: density and thickness. The fibre blankets are frequently impregnated, felted, burnt and cut in order to achieve the well-known standard products. The standard fibre blankets are available in the density range 100 to 160 kg/m3 and in thicknesses from 13–50 mm.

Ceramic fibres are also available as massive boards, specially designed modules and wet blankets that are impregnated with a liquid making it possible to form the fibre products into the wanted shape that will remain after heating. Because of their unique (high temperature) properties ceramic fibres are rarely used in conventional thermal insulation applications in buildings