Mixed ceramics

Mixed ceramics are defined as double- or multiphase (composite) materials, the components of which consist of different ceramic materials. The aim in this is the synergetic combination of the favourable properties of the different ceramics. The probably most well known example of this is ZTA (Zirconia Toughened Alumina) in which between 12 and 25 % of zircon oxide are deposited in an aluminium oxide matrix. By means of this a ceramic material can be produced which is characterized both by a high flectional strength and a high fracture toughness.

The situation is similar with regard to silicon carbide/ boron carbide mixed ceramics. In this case, the boron carbide phase safeguards a high fracture toughness and mechanical stability so that such mixed ceramics provide optimum body and vehicle armour. The reverse is true with regard to silicon carbide/graphite mixed ceramics. In this case, the graphite phase safeguards improved lubricating properties so that such mixed ceramics are perfectly suited as wear-resistant slide valves in dry running pumps or for tribological special applications.

The number of possible mixed ceramics is almost infinite even though the advantageous combination of the properties of different ceramics in a mixed ceramic only works with the corresponding know-how and experience. In the production all common ceramics processing technologies, such as dust pressing, slip casting or pressure diecasting and electrophoretic precipitation, are used. Depending on the respective system, densification is effected via solid or liquid phase sintering.