Technical ceramics are not to be confused with traditional ceramics. Traditional ceramics are generally made from primarily natural raw materials. In some cases, these materials can be used immediately after being extracted, while in others they are only suitable for use after one or more purification processes.
Natural and synthetic raw materials
Technical ceramics use primarily synthetic raw materials that are either not found in nature or extremely rare and are difficult to obtain or synthesize. The natural raw materials that are used in the manufacture of technical ceramics must first be refined to a precisely defined level of quality in terms of purity, particle size distribution and granular form.
The most commonly used natural raw materials that go into these ceramics are bauxite, from which aluminium oxide (Al2O3) extracted using the Bayer process, and zircon sand (ZrSiO4) for the preparation of zirconium oxide (ZrO2). Two commonly used synthetic raw materials that can be produced chemically are silicon carbide (SiC) and silicon nitride (Si3N4).
Three material groups
The world of technical ceramics roughly comprises three groups of materials:
- Oxide ceramics
Al2O3, SiO2, ZrO2, Y2O3, TiO2, MgO, ZnO, Al2TiO5
- Non-oxide ceramics
SiC, Si3N4, TiC, TiN, AlN, B4C, TiB2, ZrB2
An example of this is carbon fibre in a matrix of SiC, which is the compound used for ceramic brake discs. Another example would be nano-SiC particles in a matrix of Al2O3 for increased strength and durability. The composite ZTA - ZrO2 particles in Al2O3 – has similar properties.
Furthermore, there are combined ceramic materials such as 'SiAlON's, which get their specific properties from the combination of their individual elements. These materials offer exciting potential for many extraordinary properties and are currently the subject of much research. For example, with certain additives (impurity doping) the ceramic material can be given optical properties (fluorescence).