Processes
Alumina-zirconia composites are typically created by mixing these two materials in suspension. A differentiation is made between ZTA (Zirconia Toughened Alumina), alumina matrix, and ATZ (Alumina Toughened Zirconia), zirconia matrix. The key stage in the creation of these composites is the mixture and homogenisation of two powders which produces a homogeneous and very thin microstructure.
The ceramics are shaped using traditional processes (pressing, injection, extrusion), then sintered between 1,400°C and 1,700°C, according to the reactivity of the powder.
Properties
The main advantage of this type of material is the combining of the properties of alumina and zirconia, and being able to optimise the composition according to the intended application. For example, more zirconia can be used for an application requiring resistance to shocks, and more alumina can be used for applications requiring resistance to wear. ZTAs thus combine very high hardness (> 18GPA) with high tenacity (>5 MPa.s-1).
ZTAs are particularly known for their biocompatibility, resistance to wear and thermal shocks, and for their resistance to hydrothermal ageing.
Applications
Alumina-zirconia composites are widely used in the following applications: medical (in particular orthopaedic prosthetics), cutting tools, wear-resistant components (thread guides, bearings, nozzles, etc.), fluid management (filling pumps, ball valves, anti-abrasion and anti-corrosion coatings).