Aluminium titanate is synthesised by solid state reaction of alumina and titania at >1350°C. The powder produced may be sintered at 1400°C - 1600°C in air depending on its reactivity.

Aluminium titanate forms a psuedobrookite crystal structure.

Ceramics manufactured from aluminium titanate exhibit extremely good resistance to thermal shock. This is due largely to the very low thermal expansion coefficient, which arises from significant anisotropy in the material's properties. Expansion in the a- and b-axes direction is positive whereas in the c-axis direction thermal expansion is negative. In addition to generating almost zero thermal expansion, this has the effect of causing microcracks to form in the sintered material resulting in the relatively low strength of the material. Additives such as SiO2 and MgO are used to minimise strength degradation and strengths up to 100MPa have been quoted for experimental materials.
Key Properties

Key properties of aluminium titanate are summarised in table 1.

Table 1. typical physical properties for aluminium titanate.

Property




Density


3 - 3.4 g.cm-3

Modulus of Rupture @ RT


30MPa

Modulus of Rupture @ 1000°C


60MPa

Young's modulus


20GPa

Thermal expansion (20-600°C)


0 -1 x10-6 K-1

Thermal expansion (600-1000°C)


1-2 x 10-6 K-1

Thermal conductivity (RT-1000°C)


< 2W.m.K-1

Maximum service temperature


1000°C continuous
1100°C intermittent

Thermal shock resistance


Excellent

Resistance to molten metals


Good

Applications

The excellent thermal shock resistance and low thermal conductivity coupled with good chemical resistance to molten metals (particularly aluminium) result in the material fulfilling several metal contact applications in the foundry industry including:

· Crucibles

· Launders

· Pouring spouts

· Ladles

· Riser tubes

· Plugs etc

Components made from aluminium titanate exhibit significantly longer operating life than competing materials such as calcium silicate and fused silica.

Aluminium titanate is also used in the automotive industry as an insulating liner for exhaust manifolds where there is a need to minimise heat loss in advance of a turbocharger. In this application the metal exhaust manifold is cast around the shaped aluminium titanate liner. The thermal expansion mismatch between the steel manifold and the aluminium titanate during cooling maintains the ceramic in compression thereby overcoming the problems of its low strength.