Abstract
The formation of aluminum titanate was investigated by isothermal treatments of samples obtained from equimolar mixtures of alumina and titania, containing small amounts of silica and magnesia. Results of differential thermal analysis and Rietveld refinements of data collected by X-ray powder diffraction (XRPD) showed that additions of silica in amounts used in this work did not influence the formation of aluminum titanate. However, the presence of magnesia favored the formation of aluminum titanate in two steps, first one by incorporating Mg2+ into Al2TiO5 lattice during its initial formation, and the second one by accelerating the Al2TiO5 formation, contributing to large quantities of this phase. MgO doped samples have also developed a more suitable microstructure for stabilizing of Al2TiO5, what make them promising for applications such as thermal barriers, internal combustion engines and support material for catalyst.
Highlights
Aluminum titanate ceramics (Al2TiO5) are promising materials for insulating applications in automotive industry, such as engine components, portliners, manifolds and linings of turbochargers[1,2]
Quantitative analysis with Rietveld refinements confirms the efficiency of MgO additions to Al2TiO5 formation
Additions of MgO provided prior formation of Al2TiO5 owing to a further endothermic reaction detected at low temperature
Summary
Aluminum titanate ceramics (Al2TiO5) are promising materials for insulating applications in automotive industry, such as engine components, portliners, manifolds and linings of turbochargers[1,2] This ceramic is suitable as catalyst carriers for purification of fume produced by cars, containers and tubes for storing or conveying melted steel as well as protective tube for thermocouples. The anisotropic behavior is due to the crystal structure of the Al2TiO5 which is isomorphous with pseudobrookite (Fe2TiO5), crystallizing in the orthorhombic space group Cmcm, with a theoretical density of 3.70 g/cm[3] Another problem associated with the formation of Al2TiO5 which has limited its application field is the eutetoid-like decomposition to α-Al2O3 and TiO2 (rutile) within temperature range from 900 to 1280oC6. This reaction accompanied by an 11% molar increase contributes to a microcracking process and to deterioration of the ceramic component[7,8]
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