Synthesis and properties of functionally-gradient aluminium titanate mullite-ZTA composites

摘要

Aluminium titanate (AT), mullite and zirconia-toughened alumina (ZTA) are important ceramic materials with quite distinctive properties. ZTA is much tougher (6-9 MPam1/2) and stronger (>500MPa) than both AT (1-2 MPam1/2, <60MPa) and mullite (2-3 MPa m1/2, <200 MPa). However, ZTA (a " 8 x 10"6 K~') has much poorer thermal shock resistance than either AT (alx 1(T6 K-1) or mullite (a"4.5 x 10"6 K1). It follows that a composite with high strength, toughness and thermal shock resistance could be produced by incorporating these three phases in a composition graded microstructure. Such a composition graded functionally-gradient material (FGM) can overcome the possibility of a chemical incompatibility between the materials on either side of the interface, which may give rise to residual stress induced failure or interfacial debonding as a result of thermal expansion mismatch. It has been reported the presence of mullite and/or zirconia can reduce the grain size and porosity, and improve the mechanical properties of AT [1-3]. Functionally-gradient AT-alumina composites with promising properties have also been fabricated recently by Low et al. [4].