SA-Tyrannohex-Based Composite for High Temperature Applications

Abstract

To modify the relatively low fracture toughness of monolithic ceramics, the incorporation of long ceramic fibre within a matrix material has been extensively performed. In this case, as cracks form in the matrix material and approach the fibres, they will be deflected at the interface between the fibre and the matrix. We developed another approach toward improving the toughness of ceramics involving the creation of a textured internal structure within the ceramic itself, similar in some respects to the fibrous structure of wood. Actually, we developed a tough ceramic, which consists of a highly ordered, close-packed structure of very fine hexagonal columnar fibres with a thin interfacial carbon layer between fibres. The interior of the fibre element was composed of sintered beta-silicon carbide crystal. This concept is fundamentally different from that described previously, in that it is extremely difficult to distinguish separate “fibre” and “matrix” phases in the traditional composite sense. The toughness of the material in this case derives from the tremendous amount of interface area created within the internal structure through the close packing of the hexagonal columnar fibres. Furthermore, this ceramic also achieved the excellent high temperature properties, high thermal conductivity and low density. These properties will make it very attractive for replacement of heavy metal super alloy components.