Fabrication and properties of zirconium diboride-based ceramics for UHT applications

The present study focuses on innovative processing for the densification of ZrB2-based ceramics, suitable to fabricate components for UHT applications such as TPS systems. The addition of small quantities (2-5 vol%) of sintering aids allows to overcome the intrinsic low sinterability of zirconium diboride and to improve properties through the microstructural refinement. The introduction of second refractory phases, for instance 20 vol% of SiC in a ZrB2 matrix, has been tested with the aim to improve strength, toughness and oxidation resistance. The outstanding properties of the as produced monolithic and composite ZrB2-based ceramics show attractive data ranges: fracture toughness 3-5 MPam1/2, hardness 9-15 GPa, elastic modulus 350-420 GPa, electrical resistivity about 10 μωcm, flexural strength 300 to 750 MPa at R.T and up to 300 MPa at 1500°C. Finally, the resistance to oxidation of different materials was compared.