Effect of ZrB2 Particle Size on Pressureless Sintering of ZrB2 - ß-Sic Composites

Rosa Maria da Rocha, Frank Ferrer Sene, Mariah de Oliveira Juliani, Carolyne Oliveira Davi

Abstract


Zirconium diboride is an ultra-high temperature ceramic material that leads this emerging class of materials because of its distinct combination of properties, including high melting temperature (> 3000 °C) and the lowest theoretical density      (6.09 g·cm–3) among the borides. This combination of properties makes ZrB2 candidate for airframe leading edges on sharp bodied reentry vehicles. In this work, the effect of particle size of ZrB2 on the pressureless sintering of ZrB2-SiC composites was studied, using ZrB2 powder with an average particle size of 2.6 and 14.2μm. Four different vol% concentration of ß-SiC (0, 10, 20 and 30 vol%) was added to as-received and planetary milled ZrB2 powder. Samples were pressureless sintered at 2050 °C/1h in an argon atmosphere. The reduction of initial ZrB2 particle size led to composites with better results of densification, mechanical properties and oxidation resistance regardless ß-SiC addition, showing relative densities around 92.5 %Theoretical Density (Td) and flexural strength and microhardness around 260 MPa and     17.5 GPa, respectively. Composites processed with as-received ZrB2 powder showed increasing in densification and flexural strength with the SiC content increasing. Relative density varied from 74.7 to 90.8 %TD and flexural strength from 102 to 241 MPa, for 0 and 30 vol% of SiC, respectively.

Keywords


Ultra high temperature ceramics; ZrB2; SiC; Sintering; Thermal protection system

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