Effect of ZrB2 powders on densification, microstructure, mechanical properties and thermal conductivity of ZrB2-SiC ceramics

Abstract

With the view to improve the densification behaviour and mechanical properties of ZrB2-SiC ceramics, three synthesis routes were investigated for the production of ZrB2, prior to the fabrication of ZrB2-20 vol. % SiC via spark plasma sintering (SPS). Two borothermal reduction routes, modified with a water-washing stage (BRW) and partial solid solution of Ti (BRS), were utilised, alongside a boro/carbothermal mechanism (BRCR) were utilised to synthesise ZrB2, as a precursor material for the production of ZrB2-SiC. It was determined that reduction in the primary ZrB2 particle size, alongside a diminished oxygen content, was capable of improving densification. ZrB2-SiC ceramics, with ZrB2 derived from BRW synthesis, exhibited a favorable combination of high relative density (98.6%), promoting a marked increase in Vickers hardness (21.4 ± 1.7 GPa) and improved thermal conductivity (68.7 W·m-1K-1).