Densification and properties of in-situ synthesized ZrB2-SiC composities from ZrO2, B4C and SiC system

Abstract

Zirconium diboride-silicon carbide (ZrB2-SiC) ceramics were in-situ synthesized and densified by the spark plasma sintering (SPS) method using ZrO2, B4C and SiC as starting powders. Both synthesis and densification processes were successfully accomplished in a single SPS cycle with one step heating schedules which were designed by considering thermodynamic calculations made by Factsage software. One step synthesis/densification schedule at 1950 degrees C with a 30 min hold time under 50 MPa uniaxial pressure lead to obtain ZrB2-SiC ceramics up to 93% of its theoretical density. Considering the literature, low hardness values (max. 17.55 GPa) were achieved which were directly attributed to the low bonding between ZrB2 and SiC grains in terms of the residual stresses occurred during the synthesis and cooling steps. Fracture toughness of the ceramics was 4.12 MPa.m(1/2) and crack deflection and microcracking were believed to be primary toughening mechanisms of ZrB2-SiC composites.