LAUSR

Abstract Multi-stage Spark Plasma Sintering (MS-SPS) of ZrB 2 -20 vol% SiC-10 vol% Si 3 N 4 (ZSS) and ZrB 2 -20 vol% SiC-10 wt% Ta (ZST) composites were carried out at 1900 °C for 3 min to densify the ZrB 2 -based composites. The microstructure of ZSS composite consisted of new secondary phases (ZrO 2 , BN, ZrN) along with SiC and ZrB 2 . Interestingly, ZST sample exhibited core-shell/rim structure and it comprised of ZrB 2 core, (Zr,Ta)B 2 rim, SiC, ZrO 2 and (Zr,Ta)C phases. The presence of new phases and annihilation of Si 3 N 4 or Ta additive in both the sintered samples was clear indication of involvement of sintering reactions. The SEM of cross sectional samples revealed presence of three distinctive layers for the ZrB 2 samples after the isothermal oxidation at 1600 °C for 10 h. In particular, no SiC depleted layer was observed for ZSS and its presence was evident in ZST composite. The weight gain (varied between 15.25 and 16.66 mg/cm 2 ) of the ZrB 2 composites was comparable and significant difference in the oxide layer thickness (changed from 255 to 476 μm) was noticed. Overall the ZST sample offers better oxidation resistance in view of protective nature of its oxide layer.