Influence of SiC content to control morphology of in-situ synthesized ZrB2–SiC composite through single-step reduction process

Abstract

The present work focuses on the influence of SiC content on the morphology and microstructure of in-situ synthesized ZrB2–SiC composite using ZrO2, B4C and Si via a single-step reduction process under argon atmosphere. The ZrB2–SiC composite was synthesized with variation in mole content of starting reactant and calcination temperature. The molar ratio of ZrO2:B4C:Si was increased from 2:1.5:0.5 to 2:1.67:1.34 at 1300–1500 °C, resulting SiC content increased and average grain size reduced. Major phase of ZrB2 and SiC were detected in the composite using XRD and XPS techniques. Morphology and microstructure of synthesized ZrB2 and SiC were determined by SEM and TEM analysis. The results revealed that a homogenous layer of uniformly dispersed SiC particles was exhibited over the surface of rod and spherical granulation of ZrB2, which restricted the grain growth of ZrB2 particles during synthesis. With increasing the SiC content, the pinning effect on the grain boundary enhanced the dense structure of ZrB2–SiC composite. The feasibility of reaction for the synthesis of ZrB2–SiC composite was confirmed by thermodynamic calculation and experimental results. It can be concluded from experimental results that the composite was synthesized below the thermodynamically calculated synthesis temperature due to maintaining moderate vacuum backfilled by argon.