Pressureless Sintering of High‐Density ZrB ₂ –SiC Ceramic Composites

Abstract

Ultra‐high‐temperature ceramic composites of ZrB 2 20 wt%SiC were pressureless sintered under an argon atmosphere. The starting ZrB 2 powder was synthesized via the sol–gel method with a small crystallite size and a large specific surface area. Dry‐pressed compacts using 4 wt% Mo as a sintering aid can be pressureless sintered to ∼97.7% theoretical density at 2250°C for 2 h. Vickers hardness and fracture toughness of the sintered ceramic composites were 14.82±0.25 GPa and 5.39±0.13 MPa·m 1/2 , respectively. In addition to the good sinterability of the ZrB 2 powders, X‐ray diffraction and scanning electron microscopy results showed that Mo formed a solid solution with ZrB 2 , which was believed to be beneficial for the densification process.