Pressureless sintering of carbon-coated zirconium diboride powders

Abstract

Carbon-coated zirconium diboride powders were sintered to near theoretical density at temperatures as low as 1900 °C without an external pressure. Relative density increased from ∼70% for uncoated ZrB 2 to >99% for ZrB 2 coated with at least 1.0 wt% carbon. Thermodynamic analysis indicated that carbon reacted with and removed oxide impurities (ZrO 2 and B 2O 3) that were present on the particle surfaces, which promoted densification by minimizing grain coarsening. The effects of initial particle size and carbon content on densification, microstructure, and properties were investigated.