Modification of ZrB2 powders by a sol–gel ZrC precursor—A new approach for ultra high temperature ceramic composites

Abstract

A simple method of integrating a powder processing technique with a sol–gel process to produce ultra high temperature ceramic (UHTC) composites is reported. ZrB2 powder was treated with a zirconium oxide-carbon sol–gel coating. Carbothermal reduction produced nanosized crystalline ZrC grains on the surface of ZrB2 powder. Detailed refinement of carbon content in the sol–gel coating was necessary to control the oxide reduction on the ZrB2 surface, while providing intrinsic carbon for the nanoparticle sol–gel phase. Microstructures and crystalline phases were analyzed using TEM, SEM, and XRD. It was found that carbothermal reduction of ZrO2 to form nano ZrC can be completed on the surface of ZrB2 at 1450 °C. The sol–gel coating creates a homogenous mix of ~200 nm ZrC in close proximity to the ZrB2 surface. Densification of the ZrB2-ZrC composite can be achieved by spark plasma sintering at 1800 °C. The amount of carbon added to the sol–gel precursor needs to be carefully tailored to dictate the final porosity and grain size of sintered composites.