Densification and Structure Evolution of ZrB₂-ZrO₂ Composites Prepared by Plasma Activated Sintering using ZrB₂@ZrO₂ Powder

Abstract

The densification and the structure evolution of the plasma activated sintered (PAS sintered) ZrB₂-ZrO₂ composite via the ZrO₂-coated ZrB₂ powder (ZrB₂@ZrO₂) prepared by in situ passivation method were investigated. The composition and microstructure were characterized by XRD, Raman, SEM, and EDS techniques. The coated powder has excellent sintering performance. The relative density of the composite reaches above 90% at 1 200 °C, and the main sintering process occurs between ZrO₂ particles. While at above 1 500 °C, the relative density reaches above 95% and the main sintering process occurs between ZrB₂ and ZrO₂ particles. With the increase of ZrO₂ coating content, the structure of the sintered body changes from ZrB₂ continuous network structure to island structure. When the content is 20%, an island structure is formed. Increasing the ZrO₂ content further causes the overheating of ZrO₂. Thus, the best sintering performance reaches when the coating content is 20wt%.

Keywords

ZrB₂ / ZrO₂ / coating content / densification / structure evolution