Preparation of ZrB₂-based nanocomposites with limited grain growth by means of low-temperature hot-pressing using Cu additive

The purpose of the present study is to prepare ZrB₂-based nanocomposites with limited or no obvious grain growth. For ZrB₂ nanoparticles, the densification on-set temperature was about 1300 °C, whereas the obvious grain growth on-set temperature for ZrB₂ nanoparticles was found to be about 1500°C. Therefore, there was a temperature "window" 1300-1500°C where ZrB₂ nanoparticles could be densified with limited or no grain growth. In this study, densification of ZrB₂-based nanocomposite was finally realized by means of low-temperature hot-pressing at 1450°C for 60 min under a uniaxial pressure of 30 MPa using Cu as a sintering additive. After hot-pressing, the grain growth of ZrB₂ nanoparticles was greatly suppressed, and the average grain size for ZrB₂ was only 310 nm. The microstructure and mechanical properties were examined, and the flexural strength and fracture toughness were 472.8 ± 36.4 MPa and 12.4 ± 0.5 MPa · m ^1/2, respectively. We believe this paper can lay the foundation for the preparation of ZrB₂-based nanocomposites.