Enhanced Mechanical Properties and Oxidation Resistance of Zirconium Diboride Ceramics via Grain-Refining and Dislocation Regulation

Zirconium diboride (ZrB2) is considered as one of the most promising ultra-high temperature materials for the applications in extreme environments. However, the difficulty in fabrication of ZrB2 limits its industrial applications. In this study, fully dense and grain-refined ZrB2 is prepared under ultra-high pressure of 15 GPa at low temperature of 1450 degrees C. The as-prepared ZrB2 exhibits excellent mechanical and oxidation-resistant properties. Compared with raw powder, the grain size decreases 56%. Compared with high-temperature sintered control specimen beyond 2000 degrees C, the hardness and fracture toughness increase about 46% and 69%, respectively, the dislocation density increase 3 orders of magnitude, while the grain size considerably decrease 96%. According to work hardening, Hall-Petch and Taylor dislocation hardening effects, the refined grains, substructures, and high dislocation density caused by plastic deformation during sintering can enhance the mechanical properties. The unique structure contributes to a threshold oxidation temperature increase of approximate to 250 degrees C relative to the high-temperature sintered ZrB2, achieving one of the highest values (1100 degrees C) among the reported monolithic ultra-high temperature ceramics. A developed densification mechanism of dislocation multiplication with grain refining is proposed and proved to dominate the sintering, which is responsible for simultaneous improvements in mechanical and oxidation-resistant properties.

Automated summary

In this study, fully dense and grain-refined ZrB2 material with excellent mechanical and oxidation-resistant properties is prepared under ultra-high pressure at low temperature. The refined grains, substructures, and high dislocation density contribute to the enhancement of mechanical properties. The unique structure of ZrB2 leads to a significant increase in oxidation threshold temperature.