Ultrafine ZrB<sub>2</sub> Ceramic Powders Prepared by a Sol–Gel Method Synergized with a Carbothermic Reaction and Their Improved Sintering Performance
Mengen Hu, Zhulin Huang, Xinyang Li, Yuan Cheng, Zhen Wang, Kewei Li, Tianxu Wang, Xiaoye Hu, Yue Li, Xinghong Zhang
Abstract
The sol–gel method synergized with a carbothermic reaction has been known to be one of the most promising strategies for preparing a high-quality boride and carbon-based ultrahigh-temperature ceramic, yet their growth mechanism remains underexplored. Herein, high-purity ZrB 2 ceramic powders are prepared by a sol–gel method synergized with a subsequent carbothermic reaction. Specifically, sorbitol (C 6 H 14 O 6 ) is adopted to build molecularly disperse networks of Zr–O–C–B. Structural characterizations reveal that the calcination temperature and duration have a great influence on the phase and morphological transformation of the precursor. The ZrB 2 seeds start to be generated near ZrO 2 particles around 1100 °C and grow from the surface to the core of ZrO 2 particles with heat and mass transportation around ZrO 2 driven by B 2 O 3 at high temperature. Additionally, the ZrB 2 powders could research a hardness of 22.5 GPa and a bending strength of 540 MPa after sintering, showing improved mechanical properties. This work reveals the growth mechanism of ultrafine and high-purity ZrB 2 powders by a sol–gel method and a carbothermic reaction, which can be used as raw materials to obtain ZrB 2 ultrahigh-temperature ceramics with improved mechanical properties.