Unlocking superior mechanical properties: the synergistic enhancement of hardness and fracture toughness in nanopolycrystalline tantalum diboride

作者：Shuailing Ma, Yufei Ge, Min Lian, Xiaobai Ma, Pinwen Zhu, Akhil Tayal, Xingbin Zhao, Wei Li, Hao Song, Zihan Zhang, Yunxian Liu, Xiaobing Liu, Tian Cui · 发表于：Advanced Powder Materials · 年份：2025 · DOI：10.1016/j.apmate.2025.100374 · 被引用次数：3 · 研究领域：Boron and Carbon Nanomaterials Research、Advanced ceramic materials synthesis、MXene and MAX Phase Materials

Achieving optimal mechanical properties, including hardness and fracture toughness, by controlling grain size is a fundamental and long-standing objective in the development of hard and superhard transition metal borides (TMBs) ceramics. It is expected that the mechanical performance of TMBs will be substantially enhanced in nano-crystalline ceramics. However, the fabrication of dense, nano-scale TMBs compacts presents challenges due to poor sintering behavior and pronounced grain growth at high temperature. Here, thanks to the pressure reduced activation energy effect, nano-polycrystalline tantalum diboride (NP-TaB 2 ) monoliths were fabricated under high pressure and moderate temperature conditions. These NP-TaB 2 bulks achieve dense microstructure with an average grain size as fine as 36 nm, due to the high nucleation rates and minimal grain growth induced by high pressure. With the decreasing of grain size, the hardness of NP-TaB 2 reaches up to 27.5 GPa by the Hall-Petch effect, making it nearly 45% harder than dense, micron-scale grain specimens. Additionally, the fracture toughness of NP-TaB 2 is enhanced by 70% at the same time in the nano scale specimens, attributed to the effective energy dissipation by nano grains through crack deflection, branching, and bridging, which enhances fracture toughness with synergistic hardness improvement. This discovery demonstrates that correlating grain size and microstructure with mechanical properties offers valuable insights for ...