Lu Cheng, Chen Changfeng
School of Mathematics and Physics, China University of Geosciences (Wuhan), Wuhan 430074, China.
Department of Physics and Astronomy, University of Nevada, Las Vegas, Las Vegas, Nevada 89154, United States.
J Phys Chem Lett. 2021 Mar 25;12(11):2848-2853. doi: 10.1021/acs.jpclett.1c00434. Epub 2021 Mar 15.
Zirconium diboride (ZrB) is an important ultra-high-temperature ceramic, which exhibits outstanding mechanical properties and is widely used in extreme environments. Extensive experimental studies, however, have found that synthesized ZrB specimens show widely scattered indentation hardness values ranging from 8.7 to 26 GPa. We have performed comprehensive stress-strain calculations of ZrB to explore its structural and stress responses and found that ZrB possesses an intrinsic indentation strength of 32.7 GPa, which is on par with those of other transition-metal borides that exhibit higher indentation hardness values of ∼30 GPa. This result suggests that large variations in measured hardness are driven by extrinsic factors, and an analysis of available experimental data indicates that the quality of the crystallinity of specimens holds the key to realizing improved hardness corresponding to the predicted intrinsic indentation strength. These findings offer insights into the origin of the previously reported lower hardness values of ZrB and raise the prospects of achieving superior strengths in well-crystallized ZrB that approach or match those of other ultrahard transition-metal compounds.
二硼化锆（ZrB）是一种重要的超高温陶瓷，具有出色的机械性能，广泛应用于极端环境。然而，大量实验研究发现，合成的ZrB试样的压痕硬度值分散性很大，范围在8.7至26吉帕之间。我们对ZrB进行了全面的应力-应变计算，以探索其结构和应力响应，发现ZrB的固有压痕强度为32.7吉帕，这与其他压痕硬度值约为30吉帕的过渡金属硼化物相当。这一结果表明，测量硬度的巨大差异是由外在因素驱动的，对现有实验数据的分析表明，试样的结晶度质量是实现与预测的固有压痕强度相对应的硬度提高的关键。这些发现为先前报道的ZrB较低硬度值的起源提供了见解，并提高了在结晶良好的ZrB中实现接近或匹配其他超硬过渡金属化合物强度的卓越强度的前景。
