Since the discovery of hydride superconductors, a significant challenge has been to reduce the pressure required for their stabilization. In this context, we propose that alloying could be an effective strategy to achieve this. We focus on a series of alloyed hydrides with the AMH₆ composition, which can be made via alloying A15 AH₃ (A = Al or Ga) with M (M = a group ⅢB or IVB metal), and study their behavior under pressure. Seven of them are predicted to maintain the A15-type structure, similar to AH₃ under pressure, providing a platform for studying the effects of alloying on the stability and superconductivity of AH₃. Among these, the A15-type phases of AlZrH₆ and AlHfH₆ are found to be thermodynamically stable in the pressure ranges of 40–150 and 30–181 GPa, respectively. Furthermore, they remain dynamically stable at even lower pressures, as low as 13 GPa for AlZrH₆ and 6 GPa for AlHfH₆. These pressures are significantly lower than that required for stabilizing A15 AlH₃. Additionally, the introduction of Zr or Hf increases the electronic density of states at the Fermi level compared with AlH₃. This enhancement leads to higher critical temperatures (T_c) of 75 and 76 K for AlZrH₆ and AlHfH₆ at 20 and 10 GPa, respectively. In the case of GaMH₆ alloys, where M represents Sc, Ti, Zr, or Hf, these metals reinforce the stability of the A15-type structure and reduce the lowest thermodynamically stable pressure for GaH₃ from 160 GPa to 116, 95, 80, and 85 GPa, respectively. Particularly noteworthy are the A15-type GaMH₆ alloys, which remain dynamically stable at low pressures of 97, 28, 5, and 6 GPa, simultaneously exhibiting high T_c of 88, 39, 70, and 49 K at 100, 35, 10, and 10 GPa, respectively. Overall, these findings enrich the family of A15-type superconductors and provide insights for the future exploration of high-temperature hydride superconductors that can be stabilized at lower pressures.

无粘结剂cBN材料制作的切削刀具韧性较差, 并且这种材料的合成压力高。为此, 本研究在工业压力下制备了超硬、高韧的新型无粘结剂层状BN增韧cBN (Lt-cBN)块材, 通过切削硬质合金实验, 分析了Lt-cBN材料内部微观结构对其切削性能和耐磨性的影响。研究结果表明: Lt-cBN材料的韧性高达8.5 MPa·m^1/2, 可超精密切削硬质合金, 获得了粗糙度R_a低于10 nm的超光滑表面; Lt-cBN材料内部存在少量层状BN, 不仅提高了韧性, 还降低了表层材料的非晶化程度及磨损速率; 相对于商品化的纯相cBN材料, Lt-cBN材料展现出更好的切削性能和耐磨性; Lt-cBN材料的主要磨损形式为后刀面的部分非晶化, 并在摩擦作用下逐渐被去除而导致的磨料磨损。

Diamonds may not be forever, but research interest in diamond has never ebbed. Owing to its highly symmetric crystal structure and strong covalent C–C bonds, diamond possesses an exceptional combination of physical properties. Its hardness and thermal conductivity are the highest among covalent materials. It also has a large bandgap and electric breakdown field, as well as optical transparency over a wide range of wavelengths. All of these are essential for a wide range of applications in both industrial and scientific areas. Despite these outstanding advantages, however, diamond is extremely brittle, with inferior toughness and poor deformability. These shortcomings have caused undesired tool breakage and have imposed severe constraints on technological innovations. To surmount these intrinsic deficiencies, tremendous research effort has been dedicated to developing advanced diamond products, with great progress being achieved in the past few years.