标题： 六边形层状碳化物和氮化物作为超高温度陶瓷的探索 显示英文标题

标题： Exploration of Hexagonal, Layered Carbides and Nitrides as Ultra-High Temperature Ceramics

摘要： 层状六方晶体结构，如ζ相和η相，在超高温度陶瓷中起着重要作用，通常显著提高碳化物复合材料的韧性。 尽管它们很重要，关于其结构、稳定性和组成普遍性仍存在开放问题。 我们使用高通量密度泛函理论来表征层状碳化物和氮化物M$_{n+1}$X$_{n}$的热力学稳定性和弹性常数，其中$n$ = 1, 2, 和 3，$M$ = Ta, Ti, Hf, Zr, Nb, Mo, V, W, Sc, Cr, Mn，以及$X$ = C, N。研究的堆叠序列受到利用MXenes作为前驱体可能用途的启发，以实现相对低温加工高温陶瓷。 我们发现了67种新的六方层状材料，其热稳定性与之前观察到的ζ相相当或更好。 为了评估它们在高温应用中的潜力，我们使用机器学习和基于物理的模型，结合DFT输入来预测它们的熔点，并发现了几个与当前最先进的ζ类似相相当的候选材料，以及五个预测熔点高于2500 K的材料。这些发现扩展了高温应用的化学成分和结构范围。 显示英文摘要

摘要： Layered, hexagonal crystal structures, like zeta and eta phases, play an important role in ultra-high temperature ceramics, often significantly increasing toughness of carbide composites. Despite their importance open questions remain about their structure, stability, and compositional pervasiveness. We use high-throughput density functional theory to characterize the thermodynamic stability and elastic constants of layered carbides and nitrides M$_{n+1}$X$_{n}$ with $n$ = 1, 2, and 3, $M$ = Ta, Ti, Hf, Zr, Nb, Mo, V, W, Sc, Cr, Mn and $X$ = C, N. The stacking sequences explored are inspired by the possible use of MXenes as precursors to enable relatively low temperature processing of high-temperature ceramics. We identified 67 new hexagonal, layered materials with thermal stability comparable or better than previously observed zeta phases. To assess their potential for high temperature applications, we used machine learning and physics-based models with DFT inputs to predict their melting temperatures and discovered several candidates on par with the current state of the art zeta-like phases and five with predicted melting temperatures above 2500 K. The findings expand the range of chemistries and structures for high-temperature applications.