Multifunctional High Entropy Carbide and Boride (HECARBO) Ceramic Composites: Compositional Space, Novel Synthesis, and Property Tailoring

高熵陶瓷（HECs）是一类由五种以上组分组成的新型材料，其结构熵较高。它们引起了陶瓷研究界和工业界的广泛关注。它们是受冶金领域的启发而发展起来的，在冶金领域中，高熵合金（High Entropy alloys, HEAs）的发现大大增加了探索新合金的有用成分空间。在这些材料中，多种元素的某些组合可以产生单相材料，而不是通过增加构型能量产生多相材料。其中，高熵过渡金属碳化物（HETMCs）和硼化物（HETMBs）由于具有超高熔点和硬度、优异的耐腐蚀性和相对较低的密度等优异性能而成为研究的热点。该项目的目标是开发新的合成方法，并了解和优化hec的物理性质。为此，我们将重点研究IV族和V族过渡金属碳化物和硼化物，它们分别以简单岩盐和六边形结构作为模型体系。这些材料有可能导致具有新特性的新材料，可以在最极端的条件下找到商业应用。在工作的第一部分，第一性原理计算（DFT）将用于协助发展对HEC的深刻基础科学理解，然后用于指导具有独特和工业上适用的功能和机械性能组合的新HEC组合物的开发。在第二部分，将开发一种新的“微波和熔盐协同辅助碳/硼碳热还原”技术，以制备具有高宽高比的纯1-D/2-D HETMC/HRTMB相，纯球形HETMC/HETMB颗粒，或由两种形式的颗粒以不同比例组成的混合物（根据上述DFT计算/建模指导的成分设计）。该工艺将使用相对便宜的金属氧化物B2O3/B4C和碳前驱体，与使用传统工艺路线相比，在更低的温度（降低300-600℃）和更短的时间（可减少到20分钟）下进行加工。在第三部分中，原位形成的粉末混合物或通过将前两种形式的预合成粉末以适当的比例结合而形成的混合物将使用SPS或闪速SPS烧结来制备自增强HE碳化物/硼化物复合材料，可在最极端的工程条件下使用，例如在装甲，航空航天，耐火材料，切削工具，高超音速飞行器，催化和核反应堆中的应用。这项工作如果成功，不仅具有重要的学术意义，而且具有巨大的产业影响，使许多重要的社区/部门受益。

High Entropy Ceramics (HECs) are a new class of materials consisting of more than five components stablised by their high configurational entropy. They are attracting a great deal of attention from the ceramics research community and industry. They were developed following some inspiration from the field of metallurgy, in which the useful compositional space for the exploration of new alloys was drastically increased upon the discovery of High Entropy Alloys (HEAs). In these materials some combination of multiple elements can produce single phase materials, rather than multiple phases by their increased configurational energy. Among HECs, high entropy transition metal carbides (HETMCs) and borides (HETMBs) are the subject of investigation because of their superior properties such as ultra-high melting point and hardness, excellent corrosion resistance, and relatively low density. The goal of this project is to develop novel synthesis methods, and understand and optimise the physical properties, of HECs. To do this we will focus on Group IV and V transition metal carbides and borides with respectively simple rock salt and hexagonal structures as model systems. These materials have the potential to lead to new materials with novel properties that could find commercial applications under the most extreme conditions.In the first part of the work, first principles calculations (DFT) will be used to assist in developing a deep fundamental scientific understanding of HECs, and this will then be used to guide the development of new HEC compositions with unique and industrially-applicable combinations of functional and mechanical properties.In the second part, a novel "microwave and molten salt co-assisted carbo-/borocarbo-thermal reduction" technique will be developed to make pure 1-D/2-D HETMC/HRTMB phase with a high aspect ratio, pure spherical HETMC/HETMB particles, or a mixture consisting of both forms of particles in various ratios (compositional design guided by the above DFT calculations/modelling). The process will use relatively inexpensive metal oxides, B2O3/B4C, and carbon precursors, processed at much lower temperatures (reduction by 300-600oC) and in shorter times (could be reduced to 20min) compared to using traditional processing routes.In the third part, in-situ formed powder mixtures or mixtures formed by combining the first two forms of presynthesised powders in appropriate ratios will be sintered using SPS or flash-SPS sintering to prepare self-reinforced HE carbides/borides composites that can be used under the most extreme engineering conditions, for example applications in, armour, aerospace, refractories, cutting tools, hypersonic vehicles, catalysis, and nuclear reactors. This work, if successful, would not only have significant academic significance, but also great industrial impact, benefiting a number of important communities/sectors.