Developing CALPHAD-type models for Zr-C-O high-temperature ceramics considering the effects of short-range-ordering

在2022财年，进行密度泛函理论（DFT）计算以进一步检验C-O-Zr体系，包括改进先前计算的簇展开方法计算，并生成特殊的准随机结构（SQS）以检验不同成分下的无序相。根据这些结果对晶格参数进行评估，并按照计划在计算的组合空间中进行映射。结果在国际会议上发表：MS&T2022（在美国匹兹堡亲自）-邀请，ICAMMM（在印度昌迪加尔虚拟）-邀请主题演讲，以及国际研讨会：thermocalc（在瑞典斯德哥尔摩虚拟）研究网络研讨会-邀请，加州大学戴维斯分校（在美国戴维斯亲自）研究研讨会-邀请。本研究的目的是探索C-O-Zr体系，以了解超高温陶瓷（UHTC） ZrC的氧化行为。近年来，基于ZrC结构的“高熵”超高温超导出现了一个令人兴奋的新领域，其中Zr被多主成分难熔过渡金属如Zr， Hf, Ti, Ta， Nb所取代。与单一金属碳化物（如ZrC）相比，这些高熵超高温碳化物具有更好的抗氧化性。因此，除了探索C-O-Zr相图外，还探索了一些高熵UHTCs的性质。这项工作的结果在ICACC2023会议（在美国代托纳海滩举行）上发表，随后提交给ECerS 2023（将于2023年7月在法国里昂举行）的摘要被选为重点报告。

In FY2022, density functional theory (DFT) calculations were performed to further examine the C-O-Zr system, including improving the cluster expansion method calculations calculated previously and generating special quasirandom structures (SQS) to examine disordered phases at different compositions. The lattice parameter was evaluated for these results and mapped as planned across the calculated composition space. Results were presented at international conferences: MS&T2022 (in-person in Pittsburgh, USA) - Invited, ICAMMM (virtually in Chandigarh, India) - Invited keynote, and international seminars: Thermo-Calc (virtually in Stockholm, Sweden) research webinar - Invited, UC Davis (in-person in Davis, USA) research seminar - Invited.The aim of the proposed work was to explore the C-O-Zr system to understand oxidation behaviour of the ultra-high temperature ceramic (UHTC) ZrC. In very recent years, an exciting new field has emerged of “high-entropy” UHTCs based on the ZrC structure, where Zr is replaced with multi-principal component refractory transition metals such as Zr, Hf, Ti, Ta, Nb. These high-entropy UHTCs have improved oxidation resistance compared to the single metal carbides such as ZrC. Therefore, in addition to exploring the C-O-Zr phase diagram, the properties of some high-entropy UHTCs have also been explored. Results from this work was presented at the ICACC2023 conference (in-person in Daytona Beach, USA), and following this an abstract submitted to ECerS 2023 (to take place in Lyon, France, in July 2023) has been selected as a highlight presentation.