U.S.-Korea Cooperative Research on Microstructural Develop- ment and Characterization of Cyclic Fatique Crack Behavior of In Situ Toughened Monolithic SiC Ceramics

9507653 Ritchie本奖项提供资金，以允许加州大学伯克利分校材料科学与矿物工程系Robert O.Ritchie博士与韩国高等科学技术研究院陶瓷科学与工程系Do Kyung Kim博士开展为期24个月的合作研究计划，研究原位增韧单块碳化硅陶瓷的微结构发展和循环疲劳裂纹行为表征。联合研究将集中在氧化物添加剂烧结的碳化硅陶瓷的微观结构发展，以促进最佳的力学性能，特别是高温下的疲劳裂纹扩展行为。这位韩国合作者将主要致力于最新开发的原位增韧碳化硅的加工(包括微结构控制)、微观结构表征以及添加剂对烧结行为和机械性能(包括韧性和弯曲强度)的作用。在KAIST制备的碳化硅材料将被送到PI的实验室，在那里将对循环疲劳行为进行表征。疲劳裂纹扩展行为将在环境温度到1800摄氏度的温度范围内进行评估。这一阶段的工作将包括宏观增长率测量和微观结构损伤机制的表征。单块碳化硅陶瓷具有优异的抗氧化性、高温强度保持性、高耐磨性、良好的导热性和较低的热膨胀系数，是热机、换热器等超高温结构部件的理想候选材料。KAIST在生产这些具有改进的微结构的单片陶瓷方面已经开发了相当多的专业知识。PI的研究小组已经在常温和高温下表征这类陶瓷方面发展了相当多的专业知识。PI和他的韩国合作者是这一提议领域备受尊敬的研究人员。该项目与美韩合作科学计划的目标相关，该计划旨在通过交流科学信息、想法、技能和技术以及通过在互利问题上的合作来提高美国和韩国科学家和工程师之间的合作水平。本项目与美国国家科学基金会资助的PI的研究有关。DMR-9123279，为美国研究生提供国际研究经验。***

9507653 Ritchie This award provides funds to permit Dr. Robert O. Ritchie, Department of Materials Science and Mineral Engineering, University of California, Berkeley, to pursue with Dr. Do Kyung Kim, Department of Ceramic Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), for 24 months, a program of cooperative research on microstructural development and characterization of cyclic fatigue crack behavior of in situ toughened monolithic silicon carbide (SiC) ceramics. The joint research will focus on the microstructural development of SiC ceramics sintered with oxide additives in order to promote optimal mechanical properties, especially, fatigue crack-growth behavior at elevated temperatures. The Korean collaborator will work primarily on the processing of recently developed in situ toughened SiC (including microstructural control), characterization of the microstructure, and determination of the role of additives on sintering behavior and mechanical properties, including toughness and flexural strength. SiC materials prepared at KAIST will be sent to the PI's laboratory where cyclic fatigue behavior will be characterized. Fatigue-crack propagation behavior will be evaluated over temperatures ranging from ambient to 1,800 C. This phase of the work will involve both macroscopic growth-rate measurements and characterization of microstructural damage mechanisms. Monolithic SiC-based ceramics are promising candidate materials for ultra-high temperature structural components in heat engines, heat exchangers, and many other devices because of their excellent oxidation resistance, strength retention at high temperatures, high wear resistance, good thermal conductivity, and relatively low coefficient of thermal expansion. Considerable expertise has been developed at KAIST in the production of these monolithic ceramics with improved microstructures. The PI's research group has developed considerable expertise in the characteriza tion of such ceramics at ambient and elevated temperatures. The PI and his Korean collaborator are highly respected researchers in the field of this proposal. This project is relevant to the objectives of the U.S.-Korea Cooperative Science Program which seeks to increase the level of cooperation between U.S. and Korean scientists and engineers through the exchange of scientific information, ideas, skills, and techniques and through collaboration on problems of mutual benefit. This project is related to the PI's research supported under NSF Grant No. DMR- 9123279 and provides an international research experience for a U.S. graduate student. ***