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. ***
