主讲人：Dr. Hai-Doo Kim
时间：2018年9月11日（星期二）上午10:00-11:00
地点：大学城校区实验三号楼201会议室
摘要：
Silicon nitride is one of the best ceramic materials with many useful properties, however, actual application is limited mostly due to its high production cost. Use of silicon powder instead of expensive silicon nitride powder is, therefore, attractive. The development history of RBSNand SRBSNas well as the pros and cons of SRBSN will be reviewed.
Dense SRBSN(sintered reaction bonded silicon nitride) ceramics with high strength and toughness was obtainedby modifying the structure of RBSNfollowed by the hightemperature gas pressure sintering. Optimization of gas pressure sintering and hot pressing conditions were investigated by modifying the heating and pressurizing schedule.
A fraction of fine silicon powder was added to modify the structure of RBSN after nitridation.Addition of fine silicon powder to coarse silicon powder leads to the early onset of phase transformation and sintering, which lowers the post sintering temperature to give full densification. Microscopically, addition of fine silicon powder generates fine silicon nitride grains after nitridation, which gives rise to the fine pore structure. During intermediate temperature range of post-sintering process the newly generated fine silicon nitride grains leads to the enhanced phase transformation and densification. The resulting microstructure after post-sintering is such that the matrix grain size is smaller than the conventional case without fine silicon addition.10% addition of fine silicon powder to the silicon powder compact with 8% Lu2O3 and 2% SiO2 system showed near TD when sintered at 1850°C with high fracture strength of above 900 MPa.The fracture toughness values measured by DCB method show therangeupto9MPa?m0.5whichishigherthanconventionalcasewithoutfinesiliconaddition,whichispossiblyduetothemodifiedmicrostructure.
The conditions to give porous microstructure with acicular grains was investigated in sintered RBSN in order to modify the pore structures.SRBSN DPF filter shows better trapping efficiency of PM compared to commercial cordierite filter. Especially SRBSN filter shows better trappingefficiency for nanosized PM possibly due to the smaller pore size with minimum pressure drop compared to the commercial cordierite filter. Future works to be done in SRBSN will be explained and future possibilities and directions will be discussed.
主讲人简介：
Dr. Hai-Doo Kim, the past President of KIMS (Korea Institute of Materials Science) and Korean Ceramic Society, has made outstanding contribution to the science and technology of advanced ceramics. He received Ph.D. in ceramic engineering at TH Aachen, Germany in 1987. Dr. Kim is one of the leading experts on the engineering design of SRBSN ceramics and components targeting various industrial applications in Korea. Dr. Kim is the Academician of the World Academy of Ceramics and Fellow of the American Ceramic Society. He received Samual Geijsbeek PacRim International Award by American Ceramic Society (2017), Bridge Building Award by American Ceramic Society (2016)Grand Prix in Science and Technology awarded by the Governor of Gyeongnam Province (2010), Academic Award by the President of Korean Ceramic Society (2008), Academic Award by the Minister of Science and Technology, Korea (2006), and Best Researcher by the Minister of Science and Technology, Korea (1997). Dr. Kim published 120 peer reviewed SCI papers, 57 papers (domestic journals), edited 1 books, 65 patents on novel fabrication process of alumina, zirconia, silicon nitride, silicon carbide, porous ceramics and strong/tough ceramics.
