主讲人：张国军（教授）

时间：2018年10月30日（星期二）下午2:00-4:00

地点：大学城校区实验三号楼201会议室

摘要：

ZrB₂-based ultra-high temperature ceramics (UHTCs) with chemical and physical stability at high temperatures (e.g., above 2000°C) and in reactive atmospheres (e.g., monatomic oxygen) are key materials for applications in liquid/solid rocket engines and thermal protective systems of hypersonic flight (nose cones and leading edges).StrongUHTCs are generally desired for their service at high temperatures.About six years’ ago, strong ZrB₂-SiC-WC ceramics with strength higher than 650 MPa at 1600°C were developed in my group. It is one of the few reports on the ceramics without any strength degradation up to 1600°C ininert atmosphere at that time. Byoptimizing the types and amounts of the sintering additives, super-strong ZrB₂-WC ceramics with strength values exceeding 1GPa have been recently realized at 1800^oC. To understand the excellent behavior of these W containing diboride ceramics, a comprehensive investigation on their detailed microstructure including interface is thereforenecessary. In this presentation,severalstate-of-the-arttechnologies werecombinedtoinvestigate the bonding character, morphology and composition of oxygen contaminationin diboride powders and ceramics. Thetrajectories of theseimpurities during sintering were analyzed, their removal by WC and getter by WB were confirmed from experimental observationsand theoretical calculations. The segregation of W in the grain boundary of ZrB₂ was alsoidentified. The combination of these features makes the obtaining of“clean” ZrB₂ ceramics with excellent high temperature mechanical property feasible. In addition, the residual thermal stresses in different samples were evaluated by both Raman spectroscopy (RS) and X-ray diffraction (XRD). The temperatures atwhich the stresses began to accumulate were calculated. At the same time high-temperature resistances to deformation were evaluated via four-point flexure test under different conditions. The relationships between the high-temperature bending strength and the above behaviors as well as the related mechanisms were discussed, whichprovides a train of thought and method fordesigningofmaterials with high temperature strength.

主讲人简介：

张国军，工学博士，东华大学纤维材料改性国家重点实验室，功能材料研究所教授、博导。1984年毕业于湖南大学获学士学位，1987年毕业于天津大学获硕士学位，1992年毕业于中国建筑材料研究院获博士学位。1987年至1996年在中国建筑材料科学研究院从事特种陶瓷的研究与开发工作，1996年获STA Fellowship资助赴日本产业技术综合研究所九州中心（AIST Kyushu Center）从事博士后研究，1999年至2005年参加日本Synergy Ceramics项目（NEDO Fellow），在日本产业技术综合研究所中部中心（AIST Chubu Center）从事先进陶瓷的研究与开发工作。2005年获中科院“百人计划”资助回中国科学院上海硅酸盐研究所工作，任高性能陶瓷和超微结构国家重点实验室副主任，2016年起调入东华大学。中科院百人计划、上海市浦江人才计划获得者。长期从事硼化物、氮化物、碳化物等非氧化物陶瓷的制备科学、微结构调控与性能表征研究，至今已发表SCI论文200余篇，H因子36，,他引2000余次，申请专利20余项。目前的主要研究方向包括新型功能化结构陶瓷、极端环境（超高温和强辐照）陶瓷及其复合材料、高熵陶瓷、先进陶瓷材料的3D打印等。