主講人：張國軍（教授）

時間：2018年10月30日（星期二）下午2:00-4:00

地點：大學城校區實驗三号樓201會議室

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.

主講人簡介：

張國軍，工學博士，東華大學纖維材料改性國家重點實驗室，功能材料研究所教授、博導。1984年畢業于湖南大學獲學士學位，1987年畢業于天津大學獲碩士學位，1992年畢業于中國建築材料研究院獲博士學位。1987年至1996年在中國建築材料科學研究院從事特種陶瓷的研究與開發工作，1996年獲STA Fellowship資助赴日本産業技術綜合研究所九州中心（AIST Kyushu Center）從事博士後研究，1999年至2005年參加日本Synergy Ceramics項目（NEDO Fellow），在日本産業技術綜合研究所中部中心（AIST Chubu Center）從事先進陶瓷的研究與開發工作。2005年獲中科院“百人計劃”資助回中國科學院上海矽酸鹽研究所工作，任高性能陶瓷和超微結構國家重點實驗室副主任，2016年起調入東華大學。中科院百人計劃、上海市浦江人才計劃獲得者。長期從事硼化物、氮化物、碳化物等非氧化物陶瓷的制備科學、微結構調控與性能表征研究，至今已發表SCI論文200餘篇，H因子36，,他引2000餘次，申請專利20餘項。目前的主要研究方向包括新型功能化結構陶瓷、極端環境（超高溫和強輻照）陶瓷及其複合材料、高熵陶瓷、先進陶瓷材料的3D打印等。