“陶瓷晶界非晶膜的EELS定量分析及其对异常生长微结构的作用规率”
时间：2015年12月9日周三下午1:30
地点：教十一318会议室
Sintering-additive and microstructure interaction was investigated in many ceramic systems; it is often found that additives remain at two-grain junctions to form intergranular glassy film (IGF). Si3N4 ceramics are served as a model system since IGFs are ubiquitously present and having equilibrium width independent to crystallographic orientations, which have important consequences on sintering behaviors as well as on thermal/mechanical properties. Recently, such IGFs were correlated to abnormal grain growth in Al2O3 ceramics via transitions between “complexions”, or a scheme of stable grain-boundary structures which rationalize IGFs as interfacial “phases” in a thermodynamic sense.
However, the chemical analyses of IGF reveal rather different scenarios: IGF is sensitive not only to grain surface structures but also to the structure/chemistry of neighboring multi-grain junctures. Hence it is too early to view the IGF as (meta-)stable or thermodynamically equilibrated. By using advanced analytical electron microscopy methodology, especially the spatially-resolved electron energy-loss spectroscopy (EELS) and energy dispersive spectroscopy (EDS) methods, local chemistry of such ~1nm thick IGF in ceramic systems could be characterized quantitatively to gain information on its interaction with grain, intergranular phases as well as neighboring grain-boundaries. This uncommon approach provides an alternative way to probe into the intrinsic nature of compound phase relations as well as grain-glass interfaces.
In a low-CaO-doped high-purity Si3N4 system, basal and non-basal facets exhibit a bi-modal distribution for IGF width and dopant segregation independent to the doping level, leaving the extra CaO re-partitioned in the glassy pockets [1], which set up the stage for abnormal grain growth from the connected basal facets [2]. In liquid-phase sintered SiC ceramics and in rare-earth-doped Sialon ceramics, the emergence of IGF or its composition were found subject to the adjacent pocket phases either in crystalline or glassy forms [3,4]. In low-TiO2-doped Al2O3 ceramics with minor SiO2 impurity, not only the preferential accumulation of SiO2 and TiO2 respectively to basal and non-basal IGFs was repeatedly observed [5,6], there was also several levels of SiO2 enrichment at basal facets that exposed its “transient” role in initiating the anisotropic grain growth on non-basal facets [6,7], which is dictated by a ternary melts to and from neighboring pockets [7,8].
In retrospect, we provide an alternative picture for transient IGF to initiate microstructure development in connection with the phase evolution from adjacent pockets, hence render the role of IGF as the kinetically-limited remnents of additives/impurities. This view is additionally supported by the observation of similar, hence seemingly equilibrium IGF, in the regions of normal grain growth in Al2O3, which denies a direct link between the IGF transition with abnormal grain growth.
顾辉，理学博士，专业材料物理；上海大学材料科学与工程学院、电子信息系，教授。
1983年本科毕业于北京大学物理系，86、89年分获北京大学理学硕士、理学博士。于中科院物理所、法国南巴黎大学固体物理实验室、德国斯图加特马普金属所做博士后，1996-1999年任职日本科技振兴事业团“陶瓷超塑性”项目研究员。1999年底回国，任中科院“百人计划”研究员，获聘上海硅酸盐所“高性能陶瓷和超微结构国家重点实验室”课题组长。2003年获得马普学会支持成立“马普伙伴小组”，2005年获得国家“杰出青年基金”支持。2014年任职上海大学“特聘教授”岗位，参与建立上海大学“材料基因组工程研究院”。
主要研究领域：无机非金属材料的微结构演变与界面结构特性研究。主要从事陶瓷晶界的纳米结构与形成原理、非氧化物陶瓷的复相/相变微结构形成与演变规律、非晶陶瓷的纳米亚结构规律与形成原理、功能陶瓷界面结构与介电性能关系、功能陶瓷的畴结构形成与作用原理、层状功能材料的有序-无序结构规律、热电复合材料的微纳结构形成与调控规律、温控相变的微结构机理等多方面的研究。承担基金委“面上项目”、“杰出青年基金”项目、“重点项目”，另参加基金委“重点基金”和“创新群体基金”、科技部重大基础研究计划等。在Ultramicroscopy、ActaMater.、ScriptaMater.、J.Mater.Sci.、J.Am.Ceram.Soc.、J.Eur.Ceram.Soc.等国际电镜与材料专业学术杂志上发表论文80多篇。联系方式：021-66138035，email：gujiaoshou@shu.edu.cn
