题目：ZEOLITES, AMORPHISATION and PERFECT GLASSES
报告人： Prof. G.N. Greaves
Institute of Mathematics and Physics, Aberystwyth University, SY23 3BZ, UK
Department of Materials Science & Metallurgy, University of Cambridge, CB3 0FS, UK
State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, 430070, China
地点：化学化工学院A楼五楼演讲厅
时间： 9月18日(周三) 上午 10:00
邀请人：陈接胜 教授(化学化工学院)

Abstract：
  Under pressure, crystals transform into amorphous structures well below the melting point Tm. The amorphisation of zeolite crystals is particularly interesting, as this can also be achieved at ambient pressure by employing only modest temperatures. Different thermobaric stress rates reveal the dynamics of microporous collapse as well as the existence of a supercooled intermediate.  This is topologically equivalent to the zeolitic precursor, but also extremely strong – approximately twice as strong as silica, usually considered the strongest glass-forming liquid.  A low entropy or “perfect glass” is formed on depressurising or cooling, whose mechanical properties are distinct from a glass conventionally quenched from the molten state. Both types of glass are polymorphs and the amorphisation process can be envisaged as a pair of first order phase transitions: crystal-liquid and liquid-liquid (Greaves et al, Nature Materials, 2, 622-629 (2003); Science 308, 1299 (2005)). The talk will introduce these ideas and also report recent work on the amorphisation of zeolitic imidazolate frameworks (ZIFs). Like inorganic zeolites the structural relaxation times of amorphising hybrid ZIFs extend over several minutes, comparable to time scales encountered at the glass transition Tg, and uncovering the existence of novel organic-inorganic supercooled liquids.

报告人简介：
    英国亚伯大学杰出研究教授。Greaves教授成名于他对无序材料，特别是玻璃和非晶固体的大量贡献。他是英国同步辐射材料学权威，八十年代率先开发了X射线吸收精细结构谱技术。他是最早利用同步光源X射线散射和谱学研究玻璃材料的科学家之一，并在如何“观察”这些材料方面取得了突破和原创性的成果。特别是他的“改进的随机框架”模型，虽然在早期提出时颇具争议，现在已经成为研究硅酸盐玻璃最为重要的参照。 最近他更成为在发展和应用X射线和中子散射技术在线研究氧化物熔盐的高温结构和动力学的主要带头人。他在高档次期刊上发表了大量的相关论文，在液体与玻璃态“多非晶型”这一重要现象方面的发明已经吸引了众多的不仅是来自氧化物材料和玻璃材料学术领域、甚至是理论化学和凝聚态物理方面科学家的极大兴趣。他在高压致低密度晶体的“非晶化”及相变动力学研究是固体物理学极为突出和前沿的新研究方向。Greaves先后获“上海市海外名师”和上海市外专局“高端外国专家”项目支持在上海大学开展合作与交流。