【18th Sept】ZEOLITES, AMORPHISATION and PERFECT GLASSES
日期：2013-09-18
閱讀：1215
題目：ZEOLITES, AMORPHISATION and PERFECT GLASSES
報(bào)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
地點(diǎn)：化學(xué)化工學(xué)院A樓五樓演講廳
時(shí)間： 9月18日(周三) 上午 10:00
邀請人：陳接勝 教授(化學(xué)化工學(xué)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.
報(bào)告人簡介：
??? 英國亞伯大學(xué)杰出研究教授。Greaves教授成名于他對(duì)無序材料，特別是玻璃和非晶固體的大量貢獻(xiàn)。他是英國同步輻射材料學(xué)權(quán)威，八十年代率先開發(fā)了X射線吸收精細(xì)結(jié)構(gòu)譜技術(shù)。他是最早利用同步光源X射線散射和譜學(xué)研究玻璃材料的科學(xué)家之一，并在如何“觀察”這些材料方面取得了突破和原創(chuàng)性的成果。特別是他的“改進(jìn)的隨機(jī)框架”模型，雖然在早期提出時(shí)頗具爭議，現(xiàn)在已經(jīng)成為研究硅酸鹽玻璃最為重要的參照。 最近他更成為在發(fā)展和應(yīng)用X射線和中子散射技術(shù)在線研究氧化物熔鹽的高溫結(jié)構(gòu)和動(dòng)力學(xué)的主要帶頭人。他在高檔次期刊上發(fā)表了大量的相關(guān)論文，在液體與玻璃態(tài)“多非晶型”這一重要現(xiàn)象方面的發(fā)明已經(jīng)吸引了眾多的不僅是來自氧化物材料和玻璃材料學(xué)術(shù)領(lǐng)域、甚至是理論化學(xué)和凝聚態(tài)物理方面科學(xué)家的極大興趣。他在高壓致低密度晶體的“非晶化”及相變動(dòng)力學(xué)研究是固體物理學(xué)極為突出和前沿的新研究方向。Greaves先后獲“上海市海外名師”和上海市外專局“高端外國專家”項(xiàng)目支持在上海大學(xué)開展合作與交流。
