The Intermediate Phase in Network Glasses

网络眼镜的中间阶段

• 批准号: 0101808
• 负责人: Punit Boolchand
• 金额: $ 33万
• 依托单位: University of Cincinnati Main Campus
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-04-01 至 2005-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0101808&HistoricalAwards=false
• 关键词: Intermediate; Phase; Network; Glasses

This project concerns the properties of glasses and their phase transformations. The physical nature of the Intermediate phase (IP) that separates the Floppy phase (FP) from the Rigid Phase (RP) in select chalcogenide glass systems will be examined. These properties will be investigated in four different sets of experiments. First, temperature-dependent Raman scattering studies of Ge-Se, As-Se and Ge-As-Se bearing bulk glasses will be performed over the range from 78K to Tg+200 K to examine the nature of molecular structure changes taking place across Tg in the FP, IP and the RP. Second, the same glass systems, but now synthesized as obliquely deposited thin-films (obliqueness angle in the range from 0 to 80 degrees) will be examined in their virgin and photo-illuminated state in Raman, 119Sn Mossbauer effect and photo-contraction studies. The columns formed in the porous (obliquely) deposited films may represent the elements of medium range structure responsible for the rather unique physical properties of glasses in the IP. Third, pnictide based glass systems, such as As-Se, As-S and As-Ge-Se bearing glasses will be examined in Raman, NQR, EXAFS and 129I Mossbauer spectroscopic studies to elucidate new aspects of molecular structure recently inferred from the discovery of the IP in Modulated Differential Scanning Calorimetry (MDSC) measurements. Lastly, 119Sn Lamb-Mossbauer factors in select glasses will be established as a function of mean coordination number to contrast the local elastic response of glasses in the IP from those in the FP and the RP. Students will participate in this research and will thereby be prepared to enter the scientific technical work force of the 21st Century.This research concerns the properties of glasses and glass systems. Glasses are characterized by progressive cross-linking of a floppy network that will render it rigid at a critical connectivity. This is often realized by systematically changing the chemical composition in a glass system. Experiments on sulfur- and selenium-bearing glasses have shown however that a floppy phase (FP) and a rigid phase (RP) are separated by an intermediate phase (IP). Four different sets of experiments will be performed to establish the physical nature of the IP in select glass systems. Different experimental techniques will be brought to bear on selected glass systems over a range of glass compositions that encompass the three different phases. The experiments will be performed over a wide temperature range that embraces the transitions among the phases. Furthermore, specially fabricated thin films of these glasses will be investigated. These experiments are expected to shed light on the intricacies of glass systems under various conditions of temperature and composition and the results will be of use for the incorporation of new glasses in advanced technological devices. Students will participate in these investigations. They will thereby acquire training in one of the important contemporary areas of condensed matter physics and materials science and will be prepared to enter the scientific/ technical work force in industry, academe, and the government.

本项目涉及玻璃的性质及其相变。将研究在选定的硫族化物玻璃系统中将软相（FP）与刚性相（RP）分开的中间相（IP）的物理性质。这些属性将在四组不同的实验中进行研究。首先，将在78 K至Tg+200 K的范围内对Ge-Se、As-Se和Ge-As-Se承载块体玻璃进行温度依赖性拉曼散射研究，以检查FP、IP和RP中跨Tg发生的分子结构变化的性质。第二，相同的玻璃系统，但现在合成为倾斜沉积的薄膜（倾斜角在0至80度的范围内）将在其原始状态和光照射状态下进行拉曼，119 Sn穆斯堡尔效应和光收缩研究。在多孔（倾斜）沉积膜中形成的柱可以代表负责IP中的玻璃的相当独特的物理性质的中程结构的元素。第三，磷族元素化物玻璃系统，如As-Se，As-S和As-Ge-Se轴承玻璃将在拉曼，NQR，EXAFS和129 I穆斯堡尔光谱研究中进行检查，以阐明最近从调制差示扫描量热法（MDSC）测量中发现的IP推断的分子结构的新方面。最后，119 Sn的兰姆穆斯堡尔因子在选择的玻璃将被建立为平均配位数的函数，以对比本地的弹性响应的玻璃在IP从FP和RP。学生将参与这项研究，从而为进入21世纪的科学技术工作队伍做好准备。这项研究涉及玻璃和玻璃系统的特性。玻璃的特点是逐渐交联的软网络，这将使它刚性在一个关键的连接。这通常通过系统地改变玻璃系统中的化学组成来实现。然而，对含硫和含硒玻璃的实验表明，软相（FP）和刚性相（RP）被中间相（IP）分开。将进行四组不同的实验，以确定IP在选定玻璃系统中的物理性质。不同的实验技术将被带到承担选定的玻璃系统在一系列的玻璃组合物，包括三个不同的阶段。 实验将在包含相之间的转变的宽温度范围内进行。此外，专门制作的薄膜，这些玻璃将进行调查。 这些实验有望揭示玻璃系统在各种温度和组成条件下的复杂性，其结果将用于在先进技术设备中引入新的玻璃。 学生将参与这些调查。 因此，他们将获得凝聚态物理学和材料科学的重要当代领域之一的培训，并将准备进入工业，工业和政府的科学/技术工作队伍。