GOALI: Structural and Topological Controls on Viscoelasticity and Relaxation Processes in Chalcogenide Glass-Forming Liquids

硫化物（含硫、硒或碲的非氧化物合金或化合物）玻璃是一类重要的材料，在光子学、电信、存储、光伏和环境遥感等领域有着广泛的应用。这些玻璃是由母体熔体或液体衍生而来的，对其与温度和成分相关的流动行为的动力学过程的基本理解，在工业生产的各个阶段都是至关重要的。该项目旨在通过结合尖端表征技术，首次提供关于硫系液体动力学行为的“微观（原子）”和“宏观”方面之间联系的独特知识。这些知识是优化这些材料的化学和加工参数以改进和创新功能的关键，从而使它们能够在具有强大社会影响的现代变革技术中应用。在科学上，这项工作影响了材料科学、物理化学和固态物理学。这项工作的跨学科性质在不同领域之间传递知识，并为学生提供智力发展的独特机会。毕业生通常会在学术界、玻璃和半导体行业找到工作。该项目在教育和推广方面的影响主要体现在三个方面：(1)学生参与研究；(2)与行业（康宁公司）积极紧密合作，学生得到指导并了解行业重点；(3)向更广泛的科学界传播有关玻璃科学和技术的知识。研究成果嵌入到材料科学、化学和其他相关领域的专题课程中；他们还为女性和少数族裔学生的校园项目做出贡献，并从代表性不足和经济弱势群体中招收有前途的学生。技术细节：在过冷玻璃成型液体中的动力学过程，与它们的粘性流动、结构松弛和玻璃化转变附近的退火有关，控制着玻璃和玻璃陶瓷加工和技术应用的所有方面。然而，令人惊讶的是，关于原子结构之间的联系，它的连通性和拓扑结构以及硫系液体流动行为的温度依赖性，人们知之甚少。因此，从历史上看，设计新的硫系玻璃的大部分方法都是经验的，缺乏对其成分优化和处理方法所需的预测能力。该GOALI项目汇集了来自加州大学戴维斯分校（Sen， PI）和康宁公司（Aitken, co-PI）的具有互补专业知识和共同兴趣的研究人员，使用最先进的振荡平行板流变学的独特组合，研究结构连通性和拓扑结构对过冷硫族化物（硫化物和硒化物）液体粘弹性行为和松弛过程的温度依赖性的影响。动态核磁共振（NMR）光谱和差示扫描量热测量。基于本项目获得的结果建立的结构-松弛-粘性流动关系的预测原子模型，可以优化这些复杂材料的化学、合成和加工参数，以实现广泛的现代技术应用。本项目的重点，即原子结构的各个方面如何以及为什么控制硫系玻璃形成液体中的温度依赖性粘弹性、弛豫行为和相关现象，本身就是横切材料的研究。该项目的广度、灵活性和跨学科性质为学生在学术和工业环境中提供了强大的实验技能和研究经验，这可能为未来的职业发展带来许多机会。它还通过合作科学家和参与学生之间的大量科学互动丰富了研究生教育和培训经验。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL DESCRIPTION: Chalcogenide (non-oxide alloys or compounds containing sulfur, selenium or tellurium) glasses are an important class of materials with wide-ranging applications in the areas of photonics, telecommunication, memory storage, photovoltaics and environmental remote sensing. A fundamental understanding of the dynamical processes associated with the temperature- and composition- dependent flow behavior of the parent melts or liquids from which these glasses are derived, is crucial in all stages of their industrial production. This project aims to provide unique knowledge regarding the connection between the "microscopic (atomistic)" and the "macroscopic" aspects of the dynamical behavior of chalcogenide liquids for the very first time, using a combination of cutting-edge characterization techniques. This knowledge is key to the optimization of the chemistry and processing parameters of these materials for improved and novel functionality, thereby enabling their application in modern transformative technologies with strong societal impact. Scientifically, this work impacts materials science, physical chemistry, and solid-state physics. The interdisciplinary nature of this work transfers knowledge between fields and provides students with unique opportunities for intellectual growth. Graduates typically find employment in both academia and in glass and semiconductor industry. The impact of this project in terms of education and outreach is in three major areas: (1) participation by students in research, (2) active and tight-knit collaboration with industry (Corning, Inc.) where students are mentored and gain understanding of industry priorities, and (3) dissemination of knowledge about glass science and technology to the broader scientific community. The research findings are embedded into special topics courses that are offered to students in materials science, chemistry, and other related fields; and they contribute to campus programs for women and minority students and to the recruitment of promising students from underrepresented and economically-disadvantaged groups.TECHNICAL DETAILS: The dynamical processes in supercooled glass-forming liquids, associated with their viscous flow, structural relaxation and annealing near the glass transition, control all aspects of the processing and technological utility of the resulting glasses and glass-ceramics. However, surprisingly enough, little is known regarding the connection between the atomic structure, its connectivity and topology and the temperature dependence of the flow behavior of chalcogenide liquids. Historically, therefore, much of the approach for designing new chalcogenide glasses has been largely empirical and lacked the predictive power needed for their compositional optimization and processing methods. This GOALI project brings together investigators with complementary expertise and common interests from UC Davis (Sen, PI) and from Corning Incorporated (Aitken, co-PI), to investigate the effects of structural connectivity and topology on the temperature dependence of the viscoelastic behavior and relaxation processes in supercooled chalcogenide (sulfide and selenide) liquids, using a unique combination of state-of-the-art oscillatory parallel-plate rheometry, dynamical nuclear magnetic resonance (NMR) spectroscopy and differential scanning calorimetry measurements. Predictive atomistic models of structure-relaxation-viscous flow relationships, built on the basis of the results obtained in this project, may enable the optimization of the chemistry, synthesis, and processing parameters of these complex materials for a wide range of modern technological applications. The focus of this project, namely how and why, the various aspects of the atomic structure control the temperature dependent viscoelasticity, relaxational behavior and related phenomena in chalcogenide glass-forming liquids is in itself crosscutting materials research. The breadth, flexibility and interdisciplinary nature of this project prepare the students with powerful experimental skills and research experience in both academic and industrial settings that may open many future career opportunities. It also enriches the graduate education and training experience through numerous scientific interactions between the collaborating scientists and participating students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.