SusChEM: Collaborative Research: experimental and computational study of structure and thermodynamics of rare earth oxides above 2000 C

SusChEM：合作研究：2000℃以上稀土氧化物结构和热力学的实验和计算研究

• 批准号: 1505657
• 负责人: Axel van de Walle
• 金额: $ 28.56万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1505657&HistoricalAwards=false
• 关键词: SusChEM; Collaborative; Research; experimental; computational

NON-TECHNICAL SUMMARY: Materials which are stable to very high temperatures are needed for applications in aerospace, energy, and other technologies. Many such materials contain rare earth oxides, critical materials in potential short supply. Novel experimental and computational methods are studying the structure and stability of such rare earth oxides. The methodology includes diffraction (determination of crystal structure) and calorimetry (measurement of heat effects associated with melting and other reactions) on laser heated samples levitated in a gas stream and not contaminated by contact with other materials, as well as theoretical calculations. Such studies offer a unique opportunity to obtain fundamental understanding of structures, phase transitions, and melting properties and applications to technological problems. The project will also advance general experimental and computational techniques for high temperature research. It will offer opportunities for both undergraduates and graduate students in materials science, chemistry, physics, and engineering to take part in state-of-the-art research in both university and national laboratory settings. TECHNICAL DETAILS: Rare earth oxides are critical materials essential to many important technologies yet their high temperature properties, needed for such applications, are poorly known. Their structure and thermodynamics above 2000°C are being studied using a combination of novel experimental and computational methods. Aerodynamic levitation and laser heating are being used for in situ X-ray diffraction at the Advanced Photon Source, in situ neutron diffraction at the Spallation Neutron Source and for drop calorimetry at the UC Davis Peter A. Rock Thermochemistry Laboratory. Enthalpies of solid state phase transitions and fusion are being measured by calorimetry, and volume changes on phase transitions and thermal expansion of high temperature phases are being determined by diffraction. High temperature thermal analysis complements drop calorimetry. Fusion enthalpies are required for reliable calculations of eutectics of multi-component systems containing rare earths. Ab initio computations of high temperature heat capacities, thermal expansion, and temperatures and enthalpies of phase transitions and fusion are being performed at Brown University using post-density functional theory (DFT) methods, such as hybrid functionals and DFT+U, in conjunction with statistical mechanics techniques such as cluster expansion, lattice dynamics analysis and molecular dynamics. Computed thermal expansion and enthalpies of phase transitions and fusion are being compared to experimental measurements and calculations are being extended to high temperature properties of rare earth oxides not yet accessible experimentally.

非技术概述：航空航天、能源和其他技术的应用需要在非常高的温度下稳定的材料。许多此类材料含有稀土氧化物，这是潜在短缺的关键材料。新的实验和计算方法正在研究这类稀土氧化物的结构和稳定性。方法包括衍射（晶体结构的测定）和量热法（与熔化和其他反应相关的热效应的测量）对激光加热的样品悬浮在气流中，没有与其他材料接触污染，以及理论计算。这样的研究提供了一个独特的机会，以获得基本的结构，相变，熔融性能和应用技术问题的理解。该项目还将推进高温研究的一般实验和计算技术。它将为材料科学、化学、物理和工程专业的本科生和研究生提供参与大学和国家实验室最先进研究的机会。技术细节：稀土氧化物是许多重要技术所必需的关键材料，但它们的高温特性却鲜为人知。它们的结构和2000°C以上的热力学正在使用新的实验和计算方法的组合进行研究。空气动力学悬浮和激光加热被用于先进光子源的原位x射线衍射，散裂中子源的原位中子衍射，以及加州大学戴维斯分校彼得A.岩石热化学实验室的滴量热法。用量热法测定固态相变和熔合焓，用衍射法测定相变和高温相热膨胀时的体积变化。高温热分析是滴量热法的补充。为了可靠地计算含稀土多组分体系的共晶，聚变焓是必需的。布朗大学正在使用后密度泛函理论（DFT）方法，如混合泛函和DFT+U，结合统计力学技术，如簇展开、晶格动力学分析和分子动力学，从头开始计算高温热容、热膨胀、相变和聚变的温度和焓。计算出的热膨胀和相变及聚变焓与实验测量结果进行了比较，并将计算扩展到尚未通过实验获得的稀土氧化物的高温特性。