Nanocrystalline Alumina and Titania under High Pressure and Temperature

非技术描述纳米晶体材料是一种比光波小的材料，由于有趣的物理和相关的技术影响，已经引起了极大的科学兴趣。例如，纳米晶体是骨骼和牙齿的关键成分，它们被用于药物输送系统和各种其他技术，它们的用途将变得越来越广泛。为了更好地了解这些材料，首席研究员将研究两种重要的陶瓷，氧化铝和二氧化钛，通过对它们进行高压和高温处理。应用这种极端条件可以显著改变一种材料的结构。例如，每年100多吨的石墨正是通过高压和高温转化为钻石的。在这项工作中，将研究纳米晶陶瓷在高压和高温下的反应，以便更好地了解纳米晶材料，并可能创造出新的、有用的材料。高压实验室的研究人员将与堪萨斯城科学博物馆科学城的工作人员合作，将高压物理学带给公众。将安装一个远程控制的高压钻井平台，并装载液态水。顾客将能够改变压力，并观察到当受到高压(9000倍大气压)时，液态水凝固，变成冰。这一过程是可逆的，可以重复。一个计算机化的演示将同时进行，解释正在发生的事情以及高压物理的其他方面。技术细节基于同步加速器的X射线衍射、拉曼光谱、荧光光谱和透射电子显微镜将用于研究高压和温度对氧化铝和二氧化钛纳米晶样品的影响。这些陶瓷的颗粒长大、局域结合的变化、相图、相变动力学和弹性性能都将随着颗粒尺寸、压力、传压介质和温度的变化而变化。很明显，纳米晶体的性质，甚至它的结构，可能与大块晶体非常不同，也对颗粒的大小和环境很敏感。因此，上述参数的变化将深刻地影响纳米晶体，并允许深入了解最小的晶体。氧化铝的可压缩性随颗粒大小的变化(在6 nm时为~150 Gpa，在67 nm时为~240 Gpa)，只是纳米颗粒研究领域多么丰富的一个例子。这项拟议的研究将进一步调整一种材料的性质以适应不同的技术需求，同时也为创造新的、技术上有用的材料提供机会。研究生将接受使用上述所有技术的培训，使他们能够充分描述材料的特性。研究生还将通过与堪萨斯城科学博物馆科学城的合作，接受向公众传播科学成果的培训。在这项合作中，高压小组将安装一个远程控制的钻石砧槽，以演示压力诱导的水的冻结和融化。

NON-TECHNICAL DESCRIPTION Nanocrystalline materials, materials that are smaller than light waves, have become of great scientific interest, due to interesting physics and their related technological impact. For example, nanocrystals are a key component of bone and teeth, they are used in drug delivery systems and various other technologies, and their uses will become increasingly widespread. To gain a better understanding of these materials, the principal investigator will study two important ceramics, alumina and titania, by subjecting them to high pressures and high temperatures. Application of such extreme conditions can significantly alter a material's structure. For example, it is through high pressure and temperature that more than 100 tons of graphite are converted into diamond each year. In this work, the reaction of the nanocrystalline ceramics to high pressure and temperature will studied, in order to obtain a better understanding of nanocrystalline materials in general and possibly to create new, useful materials. Researchers in the high-pressure lab will work with the staff at Science City, Kansas City's Science Museum, to bring high-pressure physics to the public. A remote-controlled, high-pressure rig will be installed and loaded with liquid water. Patrons will be able to vary the pressure, and observe that when subjected to high pressure (nine thousand times atmospheric pressure) liquid water solidifies, becoming ice. This process is reversible and can be repeated. A computerized presentation will run concurrently to explain what is going on and also other aspects of high-pressure physics. TECHNICAL DETAILS Synchrotron based x-ray diffraction, Raman spectroscopy, fluorescence spectroscopy and transmission electron microscopy will be used to study the effects of high pressures and temperatures on nanocrystalline samples of alumina and titania. Grain growth, changes in local bonding, the phase diagrams, the kinetics of phase transitions and the elastic properties of these ceramics, will be explored as functions of particle size, pressure, pressure-transmitting medium and temperature. It is clear that the properties of a nanocrystal, even its structure, can be very different from the bulk crystal and also sensitive to the particle's size and environment. Thus changes in the above listed parameters will profoundly affect the nanocrystals and allow for a deep understanding of the smallest of crystals. The variation of the compressibility of alumina with particle size (~150 GPa at 6 nm and ~240 GPa at 67 nm) is just one example of how rich a field of study nanoparticle research is. The proposed research will further the possibilities of tuning a material's properties to fit different technological needs while also opening opportunities of creating new, technologically useful materials. Graduate students will be trained in the use of all of the above-mentioned techniques, giving them the ability to fully characterize materials. Graduate students will also get training in communicating the results of science to the public, through a collaboration with Science City, Kansas City's science museum. In this collaboration, the high-pressure group will install a remote controlled diamond anvil cell to demonstrate pressure-induced freezing and melting of water.