RUI: Nuclear Magnetic Resonance Study of Hydrogen in New Materials

该个人研究者奖支持一个项目，该项目将使用核磁共振（NMR）技术来研究氢在三种不同材料中的行为：镧和钇氢化物、富勒烯和准晶体。镧和钇氢化物薄膜在低氢浓度时从反射状态切换到高浓度时的透明状态。这种“可切换的镜像”行为是由于金属到非金属的转变，但是对这种转变的详细理解仍然缺乏。核磁共振将用于表征光学跃迁背后的关键结构和电子现象。碳基材料是一种极具吸引力的新型储氢介质，近年来碳纳米管的应用备受关注。纳米管样品制备和分析的困难阻碍了测量关键性质的进展，包括氢传输速率。氢在固体富勒烯中的传输速率，作为理解更复杂的纳米管材料的第一步，将使用核磁共振技术进行研究。准晶体是具有非周期但高度有序结构和显著电子性能的固体。在电子态密度中显示精细结构的计算可以解释这些性质；然而，实验证据仍然存在争议。核磁共振弛豫测量结合控制氢含量的钛基准晶体将用于测试存在的精细结构。所有这些工作都将在文理学院进行，使用本科生研究助理，他们将在准备和追求物理及相关领域的职业生涯时获得宝贵的经验。氢可以被各种各样的固体吸收，常常产生具有重要技术意义的材料。这个个人研究者奖将支持一个主要由本科生组成的机构的项目，该项目利用核磁共振（NMR）来研究氢在三种不同材料中的行为：固体C60、稀土“可切换镜”和钛基准晶体。氢在C60中运动的核磁共振测量将作为理解C60更复杂衍生物（如碳纳米管）中氢运动的第一步。碳纳米管是下一代储氢介质的有吸引力的候选者，对于开发清洁燃烧的氢作为可行的燃料至关重要。“可切换镜”是一种薄膜，可以根据氢的含量从反射变为透明。它们的结构和电子性质的核磁共振测量将产生一个更好的基本理解的开关现象。这种理解将有助于开发有用的设备，如光纤网络的交换机。准晶体是具有不寻常原子结构的固体，具有许多新颖的电子特性。电子性质的核磁共振测量结合对准晶体氢含量的仔细控制，将用于测试一些更有争议的理论解释的不寻常的性质。所有这些工作将在一所文理学院进行，使用本科生研究助理，他们将在准备和追求物理及相关领域的职业生涯时获得宝贵的经验。***

This individual investigator award supports a project that will use Nuclear Magnetic Resonance (NMR) techniques to investigate the behavior of hydrogen in three different materials: lanthanum and yttrium hydrides, fullerenes, and quasicrystals. Thin films of lanthanum and yttrium hydrides switch from a reflecting state at low hydrogen concentrations to a transparent state at high concentrations. This "switchable mirror" behavior is due to a metal-to-non-metal transition, but a detailed understanding of this transition is still lacking. NMR will be used to characterize the crucial structural and electronic phenomena underlying the optical transition. Carbon-based materials are attractive candidates for new hydrogen storage media, and recent attention has focused on the use of carbon nanotubes. Difficulties in nanotube sample preparation and analysis have hampered progress in measuring crucial properties, including the hydrogen transport rate. The rate of hydrogen transport in solid fullerene, as a first step towards understanding the more complicated nanotube materials, will be studied using NMR techniques. Quasicrystals are solids with aperiodic yet highly ordered structures and remarkable electronic properties. Calculations showing fine structure in the electronic density of states may explain these properties; however, the experimental evidence remains controversial. NMR relaxation measurements combined with control of the hydrogen content of a titanium-based quasicrystal will be used to test for the existence of the fine structure. All of this work will be carried out at a liberal arts college using undergraduate research assistants, who will gain valuable experience as they prepare for and pursue careers in physics and related fields.%%%Hydrogen is absorbed by a surprising array of solids, often yielding materials with significant technological importance. This individual investigator award will support a project at a predominately undergraduate institution that utilizes Nuclear Magnetic Resonance (NMR) to study the behavior of hydrogen in three different materials: solid C60, rare earth "switchable mirrors, " and titanium-based quasicrystals. NMR measurements of the motion of hydrogen in C60 will serve as the first step in understanding hydrogen motion in more complicated derivatives of C60, such as carbon nanotubes. Carbon nanotubes are attractive candidates for next generation hydrogen storage media, crucial for the development of clean-burning hydrogen as a viable fuel. "Switchable mirrors" are thin films that change from reflecting to transparent depending on the hydrogen content. NMR measurements of their structure and electronic properties will yield a better fundamental understanding of the switching phenomenon. This understanding will aid the development of useful devices, such as switches for optical fiber networks. Quasicrystals are solids with unusual atomic structures that have a number of novel electronic properties. NMR measurements of the electronic properties combined with careful control of the hydrogen content of a quasicrystal will be used to test some of the more controversial theoretical explanations of the unusual properties. All of this work will be carried out at a liberal arts college using undergraduate research assistants, who will gain valuable experience as they prepare for and pursue careers in physics and related fields.***