Resonant Ultrasound Spectroscopy of Solids: Hydrogen-Metal and Other Systems

0070808休闲在这个项目中，共振超声光谱（罗斯）将用于研究通常形状为球体，圆柱体或平行六面体的材料的特性。罗斯是基于对这些样品的振动本征模式的测量。 罗斯光谱产生了完整的弹性常数以及组成样品的材料的超声衰减。 可以用这种技术研究非常小尺寸的样品。 这项工作的一个主要推动力将是研究氢金属系统，包括准晶，拉弗斯相和稀土材料。 对Ti-Zr-Ni、Al-Pd-Mn和Zn-Hg-Ho准晶系统的实验将试图获得关于H在非周期势中扩散的信息，并使用氢作为局部对称性的探针。 预计罗斯将有助于澄清的氢跳跃现象提供的数据，通过传统的核磁共振和中子散射实验获得的补充。 在毫开尔文范围内对hcp稀土型金属和Laves相材料的实验将寻找氢转变对低温声学性质的共振和弛豫效应。 所得结果将与双势阱中耗散隧穿的现代理论相联系。 罗斯也将应用于相变的研究。 Ce基磁性化合物在磁转变温度（2- 30 K）附近的弹性常数数据应该提供与竞争的Kondo和RKKY相互作用的体积依赖性相关的有价值的热力学信息。 将研究Mg 2NiH 4的模量，以深入了解表观导电状态变化的性质。研究生和本科生的参与促进了这项研究。他们在当代凝聚态物理和材料科学领域的培训将使他们在本世纪的未来几十年中进入劳动力市场。将采用一种称为共振超声光谱学（罗斯）的技术来研究固体的弹性振动。 这些测量提供了关于材料的刚性/刚度的数据。 仅需要小的样本，它们的小尺寸意味着振动频率在超声中，即，听不见的频率范围。该方法将用于金属中氢的研究。 金属中的氢是一个既有基础又有实际意义的问题。 金属中的氢系统的实际用途包括它们在电池中的使用和它们用于氢存储。 氢在金属中的高迁移率通常是成功应用所必需的。 在金属中加入氢会影响这些材料的弹性。 用罗斯技术研究了含氢金属弹性性质的这些变化。 研究生和本科生将参与这项研究。 因此，他们将获得实验和理论凝聚态物理学和材料科学的知识和技能，这将使他们在本世纪的未来几十年成为劳动力的生产力。***

0070808LeisureIn this project Resonant Ultrasonic Spectroscopy (RUS) will be used to study the properties of materials usually shaped into spheres, cylinders or parallelopipeds. RUS is based on the measurement of the vibrational eigenmodes of such samples. The RUS spectrum yields the full set of elastic constants as well as the ultrasonic attenuation of the material composing the sample. Very small size samples can be studied with this tecnique. A major thrust of this work will be the study of hydrogen-metal systems including quasicrystalline, Laves-phase and rare-earth materials. Experiments on the quasicrystalline systems Ti-Zr-Ni, Al-Pd-Mn and Zn-Hg-Ho will attempt to obtain information about H diffusion in a non-periodic potential and use hydrogen as a probe of the local symmetry. RUS will be expected to contribute to the clarification of the hydrogen hopping phenomenon by providing data complementary to those obtained by conventional NMR and neutron scattering experiments. Experiments in the millikelvin range on the hcp rare-earth type metals and Laves-phase materials will search for the resonant and relaxation effects of hydrogen transitions on the low-temperature acoustic properties. The results will be correlated with modern theories of dissipative tunneling in a double-well potential. RUS will also be applied to the study of phase transitions. Elastic constant data for Ce-based magnetic compounds near their magnetic transition temperatures (2-30K) should provide valuable thermodynamic information related to the volume dependence of the competing Kondo and RKKY interactions. The moduli of Mg2NiH4 will be studied to gain insight into the nature of the change to an apparent conducting state. This research is facilitated by the involvement of graduate and undergraduate students. Their training in a contemporary area of condensed matter physics and materials science will prepare them to enter the workforce during the next few decades of this Century. %%%A technique called Resonant Ultrasound Spectroscopy (RUS) will be employed to study the elastic vibrations of solids. These measurements provide data about the rigidity/stiffness of the material. Only small samples are required, their small size implying that the vibrational frequencies are in the ultrasound, i.e., inaudible range of frequencies. The method will be applied to the study of hydrogen in metals. Hydrogen in metals is of both fundamental and practical interest. Practical uses of hydrogen-in-metal systems include their employment in batteries and their use for hydrogen storage. High mobility of the hydrogen within the metal is usually required for successful applications. The addition of hydrogen to metals affects the elasticity of these materials. These changes in the elastic properties of the hydrogen containing metals are studied by the RUS technique. Graduate and undergraduate students will participate in this research. They will thereby acquire knowledge and skills in experimental and theoretical condensed matter physics and materials science that will prepare them to be productive members of the workforce during the next few decades of this Century. ***