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

在这个项目中，共振超声光谱（RUS）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性质。RUS是基于这些样品的振动特征模态的测量。RUS光谱产生了完整的弹性常数，以及构成样品的材料的超声波衰减。这种技术可以研究非常小的样品。这项工作的一个主要推力将是氢金属系统的研究，包括准晶，laves相和稀土材料。在准晶体系Ti-Zr-Ni、Al-Pd-Mn和Zn-Hg-Ho上的实验将试图获得氢在非周期势中的扩散信息，并将氢作为局部对称性的探针。RUS有望通过提供与传统核磁共振和中子散射实验所得数据相补充的数据，有助于澄清氢跳变现象。在毫开尔文范围内对hcp稀土型金属和laves相材料进行实验，研究氢跃迁对低温声学特性的共振和弛豫效应。结果将与双阱势的耗散隧穿的现代理论相关联。RUS也将应用于相变的研究。ce基磁性化合物在其磁转变温度（2-30K）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Mg2NiH4的模量，以深入了解转变为表观导电状态的性质。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为他们在本世纪未来几十年进入劳动力市场做好准备。一种叫做共振超声光谱（RUS）的技术将被用来研究固体的弹性振动。这些测量提供了有关材料刚度/刚度的数据。只需要小样本，它们的小尺寸意味着振动频率在超声波范围内，即，听不见的频率范围。该方法将应用于金属中氢的研究。金属中的氢既有基础意义又有实际意义。金属氢系统的实际应用包括它们在电池中的应用和用于储氢。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RUS技术研究了含氢金属弹性性能的这些变化。研究生和本科生将参与本研究。他们将因此获得实验和理论凝聚态物理和材料科学方面的知识和技能，为他们在本世纪未来几十年成为富有成效的劳动力做好准备。* * *

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. ***