NER: Exploring the Mechanical and Thermoelectric Properties of Composite Nano-Rods and Nano-Springs

这笔赠款探索了一项关于一类新的纳米结构的机械和热电性能的实验研究，这些结构是最近使用掠角沉积(GREAD)技术开发的。这些结构是纳米棒和纳米弹簧的形式，它们垂直于或与衬底成一定角度生长，并彼此对准。棒的纵横比、间距和对称性可以随意选择。该结构可以由多种元素、合金和多层形式的材料制成。这些条件是材料表征的理想条件。从力学上讲，纳米棒相当于用于宏观材料表征的圆柱形宏观样品的纳米级。一个主要的目标是在轴向压缩和弯曲两种情况下在纳米棒上加载原子力显微镜或纳米压头。这项技术比纳米压痕在纳米尺度上进行的标准测量提供了巨大的优势。单个纳米棒的热电优值将通过测量的塞贝克电压从导电的AFM尖端通过纳米棒传递到底部导电衬底来获得。在实验研究的同时，将解决几个理论问题，包括材料性质随样品尺寸的标度以及梯度非局域型材料在纳米尺度上行为本构方程的有效性。这是一项探索性研究，将检验标度概念在材料性质中的极限，从而为未来NEMS和能量转换器件中各种应用的新的纳米材料组合的设计和发现提供指导。拟议的多学科方法，包括物理、材料科学和机械工程组件，如果成功，将极大地推动纳米结构的机械和热电测量领域。

The grant explores a an experimental study of the mechanical and thermoelectric properties of a novel class of nanostructures that have been developed recently using the grazing angle deposition (GLAD) technique. The structures are in the form of nanorods and nanosprings grown perpendicular or at an angle to the substrate and aligned with each other. The aspect ratio, spacing and symmetry of the rods may be selected at will. The structures can be made from a large variety of materials in the elemental, alloy and multilayered form. These conditions are ideal for material characterization. Mechanically, the nanorods are the nanoscale equivalent of the cylindrical macroscopic specimens used for material characterization at the macroscale. A major objective is to load the nano-rods with an AFM or a nanoindenter tip both in axial compression and in bending. This technique offers tremendous advantages over the standard measurements made at the nanoscale by nanoindentation. The thermoelectric figure of merit of a single nanorod will be obtained from the measured Seebeck voltage by passing a current from a conductive AFM tip through the nanorod to the bottom conducting substrate.Along with the experimental study, several theoretical issues will be addressed that include the scaling of material properties with specimen size and the validity of constitutive equations of the gradient non-local type material behavior at the nanoscale.This is an exploratory research that will test the limit of the scaling concept in materials properties thereby providing guidance to the design and discovery of new nanoscale material combinations for various applications in future NEMS and energy conversion devices. The proposed multidisciplinary approach with Physics, Materials Science, and Mechanical Engineering components, if successful, will significantly advance the field of mechanical and thermoelectric measurements of nanostructures.