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

该基金探索了最近使用掠角沉积（GLAD）技术开发的新型纳米结构的机械和热电特性的实验研究。这些结构以纳米棒和纳米弹簧的形式生长，与衬底垂直或成一定角度，并彼此对齐。棒材的纵横比、间距和对称性可随意选择。该结构可以由元素、合金和多层形式的多种材料制成。这些条件是材料表征的理想条件。机械上，纳米棒是用于宏观材料表征的圆柱形宏观样品的纳米级等效物。一个主要的目标是在轴向压缩和弯曲中加载纳米棒与AFM或纳米压头尖端。与通过纳米压痕在纳米尺度上进行的标准测量相比，该技术具有巨大的优势。通过将导电AFM尖端的电流通过纳米棒传递到底部导电基板，可以从测量的塞贝克电压获得单个纳米棒的热电性能图。随着实验研究的进行，几个理论问题将得到解决，包括材料性能随试样尺寸的缩放和纳米尺度下梯度非局部型材料行为的本构方程的有效性。这是一项探索性研究，将测试材料特性中缩放概念的极限，从而为设计和发现新的纳米级材料组合提供指导，用于未来NEMS和能量转换设备的各种应用。提出的物理、材料科学和机械工程组件的多学科方法，如果成功，将显著推进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.