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

Rensselaer Polytechnic Institute, Troy NY

Investigators

Abstract

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.