Thermal Transport Phenomena at Contacts and Kinks of Nanowires

Abstract

Understanding thermal and electrical transport at junctions between nanostructures is of critical importance for various technological applications. However, so far only limited studies have been conducted to directly measure the thermal and electrical resistance at individual nanostructure junctions because of the tremendous challenges involved in experiments. This dissertation focuses on phonon and electron transport mechanisms at contacts between one-dimensional nanostructures. Through systematic studies of silver nanowires and their contacts, we provide the first experimental evidence to disclose the elastic stiffening effect on phonon and electron transport in silver nanowires and show the nonmonotonic effective Lorenz number of the point contact due to the non-negligible phonon contribution. Moreover, it is shown that silver nanowires could be much more effective nanofillers to enhance the thermal performance of nanocomposites due to the low contact thermal resistance. We also show that the electron hopping conduction at contacts between carbon nanotubes could significantly enhance the thermoelectric performance. In addition, we applied molecular dynamics simulation to reveal the mechanisms of how kinks induce thermal resistance. These findings are expected to facilitate the design of novel composite materials with enhanced thermal and thermoelectric properties.