Environmental Effects on Mechanical and Thermal Behaviors of Zinc Oxide Nanobelts and Dispersion of Carbon Nanostructures

One-dimensional (1-D) nanostructures, such as nanowires, nanobelts, and nanotubes of different materials, have significant applications as nanoscale interconnects and active/functional components of electronic and optoelectronic devices, sensors, actuators, nanoelectromechanical systems (NEMS), and energy generation/conversion systems. The thermal and mechanical stabilities of those nanodevices and nanoenabled energy systems are of both theoretical and practical interests. Thermodynamic properties of nanomaterials are different from those of bulk materials. As the size of a solid particle reduces to the nanometer scale, the surface-to-volume ratio increases and the melting temperature may remarkably decrease. The functionality and/or reliability of those nanodevices and nanoenabled energy systems are also determined by the elastic properties of individual 1-D nanostructures. When the environment changes, such as, humidity level, temperature, ultraviolet radiation, the mechanical behaviors of nanomaterials could simultaneously change as well. However, the mechanisms for how the mechanical and thermal behaviors of 1-D nanostructures depend on their surface conditions, size and surface structures are barely understood. ZnO nanostructure, one of the spotlights of current nanoscience and nanotechnology, will be employed to study the environmental effects on the thermal and mechanical behaviors of nanomaterials, respectively. The exceptional mechanical, superior thermal and electrical properties of carbon nanotubes (CNTs) and graphene have made them promising for many engineering applications, such as composite reinforcements, scanning probe tips, field emission sources, hydrogen storage systems, super-capacitors, quantum devices, and biosensors. A significant challenge for both fundamental research and practical applications of CNTs and graphene is to disperse CNTs and graphene sheets into certain media, such as ethanol, water, or polymers. Since CNTs and graphene are insoluble and tend to form bundles due to their strong hydrophobicity and van der Waals attractions, a great deal of effort has been invested to develop efficient and low-cost approaches to realize full dispersion of CNTs and graphene sheets. In this dissertation, the environmental effect on dispersion of CNTs and graphene sheets will also be discussed