Date of this Version
Davis, E. (2017). On the wetting states of low melting point metal Galinstan and Wetting characteristics of 3-dimensional nanostructured fractal surfaces. Unpublished master’s thesis, University of Nebraska-Lincoln, Lincoln, Nebraska.
Exergy, or the availability of energy for useful work, is a critical issue that must be addressed to accommodate growing energy demands of society. Increasing population and steady advancement of technology necessitates novel approaches to the management, conversion, and storage of energy. Per the Lawrence Livermore National Laboratory, approximately 60 percent of the energy used by the United States in 2015 was rejected as waste ; a large quantity of which can be assumed to be in the form of heat. Therefore, novel thermal management methods for waste heat are critical to increasing energy efficiency and sustainability in the future.
The primary goal of this thesis is to measure the wetting characteristics of a low melting point metal to determine the efficacy of this type of material for use in thermal energy storage applications. Galinstan, an alloy consisting of Gallium, Indium, and Tin was subjected to contact angle measurements on various substrates at varying temperatures. Due to the oxidation characteristics of Galinstan, all experiments are conducted in an inert nitrogen environment (< 0.5 ppm oxygen) to maintain fluid-like properties. This work found that although contact angle changed with substrate and surface structure, temperature had minimal effect on the contact angle. Contact angles ranged from 141° on smooth silicon to greater than 160° on silicon micropillars. Although a temperature dependence was not observed, having wetting properties of Galinstan on various surfaces is a step toward better understanding the capabilities of this and similar materials in energy management.
A secondary goal of this research is to measure the wetting characteristics of 3-dimensional nanostructured fractal surfaces (3DNFS) and explore their efficacy in physical and biological science applications. Contact angle measurements were performed on three distinct multiscale fractal surfaces to characterize their wetting properties. Average contact angles ranged from 66.8° for the smooth control surface to 0° for one of the fractal surfaces. The change in wetting behavior was attributed to modification of the interfacial surface properties due to the inclusion of 3-dimensional hierarchical fractal nanostructures. However, the wetting behavior exhibited does not exactly obey existing wetting models found in the literature.
Advisor: Sidy Ndao