| dc.description.abstract | In this research, nanomechanical and nanotribological studies have been performed though experiments, finite element analysis, and analytical modeling to obtain maximum reliability of different thin film applications in terms of contacts between the surfaces at different temperatures and environmental conditions. Three types of contact conditions were considered in this study- solid-solid contact for hard coatings, solid-solid contact for soft coatings and solid-liquid contacts. One of the applications of solid-solid contact is heat assisted magnetic recording (HAMR) that utilizes nitrogen doped carbon overcoat (NCOC) or nitrogen doped diamond like carbon (NDLC) to protect the magnetic media. Nanotribological and nanomechanical studies were performed at different temperatures on NCOCs of different thicknesses (2.5, 3.5 and 4.5 nm). It was found that thicker NCOC led to better mechanical behavior and less wear at high temperature conditions, making them tribologically robust at high temperature. Due to difficulty in extracting true mechanical properties from pure experiments, finite element analysis (FEA) was also introduced in this research to determine nanomechanical properties of NCOCs with reduced substrate effect. The effect of carbon configuration of NDLCs on their mechanical and tribological behavior was also studied and found that higher sp3 carbon contents led to better mechanical and wear performance and lower friction at different temperature conditions. Graphene oxide (GO), silicon fibroin (SF) and cellulose nanocrystal (CNC) nanocomposite was studied as a potential soft biomaterial for wearable electronics, thermal interfaces and protecting coatings for cooling components in electronic devices. Due to the nature of these applications, creep performance is crucial for overall reliability of the composite at elevated temperatures for longer time durations. In this study, nanoindentation creep experiments were performed and FEA was used to determine creep properties of GO-SF-CNC coatings at different temperatures. Surface haptics is a state-of-the-art thin film application where voltage is applied to obtain tactile sensation between fingertips and the haptic device. Electroadhesion is a widely used term for the application where adhesion between the surfaces is influenced by external voltage. Fingertip contains sweat, sebum and moisture, which creates a solid-liquid interface, and this can affect the tactile sensation. An improved single asperity electroadhesion model was developed in this research to predict interfacial forces at different environmental conditions and the model was extended to a rough surface contact model to predict interfacial forces between the fingertip and the haptics surface over a finite region. | |
