Date: December 2010
Creator: Mensah, Benedict Anyamesem
Description: Friction and wear mitigation is typically accomplished by introducing a shear accommodating layer (e.g., a thin film of liquid) between surfaces in sliding and/or rolling contacts. When the operating conditions are beyond the liquid realm, attention turns to solid coatings. Solid lubricants have been widely used in governmental and industrial applications for mitigation of wear and friction (tribological properties). Conventional examples of solid lubricants are MoS2, WS2, h-BN, and graphite; however, these and some others mostly perform best only for a limited range of operating conditions, e.g. ambient air versus dry nitrogen and room temperature versus high temperatures. Conversely, lubricious oxides have been studied lately as good potential candidates for solid lubricants because they are thermodynamically stable and environmentally robust. Oxide surfaces are generally inert and typically do not form strong adhesive bonds like metals/alloys in tribological contacts. Typical of these oxides is ZnO. The interest in ZnO is due to its potential for utility in a variety of applications. To this end, nanolaminates of ZnO, Al2O3, ZrO2 thin films have been deposited at varying sequences and thicknesses on silicon substrates and high temperature (M50) bearing steels by atomic layer deposition (ALD). The top lubricious, nanocrystalline ZnO layer was structurally-engineered ...
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