Environmental Sensitivity of Diamond-Like Carbon (DLC) Friction and Wear

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The research objective of this award is to understand and control the surface properties of diamond-like carbon (DLC) which is a technically important material. Various types of DLC are used to control friction and wear in a wide range of engineering applications due to their superior mechanical and tribological properties. The recent discovery of near-frictionless properties of hydrogenated DLC films can lead to innovations to reduce frictional energy loss and increase the service life of mechanical systems. However, the near-frictionless behavior is observed only in vacuum or extremely dry conditions after an initial induction period during which the friction is initially high and the DLC film surface wears. In atmospheric conditions, near-frictionless DLC films lose their superlubricity and are subject to wear. This research is based on a hypothesis that the DLC surface is highly reactive and can be oxidized in ambient air. Through a series of control experiments and using innovative experimental designs, this research will determine the thickness and composition of the oxidized surface layer in various environments and find vapor additives that can ensure ultra-low friction and wear-free operation of DLC in ambient air conditions.The new hypothesis and experimental findings of this research will have great impacts on not only DLC tribochemistry but also energy-saving technology. This work will change the common view that the DLC surface is inert. The DLC surface is reactive especially in oxygen and humid environments. The deeper understanding of the DLC surface chemistry will eventually help to develop coating technologies for energy conservation through reduction of parasitic frictional dissipation and material loss. Undergraduate students will be involved to analyze how much energy is lost in daily activities around us as well as in industrial places. Graduate students involved in this project will be trained with multidisciplinary skills - chemical engineering, molecular spectroscopy, tribology, and coatings. The spectral data and findings of this research will be incorporated into a graduate-level characterization. The research opportunity will be offered to underrepresented groups.