On-demand Generation of Diamond-like-carbon Layers for Efficient Lubrication of Mechanical Systems

The objective of this proposal is to explore and develop a novel approach to in situ and on-demand deposition of lubricious diamond-like-carbon films onto tribo-component surfaces. The approach uses surface-active molecules (dissolved in a base oil) that are functionalized with strained metastable carbon rings. These molecules absorb onto tribo-component surfaces. Thermal energy due to frictional heating at asperities causes the metastable carbon rings of these molecules to decompose, resulting in the formation of a lubricious diamond-like-carbon layer, which provides on-demand friction reduction and wear protection in the boundary lubrication regime. Intellectual merits. The proposed research explores a novel approach to in situ and on-demand deposition of lubricious carbon coatings onto asperities of surfaces in the boundary lubrication regime. The concept is based on the incorporation of a special additive into the base oil whose molecular structure has two special components. One is a surface-active group that allows the additive molecule to adsorb readily onto a tribological surface. The second component is a metastable carbon ring that decomposes into lubricious diamond-like-carbon film upon heating. An important part of the exploration is to determine how the decomposition kinetics is related to temperature and the structure of the additive molecule, especially how the kinetics will be affected by the insertion of spacer groups between the surface-active group and the metastable carbon ring of the molecule. Taken together, these additive molecules act as precursors to the formation of a replenishable solid lubricant where and when it is needed for friction reduction and wear protection. Broader impact. The proposed concept should lead to a new technology for improving energy efficiency and durability of mechanical systems whose contact and relative-motion interfaces operate in the boundary regime with a significant fraction of asperity contacts. By providing replenishable lubricious carbon films when and where they are needed to reduce friction and wear, this concept has wide-ranging applications, from automotive engine and drivetrain components, machining and manufacturing processes, turbines for electricity generation, etc. When applied to the light-duty-vehicle sector alone, even a few percent improvement in fuel economy will have strong ramifications in energy security and environmental impact. Just as important, the proposed research entails what we consider to be modern tribology training for both undergraduate and graduate students, involving mechanics, tribology, simulation-based computation, materials science, surface chemistry, communication skills, and networking. This will be the appropriate setting to train new tribology leaders in an increasingly multidisciplinary and international environment.