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

Northwestern University, Evanston IL

Investigators

Abstract

Transportation accounts for 70 percent of the oil consumption in the US. Improving lubrication in transportation and other mechanical systems results in better efficiency, reduced maintenance and cost associated with oil consumption. Just as critical, mechanical systems such as automotive engines are prone to wear during starts and stops. This is particularly important for hybrid vehicles, whose engines start and stop each time the drivetrain switches from and to the battery as the power source, and for many new conventional passenger cars that are implementing such "start-stop" technology to reduce fuel consumption by automatically shutting the engine off when the vehicle is idling in traffic or at stoplights. There is a need for new lubricants designed for these modern engine systems with frequent start-stop cycles. The research team explores the introduction of new lubricant additives into regular engine oils that readily decompose into lubricious and protective diamond-like-carbon layers when subjected to conditions experienced in start-stop cycles. These layers therefore provide friction reduction and wear protection when and where they are needed. This multidisciplinary research involves surface chemistry, materials science, and mechanical engineering; it provides broad-based graduate training not only in subject areas, but also in communications, entrepreneurship, international and multi-cultural exposure, and active participation in professional activities. The objective of this research 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 base oil) that are functionalized with strained metastable carbon rings. The surface-active group of these molecules allows them to readily absorb onto tribo-component surfaces. Under boundary conditions, 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, thus providing in situ and on-demand friction reduction and wear protection. The research team plans to systematically modify the chemical structure of these additive molecules in two aspects: the chemical nature of the surface-active group and the number of -CH2 spacers between the surface-active group and the strained metastable carbon ring. Research investigations will explore the relationship among the chemical structure of these additive molecules, decomposition kinetics, and the tribological performance under different boundary lubrication conditions.