Lubrication by Chemical Reaction Products at Sliding Interface

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Sliding and rubbing interfaces of machineries, whether they are big or small, need lubrication to mitigate friction and wear for reliable operation. Otherwise, these interfaces are bound to fail eventually. The last defense of the sliding interface from such failure is boundary lubrication layers which are chemically or physically adhered to solid surfaces. This layer can be applied to the tribological interface before the assembly and full operation of mechanical devices, or formed in-situ during the operation of the devices. This work focuses on in-situ synthesis of boundary lubrication films directly at the sliding interfaces during the device operation. This research can generate a new lubricant additive chemistry which can reduce parasitic frictional energy losses for automobile industries. This work could also revive the microscale electromechanical technology requiring reliable operations of moving and sliding structural components. This project will train students with multidisciplinary skills covering surface science, molecular characterization and imaging, and tribology; these students will make substantial contributions to newly emerging nano-engineering fields as well as traditional lubrication sectors. The research outcome will be incorporated into a graduate surface characterization course and disseminated through to a broad range of science and engineering fields covering chemistry, chemical engineering, mechanical engineering, materials science, and tribology.Mechanochemical reactions readily occur at all length scales; however, key parameters governing the reaction yield and selectivity are not well documented or understood. This study aims at advancing mechanistic understanding of mechanochemical reactions that can produce reliable boundary lubrication films with complementary properties such as low interfacial shear and high load-bearing. Two specific systems to be studied are (i) mechanochemical polymerization of unsaturated alcohols and esters adsorbed from the vapor phase for synthesis of multilayer films of polyols and polyolesters and (ii) ferrocene-catalyzed mechanochemical reactions of organic precursors in lubricant oils and their graphitization at the sliding interface. This work will undertake systematic studies to understand how contact pressure, shear rate, structure of reactant molecules, and chemistry of substrate materials affect the mechanochemical reaction yield and selectivity as well as the lubrication properties of the produced films. The outcome of this study will not only make breakthroughs in surface engineering for extreme-condition lubrications, but also advance fundamental knowledge of tribochemistry which is still empirical and qualitative.