This Faculty Early Career Development (CAREER) Program grant supports fundamental studies of the friction and wear processes of the important dry, non-oil-based, solid lubricant materials that are critical for use in harsh environments, including space. The work serves to promote our scientific base of understanding of the mechanism of lubrication aiding in the further development of dry lubricants. These lubricants are critical to our national defense and prosperity by impacting the many commercial applications where poor lubrication can lead to wear that limits the machine lifetime and wastes energy. The research will use atom-level tools to understand surface structure of these dry lubricants, with an emphasis on MoS2 which is the most important dry lubricants in use. This lubricant fails in use through the development of defects and a defect structure within the MoS2. To determine the evolution of this defect structure, samples will undergoing controlled wear in the laboratory or will have been exposed to the environment of space on the international space station (ISS) for an extended time. The changes in friction and lubricating properties together with the atomic level structure will be ascertained. This information will generate the basic understanding of the defect formation process aiding in the design of new lubricants and additives with extended lifetime in all environments. The outreach and education features include an integrated research/education plan to increase education, exposure and interest in tribology at all levels of society, with hands-on K-12 outreach activities, curriculum development, and student undergraduate and graduate research experiences.
Experiments, advanced characterization and models will probe the links between structure, processing, properties and tribological performance of MoS2 coatings for extreme environments (including space). The technical program is centered 2 research themes: 1) assess the role of molybdenum disulphide microstructure and composition in preventing chemical and tribological degradation during exposure to oxidative and humid environments; 2) understand the energetics of MoS2 tribology to develop a model of friction based on orientation, commensurability, defect density and crystallite size as a function of temperature, environment and starting/evolving microstructure of tribofilms formed during sliding. MoS2 films of varying microstructure, composition and processing techniques will be systematically tested to develop a mechanistic framework for tribological interactions of MoS2. Experiments include environmental tribological studies looking to the effects of ultrahigh vacuum, humidity, O2, atomic oxygen and temperature extremes through state-of-the-art surface chemical characterization and atomistic molecular dynamics models. Finally, tribological experiments and material samples returned from the international space station will be analyzed.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.