Design criteria for superlubricity in carbon films and related microstructures

Carbon offers the kind of flexibility that one needs in the design and production of chemically unique microstructures with properties ranging from superlubricity to super-hardness and/or -softness. This flexibility can be exploited for numerous tribological applications, ranging in sizes from nano-scale electromechanical systems to meso-scale engine parts and components. Recently, carbon was used in our laboratory to produce nearly frictionless carbon (NFC) films having friction coefficients as low as 0.001 and wear rates of 10−11–10−10 mm3/N m even under dry sliding conditions and at very high contact pressures. Using advanced fabrication and chemical vapor deposition methods, our research team has pioneered the development of other unique microstructures possessing exceptional physical, chemical, mechanical, electrical, and tribological properties. The combination of such exceptional properties in one material is rather rare, but urgently needed by the industry to meet the increasingly multifunctional needs of advanced mechanical systems and devices. This paper provides an overview of recent progress in the study and understanding of the tribological properties of carbon-based coatings. The design and surface engineering aspects of such coatings are discussed and the principles of superlubricity in these films are presented. Examples of current and future applications for two- and three-dimensional carbon-based structures are also provided.