AVS 49th International Symposium
    Nanometer Structures Tuesday Sessions
       Session NS+SE+SS+MM-TuM

Invited Paper NS+SE+SS+MM-TuM1
Ultralow Friction Coatings and Surfaces

Tuesday, November 5, 2002, 8:20 am, Room C-207

Session: Nanotribology
Presenter: J.M. Martin, Ecole Centrale de Lyon, France
Correspondent: Click to Email

From a technological point of view, very low friction in solid lubrication may be interesting in micromechanisms requiring neither friction noise nor instabilities, together with low power consumption. Theoretical approaches at the atomic scale coupled with experimental approaches using proximal probe techniques have been developed to study atomic scale friction behaviors and energy dissipation modes. The two limiting factors for friction reduction at the macro-scale are S0 (shear strength of the interface film) and a (pressure coefficient).@footnote 1@ Approaching very low friction requires the reduction of both S0 and a below the MPa range. Thus lowering to zero friction would require the vanishing of both the adhesive and the external pressure. However these conditions are unlikely to be perfectly achieved in practice. Thus zero friction may not be possible. However, friction values in the 10-3 range or even less (near-frictionless sliding) have been experimentally reached in some practical situations. Here we examine ultralow friction by using a macro-scale sphere/plane contact configuration (maximum pressure of 1 GPa). Friction in the 0.001 range is associated with a shear strength of 1 MPa. We report experimental evidence of superlow friction with different coatings: pure molybdenum disulfide MoS2,@footnote 2@ molybdenum dithiophosphate (Modtp) tribofilms and hydrogenated diamondlike carbon a-CH.@footnote 3@ @FootnoteText@ @footnote 1@ I. Singer, J. Vac. Sci. Technol., A12(5), (1994) 2605. @footnote 2@J.M. Martin, C. Donnet, Th Le Mogne and Th Epicier, Physical Review B 48, No 14, (1993) 10583.@footnote 3@ C. Donnet et al, Surface and Coating Technology, 94, (1997) 456.