Influence of silicon contamination on tribology in low earth orbit

To investigate the silicon contamination effects on tribology in low earth orbit, diamond-like carbon (DLC) film, Ti plate, and single crystal MoS₂ were exposed to dimethylsilicone (PDMS) in an ultra high vacuum (UHV) facility equipped with a tribometer and X-ray photoelectron spectroscopy (XPS). In-situ tribological tests and surface analyses were conducted without ambient air exposure. The PDMS exposure led to their adsorptions on the DLC and Ti sample surfaces and did not affect the friction property of the DLC samples. The friction of the Ti sample became low due to the PDMS adsorption. A little of PDMS were adsorbed on the MoS₂ sample. The hyperthermal atomic oxygen (AO) irradiation broke C-O and C-Si bonds included in PDMS that adsorbed on the DLC and Ti surfaces. The low friction due to the PDMS adsorption for the Ti sample disappeared due to the hyperthermal AO irradiation.