Comparison of Macro and Microtribological Property of Molybdenum Disulfide Film Exposed to LEO Space Environment

Macro- and microtribological properties of the MoS₂ film exposed to atomic oxygen, ultraviolet rays and radiation both in low earth orbit (LEO) and in ground-based facility were evaluated relevance to micro/nano satellites. MoS₂ samples are exposed to LEO space environment by the space environment exposure device experiment on international space station. Laser-detonation atomic oxygen beam source was used for atomic oxygen simulation on the ground. X-ray photoelectron spectroscopy and energy dispersive spectroscopy measurements suggested that electron beam and ultraviolet exposure did not affect chemical structure of MoS₂ surfaces. However, atomic oxygen-exposed and flight samples showed surface oxidation. It was found that the macroscopic friction coefficient of the flight sample was similar to that of the control sample. In contrast, remarkable increase in friction coefficient in microscopic properties was observed.