Origin of low-friction behavior in graphite investigated by surface x-ray diffraction

The origin of low-friction behavior in graphite was analyzed using surface x-ray diffraction from a synchrotron source. Surface x-ray diffraction measurements were conducted on c-axis oriented single crystal graphite in high vacuum, in laboratory air and in water saturated air. It was shown that the basal plane spacing at the surface is the same in vacuum, ambient air, or water vapor saturated air. It was found that these results refute this long-held view that the low friction behavior of graphite is due to shearing of weakened basal planes.