Lubricant thickness effects on friction between Pd(100) surfaces

Friction measurements have been made between pairs of Pd(100) surfaces prepared in vacuum with adsorbed n-octane films ranging in thickness from 0 to 20 monolayers on each surface. These measurements have been made at lattice misorientation angles of 0° and 45°. Both sets of measurements reveal friction anisotropy at all except the highest n-octane coverages. The friction coefficient drops with increasing n-octane coverage until it reaches a limiting value of μs ≈ 0.4. The static friction coefficient reveals a different dependence on n-octane coverage than has been observed for alcohols. The friction coefficient decreases more slowly with increasing n-octane coverage than for increasing alcohol coverage.