Figure 6. Schematic illustrations of partially di-hydrated hydrogen of the friction pair in lubrication model and molecular schematic presentation of the coordination layer and metal oxy-hydroxide.

(a) The lubrication diagrammatic sketch of the friction pair under castor oil lubrication; (b) The hexanoic acid bonded metal oxy-hydroxide and fragment of a general intercalation NiOOH and FeOOH structure displaying the repulsive electrostatic forces that lead to slid easily between the contacting asperities.