Thin film lubrication of hexadecane confined by iron and iron oxide surfaces: A crucial role of surface structure

A comparative analysis of thin film lubrication of hexadecane between different iron and its oxide

surfaces has been carried out using classical molecular dynamic simulation. An ab initio force-field,

COMPASS, was applied for n-hexadecane using explicit atom model. An effective potential derived

from density functional theory calculation was utilized for the interfacial interaction between hexadecane

and the tribo-surfaces. A quantitative surface parameterization was introduced to investigate the

influence of surface properties on the structure, rheological properties, and tribological performance

of the lubricant. The results show that although the wall-fluid attraction of hexadecane on pure iron

surfaces is significantly stronger than its oxides, there is a considerable reduction of shear stress

of confined n-hexadecane film between Fe(100) and Fe(110) surfaces compared with FeO(110),

FeO(111), Fe2O3(001), and Fe2O3(012). It was found that, in thin film lubrication of hexadecane

between smooth iron and iron oxide surfaces, the surface corrugation plays a role more important than

the wall-fluid adhesion strength.