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Impact and friction model of nanofluid for molecular dynamics simulation was built which consists of two Cu plates and Cu-Ar nanofluid. The Cu-Ar nanofluid model consisted of eight spherical copper nanoparticles with each particle diameter of 4 nm and argon atoms as base liquid. The Lennard-Jones potential function was adopted to deal with the interactions between atoms. Thus motion states and interaction of nanoparticles at different time through impact and friction process could be obtained and friction mechanism of nanofluids could be analyzed. In the friction process, nanoparticles showed motions of rotation and translation, but effected by the interactions of nanoparticles, the rotation of nanoparticles was trapped during the compression process. In this process, agglomeration of nanoparticles was very apparent, with the pressure increasing, the phenomenon became more prominent. The reunited nanoparticles would provide supporting efforts for the whole channel, and in the meantime reduced the contact between two friction surfaces, therefore, strengthened lubrication and decreased friction. In the condition of overlarge positive pressure, the nanoparticles would be crashed and formed particles on atomic level and strayed in base liquid.

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The temperature of a friction pair exerts considerable influence on the tribological behavior of a system. In two cases, one with and the other without Cu (copper) nanoparticles, the temperature increase in friction pairs caused by frictional heating and its tribological properties at various temperatures are studied by using the molecular dynamics approach. The results show that temperature distribution and surface abrasion are significantly improved by the presence of Cu nanoparticles. This is one of the reasons for the improvements in tribological properties achieved in the presence of nanoparticles. The temperature and range of influence of frictional heating for the model without nanoparticles are significantly increased with the increase in the sliding velocity; however, in the model with nanoparticles, the temperature gradient is confined to the area near the Cu film. With an increase in the temperature of the friction pair, the improvement in anti-wear properties associated with the presence of Cu nanoparticles becomes more significant.

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Deformation of MoS2 layers directly leads to decrease in potential and ultimately leads to decrease in friction coefficient.