The tribological behaviors of ordered system ultrathin films

Abstract

The tribological behaviors of various long chain organic molecule LB films, organic molecule modified inorganic nanoparticle LB films, and the C60-LB films were systematically investigated. The correlation between the structure and tribological behavior of the LB films has been explored, while the structural changes of the LB films during friction process were analyzed with Fourier transform infrared (FTIR) microscope. Three kinds of C60-LB films were prepared; its micro-frictional behaviors were investigated by AFM. As the results, the tribological behavior of long chain organic molecule LB films is highly dependent on the molecular chain length and the characteristics of the polar end groups. The optimal tribological behavior is reached at a balanced stiffness and toughness of the molecular chain, which is also related to the bonding strength of the LB film to the substrate. The LB films of nanoparticles modified with organic molecules are superior to long chain organic molecule ones in terms of resisting wear. This is attributed to the enhanced load-carrying capacity of the inorganic nanocores in the LB films of nanoparticles modified with organic molecules. The tribochemical changes including ordering and partial decomposition of the organic modifier have been observed in the sliding of the LB films of inorganic nanoparticles modified with organic molecules against steel. C60-LB film shows excellent tribological behavior, which is highly dependent on the interaction between the C60 nanocluster and the organic long chain molecules.