Structure and frictional properties of Langmuir-Blodgett films of Cu nanoparticles modified by dialkyldithiophosphate

Abstract

Langmuir-Blodgett (LB) films of dialkyldithiophosphate (DDP) modified Cu nanoparticles were prepared. The structure, microfrictional behaviors and adhesion of the LB films were investigated by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and atomic/friction force microscopy (AFM/FFM). Our results showed that the modified Cu nanoparticles have a typical core-shell structure and fine film-forming ability. The images of AFM/FFM showed that LB films of modified Cu nanoparticles were composed of many nanoparticles arranged closely and orderly and the nanoparticles had favorable behaviors of lower friction. The friction loop of the films indicated that the friction force was affected prominently by the surface slope of the Cu nanoparticles and the microfrictional behaviors showed obvious ''ratchet effect''. The adhesion experiment showed that the modified Cu nanoparticle had a very small adhesive force.

Adhesion and tribological property of Cu nanoparticles‐doped hydrophobic polyelectrolyte multilayers

“…Adhesion force was measured from the force–distance curve recorded on AFM . Figure shows the force–distance curve recorded from frictional image of PEMs with three reaction cycles.…”

Preparation and characterization of layer-by-layer self-assembled polyelectrolyte multilayer films doped with surface-capped SiO2 nanoparticles

“…(SiO 2 /PAA) 9 film has the lowest friction coefficient among the three kinds of tested multilayer films, and its friction coefficient keeps almost unchanged (0.15) with increasing sliding velocity. This might be attributed to the presence of SiO 2 nanoparticles which act as "miniature ball bearings" [20,21] and transform the sliding between the multilayer film and stainless steel to rolling, resulting in lowered friction coefficient. However, (SiO 2 /PAA) 9 film has poor antiwear ability, largely because it has poor adhesion to the silicon substrate when SiO 2 nanoparticles are directly assembled onto the Si substrate.…”

Tribology research in China: A personal view

“…Despite the benefit of low friction, however, the LB films are not strong enough to resist wear. Techniques have been developed to enhance the wear resistance of LB films, for example, by introducing nano-particles into the film to improve load-carrying capacity [47,48], or by using a polymerization process to strengthen intermolecular cohesion forces and film stability [49]. Another interesting piece of work concerns the incorporation of C60 molecules into the ordered structure of chain molecules, in the expectation that the spherical molecules of C60 would serve as 'all bearings' inserted between sliding surfaces.…”