The Chemical Preparation And Tribological Property Evaluation Of Surface-modified Nanoparticles

In this thesis, stearic acid surface-modified r-Fe2O3, TiO2 nanoparticles and stearyl alcohol surface-modified different size monodisperse SiO2 nanoparticles were synthesized by chemistry methods. Transmission electron microscope(TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy(XPS), X-ray powder diffraction spectroscopy(XRD) were used to characterize the morphologies and structures of these surface-modified nanoparticles. The formation mechanisms and structure models of these surface-modified nanoparticles were proposed and canvassed. The factors that affect the preparation of these surface-modified nanoparticles were investigated and analyzed. The measures to overcome the affecting factors were proposed. According to demand, four different diameters of surface-capped SiO2 nanoparticles were prepared through adjusting and controlling concentrations of reacting agents. All these prepared nanoparticles were used as additives in lubricating oil liquid paraffin and their tribological properties were evaluated on a four-ball machine. The following main conclusions were reached:1. These surface-capped nanoparticles consist of inorganic nanocores with organic capped-layer chemically absorbed on the surface of the nanocores. Owing to the hydrophobic property of hydrocarbon chain in the organic modification layer, these surface-modified nanoparticles have a good dispersity in organic solvents and exhibit a rather uniform size distribution.2. As lubricating oil additives, all the three surface-capped nanoparticles can markedly promote its friction-reducing and antiwear ability and exhibit higher load-carrying capacity at proper concentrations. The tribological properties of surface-capped TiO2 nanoparticles were best.3. When stearyl alcohol surface-modified SiO2 nanoparticles of different diameters were used as lubricating additives in liquid paraffin, it was foundthat the tribological properties of the nanoparticles were closely related to nanoparticles size. The smaller the diameter of stearyl alcohol surface-modified SiO2 nano-particles, the more excellent the tribological properties of the nanoparticles. When the diameter is under 15 nm, the nanoparticles used as additive in oil show good friction-reducing, excellent antiwear and high loading capacity.