Research On Preparation And Lubrication Behavior Of Bifunctional Silica Nanoparticles

As an economical and environmental friendly nanomaterial, silica nanoparticles show advantages as high surface activity, large surface area and stably chemical properties and are applied in variety of fields. As one of the important applications for nanoparticles, increasing researchers focused on nanoparticles in tribology field, especially used as lubricant additives. It was found that silica nanoparticles exhibited excellent tribological properties as lubricant additives and nanoparticles successfully improved the anti-wear and friction reduction properties of lubricants. However, no systematic study on the tribology properties were found for organic inorganic silica nanoparticles and the relationship between particle size, functional groups and the tribological properties of nanoparticles was not clear. The dispersity and stability of nanoparticles in lubricant were bad. Those problem limited the application of silica nanoparticles. In this dissertation, we studied the influence of particle size and functional groups on the tribological properties of nanoparticles, proposed the mechanism of the anti-wear and friction reduction properties of nanoparticles and optimization design the silica nanoparticles based on experimental result.We first studied the tribological properties of organic inorganic silica nanoparticles with different diameter. A preparation process was proposed based on st?ber method. Silica nanoparticles with four kinds of diameters were prepared, surface modified and then transferred from ethanol to toluene by azeotropic distillation, and finally transferred into PAO lubricants. The rheology properties and tribological properties were tested and the optimal diameter of nanoparticles were studied. The relationship between nanoparticle size and the tribological properties were proposed based on the test result.Based on the study of nanoparticle size, we studied the tribological prop erties of nanoparticles with optimal diameter and different functional groups. The rheology and tribology properties of nanoparticles were studied. The relationship between viscosity, temperature-viscosity relationship of the lubricant with different kinds of nanoparticles were studied. The relationship between functional groups and the tribological properties of nanoparticles were proposed. The mechanism of functional groups on nanoparticles’ tribological performance were discussed.Based on the study of and particle size and functional group of silica nanoparticles. We designed and prepared a bifunctional hairy silica nanoparticles with two kinds of functional groups on the particle surface. The amino groups and alkyl groups were linked onto nanoparticle surface as their good adosrbility and dispersity in lubricant respectively and the ratio of two kinds of functional groups on nanoparticle surface were controlled. Bifunctional hairy silica nanoparticles with different ratio of functional groups on nanoparticle surface were studied with their rheological and tribological properties. The relationship between functional groups ratio and the tribological properties of nanoparticles were studied.The mechanism of organic inorganic silica nanoparticles were studi ed by examining the wear surface of steel ball, testing the flowing properties of tracing particles by high speed camera and simulating the flowing properties of particles in contacting filed using COMSOL. The protecting effect, filling and polishing effec t and entrainment effect of nanoparticles were studied, the mechanism and the development process of those effect were proposed.