Modification Of Lubricant Oil With Magnetic Nanoparticals As Additive

Performance of lubricant oil depends on additive contents and its properties. High performance additives can largely improve the load-carrying and antiwear capacity of lubricant oil. Nanoparticles as lubricant additives and magnetic fluid lubrication are research hotspots at home and abroad. Researches show that lubricant performance can be largely improved with different types of nanoparticles. Magnetic fluid lubrication can brim lubricant surfaces and realize continuous lubrication. However, studies on the nano additives and magnetic fluid lubrication tend to focus on one aspect, are not systematic.MnZnFe₂O₄ magnetic nanoparticles with a mean particle size of 5.2nm can be prepared. MnZnFe₂O₄ magnetic nanoparticles can be directly added into lubricant oil and also be used as magnetic additives under external magnetic field.This article had a comprehensive discussion on the effect of nano-additives, magnetic field on the lubrication and friction properties from some important impact factors and studied lubricant mechanism:1) Viscosity . In terms of hydrodynamic lubrication, elastohydrodynamic lubrication, thin film lubrication and boundary lubrication, the lubricant viscosity will affect the film formation, film thickness, film morphology, as well as the load-carrying capability.2) The film-forming ability. With a high film-forming ability, lubricant oil can quickly form a stable, high strength, thick film which separate friction interface in the friction process,and get better anti-wear ,friction-reducing capability.3) Load carrying capability. Load-carrying capacity indicates lubricant film strength.4) Tribological properties. Friction coefficient, wear scar diameter, oil temperature assess the comprehensive lubricant performance .The results showed that: For the lubricant oil with magnetic nanoparticals as additive, under no magnetic field,â‘ When mass fraction was less than 5.00%, the viscosity was reduced; when the mass fraction was less than 50%, more than 5.00%, the viscosity increases slowly; when the mass fraction was greater than 50%, the viscosity increased significantly.â‘¡when the mass fraction was less than 5%, viscosity decreases, while oil film strength increased greatly and load-carrying capability increased to 2 times that of the base oil.â‘¢In the same working conditions, film center thickness increased, especially critical film thickness of the thin film lubrication increased to 3 times that of the base oil.â‘£Compared with the base oil, friction coefficient and wear scar diameter decreased at high-load and start-up phase. Under external magnetic field, lubricant oil with magnetic nanoparticals as additive exhibited a better performance than base oil: viscosity, load-carrying capacity further increased, while the friction coefficient, the wear scar diameter further decreased in the same conditions.Therefore, it was pointed out: When distance is smaller to some value, weak magnetic-moment will be formed among magnetic particles, magnetic particles and the metal surface. It makes part of the adjacent magnetic particles form a dynamic aggregation, some magnetic particles be adsorbed on the metal surface, which contribute to form a high strength and thick physical adsorbed film.The external magnetic field can further enhance the viscosity and the surface adsorption potential of the friction pair. It can also help to form shorter, unstable particle chains among the magnetic nanoparticles. So a higher strength, thicker adsorbed film is formed rapidly. Experiment showed that magnetic field can further improve tribological properties of lubricating oil with magnetical nanoparticles as additive, and help to form a high-intensity physical adsorbed film quickly, improve the lubrication performance in high-load and start-up state.Based on the test and theoretical analysis, physical models of thin film lubrication which contained magnetic nanoparticles under no external magnetic field and external magnetic field was established. It provides a theoretical basis to study the lubricant mechanism of lubricant oil with magnetic nanoparticles as Additive.