Preparation and tribological properties of a kind of lubricant containing calcium borate nanoparticles as additives

摘要

Purpose - Nanoparticles are not well dispersed in non-polar organic solvents due to their hydrophilic property which limits their applications in lubricant oils. To improve the oil-solubility of nanoparticles, a novel technology was used to prepare a kind of lubricant containing calcium borate nanoparticles. Design/methodology/approach - The microstructures of the prepared nanoparticles were characterized by transmission electron microscope (TEM) and infrared spectra (IR). Tribological properties of calcium borate nanoparticles used as additive in base oil were evaluated using four-ball tribotester and SRV tribotester, and the worn surface of the steel ball was investigated by Polarized microscope (PM) and X-ray photoelectron spectroscopy (XPS). In addition, the dispersing stability and antioxidation property of lubricant containing nanoparticles were also studied. Findings - The results indicate that the average size of the prepared nanoparticles is in the range of 50-100 nm, and the surface of the nanoparticles was altered from hydrophilicity to hydrophobicity. At the same time, the nanoparticles can be well dispersed in the base oil totally under novel process which has no significantly negative effect on the antioxidation property. The results of tribological tests show that calcium borate nanoparticles under the novel process (CBNN) show better antiwear property and friction-reducing property in base oil compared to calcium borate nanoparticles under tradition process (CBNT). Based on the results of PM and XPS, it can be deduced that a continuous resistance film containing depositions and the tribochemical reaction products such as B_2O_3, FeB, Fe_2O_3 and CaO formed during the sliding process. Originality/value - The main innovative thought of this work lies in dealing with the oil-solubility problem through the combination effect of surface modification and special blend process of lubricating oil, and this method was first used to prepare lubricant containing calcium borate nanoparticles. It should be helpful for the borate nanoparticles used as additives in engine oil, gear oil and other industrial lubricants.