The tribochemical performance of nano/micrometre borate modified by an N-containing compound as an oil additive

An N-modified nano/micrometre borate (MNMB) as an oil additive was synthesised by an ultrasonic dispersion and emulsion reaction in the microemulsion phase. The particles of the MNMB additive were between 20 and 500 nm in diameter. The tribological properties of the MNMB as an oil additive were investigated using a four-ball tester. The results reveal that the MNMB possesses good tribological properties. When the boron concentration is 0.05 wt.%, the wear-scar diameter is smallest and the seizure load is highest. The antiwear and extreme-pressure properties of the MNMB were best at a viscosity of 65.3 mm/s². Small-area X-ray photoelectron spectroscopy (XPS) and electron probe microanalysis (EPMA) indicate that the MNMB additive can form a tribological mixed reaction film containing C, O, B, N, and Na on a rubbing surface. The elemental boron exists in four different chemical states, but is mainly present in the form of BN on the rubbing surface.