Diisooctyl Sebacate-Containing Nickel Nanoparticles for Lubrication of Steel Sliding Parts under Magnetic Fields

Cubic and ellipsoidal nickel nanoparticles surface-capped by oleylamine were used as the additives of diisooctyl sebacate (DIOS) to achieve boundary lubrication of a bearing steel sliding pair. The microstructure, composition, and chemical state of the tribo-films formed on the worn surfaces of the steel blocks lubricated with DISO–Ni nanoparticles were analyzed by X-ray photoelectron spectroscopy, energy-dispersive spectrometry, transmission electron microscopy, and Raman spectroscopy. The findings indicated that both the cubic and ellipsoidal nickel nanoparticles can form in situ repair tribo-films on rubbed steel surfaces under the manipulation of an external magnetic field, which is due to the enhanced adsorption and deposition upon applying a magnetic field. In the meantime, the two kinds of nickel nanoparticles undergo tribochemical reaction during the friction process and catalyze the carbonization of DIOS to form amorphous carbon. The as-generated amorphous carbon is chemically bonded with nickel and nickel oxide nanocrystals to form the in situ repair tribo-film. The as-formed tribo-film composed of a nanocrystal layer, an amorphous carbon layer, and a composite layer consisting of carbon embedded around nickel nanocrystals contributes to the wear reduction of the steel–steel sliding pair under boundary lubrication conditions.