Preparation of Bismuth Nanoparticles via a Thermal Decomposition Process and Evaluation of their Tribological Properties in Synthetic Ester Oils

Abstract

Suface-capped Bismuth nanoparticles were successfully synthesized via solvent thermolysis of bismuth dodecanethiolate as single-source precursors. The morphology and structure of Bi nanoparticles were characterized by means of X-ray power diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectrometry. Tribological properties of as-synthesized Bi nanoparticles as additives in three kinds of synthetic ester oils were evaluated with a four-ball friction and wear tester. It has been found that Bi nanoparticles have an average size of 17 nm and they have good dispensability in base oils. As-synthesized Bi nanoparticles as lubricant additives in synthetic ester oils exhibit excellent friction reducing, antiwear properties as well as load-carrying capacity. The surface morphology of wear scar has been tested and analyzed by scanning electron microscope (SEM) and the chemical states of some typical elements thereon were investigated by energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). The results indicated that as-prepared Bi nanoparticles as an additive in synthetic oils exhibit excellent tribological properties, especially antiwear ability, due to the deposition of nano-Bi with low melting point on worn steel surface leading to the formation of a self-repairing protective layer.