Reverse Micro-Emulsion Synthesis of Oxygen-Enriched Low-Friction Boron Nitride/Calcium Borate Microspheres

Abstract

Oxygen enriched boron nitride microspheres (BNOs) coated with nano-sized calcium borate (CB) were synthesised by a reverse micro-emulsion method, in which calcium chloride and sodium borate were selected as the calcium and boron source, respectively. The phase identification and chemical bonding of the composite were confirmed by X-ray driffraction (XRD) and FT-IR spectroscopy. The chemical composition and valence state were determined by X-ray photoelectron spectroscopy (XPS). The morphology and microstructure of the samples were characterised by transmission electron microscopy (TEM) along with surface area analysis. The tribological property of the microspheres as a wear resistance additive in base oil was evaluated by a four-ball tester. The results show that the strawberry-like BNO/CB nanocomposites were fabricated successfully and possess a relatively high friction-reducing and antiwear performance. After the addition of BNO/CB nanocomposites, the friction coefficients of the base oil decreased by 13.3% while the diameter of the grinding spot decreased by 16.4%.