Improving the tribological properties of mineral oils is necessary for energy conservation and enhancing machine efficiency. The antifriction and antiwear properties of 10W40 oil were significantly improved by the addition of small amounts of oxidized graphite flakes. According to the X-ray photoelectron spectroscopy (XPS), this improvement was related to the oxidation of ultrasonicated graphite flakes in an ambient atmosphere accompanied by the adsorption of oxygenated compounds. The oxidation induces the defects which modify the chemical structure in an sp 2 graphite lattice. The dispersion stability of graphite
flakes increased in 10W40 oil due to their structural defects and adsorbed oxygen functional groups. This was found to be the main reason behind the improvement of the lubricating properties of graphite flake additives. The formation of transfer films of the graphite structure on the sliding interfaces was shown by the micro-Raman spectroscopy, which explained the improvement of the antifriction and antiwear properties of the mixture by the mechanical reasons.

EB00000003305K

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