Synthesis of nanostructured lanthanum fluoborate modified by oleylamine and evaluation of its tribological properties as a lubricating additive in synthetic ester

Lanthanum fluoborate modified by oleylamine [denoted as La(BF 4 ) 3 ‐OA] was synthesized as a potential lubricant additive by direct precipitation method with sodium tetrafluoroborate and lanthanum nitrate [La(NO 3 ) 3 ] as the staring materials and oleylamine (OA) as the surface‐modifying agent in distilled water‐ethanol mixed solvent. The effects of reaction temperature, OA to La(NO 3 ) 3 ratio, and surfactant cetyltrimethyl ammonium bromide on the size and shape of as‐synthesized La(BF 4 ) 3 ‐OA were investigated. The crystalline structure and morphology of as‐obtained La(BF 4 ) 3 ‐OA were characterized by X‐ray diffraction, transmission electron microscopy, Fourier transform infrared spectrometry, and X‐ray photoelectron spectroscopy. Moreover, the tribological properties of La(BF 4 ) 3 ‐OA as an additive in dioctyl sebacate, a synthetic ester, were evaluated with a four‐ball machine, and the worn surfaces of the steel balls were analyzed with a field emission scanning electron microscope equipped with an energy dispersive spectrometer accessory. It was found that the as‐synthesized La(BF 4 ) 3 ‐OA exhibits disk‐like nanoflake shape and have a diameter of 10–45 nm, depending on varying synthetic conditions. As‐synthesized La(BF 4 ) 3 ‐OA as an additive in DIOS possesses excellent antiwear and friction‐reduction performance for the steel–steel pair, which is because the as‐synthesized additive simultaneously contain tribologically active elements La, B, and F that facilitate the formation of a boundary lubricating and protecting film on sliding steel surfaces thereby avoiding direct contact of the steel–steel pair and significantly reducing the friction and wear. Copyright © 2016 John Wiley & Sons, Ltd.