Self-assembly of monodisperse SiO2–zinc borate core–shell nanospheres for lubrication

Spherical SiO2 particles have been successfully coated with zinc borate layers through a self-assembly process. The resulted SiO2–Zn5B4O11 core–shell nanospheres were characterized by X-ray diffraction (XRD), infrared spectra (IR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS). The obtained SiO2–Zn5B4O11 core–shell nanospheres have perfect spherical shape with narrow size distribution (average diameters 50 nm), i.e., the cores with mean diameters of 40 nm and the shells with an average thickness of 5 nm, monodisperse and smooth surface. Moreover, the friction coefficient of the base oil was decreased by the addition of SiO2–Zn5B4O11 core–shell nanospheres.