In situ preparation and surface modification of barium sulfate nanoparticles

Hydrophobic BaSO4 nanoparticles were successfully produced via a one-step process through precipitation reaction in aqueous solution of BaCl2 and (NH4)2SO4 with octadecyl dihydrogen phosphate (n-C18H37OPO3H2, ODP) as a modifying agent. The ODP was used to control the BaSO4 particle size and to modify the surface property of the particles produced from the precipitation. Measurements of relative contact angle and active ratio indicated that BaSO4 samples were hydrophobic. The samples were characterized by using field emission scanning electron microscope, transmission electron microscopy, X-ray diffraction, infrared analysis, thermogravimetric analysis and energy dispersive X-ray analysis. The results suggested that the hydrophobic property was attributed to presence of a thin layer of barium alkyl phosphates, which was formed and coated onto the surface of BaSO4 particles during the reaction process. The thin films at the surface of the BaSO4 modified the surface property and control the particle size and morphology.