Preparation of TiC-SiC composite coatings on graphite flakes and their effects on hydrophilicity and dispersivity

To improve the water affinity and aqueous dispersivity of graphite, TiC-SiC composite coatings were successfully formed in situ on graphite flakes via a facile molten salt technique. The coatings contain TiC nanoparticles and SiC nanoparticles/nanowhiskers which envelop graphite homogeneously according to the X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and scanning electronic microscope (SEM) observations. Such coatings decreased the contact angle between water and graphite from similar to 101 to similar to 72 degrees, increased the absolute zeta potential to similar to 50 mV in the basic pH range, and lowered the apparent viscosity of its water suspension by at least 50%. It is believed that Ti and Si had been dispersed, slightly dissolved in the NaCI-NaF melt and then transported/diffused to graphite surfaces to form the in-situ composite coatings. The formation mechanisms of the composite coatings and the intermediate phase TiSi2 are proposed based on the characterization results, along with corresponding thermodynamic and kinetic evaluations. The improved water wettability and dispersivity of graphite would make it applicable to various water-based systems.