Effects of titania films on the oxidation resistance and dispersibility of ultrafine diamond

•The titania-coated ultrafine diamond (UFD/TiO2) composites with core/shell structures have been prepared in acidic condition.•The coated UFD powders have higher dispersion stability than the pristine in the multi-component inorganic salts aqueous solution.•The oxidation resistance temperature of the coated UFD powders is higher approximately 150 °C than the pristine.

Titania-coated ultrafine diamond (UFD/TiO2) composites had been prepared successfully, which were the core/shell structures with amorphous titania shells of approximately 4 nm thickness using tetrabutyl titanate (TBOT) as the precursor of titania in acidic condition via sol–gel process. It had a great influence on the synthesis of UFD/TiO2 composites to control the hydrolysis and polymerization of TBOT. Contrasting to the pristine ultrafine diamond powders (UFDs), the coated UFDs could be kept dispersed in the multi-component inorganic salts aqueous solution at least 12 h without aggregation. More importantly, the oxidation resistance temperature of the coated UFDs was enhanced nearly 150 °C than the pristine, improving greatly the sintering temperature of UFD-vitrified bond composite powers obtained by polyacrylamide gel (P–G) method.