Preparation of silica-coated ultrafine diamond and dispersion in ceramic matrix

•The silica-coated ultrafine diamond composites with core/shell structures have been prepared.•The coated ultrafine diamonds have higher dispersion stability than the pristine in the multi-component inorganic salts aqueous solution.•The oxidation resistance temperature of the ultrafine diamond coated with silica is increased by about 101.0 °C.•The coated ultrafine diamonds can be dispersed uniformly in ceramic matrix.

Silica-coated ultrafine diamond (UFD/SiO2) composites were prepared, which were core/shell structures with amorphous silica shell of approximately 5 nm thickness. Contrasting to the pristine UFDs, the dispersion stability of the UFD/SiO2 composites was improved greatly in the multi-component inorganic salts aqueous solution, and the chemical compositions of the ceramic matrix were introduced by multi-component inorganic salts. Meanwhile, the oxidation resistance temperature of the coated UFDs was also increased by around 101.0 °C. Furthermore, by using the polyacrylamide gel method and hot-press sintering process, ceramic composites were fabricated with the UFD/SiO2 aqueous suspension containing multi-component inorganic salts. The results indicated that the UFDs coated with silica could be dispersed uniformly in ceramic matrix, where no obvious UFD agglomerates were observed.