Preparation and sintering of silica-coated ultrafine diamonds–vitrified bond composite powders

•The silica-coated ultrafine diamond (UFD) was synthesized by using a PVP-aided method.•The silica-coated UFD bond composite powders with higher homogeneity were prepared by a polyacrylamide gel method.•The porous vitrified bond UFD wheels with no obvious aggregation and degradation of UFD were fabricated.•The porosity and bending strength of porous vitrified bond UFD wheels were 36.3% and 62.9 MPa, respectively.

The oxidation resistance of ultrafine diamonds (UFDs) was improved by encapsulating UFDs into silica shells forming core/shell structures with a PVP-aided method. Meanwhile, the dispersion stability of the UFDs in the inorganic salt aqueous solution was also improved greatly. In addition, adopting the silica-coated UFD aqueous suspension including multi-component inorganic salts, the coated UFDs–vitrified bond composite powders with higher homogeneity were obtained by using a polyacrylamide gel method, which was used for manufacturing the vitrified-bonded UFD wheels. The porous specimens of the UFD grinding wheels were fabricated with the above composite powders at low temperature in the air and in a muffle furnace. The results suggested that the porosity, bulk density and bending strength of the specimens were 36.3%, 1.71 g/cm− 3 and 62.9 MPa, respectively. Moreover, no obvious aggregation and degradation of UFDs were observed in the above UFD specimens. These results demonstrate a new pathway of preparing multifunctional nanostructure with a low-aggregation and high oxidation resistance that can be applied for manufacturing vitrified-bonded UFD wheels.