Ultra-fine polishing of glass-ceramics by disaggregated and fractionated detonation nanodiamond

Ultra-fine polishing of glass-ceramics is extraordinarily difficult because of structure inconsistency, chemical inhomogeneity and high rigidity. Detonation nanodiamond particles(NDs) were disaggregated and fractionated by serial centrifuge separation to obtain four stable suspension with average sizes of 54.9 nm，103.8 nm，145.6 nm and 245.4 nm respectively. Those suspensions were then employed to polish glass-ceramics. The evolution of NDs has been carefully characterized by FTIR, Raman and XRD analysis and the finish surfaces of glass-ceramics were investigated with AFM. Results showed that disaggregation treatment modified only nanodiamond surface other than its structure. The amount of nitro-groups on NDs surface increased and the absolute value of ξ-potential was enhanced by least 6 times at the pH 4-5, which was propitious to disperse NDs in mild acidic solution and polish glass-ceramics. Coarse particles performed both higher removal rate and average roughness (Sa) than the finer one. By using the suspension with average size of 54.9 nm, a super smooth surface with Sa 0.208 nm (5 µm×5 µm) was achieved.