Tribochemical polishing of silicon carbide in oxidant solution

Tribochemical polishing (TCP) has been applied to finish polycrystalline silicon carbide samples. With this technique, material is removed without intentionally using abrasives, by chemical dissolution stimulated by friction in a suitable reactive fluid. For the latter, oxidant solutions such as CrO 3, H 2O 2 and KMnO 4 were used. A smooth (Ra=1 nm), defect-free SiC surface is achieved when a SiC sample is polished in a 3 wt.% CrO 3 solution at speeds of 4–6 cm/s and loads of 1.96 N–9.8 N. The polishing rate is 3–7×10 −6 mm 3/N m when rubbing against a Si 3N 4 tool. Plane samples with surface dimensions of 2 cm×2 cm were polished by rubbing against cast iron. The surface roughness was less than 1 nm, analyzed by atomic force microscopy. The polishing rate is 0.2–0.4 μm/h, which is comparable to that of the finishing step in ceramic lapping. The polishing mechanism of SiC is discussed in terms of interaction between mechanics and chemistry.