Preparation and characterization of highly catalytic and corrosion resistant Fe–Ti–O magnetorheological composite powders

Magnetorheological finishing (MRF) is one of the candidate technologies for the efficient polishing of single crystal silicon carbide (SiC). It is of great importance to improve the efficiency of MRF and reduce the costs by improving the catalytic activity and corrosion resistance of iron-based magnetic particles while maintaining the magnetic properties. In this work, α-Fe2O3 and TiH2 powders were used as raw materials, and Fe–Ti–O composite powders for MRF were prepared by three processes: ball milling + reduction (R1), ball milling + calcination (R2) and ball milling + calcination + reduction (R3). The effects of TiH2 content (5 wt%-15 wt%) on the phase composition, microstructure, catalytic activity and corrosion resistance of the composite powders were investigated. The results demonstrated that submicron α-Fe2O3/TiH2 mixed powders with uniform composition were obtained by ball milling. Compared to the powders prepared by the R1 and R2 routes, the Fe–Ti–O composite powders prepared by the R3 were composed of Fe2TiO4 particles (500–800 nm) and iron-rich particles (30–200 nm). The iron-rich particles were uniformly distributed on the surface of the agglomerated Fe2TiO4 spheres, forming a unique ''Ferrero'' structure. When the TiH2 content was 15 wt%, the Fe–Ti–O composite powders exhibited the required saturation magnetization (Ms) for MRF (61.0 emu/g), the highest catalytic activity and the best corrosion resistance.