Recently,ultra-precision polishing processes using smart materials such as magnetorheological(MR)fluids have been used for optics parts such as aspheric lenses.The MR fluid applied in MR polishing is a phase controllable suspension comprising a mixture of CI particles and non-magnetic fluids such as mineral oil and water.The fluids are a kind of smart material that can be controlled according to their flow properties such as viscosity and stiffness.Water-based MR fluids are easily oxidized if the fluids are exposed and this oxidation can bring irregular polishing results.Also,this phenomenon is one of several factors that reduce the life time of MR fluids.In a previous work,CI particles were coated with a polymer or a composite for the improvement of dispersion stability and prevention of corrosion due to oxidation.From this study,the rheological properties such as viscosity and sedimentation of coated CI particles with silica were investigated with a rotational rheometer;MR polishing characteristics of BK7 glass were studied in order to investigate the surface roughness.The wheel speed and magnetic field intensity were chosen as variables. Recently, ultra-precision polishing processes using smart materials such as magnetorheological (MR) fluids have been used for optics parts such as aspheric lenses. MR Fluid applied in MR polishing is a phase controllable suspension comprising a mixture of CI particles and non-magnetic fluids such as mineral oil and water.The fluids are a kind of smart material that can be controlled according to their flow properties such as viscosity and stiffness. Water-based MR fluids are readily oxidized if the fluids are exposed and this oxidation can bring bring irregular polishing results. Also, this phenomenon is one of several factors that reduce the life time of MR fluids. In a previous work, CI particles were coated with a polymer or a composite for the improvement of dispersion stability and prevention of corrosion due to oxidation. From this study, the rheological properties such as viscosity and sedimentation of coated CI particles with silica were investigated with a rotational rheometer; MR polishing characteristics of BK7 glass were studied in order to investigate the surface roughness. wheel speed and magnetic field intensity were chosen as variables.