Study On The Material Removal Mechanism And Technique In Fenton Assisted Polishing Of Silicon Carbide Optical Material

With the excellent mechanical, physical and optical properties, Silicon Carbideoptical material (SiC) gradually becomes the preferred material of the spatial opticalsystem mirror. But for the high hardness, the SiC polishing is low efficiency. So it’srequested to develop new technologies to improve the polishing efficiency. In this thesis,the mechanism and technique of the Fenton Assisted Polishing of SiC (FAPS) arestudied. Firstly, based on studying the reaction principle between Fenton reagent andSiC, the material removal mechanism of the FAPS is analyzed and an FAPS fluid isprepared. Then, the FAPS processing property is researched and a typical FAPS processflow is finalized. At last, an135mm Sinter SiC flat mirror is figured by FAPS process.A high convergence ratio is verified. The main work of this thesis includes thefollowing sections:(1) The FAPS mechanism is analyzed. When the corrosion depth and hardness ofthe SiC surface measured after dipped in Fenton reagent, the reaction between Fentonreagent and SiC is confirmed and the effects between Fenton reagent and SiC polishingcharacter is researched. Based on the maximum grinding depth of a single particle andgrinding surface topography, the material removal mechanism of the FAPS is analyzed,and the material removal rate ratio between FAPS and classic polishing of SiC isemulated.(2) The FAPS fluid preparing process is researched. The requirements of the FAPSfluid are satisfied, when the FAPS stay long. The stability of the FAPS fluid isevaluated. The availability of the FAPS fluid by the removal function stabilityexperiments is verified.(3) The FAPS processing property is approached. The polishing parameters effectson the removal efficiency and the surface quality are evaluated by Taguchi method. Thepeak material removal rate of the FAPS using asphalt pad is5.8times greater than theclassic SiC polishing using asphalt pad, using the0.5μm particle size diamond abrasive.The surface quality of the FAPS using iron disk can be achieved slightly better than thatof classic SiC polishing using asphalt pad.(4) The typical FAPS process is expounded, with the FAPS using asphalt pad andthe FAPS using iron disk. An135mm Sinter SiC flat mirror is figured by the FAPSprocess. Results showed that in the95%effective aperture, the surface error PV andshape accuracy RMS are converged from1.322λ to0.241λ and0.337λ to0.034λrespectively, and the finial surface roughness is RMS2.963nm in average.