Ultraprecision Machining of Si<sub>3</sub>N<sub>4</sub> Ceramics with Shear-Thickening Polishing

Shear-thickening polishing (STP) technology was used on ultraprecision machining of Si 3 N 4 ceramics. The STP slurry with diamond abrasives was prepared for STP process and its rheological property was studied. The polishing performance of Si 3 N 4 ceramics with STP was analyzed. Results show that STP slurry with diamond abrasives exhibits non-Newtonian power-law fluid characteristics with shear-thickening effect. As using STP slurry with abrasive particle size of 0.2 μm, the material removal rate changed from 4.22 to 4.05 μm/h after 60 mins ́ polishing; and decreased from 3.88 to 3.75 μm/h after 120 mins ́ polishing. The average surface roughness reduced from R a 107.2 to R a 6.5 nm after 120 mins ́ polishing.