14 May 2007 Pitch polishing of silica: correlation between material removal rates and obtainable surface finishes
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Nano-sized particles with well defined geometries and size distributions suitable for polishing glass and glass ceramics are readily available. Understanding how effective these particles are at removing material and smoothening surfaces during pitch polishing processes is essential for process optimization and achieving better surfaces. This paper details work conducted to measure how effective sub-micron sized particles are at polishing and to isolate the influence of process chemistry and slurry density on the material removal rate (MRR). The paper also details how modifying the slurry pH affects the polishing coefficient of friction (CoF). Fused silica was polished on a synthetic pitch polishing tool with a range of different polishing slurries. Slurries tested included 40nm diameter ceria based slurries with varying density and pH, and both 20nm and 750nm diameter ceria based slurries with fixed density and pH values. Findings include that a) the material removal rate decreases with particle size and decreasing slurry density, b) the surface finish is not strongly dependent on particle size, c) slurries with a pH of 7 are most effective in removing material, while slurries with a pH value of 4 have the lowest MRR, and finally that d) the polishing CoF is greatest at pH 4 and lowest at pH 10. The results indicate that while process chemistry is very influential when polishing with submicron sized particles, the actual nature of the interaction between the abrasive, the workpiece and the tool requires further investigation.
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B. Mullany, B. Mullany, A. Landis, A. Landis, W. Williams, W. Williams, P. Murray, P. Murray, I. Roberts, I. Roberts, } "Pitch polishing of silica: correlation between material removal rates and obtainable surface finishes", Proc. SPIE 10316, Optifab 2007: Technical Digest, 103161H (14 May 2007); doi: 10.1117/12.719782; https://doi.org/10.1117/12.719782

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