Nanoscratching of Optical Glass Surfaces Near the Elastic–Plastic Load Boundary to Mimic the Mechanics of Polishing Particles
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2016-01-25 |
| Journal | Journal of the American Ceramic Society |
| Authors | Nan Shen, Tayyab I. Suratwala, William A. Steele, Lana L. Wong, Michael D. Feit |
| Institutions | Lawrence Livermore National Laboratory |
| Citations | 37 |
Abstract
Section titled “Abstract”The nanomechanical deformations on glass surfaces near the elastic-plastic load boundary have been measured on various glasses by nanoscratching using an atomic force microscope ( AFM ) to mimic the mechanical interactions of polishing particles during optical polishing. Nanoscratches were created in air and aqueous environments using a 150‐nm radius diamond‐coated tip on polished fused silica, borosilicate, and phosphate glass surfaces; the topology of the nanoscratches were then characterized by AFM . Using load ranges expected on slurry particles during glass polishing (0.05-200 μN), plastic‐type scratches were observed with depths in the nm range. Nanoscratching in air generally showed deeper & narrower scratches with more pileup compared to nanoscratching in water, especially on fused silica glass. The critical load needed to observe plastic deformation was determined to range from 0.2-1.2 μN for the three glasses. For phosphate glass, the load dependence of the removal depth was consistent with that expected from Hertzian mechanics. However, for fused silica and borosilicate glass in this load range, the deformation depth showed a weak dependence with load. Using a sub‐ T g annealing technique, material relaxation was observed on the nanoscratches, suggesting that a significant fraction of the deformation was due to densification on fused silica and borosilicate glass. Repeated nanoscratching at the same location was utilized for determining the effective incremental plastic removal depth. The incremental removal depth decreased with increase in number of passes, stabilizing after ~10 passes. In water, the removal depths were determined as 0.3-0.55 nm/pass for fused silica, 0.85 nm/pass for borosilicate glass, and 2.4 nm/pass for phosphate glass. The combined nanoscratching results were utilized to define the composite removal function (i.e., removal depth) for a single polishing particle as a function of load, spanning the chemical to the plastic removal regimes. This removal function serves as an important set of parameters in understanding material removal during polishing and the resulting workpiece surface roughness.
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
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