Defect-free surface of quartz glass polished in elastic mode by chemical impact reaction

PENG Wen-qiang(彭文强)^{1, 2}, GUAN Chao-liang(关朝亮)^{1, 2}, LI Sheng-yi(李圣怡)^{1, 2}

(1. College of Mechatronics and Automation, National University of Defense Technology, Changsha 410073, China;
2. Hunan Key Laboratory of Ultra-precision Machining Technology, Changsha 410073, China)

Abstract:Removal of brittle materials in the brittle or ductile mode inevitably causes damaged or strained surface layers containing cracks, scratches or dislocations. Within elastic deformation, the arrangement of each atom can be recovered back to its original position without any defects introduced. Based on surface hydroxylation and chemisorption theory, material removal mechanism of quartz glass in the elastic mode is analyzed to obtain defect-free surface. Elastic contact condition between nanoparticle and quartz glass surface is confirmed from the Hertz contact theory model. Atoms on the quartz glass surface are removed by chemical bond generated by impact reaction in the elastic mode, so no defects are generated without mechanical process. Experiment was conducted on a numerically controlled system for nanoparticle jet polishing, and one flat quartz glass was polished in the elastic mode. Results show that scratches on the sample surface are completely removed away with no mechanical defects introduced, and micro- roughness (R_a) is decreased from 1.23 nm to 0.47 nm. Functional group Ce—O—Si on ceria nanoparticles after polishing was detected directly and indirectly by FTIR, XRD and XPS spectra analysis from which the chemical impact reaction is validated.

Key words:defect-free surface; chemical impact reaction; nanoparticle jet polishing; elastic mode