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Influence of partial charge on the material removal rate during chemical polishing
Author(s) -
Suratwala Tayyab,
Steele Rusty,
Miller Philip E.,
Wong Lana,
Destino Joel F.,
Feigenbaum Eyal,
Shen Nan,
Feit Michael
Publication year - 2019
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.15995
Subject(s) - polishing , materials science , slurry , chemical mechanical planarization , particle size , particle (ecology) , mineralogy , chemical engineering , analytical chemistry (journal) , composite material , chemistry , oceanography , engineering , geology , chromatography
A partial charge‐based chemical polishing model has been developed, which can serve as metric for describing the relative polishing material removal rate for different combinations of slurries and workpieces. A series of controlled polishing experiments utilizing a variety of colloidal polishing slurries (SiO 2 , CeO 2 , ZrO 2, MgO, Sb 2 O 5 ) and optical materials [single crystals of Al 2 O 3 (sapphire), SiC, Y 3 Al 5 O 12 ( YAG ), CaF 2 , and LiB 3 O 5 ( LBO ); a SiO 2 ‐Al 2 O 3 ‐P 2 O 5 ‐Li 2 O glass ceramic (Zerodur); and glasses of SiO 2 :TiO 2 ( ULE ), SiO 2 (fused silica), and P 2 O 5 ‐Al 2 O 3 ‐K 2 O‐BaO (Phosphate)] was performed and its material removal rate was measured. As previously proposed by Cook ( J Non‐Cryst Solids . 1990;120:152), for many polishing systems, the removal rate is governed by a series of chemical reactions which include the formation of a surface hydroxide, followed by condensation of that hydroxyl moiety with the polishing particle, and a subsequent hydrolysis reaction. The rate of condensation can often be the rate limiting step, thus it can determine the polishing material removal rate. By largely keeping the numerous other factors that influence material removal rate fixed (such as due to particle size distributions, interface interactions, pad topography, kinematics, and applied pressure), the material removal rate is shown to scale exponentially with the partial charge difference ( δ wp‐s ) between the workpiece and polishing slurry particle for many of the slurry‐workpiece combinations indicating that condensation rate is the rate limiting step. The partial charge ( δ ) describes the equilibrium distribution of electron density between chemically bonded atoms and is related to the electronegativity of the atoms chemically bonded to one another. This partial charge model also explains the age‐old experimental finding of why cerium oxide is the most effective polishing slurry for chemical removal of many workpieces. Some of the slurry‐workpiece combinations that did not follow the partial charge dependence offer insight to other removal mechanisms or rate limiting reaction pathways.