Title: Influence of partial charge on the material removal rate during chemical polishing

Abstract

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 (SiO₂, CeO₂, ZrO₂, MgO, Sb₂O₅) and optical materials [single crystals of Al₂O₃ (sapphire), SiC, Y₃Al₅O₁₂ (YAG), CaF₂, and LiB₃O₅ (LBO); a SiO₂-Al₂O₃-P₂O₅-Li₂O glass ceramic (Zerodur); and glasses of SiO₂:TiO₂ (ULE), SiO₂ (fused silica), and P₂O₅-Al₂O₃-K₂O-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 themore » 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. Finally, 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.« less

Authors:

Suratwala, Tayyab  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-9086-1039"

Steele, Rusty ^[1]; Miller, Philip E. ^[1]; Wong, Lana ^[1]; Destino, Joel F. ^[2]; Feigenbaum, Eyal ^[1]; Shen, Nan  ^[1];

• Search DOE PAGES for author "Shen, Nan"
• Search DOE PAGES for ORCID "0000-0003-2164-8773"

Feit, Michael ^[1]

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+ Show Author Affiliations

1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2. Creighton Univ., Omaha, NE (United States)

Publication Date:

Wed Sep 05 00:00:00 EDT 2018

Research Org.:

Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1755833

Alternate Identifier(s):

OSTI ID: 1468661

Report Number(s):

LLNL-JRNL-746065
Journal ID: ISSN 0002-7820; 900931

Grant/Contract Number:  

AC52-07NA27344

Resource Type:

Accepted Manuscript

Journal Name:

Journal of the American Ceramic Society

Additional Journal Information:

Journal Volume: 102; Journal Issue: 4; Journal ID: ISSN 0002-7820

Publisher:

American Ceramic Society

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; materials science; lasers