On the Chemo-Mechanical Polishing (CMP) of Si3N4 Bearing Balls With Water Based CeO2 SlurrySource: Journal of Engineering Materials and Technology:;1998:;volume( 120 ):;issue: 004::page 304DOI: 10.1115/1.2807019Publisher: The American Society of Mechanical Engineers (ASME)
Abstract: Among various abrasives investigated for the chemo-mechanical polishing (CMP) of Si3 N4 balls (Jiang, 1998), cerium oxide (CeO2 ) was found to be the most effective polishing medium (even superior to Cr2 03 , Bhagavatula and Komanduri, 1996), yielding an extremely smooth and damage-free surface with a finish Ra of ≈4 nm and Rt of ≈40 nm. In this investigation, the underlying reasons for the superior finish with CeO2 were investigated. Various chemical reactions involved in CMP of Si3 N4 balls with CeO2 were investigated (Gibbs free energy minimization) and a mechanism for the CMP is proposed. The two important functions that CeO2 performs in the CMP of Si3 N4 are: 1. It participates directly in the chemical reaction (oxidization-reduction reaction) with Si3 N4 workmaterial leading to the formation of a thin SiO2 layer, 2. The hardness of CeO2 is closer to that of the thin SiO2 layer formed on Si3 N4 but significantly lower than Si3 N4 workmaterial (≈1/3). It can thus remove the brittle SiO2 reaction product effectively without damaging the Si3 N4 substrate as no abrasion can take place by CeO2 on Si3 N4 . The kinetic action, which involves the removal of the reaction products from the interface by subsequent mechanical action of flowing water and CeO2 is critical to CMP. The chemical reaction could proceed on a continuing basis so long as the passivation layers are removed by the mechanical action at the same time. CeO2 is found to be very effective in a water environment (hydrolysis) leading to the formation of additional SiO2 by reacting with Si3 N4 thereby enhancing the CMP of Si3 N4 . Several similarities between polishing of Si3 N4 and glass (SiO2 ) (Cook, 1990), including the polishing environment (CeO2 plus the magnetic fluid, pH value ≈6) and the mechanism of polishing were observed. Also, after investigating various reaction species in the CMP of Si3 N4 with CeO2 and Cr2 03 , the former is found to be much safer from an environmental point of view (Reddy and Komanduri, 1998).
keyword(s): Polishing , Silicon nitride ceramics , Bearings , Slurries , Water , Mechanisms , Finishes , Gibbs' free energy , Abrasion , Abrasives , Glass , Brittleness , Magnetic fluids AND Functions ,
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contributor author | Ming Jiang | |
contributor author | Nelson O. Wood | |
contributor author | R. Komanduri | |
date accessioned | 2017-05-08T23:56:43Z | |
date available | 2017-05-08T23:56:43Z | |
date copyright | October, 1998 | |
date issued | 1998 | |
identifier issn | 0094-4289 | |
identifier other | JEMTA8-26994#304_1.pdf | |
identifier uri | http://yetl.yabesh.ir/yetl/handle/yetl/120506 | |
description abstract | Among various abrasives investigated for the chemo-mechanical polishing (CMP) of Si3 N4 balls (Jiang, 1998), cerium oxide (CeO2 ) was found to be the most effective polishing medium (even superior to Cr2 03 , Bhagavatula and Komanduri, 1996), yielding an extremely smooth and damage-free surface with a finish Ra of ≈4 nm and Rt of ≈40 nm. In this investigation, the underlying reasons for the superior finish with CeO2 were investigated. Various chemical reactions involved in CMP of Si3 N4 balls with CeO2 were investigated (Gibbs free energy minimization) and a mechanism for the CMP is proposed. The two important functions that CeO2 performs in the CMP of Si3 N4 are: 1. It participates directly in the chemical reaction (oxidization-reduction reaction) with Si3 N4 workmaterial leading to the formation of a thin SiO2 layer, 2. The hardness of CeO2 is closer to that of the thin SiO2 layer formed on Si3 N4 but significantly lower than Si3 N4 workmaterial (≈1/3). It can thus remove the brittle SiO2 reaction product effectively without damaging the Si3 N4 substrate as no abrasion can take place by CeO2 on Si3 N4 . The kinetic action, which involves the removal of the reaction products from the interface by subsequent mechanical action of flowing water and CeO2 is critical to CMP. The chemical reaction could proceed on a continuing basis so long as the passivation layers are removed by the mechanical action at the same time. CeO2 is found to be very effective in a water environment (hydrolysis) leading to the formation of additional SiO2 by reacting with Si3 N4 thereby enhancing the CMP of Si3 N4 . Several similarities between polishing of Si3 N4 and glass (SiO2 ) (Cook, 1990), including the polishing environment (CeO2 plus the magnetic fluid, pH value ≈6) and the mechanism of polishing were observed. Also, after investigating various reaction species in the CMP of Si3 N4 with CeO2 and Cr2 03 , the former is found to be much safer from an environmental point of view (Reddy and Komanduri, 1998). | |
publisher | The American Society of Mechanical Engineers (ASME) | |
title | On the Chemo-Mechanical Polishing (CMP) of Si3N4 Bearing Balls With Water Based CeO2 Slurry | |
type | Journal Paper | |
journal volume | 120 | |
journal issue | 4 | |
journal title | Journal of Engineering Materials and Technology | |
identifier doi | 10.1115/1.2807019 | |
journal fristpage | 304 | |
journal lastpage | 312 | |
identifier eissn | 1528-8889 | |
keywords | Polishing | |
keywords | Silicon nitride ceramics | |
keywords | Bearings | |
keywords | Slurries | |
keywords | Water | |
keywords | Mechanisms | |
keywords | Finishes | |
keywords | Gibbs' free energy | |
keywords | Abrasion | |
keywords | Abrasives | |
keywords | Glass | |
keywords | Brittleness | |
keywords | Magnetic fluids AND Functions | |
tree | Journal of Engineering Materials and Technology:;1998:;volume( 120 ):;issue: 004 | |
contenttype | Fulltext |