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Ion exchange processes on float glass surfaces
Linnaeus University, Faculty of Science and Engineering, School of Engineering. (Glasteknologi)
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Glass can be strengthened by ion exchange and this process is presently used inspecial applications e.g. aircraft windshields, displays and spectacle lenses allowinga higher production cost. Chemically strengthened float glass is moreexpensive than thermally strengthenened, but will likely find applications in futurebuilding and interior constructions where strength demands, design andshape prevent the use of thermal strengthening. The aim of this work is tostudy ion exchange on float glass surfaces. In longer terms, the chemicalstrengthening is planned to be applied to specific critical area e.g. around adrilled hole which without treatment deteriorates the overall strength of theglass.Strengthening the glass through ion exchange can be done in several ways butis most often referred to as the replacement of smaller ions in the glass structureby larger ions from the salt used for treatment. By determining concentrationvs. depth profiles of ion exchanged float glasses, it is possible to calculate thediffusion coefficients and activation energy for different ions. In this study, theless frequently studied approach single-side ion exchange of different ions ofcommercial float glass is described. The concentration vs. depth profiles weredetermined either by the use of the Surface Ablation Cell (SAC), which allowsthe continuous removal of the material from a flat glass surface by slow controlledisotropic dissolution or SEM-EDX.The results of the work are that similar diffusivities and concentration vs. depthprofiles are achieved with single-side ion exchange as from the traditional wayof immersing glass in molten salt bath. Ion exchange of Ag+ stains the floatglass on both sides giving it a yellow or amber-brownish colour. Unlike Ag+ ionexchange of Cu+ stains the float glass on the tin-side only, giving it a yellow,red or red-brown colour. Determining the concentration vs. depth profiles ofion exchanged float glasses with the SAC was convenient except for Ag+ whichwas determined with SEM-EDX. The work confirms that the procedure andequipment of the SAC are very cheap, easy to use and gives data similar tothose gained by much more expensive equipment. Calculated diffusion coefficientsof K+, Ag+ and Rb+ are in accordance with literature data while Cu+ and Cs+ diffusion coefficients were slightly lower. The diffusion coefficients of the different ions follow the order Ag+>K+>Cu+>Rb+>Cs+ and ranges between9.4E-10 and 4.8E-13 cm2s-1. The calculated activation energies for diffusion of K+, Ag+ and Cu+ corresponds with reported literature data and were calculated to: Ag+(air-side) 152 kJ/mol, Ag+(tin-side) 185 kJ/mol, K+ 108 kJ/mol and Cu+115 kJ/mol.

Place, publisher, year, edition, pages
Växjö: School of Engineering, Linnaeus University , 2010. , p. 70
Series
Rapporter: Institutionen för teknik, Linnéuniversitetet ; 1
National Category
Other Materials Engineering
Research subject
Technology (byts ev till Engineering), Glass Technology
Identifiers
URN: urn:nbn:se:lnu:diva-17336Libris ID: 11904336ISBN: 978-91-86491-02-4 (print)OAI: oai:DiVA.org:lnu-17336DiVA, id: diva2:491678
Presentation
2010-01-12, Södrasalen, Växjö, 13:00
Opponent
Supervisors
Available from: 2012-02-13 Created: 2012-02-07 Last updated: 2017-09-05Bibliographically approved
List of papers
1. Diffusion and ion exchange of float glass: Na+ substitution by Cu+, Ag+, Rb+ and Cs+
Open this publication in new window or tab >>Diffusion and ion exchange of float glass: Na+ substitution by Cu+, Ag+, Rb+ and Cs+
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this paper, single-side ion exchange on commercial float glass of the monovalent cations Cu+, Ag+, Rb+ and Cs+ is described. Data on the concentration profiles and calculations on thediffusion coefficients as well as activation energies are reported. The ion exchange of sodiumfor copper or silver is complex, since it is affected by the distribution of the element indifferent oxidation states. Anyhow, it was possible to determine the Cu+ diffusion coefficientsto be in the range 8.0E-12 to 3.4E-11 cm2s-1 and the activation energy 115 kJ/mol. Thepenetration depth of Cu+ exceeds 25 μm. The average diffusion coefficients of silver werecalculated to be in the range 2.1E-10 to 9.9E-10 cm2s-1 and the activation energies for samplestreated at temperatures higher than 470 ºC to 152 kJ/mol and 185 kJ/mol for air-side and tinsiderespectively. The Ag+ penetration depth is beyond 150 μm for the highest temperatures.Rb+-Na+ ion exchange reaches a penetration depth of approximately 10 μm with diffusioncoefficients ranging from 1.7E-12 to 8.6E-13 cm2s-1 while Cs+-Na+ ion exchange reaches apenetration depth of approximately 7 μm with diffusion coefficients ranging from 6.2E-13 to3.8E-13 cm2s-1.

Keywords
ion exchange, surface analysis, diffusion, concentration profile, float glass, monovalent cations
National Category
Other Materials Engineering
Research subject
Technology (byts ev till Engineering), Glass Technology
Identifiers
urn:nbn:se:lnu:diva-17335 (URN)
Available from: 2012-02-07 Created: 2012-02-07 Last updated: 2016-04-22Bibliographically approved
2. The technology of chemical glass strengthening - a review.
Open this publication in new window or tab >>The technology of chemical glass strengthening - a review.
2010 (English)In: Glass Technology, ISSN 0017-1050, Vol. 51, no 2, p. 41-54Article, review/survey (Refereed) Published
Abstract [en]

The methods of chemical strengthening for improving the mechanical properties of oxide glasses are reviewed. Chemical strengthening in compared with thermal strengthening and different methods of measuring strength are discussed. Different ions, salts and other related methods for improving the ion exchange process and mechanical properties are described as well as applications of strengthening.

National Category
Chemical Sciences
Research subject
Technology (byts ev till Engineering), Glass Technology
Identifiers
urn:nbn:se:lnu:diva-5819 (URN)
Available from: 2010-06-04 Created: 2010-06-04 Last updated: 2017-12-12Bibliographically approved
3. Surface Analysis of float glass using Surface Ablation Cell (SAC) Part 2: Determination of the diffusion characteristics of K+-Na+ ion exchange
Open this publication in new window or tab >>Surface Analysis of float glass using Surface Ablation Cell (SAC) Part 2: Determination of the diffusion characteristics of K+-Na+ ion exchange
2010 (English)In: Glass Technology, ISSN 0017-1050, Vol. 51, no 2, p. 55-62Article in journal (Refereed) Published
Abstract [en]

The Surface Ablation Cell (SAC), a laboratory equipment for determining surface concentration profiles, has been utilised to characterise float glass surface ion exchange processes. In this paper, single-side ion exchange is reported. Data on the ion concentration profiles were used to calculate diffusion coefficients as well as the activation energy for K+-Na+ ion exchange. The air-sides of float glass samples were treated with two different salt mixtures, I) KNO3:KCl, 2:1 and II) KNO3:KCl, 1:2, and heated to different temperatures under Tg, 460-520 °C. The diffusion coefficients calculated with Green’s function were in the range I) 1.4x10-11 to 6.8x10-11 and II) 1.8x10-11 to 6.0x10-11 cm2/s while calculated according to Boltzmann-Matano I) 5.7x10-12 to 1.4x10-11 and II) 3.4x10-12 to 6.0x10-12 cm2/s. Average values of the activation energies obtained through Green’s function were I) 111.0 kJ/mol and II) 99.8 kJ/mol for the different salt mixtures.

National Category
Chemical Sciences
Research subject
Technology (byts ev till Engineering), Glass Technology
Identifiers
urn:nbn:se:lnu:diva-5820 (URN)
Available from: 2010-06-04 Created: 2010-06-04 Last updated: 2017-12-12Bibliographically approved

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