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Surface Analysis of float glass using Surface Ablation Cell (SAC) Part 2: Determination of the diffusion characteristics of K+-Na+ ion exchange
Linnaeus University, Faculty of Science and Engineering, School of Engineering.
Linnaeus University, Faculty of Science and Engineering, School of Engineering.
Glafo AB.
Glafo AB.
2010 (English)In: Glass Technology, ISSN 0017-1050, Vol. 51, no 2, 55-62 p.Article 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.

Place, publisher, year, edition, pages
2010. Vol. 51, no 2, 55-62 p.
National Category
Chemical Sciences
Research subject
Technology (byts ev till Engineering), Glass Technology
Identifiers
URN: urn:nbn:se:lnu:diva-5820OAI: oai:DiVA.org:lnu-5820DiVA: diva2:322187
Available from: 2010-06-04 Created: 2010-06-04 Last updated: 2012-05-09Bibliographically approved
In thesis
1. Ion exchange processes on float glass surfaces
Open this publication in new window or tab >>Ion exchange processes on float glass surfaces
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: S. Karger, 2010. 70 p.
Series
Report (Linnæus University, School of Engineering), 1
National Category
Other Materials Engineering
Research subject
Technology (byts ev till Engineering), Glass Technology
Identifiers
urn:nbn:se:lnu:diva-17336 (URN)978-91-86491-02-4 (ISBN)
Presentation
2010-01-12, Södrasalen, Växjö, 13:00
Opponent
Supervisors
Available from: 2012-02-13 Created: 2012-02-07 Last updated: 2012-02-13Bibliographically approved
2. Modification of Float Glass Surfaces by Ion Exchange
Open this publication in new window or tab >>Modification of Float Glass Surfaces by Ion Exchange
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Glass is a common material in each person’s life, e.g. drinking vessels, windows, displays, insulation and optical fibres. By modifying the glass surface it is possible to change the performance of the entire glass object, generally known as Surface Engineering. Ion exchange is a convenient technique to modify the glass surface composition and its properties, e.g. optical, mechanical, electrical and chemical properties, without ruining the surface finish of the glass.

 

This thesis reports the findings of two different research tasks; characterisation of the single-side ion exchange process and the novel properties induced. The characterisation of the ion exchange process was mainly performed by utilising a novel analytical equipment: the Surface Ablation Cell (SAC), allowing continuous removal of the flat glass surface by controlled isotropic dissolution. SAC-AAS has provided concentration vs. depth profiles of float glass ion exchanged with K+, Cu+, Rb+ and Cs+. In addition, SEM-EDX has provided concentration vs. depth profiles of Ag+ ion exchanged samples and validation of a copper concentration vs. depth profile. From the concentration vs. depth profiles, the effective diffusion coefficients and activation energies of the ion exchange processes have been calculated. Depending on the treatment time and treatment temperature, penetration depths in the range of 5-10 μm (Rb+, Cs+), 20-30 μm (K+, Cu+) and 80-100 μm (Ag+) can be readily obtained. The effective diffusion coefficients followed the order Ag+>K+>Cu+>Rb+>Cs+. This is in accordance with the ionic radii for the alkali ions (K+<Rb+<Cs+) but reverse for the noble metal ions (Cu+<Ag+).

 

The glass properties modified by single-side ion exchange have mainly been characterised by UV-VIS spectroscopy and flexural strength measurements. Cu+ and Ag+ ion exchange give rise to surface colouration, Cu+ copper-ruby and Ag+ yellow/amber. The surface-ruby colouration was found to depend on the residual tin ions in the tin-side of the float glass. The flexural strength was studied using the coaxial double ring-test method which also was suitable for holed specimens. The flexural strength of K+ ion exchanged float glass samples was found to substantially increase compared to untreated.

Place, publisher, year, edition, pages
Växjö, Kalmar: Linnaeus University Press, 2012. 176 p.
Series
Linnaeus University Dissertations, 89/2012
Keyword
Ion exchange, float glass, surface modification, surface colour, flexural strength
National Category
Other Materials Engineering
Research subject
Technology (byts ev till Engineering), Glass Technology
Identifiers
urn:nbn:se:lnu:diva-18447 (URN)978-91-86983-62-8 (ISBN)
Public defence
2012-06-14, Sal Myrdal, Hus K, Växjö, 14:00 (English)
Opponent
Supervisors
Available from: 2012-05-09 Created: 2012-04-23 Last updated: 2012-05-09Bibliographically approved

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