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Redox reactions and structure - properties relations in mixed alkali/alkaline earth glasses: - The role of antimony oxides during the fining process- A structural study of copper(I) and copper(II)
Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. (Glass group)
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

It is important to optimize glass compositions for their specific purpose but also for the efficiency of the production process, the manufacturing of glass. This will be beneficial economically and environmentally. Today many processes and glass compositions are already optimized, but due to more strict legislation on toxic elements and substances there must be changes in many glass compositions. One of these elements is antimony; the oxide is used as fining agent to obtain a bubble free glass within a reasonable process time. One aim with this thesis is to obtain a deeper understanding of the fining mechanism in 20R2O-10MO-70SiO2 (R=Na and/or K, M = Ca and/or Ba, Mg, Sr) glasses in order to minimise the amount of Sb2O3. Another intention is to study the structure of 20R2O-10CaO-70SiO2 (R = Na, K) with Cu2+ as probe ion and thus get a deeper knowledge of the surrounding glass matrix.  The optical basicity scale is used to determine the acid/base character of the different glass compositions.

 

Fining efficiency results showed a remarkable increase of the number of remaining bubbles when the glass contains either approximately equal amounts of Na and K or Ca and Ba, Mg or Sr. The much higher number of bubbles in the potassium containing glasses compared to the sodium containing is explained by the increase in viscosity, the increase in optical basicity and thus lower oxygen activity. The differences in the fining efficiency when altering alkaline earth ions cannot be explained by the optical basicity values, it seems to be a more complicated situation.

 

This thesis also reports maximum in Vickers hardness and packing density as well as minimum in glass transition temperature for the mixed alkali glasses. The mixed alkaline earth glasses do not exhibit any clear nonlinear behaviour. Raman spectroscopy measurements showed a variation in the network connectivity which has a clear relation to the optical basicity of the different glass compositions. The combination of UV-Vis-NIR and X-ray absorption spectroscopy measurements showed that the coordination sphere for Cu(II) is a tetragonal distorted octahedron with two elongated Cu-O bonds along the z axis. There were no trends in the degree of tetragonal distortion, thus it was about the same for all the investigated glass compositions. Cu(I) is found to be coordinated by two oxygen ligands in mainly linear coordination sphere, evidenced from X-ray absorption spectroscopy.

Place, publisher, year, edition, pages
Växjö: Linnaeus University Press, 2015. , 73 p.
Series
Linnaeus University Dissertations, 231
Keyword [en]
Fining, oxygen activity, redox reactions, mixed alkali effect, mixed alkali silicate glasses, copper, antimony
National Category
Civil Engineering
Research subject
Technology (byts ev till Engineering), Glass Technology
Identifiers
URN: urn:nbn:se:lnu:diva-46782ISBN: 978-91-87925-82-5 (print)OAI: oai:DiVA.org:lnu-46782DiVA: diva2:861631
Public defence
2015-11-06, Södrasalen, Universitetsplatsen 1, Växjö, 13:00 (English)
Opponent
Supervisors
Available from: 2015-10-20 Created: 2015-10-19 Last updated: 2016-01-27Bibliographically approved
List of papers
1. Compositional effect on fining and oxygen activity in mixed alkali silicate glasses
Open this publication in new window or tab >>Compositional effect on fining and oxygen activity in mixed alkali silicate glasses
2009 (English)In: European Journal of Glass Science and Technology. Part A: Glass Technology, ISSN 1753-3546, Vol. 50, no 1, 62-64 p.Article in journal (Refereed) Published
Abstract [en]

This study monitors, in situ, how alterations of the glass composition affect the results of fining and the oxygen activity (aO2) of the melt. The number of bubbles in annealed glass samples was determined in order to evaluate the fining efficiency. Electrochemical measurement of aO2 was used to monitor in situ the fining charcteristics and conditions of Na2O-K2O-CaO-SiO2 glasses. The glasses investigated had a constant alkali oxide content, but a varying ratio of Na2O/(Na2O+K2O). The Sb2O3 content was o.2 mole-% and NaNO3 or KNO3 was added as oxidising agent in most of the glasses. The results show that the number of bubbles decreases from approximately 1100 to 200 bubbles/ 100 g glass and that aO2 at 1400 deg C increases from 0.2 to 1.2 bar in the glass melt when increasing the Na2O/(Na2O+K2O) ratio from 0 to 1.

Place, publisher, year, edition, pages
Society of Glass Technology, 2009
Keyword
glass. oxygen activity, fining
National Category
Engineering and Technology
Research subject
Technology (byts ev till Engineering)
Identifiers
urn:nbn:se:vxu:diva-4240 (URN)
Available from: 2009-03-09 Created: 2009-03-09 Last updated: 2017-12-13Bibliographically approved
2. The influence of basicity on oxygen activity and antimony oxide fining efficiency in alkali alkaline earth aluminosilicate glasses
Open this publication in new window or tab >>The influence of basicity on oxygen activity and antimony oxide fining efficiency in alkali alkaline earth aluminosilicate glasses
2009 (English)In: European Journal of Glass Science and Technology. Part A: Glass Technology, ISSN 1753-3546, Vol. 50, no 5, 241-246 p.Article in journal (Refereed) Published
Abstract [en]

The number of bubbles was monitored in antimony oxide fined R2O-MxOy-SiO2 and R2O-CaO-Al2O3-SiO2 glasses (R = Na, K; M = Ca, Mg, Ba, Sr, Zn, B, Al, Ti, x = 1 or 2, y = 1, 2 or 3) in order to evaluate the fining efficiency. Electrochemical measurements of oxygen activity were used to, in situ, monitor the fining characteristics and conditions in some of the investigated glass melts. The results showed that an increase of the calculated optical basicity was related to an increased number of bubbles in the glass samples. The oxygen activity in the melt during fining decreased with increased optical basicity.

Place, publisher, year, edition, pages
Sheffield: Society of Glass Technology, 2009
National Category
Materials Engineering
Research subject
Technology (byts ev till Engineering), Glass Technology
Identifiers
urn:nbn:se:vxu:diva-6605 (URN)
Available from: 2010-01-13 Created: 2010-01-13 Last updated: 2017-12-12Bibliographically approved
3. Electronic spectra and molar extinction coefficient of Cu2+ in mixed alkali-alkaline earth-silica glasses
Open this publication in new window or tab >>Electronic spectra and molar extinction coefficient of Cu2+ in mixed alkali-alkaline earth-silica glasses
2015 (English)In: Physics and Chemistry of Glasses-European Journal of Glass Science and Technology Part B, ISSN 1753-3562, Vol. 56, no 1, 8-14 p.Article in journal (Refereed) Published
Abstract [en]

CuO is a very common colorant in blue to turquoise-blue glasses. It is well known that the absorption peak at about 800 nm for silicate glasses is caused by Cu2+, octahedrally coordinated by 6 oxygen ions. It is also known that the [Cu+]/[Cu2+] ratio, the location of the absorption peak and the extinction coefficient of Cu2+ depends on the glass composition. Many investigations have been published with CuO as a colouring agent, but almost none with a mix of Na2O and K2O or CaO and BaO in the base glass. In this study, a base glass composition of 20R2O-10MO-70SiO2 (mol%, R=Na, K and M=Ca, Ba) is used and 0.40 mol% CuO is added. The molar extinction coefficient of Cu2+ is determined for the glasses and peak positions and heights are also presented and discussed.

National Category
Materials Chemistry
Research subject
Technology (byts ev till Engineering), Glass Technology
Identifiers
urn:nbn:se:lnu:diva-45917 (URN)000352247300002 ()2-s2.0-84944036401 (Scopus ID)
Available from: 2015-08-27 Created: 2015-08-27 Last updated: 2017-06-01Bibliographically approved

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