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Compositional effect on fining and oxygen activity in mixed alkali silicate glasses
Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
2009 (engelsk)Inngår i: European Journal of Glass Science and Technology. Part A: Glass Technology, ISSN 1753-3546, Vol. 50, nr 1, s. 62-64Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
Society of Glass Technology , 2009. Vol. 50, nr 1, s. 62-64
Emneord [en]
glass. oxygen activity, fining
HSV kategori
Forskningsprogram
Teknik
Identifikatorer
URN: urn:nbn:se:vxu:diva-4240OAI: oai:DiVA.org:vxu-4240DiVA, id: diva2:204197
Tilgjengelig fra: 2009-03-09 Laget: 2009-03-09 Sist oppdatert: 2017-12-13bibliografisk kontrollert
Inngår i avhandling
1. 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)
Åpne denne publikasjonen i ny fane eller vindu >>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)
2015 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Växjö: Linnaeus University Press, 2015. s. 73
Serie
Linnaeus University Dissertations ; 231
Emneord
Fining, oxygen activity, redox reactions, mixed alkali effect, mixed alkali silicate glasses, copper, antimony
HSV kategori
Forskningsprogram
Teknik, Glasteknologi
Identifikatorer
urn:nbn:se:lnu:diva-46782 (URN)978-91-87925-82-5 (ISBN)
Disputas
2015-11-06, Södrasalen, Universitetsplatsen 1, Växjö, 13:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2015-10-20 Laget: 2015-10-19 Sist oppdatert: 2018-12-12bibliografisk kontrollert

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