| 1. |
- Ali, Sharafat, Associate Professor, 1976-, et al.
(författare)
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Synthesis, structural characterization, and thermal properties of Ca- and La-doped soda-lime glasses by laser melting
- 2020
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Ingår i: International Journal of Applied Glass Science. - : American Ceramic Society. - 2041-1286 .- 2041-1294. ; 11:4, s. 699-706
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Tidskriftsartikel (refereegranskat)abstract
- Laser melting techniques have been used in the preparation of unconventional glasscompositions with high melting temperatures. Thus, we wanted to test the feasibilityof using a CO2 laser in the preparation of nitrogen-rich oxynitride glasses and nitridesilicate glasses. Melting from oxides and metallic raw materials, we wanted to studyfirst glass formation and possible evaporation losses of the glass components. Twoglass series were prepared and studied for their structure and thermal properties, onewith Ca2+- and a higher melting La3+-doped soda-lime-silicate (SLS) series. In lessthan 3 minutes of laser melting, spheres of up to 6 mm diameter were successfullyfabricated. The obtained glass samples were homogeneous and transparent in thevisible region. X-ray diffraction and Raman spectroscopic analysis confirmed theamorphous nature of the synthesized samples. Sodium losses increase as calcium isadded to the soda-lime-silicate glass. As expected, increasing Ca2+ or La3+ additionlead to increased depolymerization of the silicate network. Moreover, the increasesin Tg with the addition of Ca2+ or La3+ ions indicating strengthening of the sodalime-silicate glass by increasing strength of the M-O bonds of divalent and trivalentions over monovalent sodium ions, weak Na-O bonds also resulting in significantevaporation loss during the short laser melting times. The thermal stability decreasesupon addition of Ca2+ or La3+ ions to the soda-lime-silicate glasses.
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| 2. |
- Grund Bäck, Lina, 1974-, et al.
(författare)
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Mixed alkali/alkaline earth‐silicate glasses : Physical properties and structure by vibrational spectroscopy
- 2019
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Ingår i: International Journal of Applied Glass Science. - : American Ceramic Society. - 2041-1286 .- 2041-1294. ; 10:3, s. 349-362
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we investigate the correlation of selected physical properties with structural changes in quaternary mixed modifier alkali/alkaline earth oxide silicate glass systems, focusing either on the mixed alkali effect [(20−x)Na2O–xK2O–10CaO–70SiO2 (x = 0, 5, 10, 15, 20)] or on the mixed alkaline earth effect [20Na2O–(10−y)CaO–yBaO–70SiO2 (y = 0, 5, 10)]. A maximum microhardness and packing density, as well as a minimum glass transition temperature were observed for mixed alkali glasses. The mixed alkaline earth glasses do not exhibit any clear extrema in any of the properties studied. The hardness and glass transition temperature decreases, while the density and molar volume increases with increasing BaO content. Raman spectroscopy showed an increase in the Q3 group compared to the Q2 and Q4 groups as the high field strength ions Na+ or Ca2+ are substituted by their low field strength analogs K+ or Ba2+. In the mixed alkali series, the high field strength ion Na+, seems to push the low field strength ion K+ into lower energy sites when present simultaneously, while such an effect is not apparent for the mixed alkaline earth glasses, where the far IR spectra of mixed glasses are equivalent to the weighted averages of the pure glasses.
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| 3. |
- Weaver, Jamie L., et al.
(författare)
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Pre‐Viking Swedish Hillfort Glass : A Prospective Long‐Term Alteration Analogue for Vitrified Nuclear Waste
- 2018
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Ingår i: The International Journal of Applied Glass Science (IJAGS). - : John Wiley & Sons. - 2041-1294 .- 2041-1286. ; 9:4, s. 540-554
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Tidskriftsartikel (refereegranskat)abstract
- Models for long‐term glass alteration are required to satisfy performance predictions of vitrified nuclear waste in various disposal scenarios. Durability parameters are usually extracted from short‐term laboratory tests, and sometimes checked with long‐term natural experiments on glasses, termed analogues. In this paper, a unique potential ancient glass analogue from Sweden is discussed. The hillfort glass found at Broborg represents a unique case study as a vitrified waste glass analogue to compare to Low Activity Waste glass to be emplaced in near surface conditions at Hanford (Washington State). Glasses at Broborg have similar and dissimilar compositions to LAW glass, allowing the testing of long‐term alteration of different glass chemistries. Additionally, the environmental history of the site is reasonably well documented. Initial investigations on previously collected samples established methodologies for handling and characterizing these artifacts by laboratory methods while preserving their alteration layers and cultural context. Evidence of possible biologically influenced glass alteration, and differential alteration in the two types of glass found at the Broborg site is presented.
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| 4. |
- Wójcik, Natalia A., et al.
(författare)
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Niobate in silicate and phosphate glasses : Effect of glass basicity on crucible dissolution
- 2022
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Ingår i: International Journal of Applied Glass Science. - : John Wiley & Sons. - 2041-1286 .- 2041-1294. ; 13:1, s. 121-134
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Tidskriftsartikel (refereegranskat)abstract
- Using niobium crucibles for melting phosphate and silicate glasses of various modifier oxide contents, and therefore varying optical basicity (Lambda), was found to result in varying dissolution rates of niobate during melting. Because of their high electronic polarizability, even small concentrations of niobates are detectable in the Raman spectra of glasses. Even <1 mol% Nb2O5 can be identified, as independently confirmed by SEM-EDX analysis. Silica-rich glasses (similar to 60% SiO2, Lambda similar to 0.6) did not show significant Nb dissolution from the crucible, while higher basicity metasilicate glasses (similar to 50% SiO2, Lambda similar to 0.65) and pyrophosphate glasses (similar to 30% P2O5, Lambda similar to 0.7) did show the typical niobate signature in the Raman spectra at 810-840 cm(-1), depending on composition. While niobium is well-dissolved throughout the pyrophosphate glass, metasilicate glasses showed a much more intense Raman signature of niobate units near the outer surface of the glass. Measurements along the cross-section of a fractured metasilicate glass showed a steady decrease of the strength of the niobate signature from the surface toward the bulk of the material. Besides correlation with optical basicity, the tendency of melts to dissolve Nb crucible was discussed in terms of the connectivity or polymerization of the network and the corresponding melt viscosity.
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