Structure of borosilicate glasses and melts: A revision of the Yun, Bray and Dell model (original) (raw)
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New Insight into the Residual Rate of Borosilicate Glasses: Effect of S/V and Glass Composition
International Journal of Applied Glass Science, 2013
a b s t r a c t Ten borosilicate glass compositions consisting of a ternary sodium borosilicate containing increasing numbers of some of the key elements (Al, Ca, Zr, Ce) present in nuclear glasses were leached in pure water at 90°C and monitored for up to 14 years. They were then characterized to establish correlations between the glass composition and the short-and long-term alteration rates. We first qualitatively explain the variations of the initial dissolution rate by structural considerations. Then we evidence a qualitative inverse correlation between the initial and residual rates. This counterintuitive result is in fact related to the effect of gel reorganization on the diffusive properties of the passivating layer. Since no equilibrium can be reached between glass and solution, these long-term experiments help in understanding how glasses behave once the solution is saturated with respect to the main glass formers. Very efficient synergy between Ca and hardener elements (Al or Zr) leads to the lowest residual rates, compared with glasses having only one of the two categories of elements. We also confirm the detrimental effect of precipitation of silicate minerals on the residual rate.
Structure of alkali borosilicate glasses and melts according to Raman spectroscopy data
Glass Physics and Chemistry
Using the technique of high temperature Raman scattering spectroscopy, we studied the structure of glasses and melts of the systems Na 2 O-B 2 O 3-SiO 2 , K 2 O-B 2 O 3-SiO 2 , and Cs 2 O-B 2 O 3-SiO 2 with the relations X M 2 O / = 1 (M = Na, K, Cs) and / = 3 and 4/3. Based on the analysis of the regis tered spectra, we have shown that, at a high content of SiO 2 , the disordered network of glasses is composed of the Q 4 , Q 3 , [BO 4/2 ]tetrahedrons and BO 3/2 triangles. When the content of SiO 2 reduces, asymmetric borate triangles BØ 2/2 Oare formed in the structure in addition. A substantial part of borate tetrahedrons are included into the content of mixed borosilicate rings composed of two silicon-oxygen and two boron-oxy gen tetrahedrons. The amount of borate structural units joined into purely borate superstructural groups increases with a decrease of the silicon oxide content, depends on the alkali kation type, and grows in the direction from Cs to Na. An increase in the temperature causes a decrease of various types of rings and growth of the concentration of asymmetric triangles. Both in glasses and melts, the fraction of the BO 2/2 Otriangles depends on the alkali cation type and increases in the succession Cs → K → Na. The results obtained present the basis to suggest that there is some differentiation in the mechanisms of structural reconstruction of the glasses under study by their heating depending on the modifying oxide.
Development and Optimization of Borosilicate Glasses
Review Journal of Chemistry, 2019
Glass has been investigated since pre historic period. Various glasses have been developed in due course of time. It was a long journey, starting from simple soda glasses to highly technical borosilicate glasses. The following sections deal with the chronological developments taken place in pursuit of making heat resistant good quality borosilicate glasses.
Glass samples with the molecular formula (mol%): (30+x) SiO2–(10−x)B2O3–5Al2O3–54Na2O–1MnO2 where x=0, 5, 7·5 and 10 mol% were prepared. The density, glass forming ability, fragility, Vickers hardness and magnetic susceptibility were measured and the results were used to investigate the changes caused by the replacement of boron oxide by silicon oxide. It was found that the density, glass forming ability, fragility and Vickers hardness at first increase at 5 mol% B2O3 (35 mol% SiO2) and then decrease at 2·5 mol% B2O3 (37·5 mol% SiO2) and increase again with increasing SiO2. The replacement of B2O3 by SiO2 increases the concentration of nonbridging oxygens and changes the ratio between BO4 and BO3. The higher density, glass forming ability and fragility of the sample containing 5 mol% B2O3 is due to the ratio between B2O3 and Al2O3 which equals 1, causing BO3 to change to BO4. The magnetic susceptibility increases as the silicon oxide content increases up to 37·5 mol% and then decreases.
Redrawn Phase-Separated Borosilicate Glasses: A TEM Investigation
Microscopy Microanalysis Microstructures, 1997
PACS.61.16.Bg -Transmission, reflection and scanning electron microscopy (including EBIC) PACS.61.43.Fs -Glasses PACS.81.40.-z -Treatment of materials and its effects on microstructure and properties Abstract. 2014 Two alkali aluminoborosilicate glasses containing oriented crystalline particles have been investigated by Transmission Electron Microscopy (TEM). Both materials have been
Thermal poling induced structural changes in sodium borosilicate glasses
… and Chemistry of …, 2009
Abstract: Inorganic glassy materials can exhibit large second order nonlinear optical (NLO) coefficients, χ (2), after thermal poling. Sodium borosilicate glasses with various SiO 2 contents and constant Na 2 O: B 2 O 3 ratio of 0· 2, which characterises the boric oxide ...
The microstructure and optical transmittance thermal analysis of sodium borosilicate bio-glasses
Journal of Thermal Analysis and Calorimetry, 2004
The conditions to fabricate the bulk porous specimens have been studied on account of sodium borosilicate (NBS) glasses. Glass composition, heat treatment at phase separation and TiO 2 addition have been considered in this study. Original glass samples of composition in mol%: sample A: 9.19 Na 2 O-23.58 B 2 O 3-67.23 SiO 2 , sample B: 9.29 Na 2 O-3.17 TiO 2-23.82 B 2 O 3-63.72 SiO 2 were prepared by melting reagent grade chemicals (Na 2 CO 3 , HBO 3 , SiO 2 and AgNO 3) in platinum crucibles at 1480°C for 1h in air. The melts were poured onto stainless steel plates and were annealed at 500°C for 0.5h after cooling. Thus, obtained samples were phase separated at 700°C for 2, 15, 25 and 50h to study their microstructure by scanning electron microscope (SEM). Besides the direct study of the microstructure by SEM, information on glass structural changes of samples are provided by measuring in situ changes by the optical transmittance thermal analysis. The isothermal measurements were carried out at 700, 720 and 740°C. The temperature of phase separation, the leaching and nucleator addition (TiO 2), significantly influence the microstructure of the resulting leached product. TiO 2 additive seems to suppress crystallization of cristobalite: especially at the extended above heat treatment phase separation runs. The phase-separated domains of glasses containing above 80 moles of SiO 2 are so small that it is very hard to observe them by SEM. The glass composition in our case was selected in a way to have relatively large phase separated areas easily observed by SEM at magnification 20,000x. The influence of TiO 2 is not too pronounced. It seems to suppress the cristobalite crystallization, especially of longer heating runs. The image analysis of leached glasses shows the prevailing content of the skeletal phase in a comparison to pores. The TiO 2 content diminishes the content of the skeletal phase.
Structural studies on boroaluminosilicate glasses
Journal of Non-Crystalline Solids, 2008
Two series of boroaluminosilicate glasses having varying mole ratios of B 2 O 3 /Na 2 O (series 1) and B 2 O 3 /SiO 2 (series II) were prepared by conventional melt-quench method. Based on 29 Si and 11 B MAS NMR studies, it has been established that for series I glasses up to 15 mol% B 2 O 3 content, Na 2 O preferentially interacts with B 2 O 3 structural units resulting in the conversion of BO 3 to BO 4 structural units. Above 15 mol% B 2 O 3 for series I glasses and for all the investigated compositions of the series II glasses, silicon structural units are unaffected whereas boron exist in both trigonal and tetrahedral configurations. Variation of microhardness values of these glasses as a function of composition has been explained based on the change in the relative concentration of BO 4 and BO 3 structural units. These glasses in the powder form can act as efficient room temperature ion exchangers for metal ions like Cu 2+ . It is seen that the ion exchange does not affect the boron and silicon structural units as revealed by IR studies. Ó 2007 Published by Elsevier B.V.
Influence of Al2O3 Addition on Structure and Mechanical Properties of Borosilicate Glasses
Frontiers in Materials, 2020
Alkali-borosilicate glasses are one of the most used types of glasses with a high technological importance. In order to optimize glasses for diverse applications, an understanding of the correlation between microscopic structure and macroscopic properties is of central interest in materials science. It has been found that the crack initiation in borosilicate glasses can be influenced by changes in network interconnectivity. In the NBS2 borosilicate glass system (74.0SiO 2-20.7B 2 O 3-4.3Na 2 O-1.0Al 2 O 3 in mol%) two subnetworks are present, i.e., a silicate and a borate network. Increasing cooling rates during processing were found to improve glasses crack resistance. Simultaneously, an increase in the network interconnectivity accompanied by an increasing capacity for densification were noticed. Their individual contribution to the mechanic response, however, remained unclear. In the present study the borosilicate glasses were systematically modified by addition of up to 4.0 mol% Al 2 O 3. Changes in the network connectivity as well as the short-and medium-range order were characterized using Raman and NMR spectroscopy. Both the Raman and the 11 B NMR results show that four-fold-coordinated boron is converted into threefold coordination as the Al 2 O 3 content increases. Additionally, 27 Al NMR experiments show that aluminum is dominantly present in four-fold coordination. Aluminum-tetrahedra are thus charge balanced by sodium ions and incorporated into the silicate network. Finally, nanoindentation testing was employed to link the inherent glass structure and its network configuration to the mechanical glass response. It was found that the glass softens with increasing Al 2 O 3 content, which enhances the crack resistance of the borosilicate glass.