Devitrification inhibitors in borosilicate glass and binary borosilicate glass composite

1995 ◽  
Vol 10 (5) ◽  
pp. 1312-1320 ◽  
Author(s):  
Jau-Ho Jean ◽  
Tapan K. Gupta
Keyword(s):  
Borosilicate Glass ◽  
Silica Glass ◽  
Elevated Temperatures ◽  
Glass Composite ◽  
Binary Glass ◽  
High Silica ◽  
Glass Mixture

Cristobalite is known to precipitate out of borosilicate glass (Corning 7740) and a binary glass mixture of borosilicate glass and high silica glass when these glasses are heated to elevated temperatures. To prevent cristobalite from forming in these glass systems, a devitrification inhibitor needs to be found. Among oxides selected for testing, both Al2O3 and Ga2O3 are found to prevent cristobalite from forming in these glass systems.

Effect of alumina on densification of binary borosilicate glass composite

1994 ◽  
Vol 9 (8) ◽  
pp. 1990-1996 ◽  
Author(s):  
Jau-Ho Jean ◽  
Tapan K. Gupta
Keyword(s):  
Activation Energy ◽  
Reaction Layer ◽  
Borosilicate Glass ◽  
Densification Rate ◽  
Glass Composite ◽  
Alkali Ions ◽  
Slowing Down ◽  
Binary Glass ◽  
High Silica ◽  
Glass Mixture

The effect of alumina on densification of the binary borosilicate glass composite, containing low-softening borosilicate glass (BSG) and high-softening high silica (HSG) glass, has been investigated. It is found that with a small amount of alumina, 2-10 vol. %, present as a dopant in the binary glass mixture of BSG and HSG, both densification and densification rate are significantly reduced, but the activation energy of densification at a given densification is dramatically increased. However, no significant change in densification behavior with increasing alumina content from 2 to 10 vol. % is observed. These results are attributed to a chemical reaction taking place at the interface of alumina/BSG, forming a reaction layer adjacent to alumina. Since the composition of the reaction layer is known to be rich in aluminum and alkali ions and poor in silicon, the alkali ions content in BSG is continuously decreased during sintering. Accordingly, the resultant loss of alkali ions from BSG causes a rise in viscosity of BSG, thus slowing down the densification kinetics and increasing the activation energy of densification.

Devitrification inhibitor in binary borosilicate glass composite

1993 ◽  
Vol 8 (2) ◽  
pp. 356-363 ◽  
Author(s):  
Jau-Ho Jean ◽  
Tapan K. Gupta
Keyword(s):  
Binary Mixture ◽  
Reaction Layer ◽  
Borosilicate Glass ◽  
Crystalline Phase ◽  
Silica Glass ◽  
Glass Composite ◽  
Alkali Ions ◽  
Strong Affinity ◽  
Alumina Particles ◽  
High Silica

When an appropriate mixture of a low-softening borosilicate glass (BSG) and a high-softening high silica glass (HSG) is sintered at temperatures ranging from 800 to 1000 °C, a crystalline phase, identified as cristobalite by XRD, is known to precipitate out of the initial amorphous binary mixture of glasses as the sintering continues. The precipitation of cristobalite is found to originate in HSG, and is controlled by the transport of alkali ions (e.g., K+, Na+, and Li+) from BSG to HSG.1 In this paper, we report that when a small amount of alumina is present as a dopant in the above binary mixture of BSG and HSG, the cristobalite formation is completely prevented at the sintering temperatures investigated. The above result is attributed to a strong affinity between Al+3 from alumina and alkali ions from BSG, which diverts the diffusion of alkali ions from HSG to alumina, thus forming a K+ and Al+3-rich reaction layer adjacent to the alumina particles far too rapidly compared to that of cristobalite formation.

An Experimental Comparison of Alternative Solid Forms for Savannah River High-Level Wastes

1981 ◽  
Vol 6 ◽  
Author(s):  
John A. Stone
Keyword(s):  
Borosilicate Glass ◽  
Silica Glass ◽  
Deionized Water ◽  
Experimental Comparison ◽  
Savannah River ◽  
Waste Forms ◽  
High Silica ◽  
High Level ◽  
Selection Of ◽  
High Aluminum

ABSTRACTSamples of borosilicate glass, high-silica glass, tailored ceramic, and SYNROC, incorporating simulated Savannah River high-level defense waste sludges, were leached by the MCC-1 procedure for times up to 28 days. Cesium, uranium, and cerium leach rates are reported for waste forms containing a composite sludge, at 40°C in deionized water, and at 90°C in deionized water, silicate water, and brine. The ordering of the waste forms from best to worst differs for each element leached, and none of the forms show a clear advantage for all the key radwaste elements. Some cesium leach rates for forms containing high-aluminum or high-iron sludges also are presented. So far, only small effects of sludge type have been observed, with one exception. This study is one of several inputs for selection of an alternative waste form for Savannah River waste.

Origin of cristobalite formation during sintering of a binary mixture of borosilicate glass and high silica glass

1994 ◽  
Vol 9 (4) ◽  
pp. 999-1005 ◽  
Author(s):  
Tapan K. Gupta ◽  
Jau-Ho Jean
Keyword(s):  
Binary Mixture ◽  
Borosilicate Glass ◽  
Silica Glass ◽  
High Silica ◽  
Dissolution And Precipitation

It was shown previously1 that cristobalite precipitates out of a mixture of borosilicate glass (BSG) and high silica glass (HSG) when sintered at temperatures ranging from 800 to 1200 °C. In this paper, both direct and indirect evidences are presented to conclude that the formation of cristobalite originates in HSG. It is proposed that the cristobalite is formed as a result of dissolution of HSG in BSG and precipitation at heterogeneously nucleated sites. The process of dissolution and precipitation continues until the whole HSG particle is consumed.

Densification kinetics of binary borosilicate glass composite

1994 ◽  
Vol 9 (2) ◽  
pp. 486-492 ◽  
Author(s):  
Jau-Ho Jean ◽  
Tapan K. Gupta
Keyword(s):  
Activation Energy ◽  
Viscous Flow ◽  
Borosilicate Glass ◽  
Critical Value ◽  
Energy Estimates ◽  
Glass Composite ◽  
Densification Mechanism ◽  
Microstructural Observation ◽  
High Silica ◽  
Kinetics Of

Densification kinetics and mechanism of a binary borosilicate glass composite, containing low-softening borosilicate (BSG) and high-softening high silica (HSG) glasses, have been studied. Apparent activation energy of densification varies from 200 to 400 kJ/mol, and decreases with increasing BSG content at a given densification factor. At a given BSG content, the activation energy of densification initially remains relatively unchanged with increasing densification factor (DF), but increases with densification when DF reaches a critical value (DF∗). Moreover, the value of DF∗ increases with increasing BSG content. From the activation energy estimates of densification, it is concluded that the predominant densification mechanism for BSG ≥ 30 vol. % with DF < DF∗ is viscous flow of low-softening BSG. For BSG ≥ 30 vol. % with DF < DF∗ and BSG ⋚ 20 vol. % with all DF investigated, the activation energies are within the range governed by viscous flow of both BSG and HSG, indicating that the densification is controlled by viscous flow of a new glass with a composition between BSG and HSG. The latter evidence stems from the microstructural observation that as sintering proceeds, the HSG particle undergoes an extensive dissolution process.

High-temperature creep of low-dielectric-constant glass composites

1996 ◽  
Vol 11 (8) ◽  
pp. 2098-2103 ◽  
Author(s):  
Jau-Ho Jean
Keyword(s):  
Dielectric Constant ◽  
Creep Behavior ◽  
Borosilicate Glass ◽  
Softening Point ◽  
Low Dielectric Constant ◽  
Glass Composite ◽  
Glass Composites ◽  
Low Dielectric ◽  
High Silica ◽  
Good Agreement

The constant-stress compressive creep behavior of a low-dielectric constant (low-k) glass composite, containing a low-softening-point borosilicate glass (BSG) and a high-softening-point high silica glass (HSG), has been investigated at 800–950 °C. For all stages of creep, the deformation behavior exhibits linear viscoelasticity, and is controlled by viscous flow of the low-softening-point borosilicate glass. An analytical expression is proposed to describe mathematically the creep behavior of the glass composite, and the results show a fairly good agreement with experimental observations.

Effect of gallium oxide in preventing cristobalite formation in binary borosilicate glass composite

1993 ◽  
Vol 8 (9) ◽  
pp. 2393-2399 ◽  
Author(s):  
Jau-Ho Jean ◽  
Tapan K. Gupta
Keyword(s):  
Binary Mixture ◽  
Reaction Layer ◽  
Borosilicate Glass ◽  
Crystalline Phase ◽  
Gallium Oxide ◽  
Oxide Particle ◽  
Glass Composite ◽  
Alkali Ions ◽  
High Silica ◽  
Oxide Particles

When an appropriate mixture of low-softening borosilicate (BSG) and high-softening high silica (HSG) glasses is sintered at temperatures ranging from 800 to 1000 °C, a crystalline phase, identified as cristobalite by XRD, is known to precipitate out of the initial amorphous binary mixture of glasses as the sintering continues. The precipitation of cristobalite is found to originate in HSG and is controlled by the transport of alkali ions (e.g., K, Na, and Li) from BSG to HSG.1 In this paper we report that when a small amount of gallium oxide is present as a dopant in the above binary mixture of BSG and HSG, the cristobalite formation is completely prevented at the sintering temperatures investigated. The above result is attributed to a strong affinity between Ga+3 from gallium oxide particle and alkali ions from BSG, which diverts the diffusion of alkali ions from HSG to gallium oxide, thus forming a K+ and Ga+3-rich reaction layer adjacent to gallium oxide particles far too rapidly compared with that of cristobalite formation.

An electron spin resonance study of ultraviolet photolyzed methanol adsorbed on porous high-silica glass

1969 ◽  
Vol 47 (8) ◽  
pp. 1375-1379 ◽  
Author(s):  
Michie Shimizu ◽  
H. D. Gesser ◽  
M. Fujimoto
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Silica Glass ◽  
Electron Spin Resonance Study ◽  
Surface Contaminants ◽  
Spin Resonance ◽  
High Silica ◽  
Glass Surfaces ◽  
Spin Resonance Study

The electron spin resonance (e.s.r.) spectra of •CH3, •CHO, H and/or D, and possibly •CH2OH or •CH2OD were found by the ultraviolet (u.v.) photolysis of methanol —OH or —OD on porous high-silica glass at 77 °K. These e.s.r. spectra resemble the results of the u.v. photolysis of X-irradiated methanol indicating that some perturbation and/or sensitization occurred in the molecules by the glass surface. The absence of e.s.r. spectra from the same systems on the acid-leached glass, on the totally fluorinated glass, or on the totally —OH covered glass suggests that (i) the co-existence of surface contaminants, such as Al and Zr and not B, and some of surface —OH could be responsible for producing these free radicals, and (ii) the methanols adsorbed on these glass surfaces are stabilized against u.v. photolysis.

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