Ion Exchange Of Mixed Alkali Glasses

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Ion Exchange Of Mixed Alkali Glasses

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Author : Louis Mattos (Jr)
language : en
Publisher:
Release Date : 1999

Ion Exchange Of Mixed Alkali Glasses written by Louis Mattos (Jr) and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999 with categories.

Investigation Of A Two Step Ion Exchange In Mixed Alkali Glasses

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Author : David Gauss
language : en
Publisher:
Release Date : 2016

Investigation Of A Two Step Ion Exchange In Mixed Alkali Glasses written by David Gauss and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.

Structure Property Relations Of Mixed Alkali And Ion Exchange Silicate Glasses

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Author : Courtney Marie Calahoo
language : en
Publisher:
Release Date : 2016

Structure Property Relations Of Mixed Alkali And Ion Exchange Silicate Glasses written by Courtney Marie Calahoo and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.

Improvement of the mechanical properties of glass was undertaken by furthering understanding of the fundamental relationships between composition, structure and mechanical response. Glasses which were known to already have desirable mechanical properties were made and analysed in order to establish correlations between different properties. Ion exchange (IE), where a smaller ion is replaced by a larger ion without subsequent structural relaxation, causes surface compressive stresses which increase strength and scratch resistance significantly. Micro-Raman spectroscopy was employed to directly measure the volumetric negative strain (contraction) and compressive stress as a function of IE processing temperature by observing changes in Raman peaks correlated with Si-O bond lengths and Si-O-Si bond angles. From the Raman data, the strain of the glass network and consequent stress was calculated relative to several reference states. The reference state of relaxed, fully exchanged glass produced results which matched the complex experimental behaviour. The mechanical response of the IE layer was probed using nano-indentation. Stiffness and hardness were measured as a function of distance from the surface and IE temperature. Additionally, elastic recovery and resistance to plastic deformation were determined. Low IE temperatures (which the Raman results indicated contained the most compressive stress) were observed to improve mechanical properties more than higher IE temperatures, likely due to increased thermal relaxation. The mixed-modifier effect (MME), a deviation from additivity when two or more different types of modifying cations are combined, is known to exist in in static, dynamic and mechanical properties. Yet, the underlying mechanism of the MME is poorly understood, thus, a comprehensive study of several mixed-modifier glass series was undertaken to better elucidate the complex relationships between these three categories of properties. The most significant predictor of the MME was the valence(s) of the mixed cations. Furthermore, the MME in conductivity, packing fraction, bulk modulus, hardness and fracture toughness was related to relative cationic field strength and ionic radii. The MME in shear modulus, Young's modulus and Poisson's ratio was related to structural connectivity rather than the properties of the modifier cations.

Ionic Diffusion In Oxide Glasses

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Author : Günther Heinz Frischat
language : en
Publisher:
Release Date : 1975

Ionic Diffusion In Oxide Glasses written by Günther Heinz Frischat and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1975 with Science categories.

Comparative Raman Study Of Mixed Alkali And Similar Ion Exchanged Glasses

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Author : Charles Windisch
language : en
Publisher:
Release Date : 1979

Comparative Raman Study Of Mixed Alkali And Similar Ion Exchanged Glasses written by Charles Windisch and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1979 with categories.

The Raman spectra of analogous ion exchanged and mixed alkali disilicate and aluminodisilicate glasses of the same relative composition of dissimilar cations have been determined and employed to investigate the origin of the similarity of the mechanical loss features exhibited by them. Ion exchange of Na+ for Li+ in Li2O-Al2O3-2SiO2 glasses is shown to yield glasses whose network structure is different from that of the mixed alkali glasses of the same stoichiometry, but to attain that structure upon annealing. The network structure of ion exchanged and conventionally mixed alkali disilicate glasses are apparently identical. These results are interpreted in light of the mechanical loss spectra of the analogous glasses prepared in the two ways. (Author).

The Effects Of Mgo Replacement Of Cao On The Ion Exchange Behavior Of Mixed Alkali Glass

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Author : Matthew J. O'Connell
language : en
Publisher:
Release Date : 1999

The Effects Of Mgo Replacement Of Cao On The Ion Exchange Behavior Of Mixed Alkali Glass written by Matthew J. O'Connell and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999 with categories.

Electrochemistry Of Glasses And Glass Melts Including Glass Electrodes

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Author : Hans Bach
language : en
Publisher: Springer Science & Business Media
Release Date : 2013-04-09

Electrochemistry Of Glasses And Glass Melts Including Glass Electrodes written by Hans Bach and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-04-09 with Science categories.

This volume presents background information on the electrochemical behaviour of glass melts and solid glasses. The text lays the foundations for a sound understanding of physicochemical redox and ion transfer processes in solid or liquid glasses and the interpretation of experimental results. Other topics discussed include: control of production processes, the field-driven ion exchange between solutions and glasses or within electrochromic thin-film systems, mechanisms responsible for glass corrosion, the concept of optical basicity, and others. Throughout, the text contains practical examples enabling readers to study the various aspects of electrochemical processes in ion-conducting materials.

Internal Friction Of Ion Exchanged Li2o A12o3 2sio2 Glasses

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Author : A. Ismail A. Abdel-Latif
language : en
Publisher:
Release Date : 1971

Internal Friction Of Ion Exchanged Li2o A12o3 2sio2 Glasses written by A. Ismail A. Abdel-Latif and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1971 with Ceramic materials categories.

"Li2O·Al2O3·2SiO2 glass fibers were ion-exchanged from 1 to 300 minutes in a sodium nitrate bath at 366°C. The internal friction was measured along with the lithium and sodium concentration profiles. As sodium progressively replaced lithium, the alkali internal friction peak became smaller while a new peak (mixed alkali peak) appeared and increased in magnitude. These changes in the internal friction are similar to those that occur upon the addition of a second alkali to glasses prepared by conventional melting. The magnitude of both internal friction peaks in ion exchanged glasses was dependent on the overall glass composition. The magnitude of the alkali peak depended upon the unexchanged glass core, whereas that of the mixed alkali peak depended upon the exchanged layer on the glass surface. Dissolving the exchanged surface layer led to the restoration of the original alkali peak and the disappearance of the mixed alkali peak. Changing the alkali distribution did not affect much the mixed alkali peak, but caused the alkali peak to shift to higher temperatures and become smaller. The activation energy for both peaks remained essentially constant during ion exchange of the chilled fibers and this is attributed to the rigid network structure at 366°C. The height of the alkali peak can be used to determine the maximum depth of penetration of the second alkali"--Abstract, leaves iv-v.

Internal Friction Of Ion Exchanged Li2o Al2o3 2sio2 Glasses

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Author : A. Ismail A. Abdel-Latif
language : en
Publisher:
Release Date : 1971

Internal Friction Of Ion Exchanged Li2o Al2o3 2sio2 Glasses written by A. Ismail A. Abdel-Latif and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1971 with Ceramic materials categories.

"Li2O·Al2O3·2SiO2 glass fibers were ion-exchanged from 1 to 300 minutes in a sodium nitrate bath at 366°C. The internal friction was measured along with the lithium and sodium concentration profiles. As sodium progressively replaced lithium, the alkali internal friction peak became smaller while a new peak (mixed alkali peak) appeared and increased in magnitude. These changes in the internal friction are similar to those that occur upon the addition of a second alkali to glasses prepared by conventional melting. The magnitude of both internal friction peaks in ion exchanged glasses was dependent on the overall glass composition. The magnitude of the alkali peak depended upon the unexchanged glass core, whereas that of the mixed alkali peak depended upon the exchanged layer on the glass surface. Dissolving the exchanged surface layer led to the restoration of the original alkali peak and the disappearance of the mixed alkali peak. Changing the alkali distribution did not affect much the mixed alkali peak, but caused the alkali peak to shift to higher temperatures and become smaller. The activation energy for both peaks remained essentially constant during ion exchange of the chilled fibers and this is attributed to the rigid network structure at 366°C. The height of the alkali peak can be used to determine the maximum depth of penetration of the second alkali"--Abstract, pages iv-v.

Ion Exchange Processes And Mechanisms In Glasses

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Author :
language : en
Publisher:
Release Date : 2001

Ion Exchange Processes And Mechanisms In Glasses written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2001 with categories.

Leaching of alkalis from glass is widely recognized as an important mechanism in the initial stages of glass-water interactions. Pioneering experimental studies [1-3] nearly thirty-five years ago established that alkali (designated as M) are lost to solution more rapidly than network-forming cations. The overall chemical reaction describing the process can be written as: {triple_bond}Si-O-M + H --> {triple_bond}Si-OH + M+ (1) or {triple_bond}Si-O-M + H3O+ --> {triple_bond}Si-OH + M+ + H2O. (2) Doremus and coworkers [4-7] fashioned a quantitative model where M+ ions in the glass are exchanged for counter-diffusing H3O+ or H+. Subsequent investigations [8], which have relied heavily on reaction layer analysis, recognized the role of H2O molecules in the alkali-exchange process, without minimizing the importance of charged hydrogen species. Beginning in the 1980s, however, interest in M+-H+ exchange reactions in silicate glasses diminished considerably because important experimental observations showed that network hydrolysis and dissolution rates were principally controlled by the chemical potential difference between the glass and solution (chemical affinity) [9]. For nuclear waste glasses, formation of alteration products or secondary phases that remove important elements from solution, particularly Si, was found to have very large impacts on glass dissolution rates [10,11]. Consequently, recent work on glass/water interactions has focused on understanding this process and incorporating it into models [12]. The ion-exchange process has been largely ignored because it has been thought to be a short duration, secondary or tertiary process that had little or no bearing on long-term corrosion or radionuclide release rates from glasses [13]. The only significant effect identified in the literature that is attributed to alkali ion exchange is an increase in solution pH in static laboratory tests conducted at high surface area-to-volume ratios [14,15]. Renewed interest in alkali ion exchange reactions has come about because of interest in development of durable Na-rich silicate glasses for immobilization of low-activity waste (LAW) at Hanford, Washington [16] and high-level wastes in China [17]. In reactive transport simulations of a LAW glass disposed in a shallow subsurface facility, Chen, McGrail, and Engel [18] showed that ion-exchange reactions increased the radionuclide release rate by over two orders of magnitude when compared with simulations where ion exchange was excluded. Sheng, Luo, and Tang [17] conducted static tests in a simulated groundwater and showed that alkali ion exchange was the dominant release mechanism over a large temperature range. Although the significance of alkali ion exchange reactions in long-term disposal system performance has now been recognized, the fundamental processes and mechanisms controlling the exchange reactions are still remarkably poorly understood, especially with regard to how glass structure affects alkali ion exchange kinetics. Experimental studies of Na release from various simple silicate glasses are numerous [19-23]. However, in all previous studies of which we are aware, no attempt was made to distinguish between M+ release through alkali exchange versus matrix dissolution. The release rate of alkali in all of the early work was convoluted by contributions from matrix dissolution, which dominates in dilute solutions. Also, none of the previous studies attempted to define the relationship, if any, between glass structure (composition) and the kinetics of the ion exchange reaction. The motivation behind this Environmental Management Science Project (EMSP) is to develop a better understanding of how glass structure impacts sodium ion exchange so that improved glasses can be developed. Development of low ion-exchange rate glasses may also permit engineers to use higher loadings in nuclear waste glasses, which would result in substantial savings in production and disposal costs. This report summarizes the experimental data, and the interpretation and analysis of this data that was collected over the duration of the project from 1997 to 2001. Three silicate glass systems were investigated: (1) Na2O-Al2O3-SiO2 system, (2) Na2O-B2O3-SiO2 system, and the (3) Na2O-Al2O3-B2O3-HfO2-SiO2 system.