Showing papers by "Morten Mattrup Smedskjær published in 2012"
TL;DR: In this article, a series of sodium boroaluminosilicate glasses from peralkaline to peraluminous compositions by substituting Al 2 O 3 for SiO 2.
Abstract: The complicated structural speciation in boroaluminosilicate glasses leads to a mixed network former effect yielding nonlinear variation in many macroscopic properties as a function of chemical composition. Here we study the composition–structure–property relationships in a series of sodium boroaluminosilicate glasses from peralkaline to peraluminous compositions by substituting Al 2 O 3 for SiO 2 . Our results reveal a pronounced change in all the measured physical properties (density, elastic moduli, hardness, glass transition temperature, and liquid fragility) around [Al 2 O 3 ]–[Na 2 O] = 0. The structural origin of this change is elucidated through nuclear magnetic resonance analyses and topological considerations. Furthermore, we find that addition of 1 mol% Fe 2 O 3 exerts a complicated impact on the measured properties.
106 citations
TL;DR: In this article, Zheng et al. proposed a method to solve the problem of glass and ceramics in Shandong Polytechnic University, Jinan, China by using graph theory.
Abstract: Q. J. Zheng,1,2 R. E. Youngman,2,* C. L. Hogue,2 J. C. Mauro,2 M. Potuzak,2 M. M. Smedskjaer,2 and Y. Z. Yue1,3 1Section of Chemistry, Aalborg University, DK-9000 Aalborg, Denmark 2Science & Technology Division, Corning Incorporated, Corning, New York 14831, USA 3Shandong Key Laboratory of Glass and Ceramics, Shandong Polytechnic University, 250353 Jinan, China (Received 28 March 2012; published 22 August 2012)
63 citations
TL;DR: In this paper, the authors propose an analogous explanation as a physical basis for the Weibull distribution, with an ensemble of flaws in the brittle material serving as a substitute for the traps in the Phillips model.
Abstract: The complicated nature of materials often necessitates a statistical approach to understanding and predicting their underlying physics. One such example is the empirical Weibull distribution used to describe the fracture statistics of brittle materials such as glass and ceramics. The Weibull distribution adopts the same mathematical form as proposed by Kohlrausch for stretched exponential relaxation. Although it was also originally proposed as a strictly empirical expression, stretched exponential decay has more recently been derived from the Phillips diffusion-trap model, which links the dimensionless stretching exponent to the topology of excitations in a glassy network. In this paper we propose an analogous explanation as a physical basis for the Weibull distribution, with an ensemble of flaws in the brittle material serving as a substitute for the traps in the Phillips model. One key difference between stretched exponential relaxation and Weibull fracture statistics is the effective dimensionality of the system. We argue that the stochastic description of the flaw space in the Weibull distribution results in a negative dimensionality, which explains the difference in magnitude of the dimensionless Weibull modulus compared to the stretching relaxation exponent.
38 citations
TL;DR: In this paper, the authors investigated the correlation between glass microstructure and glass stability in soda lime aluminosilicates and found a loss of glass stability (i.e., an onset of crystallization) in the glasses above a critical concentration of Al2O3 when heating at the standard rate of 20 K/min.
Abstract: In this letter, we investigate the correlation between glass microstructure and glass stability (GS) in soda lime aluminosilicates. We find a loss of GS (i.e., an onset of crystallization) in the glasses above a critical concentration of Al2O3 when heating at the standard rate of 20 K/min. This loss in GS may be attributed to formation of five-fold coordinated Al species when [Al2O3]/[Na2O] > 1. The primary crystalline phase is identified as nepheline, in which Al exists in four-fold coordination. This implies that the five-fold coordinated Al is energetically less stable compared to Al in a tetrahedral environment.
32 citations
TL;DR: In this article, the authors present an in situ high-temperature Brillouin spectroscopy test of the shoving model near the glass transition of eight aluminosilicate glass-forming systems and find that the measured viscosity data agree qualitatively with the measured temperature dependence of shear moduli.
Abstract: One of the remaining puzzles of the glass transition is the origin of a glass-forming liquid's ``fragility,'' which quantifies the departure of its relaxation time from Arrhenius-activated kinetics. According to the shoving model proposed by Dyre, fragility is controlled by the instantaneous shear modulus of the liquid, since any flow event requires a local volume increase, and the related activation energy is equal to the work done in shoving aside the surrounding atoms. Here, we present an in situ high-temperature Brillouin spectroscopy test of the shoving model near the glass transition of eight aluminosilicate glass-forming systems. We find that the measured viscosity data agree qualitatively with the measured temperature dependence of shear moduli, as predicted by the shoving model. However, the model systematically underpredicts the values of fragility for our aluminosilicate liquids. This suggests that the dynamics of the glass transition are governed by additional factors beyond the evolution of the shear modulus, such as configurational entropy. We have also compared the glass transition temperature $({T}_{\mathrm{g},\mathrm{vis}})$ obtained from viscosity (temperature at 10${}^{12}$ Pa s) with the onset temperatures of the decrease in elastic moduli (${T}_{\mathrm{g},\mathrm{elas}}$) and increase in the thermal expansion coefficient (${T}_{\mathrm{g},\mathrm{CTE}}$) during heating. While we find an approximate one-to-one correlation between ${T}_{\mathrm{g},\mathrm{vis}}$ and ${T}_{\mathrm{g},\mathrm{CTE}}$, it is clear that the elastic moduli probe a different frequency response of the glass structure, since ${T}_{\mathrm{g},\mathrm{elas}}$ is systematically lower than ${T}_{\mathrm{g},\mathrm{vis}}$.
30 citations
Patent•
29 Feb 2012TL;DR: In this article, the glass compositions that may be used to produce chemically strengthened glass sheets by ion exchange were chosen to promote simultaneously high compressive stress and deep depth of layer or, alternatively, to reduce the time needed to ion exchange the glass to produce a predetermined compressive strength and depth of layers.
Abstract: Glass compositions that may be used to produce chemically strengthened glass sheets by ion exchange. The glass compositions are chosen to promote simultaneously high compressive stress and deep depth of layer or, alternatively, to reduce the time needed to ion exchange the glass to produce a predetermined compressive stress and depth of layer.
30 citations
TL;DR: In this article, a simplified enthalpy landscape is proposed to capture the essential features of glass relaxation and can be solved analytically, and the results of the model show that α and β relaxation processes are largely decoupled.
Abstract: The relaxation behavior of glass is of great scientific and technological importance. However, prediction of glass relaxation behavior using direct first principles techniques is currently infeasible for realistic laboratory time scales. The enthalpy landscape approach has proven to be successful in overcoming this time scale constraint and providing insights into the fundamental physics governing glass transition and relaxation behavior. However, it is still too computationally intensive to calculate representative enthalpy landscapes for multicomponent glasses of industrial interest. It is thus interesting to consider a simplified enthalpy landscape that captures the essential features of glass relaxation and can be solved analytically. Here, we present the analytical solution for such a “minimalist landscape” model that is complicated enough to capture both primary ( α ) and secondary ( β ) relaxation processes, yet simple enough to offer a closed-form solution. Using this minimalist landscape, we perform model calculations to illustrate the relative impact of activation barriers and entropy on glass relaxation behavior. The results of our model show that α and β relaxation processes are largely decoupled, in agreement with recently published experimental results.
23 citations
TL;DR: It is found that most of the composition dependence of the stress optic response can be captured by a linear regression model and that the individual contributions from the alkaline earths to C depend on the alkalin earth-oxygen bond metallicity.
Abstract: Understanding the structural origins of the photoelastic response in oxide glasses is important for discovering new families of zero-stress optic glasses and for developing a predictive physical model. In this Letter, we have investigated the composition dependence of the stress optic coefficient C of 32 sodium aluminosilicate glasses with different types of alkaline earth oxides (MgO, CaO, SrO, and BaO). We find that most of the composition dependence of the stress optic response can be captured by a linear regression model and that the individual contributions from the alkaline earths to C depend on the alkaline earth-oxygen bond metallicity. High bond metallicity is required to allow bonds to be distorted along both the bonding direction and perpendicular to it. These findings are valuable for understanding the photoelastic response of oxide glasses.
23 citations
TL;DR: In this paper, the authors investigated the composition dependence of glass-forming ability (GFA) of a series of iron-containing soda lime borate liquids by substituting Na 2 O for B 2 O 3.
Abstract: We investigate the composition dependence of glass-forming ability (GFA) of a series of iron-containing soda lime borate liquids by substituting Na 2 O for B 2 O 3 . We have characterized GFA by measuring the glass stability against crystallization using a differential scanning calorimeter (DSC). The results show that the GFA decreases when substituting Na 2 O for B 2 O 3 . Moreover, we find that there is no direct link between the kinetic fragility and GFA for the soda lime borate series studied herein. We have also discovered and clarified a striking thermal history dependence of the glass stability against crystallization. In particular, the two glasses containing 20 and 25 Na 2 O mol% do not exhibit crystallization exotherms during the second DSC upscan at 10 and 20 K/min following prior slow (10 and 20 K/min) downscans. This indicates that the glass stability of these compositions can be enhanced by cooling their melts to the glassy state slowly, before any reheating. We explain this phenomenon in terms of the thermal history dependence of boron speciation.
23 citations
TL;DR: In this article, the effect of hydrogen annealing on the optical properties of bismuth-doped sodium aluminosilicate glasses was investigated and it was shown that surface-tinting as well as the decrease of visible luminescence follow Arrhenian kinetics.
Abstract: We report on the effect of hydrogen annealing on the optical properties of bismuth-doped sodium aluminosilicate glasses. The redox state of bismuth in the as-melted glasses is governed by the composition, viz., NIR luminescence is observed only in the glasses with low optical basicity. Upon thermal reduction, visible emission from Bi3+ and, eventually, minor amounts of Bi2+ is significantly lowered, depending on heat-treatment time and temperature, and glass composition. Hydrogen treatment was also found to result in a decrease of the NIR emission intensity and, at the same time, formation of metallic bismuth particles in the surface region. Surface-tinting as well as the decrease of visible luminescence follow Arrhenian kinetics, suggesting that hydrogen permeation is the rate-governing process. Upon re-annealing in air, the effects of thermal reduction on the optical properties are reversible only to a limited extent.
16 citations
TL;DR: In this article, the aging process of chalcogenide and chalcohalide glasses is investigated and the results show that anionic diffusion processes occur in the glasses during aging.
Abstract: The application of chalcogenide and chalcohalide glasses is limited by their uncontrolled drift in properties over time due to aging processes. In the present work, we perform aging experiments on some chalcohalide glasses in oxidizing, inert and reducing atmospheres and afterwards we measure the elemental concentration depth profiles in the surface layer of the glasses by using secondary neutral mass spectroscopy. The results show that anionic diffusion processes occur in the glasses during aging. The aging process leads to a decrease in microhardness of the studied glasses, which is attributed to both physical aging (i.e., structural relaxation) and chemical aging (i.e., compositional change of the surface layer).
TL;DR: In this paper, a general theoretical formalism for quantifying particle distinguishability in classical systems is presented, based on a classical definition of relative entropy, such as applied in quantum information theory.
Abstract: The distinguishability of particles has important implications for calculating the partition function in statistical mechanics. While there are standard formulations for systems of identical particles that are either fully distinguishable or fully indistinguishable, many realistic systems do not fall into either of these limiting cases. In particular, the glass transition involves a continuous transition from an ergodic liquid system of indistinguishable particles to a nonergodic glassy system where the particles become distinguishable. While the question of partial distinguishability of microstates has been treated previously in quantum information theory, this issue has not yet been addressed for a system of classical particles. In this paper, we present a general theoretical formalism for quantifying particle distinguishability in classical systems. This formalism is based on a classical definition of relative entropy, such as applied in quantum information theory. Example calculations for a simple glass-forming system demonstrate the continuous onset of distinguishability as temperature is lowered. We also examine the loss of distinguishability in the limit of long observation time, coinciding with the restoration of ergodicity. We discuss some of the general implications of our work, including the direct connection to topological constraint theory of glass. We also discuss qualitative features of distinguishability as they relate to the Second and Third Laws of thermodynamics.
TL;DR: In this article, the authors proposed a model to describe the relationship between the viscosity of a glass-forming liquid and its configurational contribution to liquid state thermal expansion, which is expressed in terms of three standard parameters: the glass transition temperature (Tg), the liquid fragility index (m), and the extrapolated infinite temperature (η∞), which are obtained by fitting of the Mauro-Yue-Ellison-Gupta-Allan (MYEGA) expression.
Abstract: We propose a model to describe the relationship between the viscosity of a glass-forming liquid and its configurational contribution to liquid state thermal expansion. The viscosity of the glass-forming liquids is expressed in terms of three standard parameters: the glass transition temperature (Tg), the liquid fragility index (m), and the extrapolated infinite temperature viscosity (η∞), which are obtained by fitting of the Mauro–Yue–Ellison–Gupta–Allan (MYEGA) expression to measured viscosity data. The model is tested with experimental data for 41 different glass-forming systems. A good correlation is observed between our model viscosity parameter,h(Tg, m, η∞), and the configurational coefficient of thermal expansion (i.e., the configurational CTE). Within a given class of glass compositions, the model offers the ability to predict trends in configurational CTE with changes in viscosity parameters. Since viscosity is governed by glass network topology, the model also suggests the role of topological constraints in governing changes in configurational CTE.