Network Structure of Oxide Glasses Containing Alkali & Other Ions by Diffraction and MD Simulations

1996 ◽  
Vol 455 ◽  
Author(s):  
Itaru Yasui ◽  
H. Nagasawa ◽  
H. Matsumoto ◽  
T. Mabuchi
Keyword(s):  
Network Structure ◽  
Tellurite Glass ◽  
Glass Structure ◽  
Diffraction Method ◽  
Md Simulations ◽  
Silicate Glasses ◽  
Oxide Glass ◽  
Oxide Glasses ◽  
Alkali Ions ◽  
Mixed Alkali

ABSTRACTNetwork structures of several kinds of oxide glasses were analyzed by means of neutron or x-ray diffraction method and molecular dynamics (MD) simulations including silicate, borate and tellurite glasses. The basic scheme of the structure highly depends on the bonding nature of network forming oxide, but the size of the alkali ions is another important factor to control the network structure of the glass. Structures of silicate glasses are rather easily reproduced by means of MD simulation, whereas borate or tellurite glass structures are hard to be constructed by MD calculation with only 2-body potentials. It is necessary to use adequate potentials to control the bonding angles of O-M-O or M-O-M. The network structure of tellurite glass seems very complex because of the shape of structural units with low symmetry, the use of a new kind of potential was found indispensable to reproduce the glass structure by MD.In addition to the network structure, the polarization of ions seems to be important to understand the whole vision of oxide glass structures. A new kind of MD was developed which took polarization of ions into account to understand the mixed alkali effects in silicate glasses.

scholarly journals Mixed-Alkali Effect in Borate Glasses: Thermal, Elastic, and Vibrational Properties

Solids ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 16-30
Author(s):  
Seiji Kojima
Keyword(s):  
Vibrational Properties ◽  
Borate Glasses ◽  
Lithium Borate ◽  
Cauchy Type ◽  
Oxide Glasses ◽  
Raman Scattering Spectroscopy ◽  
Alkali Ions ◽  
Mixed Alkali ◽  
Mixed Alkali Effect ◽  
Longitudinal Modulus

When oxide glasses are modified by dissimilar alkali ions, a maximum in the electric resistivity or the expansion coefficient appears, called the mixed-alkali effect (MAE). This paper reviews the MAE on the thermal, elastic, and vibrational properties of the mixed-cesium lithium borate glasses, x{(1−y)Cs2O-yLi2O}-(1−x)B2O3. For the single-alkali borate glasses, xM2O(1−x)-B2O3 (M = Li, Na, K, Rb, and Cs), the glass transition temperature, Tg = 270 °C, of a borate glass monotonically increases as the alkali content x increases. However, for the mixed-cesium lithium borate glasses the Tg shows the minimum against the lithium fraction y. The dependences of the elastic properties on the lithium fraction y were discussed regarding the longitudinal modulus, Poisson’s ratio, and Cauchy-type relation. The internal vibrational bands related to the boron-oxide structural groups and the splitting of a boson peak were discussed based on Raman scattering spectroscopy. The MAE on various physical properties are discussed on the basis of the changes in the coordination number of the borons and the nonbridging oxygens caused by the dissimilar alkali ions.

scholarly journals Towards Ultra-Tough Oxide Glasses with Heterogeneities by Consolidation of Nanoparticles

2020 ◽  
Author(s):  
Yanming Zhang ◽  
Liping Huang ◽  
Yunfeng Shi
Keyword(s):  
Cold Work ◽  
Silicate Glasses ◽  
Alumina Content ◽  
Oxide Glass ◽  
High Alumina ◽  
Oxide Glasses ◽  
Flow Strength ◽  
High Alumina Content ◽  
Dynamics Simulations ◽  
Tough Glasses

We prepared heterogeneous alumina-silicate glasses by consolidating nanoparticles using molecular dynamics simulations. Consolidated glasses from either low alumina content alumina-silicate glasses or high alumina content alumina-silicate glasses show significantly improved ductility around consolidation pressure of ~3 GPa. The introduced structural heterogeneities, namely over-coordinated network formers and their neighboring oxygen atoms, are identified as plasticity carriers due to their high rearrangement propensity. In addition, consolidated oxide glass from both 23.4Al2O376.6SiO2 and 73.1Al2O326.9SiO2 nanoparticles show improved flow strength (up to 1 GPa) due to the introduction of chemical heterogeneities. Last but not least, apparent hardening behavior appears upon cold work in consolidated glasses, with an increase of yield strength from ~3.3 GPa to ~6.4 GPa. This method is a big advancement toward ultra-strong and ultra-tough glasses by breaking the structure, composition and size limitations in traditional melt-quench process.

Nonlinear impedance in oxide glasses containing single and mixed alkali ions

2012 ◽  
Vol 225 ◽  
pp. 359-362
Author(s):  
Ryszard Jan Barczyński ◽  
Leon Murawski
Keyword(s):  
Oxide Glasses ◽  
Alkali Ions ◽  
Mixed Alkali

scholarly journals The Influence of Environment in the Alteration of the Stained-Glass Windows in Portuguese Monuments

Heritage ◽  
2018 ◽  
Vol 1 (2) ◽  
pp. 365-376 ◽  
Author(s):  
Teresa Palomar ◽  
Pedro Redol ◽  
Isabel Cruz Almeida ◽  
Eduardo Pereira da Silva ◽  
Marcia Vilarigues
Keyword(s):  
Analytical Techniques ◽  
Soda Lime ◽  
Silicate Glasses ◽  
High Humidity ◽  
Atmospheric Conditions ◽  
Stained Glass ◽  
Mixed Alkali ◽  
Alkali Silicate ◽  
High Humidity Environment ◽  
Humidity Environment

This work presents the results of the exposure of soda-lime, potash-lime and mixed-alkali silicate glasses during ten and twenty months in different Portuguese monuments with historical stained-glass windows to characterize the influence of local environmental conditions. The glass samples were exposed in the Monastery of Batalha (Batalha), the Monastery of Jerónimos (Lisbon), and the Cathedral of Évora (Évora). A set of analytical techniques to assess the physicochemical effects were used, including optical microscopy and Fourier transform infrared spectroscopy. All the samples presented crystalline deposits on their surface; however, their quantity and nature depended on the atmospheric conditions during the days before the collection. Potash-lime silicate glass was the most altered glass in comparison with soda-lime and mixed-alkali silicate glasses. The samples from the Cathedral of Évora showed a high content of dust and salts on their surface but without severe chemical pathologies; however, those samples exposed in the Monastery of Jerónimos and the Monastery of Batalha presented alteration layers due to a high humidity environment.

scholarly journals OPTICAL PROPERTIES ON Li2O-K2O-WO3-B2O3 GLASS SYSTEM

2013 ◽  
Vol 22 ◽  
pp. 278-283
Author(s):  
A. EDUKONDALU ◽  
M. A. SAMEE ◽  
SHAIKH KAREEM AHMMAD ◽  
SAIR MD. TAQIULLAH ◽  
SYED RAHMAN ◽  
...  
Keyword(s):  
Glass Structure ◽  
Glass System ◽  
Alkali Concentration ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Mixed Alkali ◽  
Absorption Studies ◽  
Mixed Alkali Effect ◽  
Oxide Ion ◽  
B2o3 Glass

Mixed alkali tungsten borate glasses xLi2O–(30–x) K2O–10WO3–60B2O3 (0 < x < 30) were prepared from the melts. These glasses were characterized using X-ray diffraction, differential scanning calorimetry and density measurements. Optical absorption studies were carried out as a function of alkali content to look for mixed alkali effect (MAE) on the spectral properties of these glasses. From the study of ultraviolet absorption edge, the optical band gap energies and Urbach energies were evaluated. The average electronic polarizability of the oxide ion, optical basicity and the interaction parameters were also evaluated for all the glasses. Many of these parameters vary non-linearly exhibiting a minima or maxima with increasing alkali concentration, indicating the mixed alkali effect. An attempt is made to interpret MAE in this glass system in terms of its glass structure.

Surface Signatures of Bioactivity: MD Simulations of 45S and 65S Silicate Glasses

Langmuir ◽  
2010 ◽  
Vol 26 (1) ◽  
pp. 545-551 ◽  
Author(s):  
Antonio Tilocca ◽  
Alastair N. Cormack
Keyword(s):  
Md Simulations ◽  
Silicate Glasses
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