Quantitative principles of silicate glass chemistry (original) (raw)
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Structure and Topology of Soda-Lime Silicate Glasses: Implications for Window Glass
The Journal of Physical Chemistry B, 2014
The structural and topological properties of soda-lime silicate glasses of the form (1−2x)SiO 2 −xNa 2 O−xCaO are studied from classical molecular dynamics using a Buckingham type potential. Focus is made on three compositions (x = 6%, 12%, and 18%) which are either silica-rich or modifier-rich. We compare the results to available experimental measurements on structural properties and find that the simulated pair correlation function and total structure factor agree very well with available experimental measurements from neutron diffraction. The detail of the structural analysis shows that the Na and Ca coordination numbers tend to evolve with composition, and with increasing modifier content, changing from 5.0 to 5.6 and from 4.0 to 5.0 for Ca and Na, respectively. The analysis from topological constraints shows that the picture derived on a heuristic basis using classical valence rules remains partially valid. Ultimately, typical elastic phases are identified from the application of rigidity theory, and results indicate that the 6% system is stressed-rigid, whereas the modifier-rich composition (18%) is flexible. These results receive support from a full analysis of the vibrational density of states showing the low-energy bands at E < 20 meV increase as the system becomes flexible, providing another indirect signature of the presence of rigid to flexible transitions in this archetypal glass. Consequences for window glass are discussed under this perspective.
Structures of Sodium Silicate Glass
2021
The structural model of sodium silicate glass plays a crucial role in understanding the properties and the nature of binary glass and other more complicated silicate glasses. This work proposes a structural model for sodium silicate glass based on the medium-range ordering structure of silica glass and the information found from the Na2O-SiO2 phase diagram. This new model is different from previous ones. First, the sodium silica glass is both structurally and chemically heterogeneous on the nanometer scale. Secondly, the sodium cation distribution is Na2O concentration-dependent. In order to reflect the structural change with Na2O concentration, it requires two different schematic graphs to present the glass structure. The model can be extended to other binary and multiple component silicate glasses and can be experimentally verified
Springer Handbook of Glass, 2019
Silicate glasses are important cultural, societal and geological materials. Geologic glasses testify for the igneous activity of the Earth and, for instance, represented important source of tools and ornamental objects during the Paleolithic. Nowadays, silicate glasses are used to build technical materials, such as smartphone screens or glass matrix for stabilizing hazardous radioactive wastes. Therefore, silicate glasses are central to the history of the Earth and of the humanity. The compositional landscape of natural and industrial silicate glasses is vast, with various elements that all influence differently the glass properties and structure. The SiO 4 tetrahedral framework, backbone of silicate glasses, is variously influenced by the introduction of network modifier metal cations or network former aluminium cations. Industrial and geologic silicate glasses further contain multivalent elements (e.g., Fe 2+/3+), rare-earth elements, and volatile elements (H, C, S, Cl, F, I) that play different roles on the glass structure and properties. This chapter proposes to review the link between the structure, the properties and the chemical composition of silicate glasses.
Effect of Sodium Oxide Modifier on Structural and Elastic Properties of Silicate Glass
The Journal of Physical Chemistry B, 2016
Molecular dynamics (MD) simulations and Brillouin Light Scattering (BLS) spectroscopy experiments have been carried to study the structure of sodium silicate glasses (SiO 2) (100-X) (Na O) X where X ranges from 0 to 45 at room temperature. The MD-obtained glass structures have been subjected to energy-minimization at zero temperature to extract the elastic constants also found by BLS spectroscopy. The found structures are in good agreement with the structural experimental data realized by different techniques. The simulations show that the values of the elastic constants as function of X Na 2 O mol% agree well with those measured by (BLS) spectroscopy. The variations of the elastic constants C11 and C44 as a function of the Na 2 O mol% are discussed and correlated to structural results and potential energies of oxygen atoms.
Structure and properties of sodium aluminosilicate glasses from molecular dynamics simulations The Journal of Chemical Physics 139, 044507 (2013); https://doi.org/10.1063/1.4816378 The structure of sodium silicate glass The Journal of Chemical Physics 93, 8180 (1990); https://doi.org/10.1063/1.459296 Cooling rate effects in sodium silicate glasses: Bridging the gap between molecular dynamics simulations and experiments Ab initio molecular dynamics has been applied to construct seven sodium silicate glass models with Na 2 O concentration ranging from 0 to 50 mol. %. The structures of the simulated (Na 2 O) x (SiO 2) 1-x glasses are critically analyzed and validated by comparing with available experimental data. Because the initial seed model is based on a near-perfect continuous random network model for amorphous SiO 2 with periodic boundaries, the structures of these silicate glasses are highly reliable. The electronic structure, interatomic bonding, and the mechanical and optical properties of seven models are calculated using the first-principles density functional method. In particular, a single quantum mechanical metric, the total bond order density (TBOD), is used to characterize the internal cohesion of sodium silicate glass. This is a significant step beyond the traditional analysis of glasses based purely on the geometric parameters. The TBOD value is found to decrease with increasing Na content, indicating the destruction of silica network connectivity. The calculated mass density and refractive index increase with x are in good agreement with experiment. The elastic coefficients and bulk mechanical properties exhibit a nonlinear variation in the series and depend greatly on the internal bonding and cohesion of the glass. The calculated Poisson's ratio indicates that the glass becomes more ductile with the addition of Na 2 O. Our results indicate that sodium silicate glass tends to be unstable for x greater than 0.4 due to the total destruction of the SiO 2 network. Published by AIP Publishing.
Journal of the American Ceramic Society, 2021
Neutron diffraction is arguably the most reliable experimental method for the determination of the bond length distribution and coordination number of ions in glasses. 1 For a cation A in an oxide glass, this is achieved by analysis of the first A-O peak in the neutron correlation function. One of the main difficulties for this analysis can arise from the overlap between the A-O peak and the first O-O peak, which arises from distances between pairs of oxygen atoms in the basic structural units. We show here that O-O coordination numbers can be calculated, even for complex glasses, provided that the environment of the glass network forming cations is known. The O-O coordination numbers can then be used as a basis for taking the O-O peak into account so that the bond length distribution of an ion can be revealed.
Basicity or Ionicity – A New Approach for Understanding Glass Properties
Advanced Materials Research, 2008
Basicity of glass is still a challenge in spite of various attempts to measure or calculate it. The values assigned for basicity of glasses, either calculated or experimentally determined, are not always in full agreement with actual facts, and discrepancies among the theoretical ones are not unusual. For instance, SiO 2 is described by a single basicity value even if the polymorphs of SiO 2 are quite different. Only few attempts were made to face this challenge. Present paper deals with a novel approach on theoretical ionicity / basicity based on electronic energy levels or band structure of solids. Another major adjustment takes into account the possibility of decomposing ionicity of complex chemical bondings into a sum of binary bondings. Considering the distribution of the interbonding angles specific for vitreous systems, it is possible to estimate both a local ionicity (basicity) of bondings and a global (mean) basicity of glass.
Structural aspects of the glass-to-crystal transition in sodium-calcium silicate glasses
Journal of Non-Crystalline Solids
The structural aspects of the glass-to-crystal transition of Na 2 O-2CaO-3SiO 2 (1-2-3) and 2Na 2 O-CaO-3SiO 2 (2-1-3) glasses have been investigated using X-ray diffraction and multinuclear NMR spectroscopy. These materials represent a small group of glasses that undergo homogeneous nucleation rather than following the thermodynamically favored path of surface crystallization. To understand this unusual nucleation mechanism the structural resemblance of the glasses and their isochemical crystals was probed on different length scales. Definitive evidence of structural similarity at the level of intermediate-range order is obtained from 23 Na spin echo decay experiments, which are sensitive to the spatial distribution of the sodium nuclei. In contrast the distributions of the silica network former units are quite different in the glassy and the crystalline states. These results suggest that a structural resemblance of the short-and intermediate-range order of the network modifiers rather than the network formers may be a key feature of homogeneously nucleating glasses.
Some effects of OH groups on sodium silicate glasses
1970
Glasses of various compositions in the Na2o-sio 2 system were prepared with different levels of OH concentration. Phase separation kinetics, thermal expansion, radiation induced optical absorption, and internal friction of these glasses were studied. The increase in OH content in these glasses was found to (a) enhance the rate of phase separation; (b) increase thermal expansion above the glass temPerature and change the dilatometric softening temperature in a way that depends on microstructure; (c) increase the radiation induced optical absorption bands associated with positive hole centers and decrease those associated with electron trap centers; and, (d) decrease the low temperature alkali peak and increase the high temperature peak of internal friction. Structural changes responsible for the effect of very small amounts of OH on these properties are described. It is imperative to determine and consider OH content in the evaluation of properties which are so significantly affected...