Structure Of Silicate Glasses Research Articles

Comparative study of the structure and durability of commercial silicate glasses for food consumption and cosmetic packaging

Four commercial glass compositions were investigated to understand their mechanisms of alteration in light of the current and future regulations on food contact materials. Lead crystal (fine glassware), soda-lime (food and cosmetic containers), borosilicate (cookware) and barium glass (tableware) powders and slabs were altered for 3 years, in acetic acid (4% vol) at pH = 2.4 and 70 °C. The leaching solution was analyzed by ICP-AES while glass slabs were investigated by ToF-SIMS and Spectroscopic Ellipsometry. As a result, in acidic medium, the polymerization of the silicate network as well as the glass composition impacted the alteration rates and depleted depths of alkalis and earth-alkalis elements. Yet the rate of hydrolysis measured from the release of Si, remained similar under identical alteration conditions, whatever the glass structure and composition. For lead crystal glass, repolymerization of the silicate network was observed in the course of alteration.

Exploring the effect of Er2O3 content on the structural, thermal, and physical characteristics of zinc silicate glasses

Glasses of chemical formula xEr2O3. (55-x) ZnO. 45SiO2 (x = 0, 0.5, 1, 3, 5, 7, 10, and 15 mol. %) were prepared using the melt-quenching route. The structure of the glasses was investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman, and NMR spectroscopy. XRD data confirmed that all zinc silicate glasses containing Er2O3 had an amorphous glassy structure. XRD showed the presence of two humps around 50° and 60° that are related to Er and Zn ions incorporated into the glass structure, and these humps' intensity changed with Er2O3 addition. The fraction of different silicate structural units is studied using FTIR and Raman spectroscopy, which is comparable to that obtained from the reported NMR values. FTIR, Raman, and NMR measurements confirmed the dual role of Er2O3 on the structure of zinc silicate glasses. Based on these results, Er2O3 content is below 5 mol. % entered as a glass modifier, creating more non-bridging oxygen atoms (NBO, increases Q1) while above 5 mol. % played a glass former, creating more bridging oxygen atoms (BO, increases Q2). Thermal heat treatment was applied for all glass samples according to DSC measurements. The thermal parameters have been discussed and correlated with the glass structure. The glass transition temperature (Tg) escalated from 377.3 at 5 mol. % to 391.04 °C at 15 mol. % Er2O3. The crystallization temperature (Tc) also increased from 548.27 °C to 598.37 °C, and the Vickers hardness (Hv) improved markedly from 646.4 kg/mm2 at 0 mol. % to 732.2 kg/mm2 at 15 mol. % Er2O3. XRD and FTIR results for glass samples after heat treatment for 24 h at 700 °C have been discussed regarding the crystallization of the glass matrix. These findings highlight the critical role of Er2O3 in modifying glass structure and properties, demonstrating its potential to enhance the glass matrix's durability and mechanical strength.

Characterizing medium‐range order structure of binary silicate glasses using ring analysis and persistent homology

AbstractSeveral fundamental questions about the medium‐range order (MRO) structure of oxide glasses remain unanswered. How do we define MRO in glass? Should we only consider the covalently bonded rings or also repeating patterns of non‐chemically bonded atom clusters? Is the first sharp diffraction peak (FSDP) in the structure factor only constituted by those rings? In this study, by focusing on binary silicate glasses, we compare the MRO structure as determined using persistent homology and classical ring analysis. While the latter only identifies chemically bonded rings, the former captures both chemically and non‐chemically bonded ring/loop structures. Our analyses are based on atomic configurations established through classical molecular dynamics simulations of three series of alkali silicate glasses with varying modifier content. First, we characterize the size and shape of chemically bonded rings using persistent homology and study how they contribute to the FSDP. We also show that the covalently bonded loops can be directly extracted using persistent homology by ignoring the modifiers from the analysis and setting the initial radii for both Si and O atoms to zero. Then, we demonstrate that although the chemically bonded rings contribute to the FSDP, especially at low modifier content, nonbonded MRO features also need to be considered to fully explain the FSDP.

Structural Unit Determination in Silica Nanoparticles Using Infrared Micro-Reflectance Spectroscopy.

A method based on infrared (IR) micro-reflectance measurements for the structural characterization of glassy nanomaterials is presented. Near-specular reflectance spectra of pressed pellets can be analyzed using a model relating the structure of silicate glasses to their dielectric response and an effective medium approximation to account for the effect of porosity. The integrated intensities of phenomenological bands attributed to , , and structural units allow quantifying their relative populations. These values are in good agreement with those obtained with magic-angle spinning nuclear magnetic resonance, which serves as validation of the method and proves the feasibility of extracting quantitative information about glass structure from IR micro-reflectance experiments.

Structure and chemical durability improvement of alkali silicate glass by zirconium dioxide and erbium oxide addition

Glass structure tailoring of alkali silicate glasses by addition of ZrO2 and Er2O3 is found to enhance the chemical durability of glasses. ZrO2 (x ranged between 5 mol% to 15 mol%) and Er2O3 (y ranged between 0.5 mol% to 1.5 mol%) were used to replace SiO2 and Na2O, respectively, in the glasses with the nominal composition of 10Li2O-(15-y)Na2O-10CaO-(65-x)SiO2-xZrO2-y Er2O3. The samples were prepared by conventional melt quenching technique. The structures of produced glasses were examined by X-ray absorption spectroscopy (XAS) and Raman spectroscopy. XAS spectra demonstrated that the oxidation numbers of Zr and Er ions were +4 and +3, respectively. The chemical environment around both cations was six-fold coordination. In addition, Raman spectra demonstrated that the Zr4+ ions formed the Q4(Zr) structure, which caused the reduction of non-bridging oxygen. In case of the Er3+ ions, the formation of the Si-O-Er bonds was explained from the Raman study. The chemical durability of glass was determined from Na+ ions leaching values. In pH 7 solution, the leached Na+ ions reduced from 25.67% to 21.43% and from 22.50% to 20.49% as a function of concentration of ZrO2 (x = 5 mol% to 15 mol%) and Er2O3 (y = 0.5 mol% to 1.5 mol%), respectively. As the results, the chemical durability of the ZrO2-containing and Er2O3-containing glasses were significantly improved due to charge compensated mechanism and enhancing network rigidity by increasing cation field strength. Moreover, the micro-hardness (580 HV to 837 HV) and density (2.54 g⸳cm-3 to 2.82 g⸳cm-3) also displayed an increased tendency with larger concentration of ZrO2 and Er2O3.

The structures of iron silicate glasses with varying iron redox ratios from molecular dynamics simulations and EXAFS analysis

Iron oxides are frequently found in natural and industrial glass compositions and can affect various physical and chemical properties of the glasses and their melts. Thus, a fundamental understanding of iron-bearing silicate melts and glasses is of both scientific and technological importance. This study investigates the structures of sodium iron silicate glasses with compositions of NaFeSiO4, NaFeSi2O6, NaFeSi3O8, and Na5FeSi4O12 using molecular dynamics simulations in combination with Extended X-ray Absorption Fine Structure (EXAFS) characterizations. Short and medium range structural features of these glasses support that ferrous (Fe2+) and ferric (Fe3+) ions play the roles of network modifier and network former, respectively, with the Fe oxidation states playing an important role in the polymerization of the glass network. These simulation results agree well with newly measured room temperature EXAFS spectra. The simulated glass structures were also compared to the melts structures with the same composition but different redox ratios. The average coordination numbers of the cations were found to be affected both by the melt temperature and iron redox ratio.

Experimental investigation of the bonding of sulfur in highly reduced silicate glasses and melts

Elucidating the role of sulfur on the structure of silicate glasses and melts at elevated pressures and temperatures is important for understanding transport properties, such as electrical conductivity and viscosity, of magma oceans and mantle-derived melts. These properties are fundamental for modeling the evolution of terrestrial planets and moons. Despite several investigations of sulfur speciation in glasses, questions remain regarding the effect of S on complex glasses at highly reducing conditions relevant to Mercury. Glasses were synthetized with compositions representative of the Northern Volcanic Plains of Mercury and containing quantities of S up to 5 wt%. Multiple spectroscopic methods and microprobe analyses were employed to probe the glasses, including in situ impedance spectroscopy at 2- and 4-GPa pressures and temperatures up to 1740 K using a multi-anvil press, 29Si NMR spectroscopy, and Raman spectroscopy. Electrical activation energies (Ea) in the glassy state range from 0.56 to 1.10 eV, in agreement with sodium as the main charge carrier. The electrical measurements indicate that sulfide improves Na+ transport and may overcome a known impeding effect of the divalent cation Ca2+. The glass transition temperature lies between 700 and 750 K, and for temperatures up to 970 K Ea decreases (0.35–0.68 eV) and the conductivities of the samples converge (∼5–8 × 10−3 S/m). At Tquench, the melt fraction is 50–70% and melt conductivity varies from 0.7 to 2.2 S/m, with the sample containing 5 wt% S the most conductive among the set. 29Si NMR spectra reveal that a high fraction of S bonds with Si in these complex glasses, a characteristic that has not been recognized previously. Raman spectra and maps reveal regions rich in Ca–S or Mg–S bonds. The evidence of sulfide interactions with both Si and Ca/Mg suggest that alkaline earth sulfides can be considered weak network modifiers in these glasses, under highly reduced conditions.

Effect of Ba+-Ion Implantation on the Composition and Electronic Structure of Silicate Glasses

Effect of Ba+-Ion Implantation on the Composition and Electronic Structure of Silicate Glasses

Issue Information

International Journal of Applied Glass ScienceVolume 14, Issue 1 p. 1-2 ISSUE INFORMATIONFree Access Issue Information First published: 02 December 2022 https://doi.org/10.1111/ijag.16586AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract Cover Photograph: (a) Snapshot of molecular model of a 0.1Na2O-0.9SiO2 sodium silicate glass structure with a loaded slit crack simulated with the ReaxFF forcefield. Bonds along a half plane (depicted with a dashed line) were severed to create the initial slit crack. The displacements of atoms in an outer annulus were prescribed by an external boundary condition to generate far-field loading conditions. Atom colors: Si (yellow), O (red), Na (blue). (b) The same sodium silicate molecule model demonstrating the radial displacement field generated by the far field loading conditions. As the distance from the crack tip increases so does the total displacement, consistent the classical linear elastic fracture mechanics continuum solution for a semi-infinite slit crack under mode I loading. Volume14, Issue1Special Issue: Glasses for tomorrowJanuary 2023Pages 1-2 RelatedInformation

Influence of Vanadium Oxide on The Structure and Properties of Silicate Glasses Modified by Zinc Oxide

Influence of Vanadium Oxide on The Structure and Properties of Silicate Glasses Modified by Zinc Oxide

The effect of V2O5/MgO substitution on SiO2-Na2O-CaO-ZnO–MgO glass structure

V2O5 incorporated sodium calcium silicate glasses of composition 55SiO2 - 25 Na2O - 5CaO - 10ZnO - 5MgO(1-x): V2O5(x) (x = 0, 0.01, 0.03, 0.05, and 0.1) have been prepared by melt-quench technique. In the determination of the glass network, a silicate glass structure was chosen for physical and chemical strength. It was preferred to use ZnO for high light transmittance and V2O5 to reduce the optical band gap. The structural and thermal properties of the samples were explored using Fourier transform infrared (FTIR) spectroscopy and differential thermal analysis (DTA), respectively. The optical properties of the glasses were detected by UV–VIS spectroscopy between the wavelength ranges of 200–1100 nm. The indirect band gap (Eg) and Urbach energy (Eo) values have been evaluated with the help of absorption spectra. Also, the refractive index values have been determined by spectroscopic ellipsometry. All data have been interpreted corresponding with V2O5 contributions.

Effect of iron redox ratio on the structures of boroaluminosilicate glasses

AbstractIron oxide is commonly found in natural or industrial glass compositions and can exist as ferrous (Fe2+) or ferric (Fe3+) species, with their ratios depending on glass composition, temperature, pressure and the redox reactions during the glass forming process. The iron redox ratio plays an important role on silicate glass structures and consequently various properties. This work aims to study the effect of iron oxide, and particularly the iron redox ratio, on the structures of borosilicate and boroaluminosilicate glasses using molecular dynamics simulations with newly developed iron potential parameters that are compatible with the borosilicate potentials. The results provide detailed cation coordination states of both iron species and the effect of redox ratio on boron coordination and other structural features. Particularly, competition for charge compensating modifier cations (such as Na+) among the fourfold‐coordinated cations such as B3+, Al3+, and Fe3+ is investigated by calculating the cation–cation pair distribution functions and coordination preferential ratios. The results show that the trivalent ferric ions, with a shorter Fe–O bond distance and better defined first coordiation shell with mainly four‐fold coordination, act as a glass former whereas the divalent ferrous ions mainly play the role of glass modifier. The ferrous/ferric ratio (Fe2+/Fe3+) was found to affect the glass chemistry and hence glass properties by regulating the amount of four‐coordinated boron, the fraction of non‐briding oxygen and other features. The results are compared with available experimental data to gain insights of the complex structures and charge compensation schemes of the glass system.

Development of potentials for molecular dynamics simulations of dry and hydrated calcium aluminosilicate glasses by force matching and refinement

Potential development and refinement to improve the applicability and transferability of the forcefield is important to atomistic simulations of glass materials and their interactions with the environment. In this paper, we demonstrate potential development of calcium aluminosilicate glasses with and without water using a reactive potential framework by adopting the force matching technique and subsequent refinement. Accordingly, we have reproduced the forces on atoms of the system from a DFT based ab-initio molecular dynamics (AIMD) simulations by adjusting the potential parameters. We chose the diffuse charge reactive potential (DCRP) as the classical potential as it has been previously demonstrated to accurately and efficiently simulate interactions between water and silicate-glasses. The obtained force matched parameters were further refined to accurately reproduce the structures and dynamics of dry and hydrated calcium alumino silicate glass and gel structures. The Ca2+ behavior in solution was correctly reproduced with an average local coordination equal to 6.12 and a diffusion coefficient close to the experimental values. This force field also correctly reproduces the local environment of Al3+ in glass, but it falls short in describing Al3+ ion coordination in solutions as compared to AIMD results, suggesting a direction of future improvement. This set of potential can thus be used for simulations of calcium aluminosilicate glasses with various technological applications and hydrated gel structures resulted from corrosions of boroaluminosilicate glasses.

Influence of different silver species on the structure of bioactive silicate glasses

Silver nanoparticles and silver species are frequently used in regenerative medicine due to their bactericidal effect and low toxicity to human cells. Ag species are prone to be converted into other silver species such as silver nanoparticles and AgCl when immersed in simulated body fluid. The aim of this study is to understand the influence of these transformations in the human body, as well as the effect of different oxidative states of Ag on bioactivity, cell viability and antibacterial activity. For this purpose, bioactive glasses with different silver species and content were used, obtaining glasses with Ag2O or Ag3PO4. The presence of Ag+ ions favored the appearance of AgCl crystals on the surface of the samples after their immersion in simulated body fluid. In all cases, Ag nanoparticles were formed due to the high concentration of NaCl in the simulated body fluid, which concentration is close to the human plasma.

Interaction mechanism between arsenate and fayalite-type copper slag at high temperatures

The interaction mechanism between sodium arsenate and fayalite-type copper slag at 1200 °C was investigated through XRD, XPS, HRTEM, TCLP and other technical means and methods. The results indicated that the proportions of sodium arsenate in the slag and flue gas phases were approximately 30% and 70%, respectively. The addition of sodium arsenate depolymerized the fayalite structure and changed it from a crystalline state to an amorphous state. The fayalite structural changes indicated that the [AsO4] tetrahedron in sodium arsenate combined with the [SiO4] tetrahedron and [FeO4] tetrahedron through bridging oxygen to form a silicate glass structure. The TCLP test results of the samples before and after the high temperature reaction of fayalite and sodium arsenate showed that after high temperature reaction, fayalite could effectively reduce the leaching toxicity of sodium arsenate, reducing the leaching concentration of arsenic from 3025.52 to 12.8 mg /L before and after reaction, respectively.

Study of dynamics and structure in sodium silicate glasses. Molecular dynamics simulation.

We conduct molecular dynamics simulations to study dynamics and structure of sodium silicate glasses through Voronoi polyhedron and diffusion path consisting of Ox-polyhedrons connected via XY-lines. The result shows that Six-polyhedrons and the number of Ox-polyhedrons do not contain Na. Most of NBFx-polyhedrons contain 1, 2 or not Na, where BO, NBF is the O bonded with 2 and 1 or not Si, respectively. Average volume per polyhedron increases in order: Six-polyhedron → BOx-polyhedron → NBFx-polyhedron. Na atoms are concentrated in NBFx-polyhedrons and frequently move through them leading to very fast diffusivity of Na in comparison with Si and O. The simulation shows that the number of neighbors around NBFx-polyhedron is larger than that around BOx-polyhedron. Major Na atoms move over BN- and NN-lines connecting with NBFx-polyhedrons. Moreover, Na atoms displace through the preferential diffusion path comprising mainly of NBFx-polyhedrons. The correlation effect is significant for sodium diffusion.

Clustering in thin silver films upon heating

The kinetics of the formation of silver clusters Ag from nanoscale continuous films of Ag on the surface of silicate glass and composite structures from films of Ag with carbon in the form of a continuous film and individual nanoparticles upon annealing in air at temperatures up to 670K is investigated. In the course of the work, the dependences of the surface morphology of silver clusters and absorption spectra in the visible wavelength range were obtained by the methods of atomic force microscopy and optical spectrophotometry.

Structures of Vanadium-Containing Silicate and Borosilicate Glasses: Vanadium Potential Development and MD Simulations

Vanadium-containing multi-component oxide glasses have found a variety of applications ranging from energy storage, sensing, to nuclear waste disposal. However, their complex structures, partly caused by the co-existence of multi-oxidation states of vanadium ions, lead to the challenges in experiments to understand the structural features and structural origin of the property change of these glasses. In this work, we aimed to develop compatible vanadium-related parameters for a widely used effective partial charge potential set to enable the simulations of the vanadium-containing multi-component oxide glasses (Deng and Du, J. Am. Ceram. Soc. 102(2019)2482). Various vanadium containing oxide crystal structures and model glass compositions (with vanadium in different oxidation states) have been used as targets to fit and refine the newly developed parameters. Both the experimental crystal structures and mechanical properties were used in the fitting process. Glass structures were characterized by performing cation coordination number, pair distribution function, and bond angle distribution analysis. The obtained parameters have been shown to be able to simulate the vanadium-containing aluminosilicate, phosphate, and borate glasses and describe the local environments of vanadium ions with various oxidation states with reasonable accuracy in comparison with available experimental data. This development thus enables atomistic simulations of vanadium containing oxide glasses to understand the structural role of vanadium ions in these glasses and how the struacture features affect various glass properties hence assist the design of vanadium containing glasses for various technological applications.

Lead silicate glass structure: New insights from diffraction and modeling of probable lone pair locations

AbstractStructures of binary PbO‐SiO2 glasses have been studied in detail over the compositional range 35 to 80 mol% PbO using high‐resolution neutron diffraction, high‐energy X‐ray diffraction, static 207Pb NMR, and structural modeling. The changes in the local environment of Pb(II) are subtle; it has a low coordination to oxygen (∼3 to 4) plus a stereochemically active electron lone pair and, thus, behaves as a glass network forming (or intermediate) cation over the entire composition range. This conclusion contradicts previous reports that Pb(II) is a network modifier at low concentrations, and is supported by an analysis of lead and alkaline earth silicate glass molar volumes. The Pb‐O peak bond length shortens by 0.04 Å with increasing PbO content, indicating stronger, more covalent bonding, and consistent with an increase in the number of short (≤ 2.70 Å) Pb‐O bonds, from 3.3 to 3.6. This is accompanied by increased axial symmetry of the Pb(II) sites, and is interpreted as a gradual transition toward square pyramidal [PbO4] sites such as those found in crystalline PbO polymorphs. An attendant decrease in the periodicity associated with the first sharp diffraction peak (FSDP) toward that of β‐PbO, accompanied by increases in the correlation lengths associated with the plumbite network (FSDP) and silicate anions (neutron prepeak), provides evidence of increased intermediate‐range order and has implications for the glass forming limit imposed by crystallization. Pb(II) electron lone pairs occupy the natural voids within the silicate network at low PbO contents, while at high PbO contents they aggregate to create voids that form part of the plumbite network, analogous to the open channels in Pb11Si3O17 and the layered structures of α‐ and β‐PbO. Si‐O and Pb‐O bond lengths have been correlated with 29Si and 207Pb NMR chemical shifts, respectively. This is the first time that such correlations have been demonstrated for glasses and attests to the accuracy with which pulsed neutron total scattering can measure average bond lengths.

Revealing the medium-range structure of glassy silica using force-enhanced atomic refinement

The medium-range order structure of silicate glasses remains poorly known as it is not directly visible from conventional experiments. In turn, although atomistic simulations offer a direct access to the structure of glasses, they face several limitations, e.g., extremely high cooling rates. Here, we adopt the force-enhanced atomic refinement (FEAR) method to overcome these limitations and reveal the atomic structure of glassy silica, both at the short- and medium-range length scales. We find that FEAR yields a glass structure that simultaneously exhibits higher thermodynamic stability and enhanced agreement with experimental structure data as compared with molecular dynamics and reverse Monte Carlo simulations. Overall, we show that the increased stability enabled by FEAR primarily arises from the fact that the generated atomic configuration exhibits a more ordered medium-range structure and a lower fraction of unstable small silicate rings.