Glass Structure Research Articles

Structural Si3N4-SiO2 glass ceramics with bioactive and anti-bacterial properties

Silicon nitride-based bioceramics have been investigated for biomedical applications due to their good thermo-mechanical, tribological and antibacterial properties. However, biological properties, such as bioactivity that promotes the interaction with tissue, are also important. Silicon dioxide has been found to promote bioactivity. With the aim of combining both advantages, a new Si3N4-SiO2 glass ceramic was developed. Three different compositions were synthesized and sintered by spark plasma sintering. The results showed that β-Si3N4 crystalline is well distributed in the SiO2 matrix. 70SiN samples exhibited the highest mechanical properties with a flexural strength of 452 ± 33 MPa and a toughness of 6.4 ± 0.5 MPa∙m1/2. 50SiN samples exhibited the best bacteriostatic effect due to the synergistic effect of surface chemistry and topography. Apatite was observed on the surfaces of all groups. This study shows that the newly developed Si3N4-SiO2 glass ceramics exhibit promising mechanical and biological properties for biomedical applications.

Geochemical variations in early Islamic glass finds from Bukhara (Uzbekistan)

Glass manufacturing processes and recipes changed fundamentally after the 8th century CE. The earlier centralised production system diversified, primary production sites multiplied, and the scale of individual productions contracted. Mineral soda was no longer used and instead replaced by plant ash as the main fluxing agent, affecting the chemical composition and properties of the glass. In this work, LA-ICP-MS and Raman spectroscopy were used to investigate the compositional and structural characteristics of 68 glass fragments recovered during recent excavations at Bukhara in Uzbekistan, dating to the 9th to early 11th centuries CE. This is the most extensive systematically collected and studied glass assemblage from Central Asia to date. The glass can be attributed to different origins, confirming on the one hand the diversification of glass production during the early Islamic period and, on the other hand, regional variations in the chemical compositions and network structure of soda-rich plant ash glasses. As clear archaeological evidence for early Islamic glass production sites in Central Asia is rare, regional production groups are distinguished primarily on relative concentrations of Mg, K, P, Cl, Li and Cs in relation to the plant ash component, while variabilities in Al, Ti, Cr, Y, Zr, Th and REEs and their ratios indicate different silica sources. Raman spectra suggest variations in network connectivity and Qn speciation that confirm compositional groupings and suggest structural differences between regional productions of plant ash glass. The results demonstrate a clear dominance of local or regional glass groups, while revealing the importation of Mesopotamian glass, notably a high-end colourless glass type from the region around Samarra in Iraq. The new analytical data allow further separation and characterisation of novel early Islamic plant-ash glass types and their production areas.

Magnetic boson peak in classical spin glasses

We revisited spin dynamics in archetypical classical spin-glass (SG) systems, such as Cu1−xMnx (x=0.017, 0.034, and 0.067) dilute alloys and iron aluminosilicate glass, using a modern neutron scattering spectrometer with high neutron flux. The former is crystalline, and the latter is amorphous, where their SG state is well separated from magnetically ordered phases. Bose-scaled localized magnetic excitations were observed in both compounds below the spin-freezing temperature (Tf). The spectrum exhibits a maximum at low energy and a broad tail on the high-energy side. The excitation energy tends to be higher for the material with higher Tf. Above Tf, the spectrum considerably changes with temperature, thereby indicating the emergence of the magnetic relaxation process. The magnetic excitation in the SG state has much in common with the boson peak in structural glasses. We consider that the Bose-scaled broad excitation peak is an elementary excitation inherent in disordered systems. Published by the American Physical Society 2024

Hydrothermal performance assessment of a parabolic trough with proposed conical solar receiver

Parabolic Trough Collectors (PTCs) are commonly employed in both industrial and residential settings for the purpose of harnessing solar energy. Several techniques have been implemented to improve performance, such as altering the geometry of the absorber tube, enhancing the selective coatings of the receiver envelope, and utilizing nanofluids. This study proposes a new method for enhancing the thermal-hydraulic efficiency of PTCs through the utilization of non-uniform heat flux distribution on conical solar receiver. The effectiveness of this approach is evaluated through numerical simulations conducted using Ansys Fluent with the aid of optical simulation performed using TracePro. The geometry under consideration is assessed at various diameter ratios (DR) spanning from 1.25 to 2 and Reynolds number (Re) ranging from 20000 to 100000, with increments of 20000. This evaluation is conducted at three distinct inlet temperatures: 150 °C, 250 °C, and 350 °C. The studied parameters include-the Nusselt number (Nu), friction coefficient (f), thermal efficiency (ηth), exergetic efficiency (ηex), and thermal enhancement factor (TEF). Furthermore, a comparative analysis is conducted between the newly proposed geometric design and a traditional straight absorber and glass structure. The findings indicated that a conical receiver generally enhances system heat transfer by a minimum of 7 % and up to 65 %, resulting in improved thermal and exergetic efficiencies. Decreasing the pipe outlet diameter from DR = 1.25 to DR = 2 led to a significant exponential rise in the friction coefficient. The TEF demonstrated that a diameter ratio of 1.25 and 1.5 resulted in maximum values of 1.19 and 1.11, respectively, at high Re and an inlet temperature of 350 °C. The results suggested that incorporating conical receivers in PTCs can greatly improve their performance. To minimize the friction coefficient and associated pumping power, it is crucial to carefully evaluate the reduction of the diameter of the absorber outlet. The results offered valuable insights for the development and improvement of PTCs in both industrial and power generation settings, promoting the adoption of renewable energy and supporting long-term sustainability.

Design of glass balustrades to CEN/TS 19100

This article seeks to describe the approach taken to designing a glass balustrade in CEN/TS 19100 Design of glass structures, a draft document which is a precursor to the publication of a Eurocode.

Atlantis The Royal hotel – designing multiperformance glass features

This article focuses on two structural glass elements located in the entry vestibule of Atlantis The Royal hotel: Deluge – a pair of all-glass lifts with water cascading on the outer surface; and Alight – a feature involving fire, water and glass.

Deciphering the structure and potassium-ion transport mechanism of potassium borate glass.

Potassium borate glass has great potential as an ion transport material. The ion transport rate is closely related to the microstructure of the glass. However, the disorder and variations in boron and oxygen atom types in the glass structure pose challenges in the analysis of this complex glass structure. In this work, the structure of potassium borate glass was unveiled through the neutron diffraction method and ab initio molecular dynamics (AIMD) simulations. The B-O, K-O, and O-O atomic interactions, bond lengths, coordination numbers, cavity distribution, ring structure distributions and other detailed information in the microstructure of potassium borate glass were obtained. By comparing the structure and properties of potassium borate glass with those of crystals of similar components, it is found that the bond lengths of 3B-BO (BO, bridging oxygen), 4B-BO and 3B-NBO (NBO, non-bridging oxygen) are longer than those of corresponding crystals, so the structure of the boron-oxygen network is looser and the density is smaller than that of similar crystals. Moreover, we found a rule that in both borate glass and crystal, the increase of NBO shortened the length of the B-O bond, and the increase of 4B increased the length of the B-O bond. The key structures affecting the transport rate of K+ were NBO, chain structure units and cavities. This work will provide reference data for designing and developing electrically conductive amorphous materials with faster potassium-ion transport rates.

Three‐Dimensional Waveguide Topological Photonic Structures in Glass Fabricated by Femtosecond Laser Direct Writing (Invited)

Three‐Dimensional Waveguide Topological Photonic Structures in Glass Fabricated by Femtosecond Laser Direct Writing (Invited)

Theoretical and experimental investigation of Al3+ ion-suppressed phase-separation structures in rare-earth-doped high-phosphorus silica glasses.

Rare-earth-doped silica-based composite glasses (Re-SCGs) are widely used as high-quality laser gain media in defense, aerospace, energy, power, and medical applications. The variable regional chemical environments of Re-SCGs can induce new photoluminescence properties of rare-earth ions but can cause the selective aggregation of rare-earth ions, limiting the application of Re-SCGs in the field of high-power lasers. Here, topological engineering is proposed to adjust the degree of cross-linking of phase-separation network chains in Re-SCGs. A combination of experimental and theoretical characterization techniques suggested that the selective aggregation of rare-earth ions originates from the formation of phase-separated structures in glasses. The decomposition of nanoscale phase separation structures to the sub-nanometer scale, enabled by incorporating Al3+ ions, not only maintains the high luminescence efficiency of rare earth ions but also increases light transmittance and reduces light scattering. Furthermore, our investigation encompassed the exploration of the inhibitory mechanism of Al3+ ions on phase-separation structures, as well as their influence on the spectral characteristics of Re-SCGs. This work provides a new design concept for composite glass materials doped with rare-earth ions and could broaden their application in the field of high-power lasers.

Structural, optical, and shielding properties of lead borate glasses doped with copper oxide

Lead borate glasses of the system 25PbO-(75-x) B2O3-xCuO (x = 0, 0.025, 0.05, and 0.1) in mol.% were synthesized via the traditional melt quenching method abbreviated as (BPbCu0, BPbCu1, BPbCu2, and BPbCu3) respectively. XRD diffraction confirmed the amorphous nature of the samples. According to FTIR spectroscopy, the function groups (BO3 and BO4) and the fraction of boron tetrahedral units (N4) were determined. The density, molar volume, packing density, and some other physical parameters were calculated and discussed. The density was increased by incorporating CuO as a substitution for B2O3, while the molar volume was decreased. The ion concentrations of Cu, inter-nuclear distance, field strength, and polaron radius were also computed. The optical absorption study suggested that the copper ions exist in the Cu2+ and act as a modifier by increasing the disorder in the glass network. Hence, the present glass behaves as a bandpass filter in the UV–vis. region. The radiation shielding properties of the as-prepared samples were theoretically calculated using the Phy-X program at energies ranging from 0.015 to 1.5 MeV. The linear and mass attenuation coefficients, as well as the half-value layer (HVL) and exposure buildup factor (EBF), have been evaluated. The results revealed that shielding parameters are affected by CuO concentrations and photon energy. Based on the results presented in the manuscript, the glass sample with 0.1 mol% CuO doping (BPbCu3) showed the best properties overall for optical and radiation shielding applications. Specifically, BPbCu3 had the highest density, refractive index, optical dielectric constant, and radiation shielding parameters such as linear attenuation coefficient and half value layer among the glass samples. The addition of 0.1 mol% CuO introduced Cu2+ ions which acted as network modifiers, increasing the disorder in the glass structure. This in turn enhanced the optical bandgap as well as the shielding capabilities against gamma radiation.

The distinguishable-particle lattice model of glasses in three dimensions.

The nature of glassy states in realistic finite dimensions is still under fierce debate. Lattice models can offer valuable insights and facilitate deeper theoretical understanding. Recently, a disordered-interacting lattice model with distinguishable particles in two dimensions (2D) has been shown to produce a wide range of dynamical properties of structural glasses, including the slow and heterogeneous characteristics of the glassy dynamics, various fragility behaviors of glasses, and so on. These findings support the usefulness of this model for modeling structural glasses. An important question is whether such properties still hold in the more realistic three dimensions. In this study, we aim to extend the distinguishable-particle lattice model (DPLM) to three dimensions (3D) and explore the corresponding glassy dynamics. Through extensive kinetic Monte Carlo simulations, we found that the 3D DPLM exhibits many typical glassy behaviors, such as plateaus in the mean square displacement of particles and the self-intermediate scattering function, dynamic heterogeneity, variability of glass fragilities, and so on, validating the effectiveness of the DPLM in a broader realistic setting. The observed glassy behaviors of the 3D DPLM appear similar to those of its 2D counterpart, in accordance with recent findings in molecular models of glasses. We further investigate the role of void-induced motions in dynamical relaxations and discuss their relation to dynamic facilitation. As lattice models tend to keep the minimal but important modeling elements, they are typically much more amenable to analysis. Therefore, we envisage that the DPLM will benefit future theoretical developments, such as the configuration tree theory, towards a more comprehensive understanding of structural glasses.

Innovative hybrid CFRP composite and Fe-SMA bonded systems for structural glass flexural strengthening

Contemporary architecture is increasingly embracing the use of structural glass for challenging applications. Glass industry has been adopting thermal toughening and lamination as advanced techniques to enhance tensile strength and avoid sudden failures. However, unexpected failure persists and hinders a more widespread application of glass, including as a structural material. Researchers have tested alternative glass composite systems, integrating reinforcements like steel, fiber-reinforced polymers (FRP), or iron-based shape memory alloy (Fe-SMA). This study explores an innovative concept that involves the simultaneous application of CFRP and Fe-SMA reinforcements via near-surface mounted (NSM) or externally bonded reinforced (EBR) techniques for glass strengthening. This system is shown to effectively prevent premature debonding, enhance post-cracking response, and ensure ductile failure modes, while being simple. Bending tests on large-scale laminated glass beams were performed to characterize the effectiveness of the system, while also the benefits of post-tensioning were investigated by inducing different prestressing levels in the glass strengthened elements. The paper first highlights the advantages of Fe-SMA reinforcements in glass composite systems through experimental evidence, followed by exploration of the proposed innovative hybrid CFRP composite and Fe-SMA bonded systems.

Structural and spectroscopic studies of lithium tetraborate glass co-doped with Sm and Cu.

The local structure and spectroscopic properties of Cu-Sm co-doped Li2B4O7 glass have been studied using XRD, EPR, UV-Vis-NIR absorption and luminescence methods and compared with the corresponding results for Sm-doped and Cu-doped Li2B4O7 glasses. The EPR spectrum reveals an axially-symmetric signal with a characteristic hyperfine structure belonging to Cu2+ ions. The Cu2+/Cutotal ratio was determined. The optical absorption spectrum shows a broad, intense band attributed to Cu2+ ions and several weaker narrow bands attributed to Sm3+ ions. Photoluminescence (PL) and photoluminescence excitation (PLE) spectra as well as PL decay kinetics of Sm3+ and Cu+ ions were registered, analyzed, and discussed. The PL spectra show a broad band assigned to the 3d94s1 → 3d10 transition of Cu+ ions and four narrow bands assigned to the 4G5/2 → 6HJ (J = 5/2-11/2) transitions of Sm3+ ions. The observed changes in PL intensity, shortening of the Sm3+ lifetime and prolongation of the Cu+ lifetime were explained by energy transfer from Sm3+ → Cu+ and re-absorption of the Sm3+ emission by Cu2+ ions.

Structural behavior of copper monatomic metallic glass under various cooling conditions investigated by molecular dynamics simulations

The present research explores the structural characteristics of pure copper (Cu) metallic glass using the embedded atom method (EAM) potential in molecular dynamics simulations. Numerous techniques were used, such as coordination number analysis, Voronoi tessellation, and the radial distribution function (RDF). The findings demonstrate that at a cooling rate of 1012 K/s, crystallization begins. However, the separation of the second RDF peak indicates that under 0 GPa, copper metallic glass forms at cooling rates between 5 × 10¹² K/s and 1014 K/s, with the glass transition temperature (Tg) rising with faster cooling. Voronoi tessellation revealed a rise in icosahedral clusters with quicker cooling, while coordination number analysis indicated changes in the local structure and topology of copper metallic glass during the cooling process.

Influence of oxygen distribution on the Li-ion conductivity in oxy-sulfide glasses - taking a closer look.

Lithium thiophosphates are a promising class of solid electrolyte (SE) materials for all-solid-state batteries (ASSBs) due to their high Li-ion conductivity. Yet, the practical application of lithium thiophosphates is hindered by their chemical instability, which remains a prevalent challenge in the field. Oxygen substitution has been discussed in the literature as a promising strategy to enhance stability. Nevertheless, the lack of understanding of the role of synthesis strategy on the resulting structure-property relationship makes it difficult to predict and control the material's behaviour, limiting our ability to fully utilize oxygen substitution as a viable solution. Here, we show that not only the total oxygen content but also the oxygen distribution within the material affects the ion conductivity. By carefully analysing the local structure of oxy-sulfide glasses, we find that few highly oxygenated structural units like [PO4]3- and [PO3S]3- are more detrimental to the ionic conductivity than a larger amount of less substituted units like [POS3]3-. Further, we demonstrate how the oxygen distribution is connected to the synthesis in high-energy ball milling by comparing two different sets of precursor materials. The results may explain the deviations in the past literature. The findings should be transferable to other Li-thiophosphate materials and enable more directed design of new materials.

STRUCTURAL FEATURES AND PROPERTIES OF MULTICOMPONENT SODIUM-CESIUM/RUBIDIUM ALUMINOBOROSILICATE MODEL MATRIX GLASSES OF BASIS COMPOSITION

Synthesis and study of the structure and various properties of Na-Cs and Na-Rb aluminoborosilicate model glasses with addition of the alkaline-earth cations have been carried out. Vibrational spectroscopy techniques have been used to establish the high degree of polymerization and noticeable structural similarity of all synthesized glasses at fixed ratio of modifying and network-forming cations. It has been shown that increasing fraction of large cations in the total content of modifying cations leads to changes in distribution of modifying cations between the silicate and borate structural units. The observed homogeneity with the similarity of anionic structure, at different content and various combinations of alkali and alkaline-earth cations, points at promising application of these glasses as a basis for synthesis of matrix materials for high-level radioactive waste disposal.

In situ high-pressure pair distribution function measurement of liquid and glass by using 100keV pink beam.

Understanding the pressure-induced structural changes in liquids and amorphous materials is fundamental in a wide range of scientific fields. However, experimental investigation of the structure of liquid and amorphous material under in situ high-pressure conditions is still limited due to the experimental difficulties. In particular, the range of the momentum transfer (Q) in the structure factor [S(Q)] measurement under high-pressure conditions has been limited at relatively low Q, which makes it difficult to conduct detailed structural analysis of liquid and amorphous material. Here, we show the in situ high-pressure pair distribution function measurement of liquid and glass by using the 100keV pink beam. Structures of liquids and glasses are measured under in situ high-pressure conditions in the Paris-Edinburgh press by high-energy x-ray diffraction measurement using a double-slit collimation setup with a point detector. The experiment enables us to measure S(Q) of GeO2 and SiO2 glasses and liquid Ge at a wide range of Q up to 20-29 Å-1 under in situ high-pressure and high-temperature conditions, which is almost two times larger than that of the conventional high-pressure angle-dispersive x-ray diffraction measurement. The high-pressure experimental S(Q) precisely determined at a wide range of Q opens the way to investigate detailed structural features of liquids and amorphous materials under in situ high-pressure and high-temperature conditions, as well as ambient pressure study.

Extraction of local structure differences in silica based on unsupervised learning.

Silica exhibits a rich phase diagram with numerous stable structures existing at different temperature and pressure conditions, including its glassy form. In large-scale atomistic simulations, due to the small energy difference, several phases may coexist. While, in terms of long-range order, there are clear differences between these phases, their short- or medium-range structural properties are similar for many phases, thus making it difficult to detect the structural differences. In this study, a methodology based on unsupervised learning is proposed to detect the differences in local structures between eight phases of silica, using atomic models prepared by molecular dynamics (MD) simulations. A combination of two-step locality preserving projections (TS-LPP) and locally averaged atomic fingerprints (LAAF) descriptor was employed to find a low-dimensional space in which the differences among all the phases can be detected. From the distance between each structure in the found low-dimensional space, the similarity between the structures can be discussed and subtle local changes in the structures can be detected. Using the obtained low-dimensional space, the β-α transition in quartz at a low temperature was analyzed, as well as the structural evolution during the melt-quench process starting from α-quartz. The proper differentiation and ease of visualization make the present methodology promising for improving the analysis of the structure and properties of glasses, where subtle differences in structure appear due to differences in the temperature and pressure conditions at which they were synthesized.

Dispersion, ionic bonding and vibrational shifts in phospho-aluminosilicate glasses.

Understanding the relationships between structure and properties of aluminosilicate glasses is of interest in magmatic studies as well as for glass applications as mechanical or optical components. Glass properties may be tailored by the incorporation of additional elements, and here we studied the effect of phosphate incorporation on refractive index and the degree of ionic bonding in aluminosilicate glasses. The studied glasses in the system SiO2-Al2O3-Na2O-P2O5 had a metaluminous composition (Al:Na = 1) with the content of SiO2 ranging from 50 to 70 mol% and of P2O5 from 0 to 7.5 mol%. Refractive index was measured at four wavelengths from visible to near-infrared and found to decrease both with increasing P2O5 content (at the expense of NaAlO2) and with increasing SiO2 content (by substitution of SiO4 for AlO4 groups). This trend correlated with a decrease in density while, additionally, the formation of Al-O-P bonds with an SiO2-like structure may account for this change. The degree of ionic bonding, assessed via optical basicity and oxygen polarisability, decreased with increasing P2O5 and SiO2 content. Despite the complexity of the studied glasses, oxygen polarisability and optical basicity were found to follow Duffy's empirical equation for simple oxide glasses. In the high frequency infrared and Raman spectra, band shifts were observed with increasing P2O5 and SiO2 content. They indicated changing average bond strength of the glass network and showed a linear correlation with optical basicity.

The unexplored role of alkali and alkaline earth elements (ALAEs) on the structure, processing, and biological effects of bioactive glasses.

Bioactive glass has been employed in several medical applications since its inception in 1969. The compositions of these materials have been investigated extensively with emphasis on glass network formers, therapeutic transition metals, and glass network modifiers. Through these experiments, several commercial and experimental compositions have been developed with varying chemical durability, induced physiological responses, and hydroxyapatite forming abilities. In many of these studies, the concentrations of each alkali and alkaline earth element have been altered to monitor changes in structure and biological response. This review aims to discuss the impact of each alkali and alkaline earth element on the structure, processing, and biological effects of bioactive glass. We explore critical questions regarding these elements from both a glass science and biological perspective. Should elements with little biological impact be included? Are alkali free bioactive glasses more promising for greater biological responses? Does this mixed alkali effect show increased degradation rates and should it be employed for optimized dissolution? Each of these questions along with others are evaluated comprehensively and discussed in the final section where guidance for compositional design is provided.