Formation Of Glass Network Research Articles

Research on the Properties of Wasteforms after Direct Involvement of Uranium-Containing Silica Gel in Glass Network Formation.

Uranium-containing silica gel (UCSG) is a secondary waste generated during the advanced treatment of nuclear wastewater. In order to reduce the growing storage pressure for UCSG, from the perspective of building a borosilicate glass network, UCSG was used to replace SiO2 in the glass-cured formula to directly achieve the immobilization of UCSG. SEM-EDS results showed that uranium was uniformly distributed in the matrix, and the maximum solid solubility of UCSG (two components: silica gel and uranyl ions) in the formula was as high as 55 wt %. At the same time, TG-MS proved that silica gel lost OH groups (down about 4.61 wt %) and formed Si-O-Si bond by condensation. FT-IR and XPS proved a change in the number of Si-O-Si bond, and new Si-O-B and Si-O-Al bond appeared on the spectrum. This was evidence that silica gel could self-involved participate in the construction of glass networks. EPR analysis obtained the changes in the coordination environment of U atom, the U atom decreased spin electrons number in the glass than in uranyl crystals. The glass also has good physical properties (hardness: 6.51 ± 0.23 GPa; density: 2.3977 ± 0.0056 g/cm3) and chemical durability (normalized leaching rate: LRU = 2.34 × 10-4 ± 2.05 × 10-6 g·m2·days-1 after 42 days), this research provided tactics for simple treatment of uranium-containing silica gel in one step.

Chemical durability and shielding study of borosilicate glass systems from solid municipal waste ash for radiation shielding applications

Based on municipal solid waste (MSW) ash as a main raw material, three novel borosilicate glasses with the composition of 70 waste + 20 borax + 10 Na2O + x ZrO2, where x = 0, 0.1 or 0.3 (wt. %),were prepared by the traditional melting-annealing technique. The prepared glasses were analyzed by EDX analysis, revealing the rich compositions of the prepared glasses correlated to the MSW ash used by 70 wt.% in preparing glasses. Some optical, chemical and radiation shielding properties of the prepared glasses were investigated. Either Zr addition or 80 kGy of gamma radiation revealed improvement of the glasses optical transmittance and chemical durability in neutral dis H2O, alkaline 0.1 N NaOH and acidic 0.1 N HCl leaching media for 70 days. Electron spin resonance (ESR) revealed the same spectra before and after irradiation, referring to the prevention of free radical formation by irradiation.The shielding parameters were measured by the experimental gamma spectroscopy (NaI detector) and the theoretical Phy-X/PSD software e.g., linear attenuation coefficients (LAC) and the findings revealed high unanimity among them at photon energies 0.662, 1.173 and 1.333 MeV. Another shielding parameters were also studied e.g., mass attenuation coefficients (MAC), effective atomic number (Zeff), effective electron density (Neff) and effective conductivity (Ceff). Presence of various metal oxides and the host trigonal BO3 and tetrahedral BO4 and SiO4 units, and ZrO2 provide the glasses compactness and effectual stability against ionizing irradiation. The prepared borosilicate glasses have highly strong and compacted structures that can inhibit the passage of radiation photons, because of the variety of many glass network formers, intermediates and modifiers present in the used waste ash. The results indicate the highly economic benefit of the prepared glasses, where the useless MSW ash are used mainly by 70 wt.% to produce effective borosilicate glass systems for promising radiation shielding purposes, especially 0.3 Zr borosilicate glass that has the best radiation shielding properties.

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.

Glass hardness: Predicting composition and load effects via symbolic reasoning-informed machine learning

Glass hardness varies in a non-linear fashion with the chemical composition and applied load, a phenomenon known as the indentation size effect (ISE), which is challenging to predict quantitatively. Here, using a curated dataset of over 3,000 inorganic glasses from the literature comprising the composition, indentation load, and hardness, we develop machine learning (ML) models to predict the composition and load dependence of Vickers hardness. Interestingly, when tested on new glass compositions unseen during the training, the standard data-driven ML model failed to capture the ISE. To address this gap, we combined an empirical expression (Bernhardt's equation) to describe the ISE with ML to develop a framework that incorporates the symbolic equation representing the domain reasoning in ML, namely Symbolic Reasoning-Informed ML Procedure (SRIMP). We show that the resulting SRIMP outperforms the data-driven ML model in predicting the ISE. Finally, we interpret the SRIMP model to understand the contribution of the glass network formers and modifiers toward composition and load-dependent (ISE) and load-independent hardness. The deconvolution of the hardness into load-dependent and load-independent terms paves the way toward a holistic understanding of the composition effect and ISE in glasses, enabling efficient and accelerated discovery of new glass compositions with targeted hardness.

A multicomponent lithium aluminum zinc germanate glass influenced by copper ions in its dielectric and spectroscopic characteristics

Multi component Li2O–Al2O3– ZnO–GeO2 glasses doped with CuO ranging from 0 to 1.0 mol% were prepared by the conventional melt quenching technique. Spectroscopic (optical absorption, IR, and EPR) and dielectric properties of the prepared glasses were examined. The EPR and optical absorption studies indicate that low-concentration CuO samples contain both Cu2+ and Cu + ions. CuO concentrations up to 0.6 mol% increased the level of disorder in the glass network, as indicated by IR studies. The dielectric study reveals the influence of copper valance states on the structural aspect of the samples. It has been shown from all these studies that the copper ions can be present in Cu3+ state in these glasses as well as Cu2+ and Cu+ states and thus participate in glass network formation. A quantitative analysis of the dielectric properties of the glasses has indicated that when the CuO concentration exceeds 0.6 mol%, the insulating strength increases. As a result, aluminum ions have been found to be tetrahedrally coordinated instead of octahedral. CuO concentrations above 0.6 mol% in the glass matrix significantly alter the physical properties of these glasses. The reduction of Cu2+ ions to Cu + ions has significantly effected the spectroscopic and dielectric investigations.

Corrosion behavior of Monofrax K‐3 refractory in borosilicate‐based model low activity waste glass melts

AbstractOwing to its good chemical and thermal durabilities at high temperatures, Monofrax K‐3 refractory is widely used in nuclear waste vitrification as a lining material in melting vessels. However, the corrosion of K‐3 refractory during the vitrification of nuclear waste is a serious problem because it affects the melter's safety, performance, and lifetime. Therefore, in the present study, we have focused on unearthing the impact of glass network formers, such as SiO2, B2O3, and Al2O3, in a model nuclear waste glass composition on the corrosion of Monofrax K‐3 refractory. The corrosion tests have been performed per ASTM C621 at 1150°C for 5 days. The dimensional measurements on corroded K‐3 refractory suggest that Al2O3 and SiO2 tend to reduce the refractory corrosion (neck loss), with the effect of Al2O3 being significant. A corroded region on the K‐3 refractory at the melt–refractory interface is observed. The corrosion occurs via a coupling of the melt infiltration induced by a capillary effect and the dissolution of Al, Mg, and Fe components from K‐3 into the melt through chemical reactions. A Cr‐rich layer is retained on the glass contact surface of the corroded K‐3 refractory.

Influence of glass matrix SiO2–B2O3–NaF on the formation of NIR-shielding functional units in energy-saving window glasses

This work presents the influence of glass matrix SiO2–B2O3–NaF on the formation of near-infrared (NIR)-shielding functional units in energy-saving glass windows. The structural analyses by XRD, XPS, and Raman confirmed that the NIR-shielding performance is insensitive to SiO2 or B2O3 glass network formers but is significantly impacted by the concentration of NaF. This is because the presence of a reasonable amount of NaF provides the much-needed sodium for the formation of NIR-shielding functional units Na5W14O44 but too much NaF (>22 mol.%) can inhibit the formation of Na5W14O44 by transforming the W–O–W chain in the interconnected [WO6] and [WO4] polyhedrons into W–O- bonds. By adjusting NaF to the optimal level (16 mol.%) and adding only a small amount of H2WO4 (1.9 mol.%) as the tungsten source in the raw materials, excellent optical properties and thermal insulation performance have been achieved in the produced bulk glass, with a high transmission of 65.8% at 550 nm in the visible light region and a low transmission of 6.6% at 1550 nm in the NIR region. This performance is much better than soda lime glass and ITO glass and is comparable to cesium tungsten bronze-based membrane coated glass. This study paves a way for glass composition design to achieve high NIR-shielding performance with the minimum amount of tungsten source, leading to cost-effective glass fabrication and enhanced mechanical strength of energy-saving glass windows.

Effects of different glass formers on Li2S–P2S5–MS2(M = Si, Ge, Sn) chalcogenide solid‐state electrolytes

AbstractChalcogenide solid‐state electrolytes (SSEs) have been receiving growing attentions due to their high ionic conductivity and suitable mechanic properties, especially the Li2S–P2S5systems incorporated with a second glass network formers (Si, Ge, Sn, and so on) besides P. Although the ionic conductivities are generally enhanced with the second glass network formers, the comprehensive effects of different glass formers on other properties, including electrochemical, cycling, and air stability, remain elusive. To acquire deeper understanding, herein, three common but representative glass network formers (SiS2, GeS2, and SnS2) were introduced into Li2S–P2S5, and their individual effects were investigated systematically. The results of multiscale characterizations before and after lithium stripping/plating cycling confirmed that the introduction of metal cations (Ge, Sn) generally leads to worse electrochemical stability and shorter cycle life of these SSEs toward lithium metal compared with SSEs with nonmetal cation (Si) modification. However, the air stability is related to the binding energy of M–S (M = Si, Ge, Sn), which is consistent with the hard base soft acid theory. This work provides valuable understanding for designing pragmatic Li2S–P2S5–MS2‐based SSEs with high electrochemistry, cycling, and air stability.

Effect of Graphene Additives on the Structure and Optical Parameters of Pure Sodium Borate Glass

This work has been performed to understand the effect of insertion of pure graphene, a two-dimensional organic material, throughout the structural matrix of the pure sodium borate glass. Different amounts (in grams), 0 ≤ x ≤ 3, of graphene have been added to 1 mol of Na2B4O7·10H2O. Four solid samples were prepared using fast cooling from their melts at 1000 ± 10°C. The prepared solids were characterized using X-ray diffraction, which indicated the amorphous nature of the four samples with an increase in the count rate when the content of graphene increased. Fourier transform infrared (FTIR) spectral analysis confirmed that the increase in the graphene content caused an increase in BO4 concentration concerning BO3. The amount of oxidized graphene was shared as glass network formers. The measured values of bulk density and the micro-hardness slightly increased as the graphene content increased. Optical measurement showed an increase in the optical absorbance, direct band gap, indirect band gap, and optical band edge. Also, the values of optoelectronic parameters increased when the graphene content increased to be larger than that of the pure ZnO and CO-ZnO, making the studied glass good candidates for nonlinear optical applications. Both the metallization factor and Urbach's energy showed that the crystallinity degree increased when the content of graphene increased.

Optical Properties of Bismuth Borate Glasses Doped with Zinc and Calcium Oxides

Some bismuth-borate oxide glass' samples were prepared by the fast quenching method, where B2O3 was replaced with equal concentrations of ZnO and CaO. X-ray diffraction (XRD) was used to examine the internal structure and Fourier transform infrared (FTIR) to identify building units and bonds throughout the studied structural matrices. XRD showed that all samples have short range order structural nature, while FTIR demonstrated some of Zn2+ acted as glass network formers and all Bi3+ acted as glass. UV-visible measurements and calculations showed a decreasing in the energy band gap from 3.83 eV to 1.73 eV with decreasing B2O3 content. Also with decreasing B2O3 content, both real refractive index and metallization factor decreased from 3.1 to 1.9 and from 0.56 to 0.71, respectively. For the studied glass' samples, density and molar volume showed inverted behaviors, where the density decreased while the molar volume increases with decreasing B2O3.

Influence of aluminum on structural properties of iron-polyphosphate glasses

Phosphate glasses are materials that can be used in many technological fields. Their possible application may be limited due to the existence of easily hydrated P–O–P bonds. Addition of Al2O3, Fe2O3 strongly improves the durability of the glasses.The subject of the studies are iron-polyphosphate glasses in which iron is gradually substituted by aluminum. The glasses have been tested using FT-IR, Raman, and Mössbauer spectroscopies. The obtained experimental results were compared to the theoretical prediction of the glass network structure by ab initio molecular dynamics.It was shown that the substitution leads to an increase in the glass network polymerization. The glass network is inhomogenous with Al/Fe-rich and poor regions. In the poor regions, Al/Fe cations are glass network modifiers whereas in the rich they can be the glass network formers. Mayer's Bond Order analysis was used to describe bonding mechanisms in the glasses. The existence of the mix-valence iron atoms has been postulated.

Molecule-like structural units in silicate-glass-forming oxides

Silica glasses are composed of multi-oxides, apart from the major component silica. Though it is a general practice in the industries to prepare glasses at specific oxide ratios, the composition rule is largely missing, complicated by the implication of multi-oxides. Necessarily, their interpretation is rooted in chemical units, on which the specific compositions depend. However, in silica glasses the inter-atomic bonding network is continuous and there is no weak bonds, like the inter-molecular ones in molecular compounds, to define molecular entities that carry the chemical information of the materials. As the first stage towards understanding the composition rule, the present paper introduces a new method, so-called the cluster-plus-glue-atom model, to unveil the molecule-like structural units of the glass-relevant oxides. It is pointed out that their respective contributions to the construction of glass networks originate from their characteristic cluster structures, and from which molecule-like structural units are proposed that represent the smallest structural units of these oxides. Oxides participating in the glass network formation mainly present triangular or tetrahedral clusters which are required for a three-dimensional glassy network. For example, the basic network former SiO<sub>2</sub> is formulated as [Si-O<sub>4</sub>]Si and contains 32 valence electrons. The intermediate oxides are characterized by the simultaneous formation of both octahedra and tetrahedra. The network modifiers present mainly cubes and octahedra. It is confirmed that the molecule-like structural units of the glass-formation oxides all meet octet rule (that is, the total number of valence electrons contained in each structural unit is an integer multiple of 8), just like common molecules. The proposed concept of molecular structural units sheds a new light on understanding the composition rule of silicate glasses and can eventually solve the long-standing problem of composition design of silica glasses.

Electrospinning 3D bioactive glasses for wound healing

An electrospinning technique was used to produce three-dimensional (3D) bioactive glass fibrous scaffolds, in the SiO2–CaO sol-gel system, for wound healing applications. Previously, it was thought that 3D cotton wool-like structures could only be produced from sol-gel when the sol contained calcium nitrate, implying that the Ca2+ and its electronic charge had a significant effect on the structure produced. Here, fibres with a 3D appearance were also electrospun from compositions containing only silica. A polymer binding agent was added to inorganic sol-gel solutions, enabling electrospinning prior to bioactive glass network formation and the polymer was removed by calcination. While the addition of Ca2+ contributes to the 3D morphology, here we show that other factors, such as relative humidity, play an important role in producing the 3D cotton-wool-like macrostructure of the fibres. A human dermal fibroblast cell line (CD-18CO) was exposed to dissolution products of the samples. Cell proliferation and metabolic activity tests were carried out and a VEGF ELISA showed a significant increase in VEGF production in cells exposed to the bioactive glass samples compared to control in DMEM. A novel SiO2–CaO nanofibrous scaffold was created that showed tailorable physical and dissolution properties, the control and composition of these release products are important for directing desirable wound healing interactions.

Structural engineering of germanosilicate glass network for enhanced Bi: NIR luminescence

Bi can experience chemical-state evolution by structural engineering of glass network, which is favorable for the efficient manipulation of final luminous property, as well as the extensive potential in new type fiber lasers and optical amplifiers. In this work, the typical structure of glass is transformed and optimized by designing and tuning both the glass network formers and modifiers. It is fist time to demonstrate that the mixed-structure effect produced by the formation of the hybrid structure (SiO2-GeO2) is conducive to the Bi-related near-infrared (NIR) emission. In addition, the dispersion of Bi-related NIR emission centers is further tailored by the AlO5 hexahedra in this multicomponent glass, which is claimed by both NMR and emission spectra. Furthermore, a suitable reduction atmosphere is designed appropriately to promote the NIR luminescence to a larger extent. This work is expected to be helpful for improving the performance of existing Bi-doped glass and fibers. Our results indicate that the tuned multicomponent germanosilicate glasses with mixed structure and optimal reduction effect can be promising material as high performance photonic glasses.

Different property studies with network improvement of CdO doped alkali borate glass

Quaternary alkali borate glass matrix doped with CdO (0, 2, 4, 6, 8, 10 mol%) have been prepared by using conventional melting and quenching technique. For these glass systems structural properties were investigated by using X-ray diffraction, FE-SEM, EDS, FTIR and Raman spectroscopy characterization techniques. X-ray diffraction pattern and FE-SEM studies confirms the amorphous nature of prepared oxide glass. The optical absorption studies were done by using UV–Vis spectroscopy technique at room temperature. The physical parameters of all the glass samples were evaluated with respect to the composition, such as bulk density (ρ), average molar mass (M), molar volume (Vm), ionic concentration (N), interionic distance (ri). They exhibit the non-linearity supporting evidence for the borate glass network modification. Investigations of FTIR and Raman spectroscopy of prepared glass samples have been employed to confirm the role of oxides in the formation of glass network. These glasses are made up from converting [BO3] to [BO4] units without increasing the concentration of non-bridging oxygen. Experimental fraction of 4-coordinated boron atoms expressed by the parameter N4 was calculated and represented with the addition of concentration of CdO (mol%). The optical absorption studies revealed that the average refractive index (nav), optical band gap energy (Eg) nonlinearly increases. The electronic polarizability and optical basicity of the oxide ion (αO2−), as function of refractive index and optical band gap energy were also examined.

Mixed Network Former Effect on Structure, Physical Properties, and Bioactivity of 45S5 Bioactive Glasses: An Integrated Experimental and Molecular Dynamics Simulation Study.

Boron-containing bioactive glasses display a strong potential in various biomedical applications lately due to their controllable dissolution rates. In this paper, we prepared a series of B2O3/SiO2-substituded 45S5 bioactive glasses and performed in vitro biomineralization tests with both simulated body fluid and K2HPO4 solutions to evaluate the bioactivities of these glasses as a function of boron oxide to silica substitution. The samples were examined with scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectrometry after immersing them in the two solutions (simulated body fluid and K2HPO4) up to 3 weeks. It was found that introduction of boron oxide delayed the formation of hydroxyapatite, but all the glasses were shown to be bioactive. Molecular dynamics (MD) simulations were used to complement the experimental efforts to understand the structural changes due to boron oxide to silica substitution by using newly developed partial charge composition-dependent potentials. Local structures around the glass network formers, medium-range structural information, network connectivity, and self-diffusion coefficients of ions were elucidated from MD simulation. Relationships between boron content and glass properties such as structure, density, glass transition temperature, and in vitro bioactivity were discussed in light of both experimental and simulation results.

Effect of exchange of Bi+3 b y Nb+5 on the structural and optical properties of some (BBiNb)2 O7 CaO oxide glasses

Series of five samples, named calcium bismuth niobium Borate glasses, were prepared by quenching their melts. The batches of all samples formed according to the chemical formula 60 mol% B2O3 – 20 mol% CaO – 20 mol% Bi2O3 – (20 − x) Nb2O5 mol%, where x = 0, 2.5, 5, 7.5 and 10 1 mol%. XRD, FTIR and UV–vis. Were used to characterize the internal structure of these glasses. Both XRD and FTIR showed the amorphous character for all samples. FTIR showed that all Nb5+ ions occupied some interstitial vacancies, as a glass network modifiers (GNM), while some of Bi3+ ions share in the glass matrix, as a glass network formers (GNF) and some other occupied some other interstitial vacancies (GNM). The BO4 was found to increase by replacing Bi2O3 by Nb2O5, in other word, increase of the non-bridging oxygen atoms. For all samples, UV–vis. exhibited two indirect (γ = 1/2) and direct (γ = 2) electronic transitions. Both the optical band gap and refractive index for direct transition case were found to have slightly increase as x increase. The density of the studied samples was found to be inversely proportional to their molar volume.

Influence of network modifiers in an acetate based sol-gel bioactive glass system

The aim of this study was to assess the influence of CaO/Na2O ratio on the structural and textural properties of mesoporous bioactive glasses generated from an acetic acid catalysed acetate based sol-gel system. The glass network formers (SiO2 and P2O5) were fixed and the network modifiers were varied [75SiO2:XCaO:(15-X)Na2O:10P2O5 where X = 5, 10, 15, in mole percent] such that increasing alkaline earth oxide is compensated by decreasing alkali oxide. The glass properties were assessed using techniques such as XRF, XRD, FTIR, BET/BJH, SEM, TEM and ICP. The rapid gelling of the sol resulted in the deposition of the calcium and sodium acetate precursors on the particle surface which required thermal treatment to facilitate their entry into the glass network. The results of our study demonstrated that the porosity was clearly driven by CaO in the composition possibly due to its inferior fluxing effect in comparison to Na2O. The sample with highest CaO content reached a high surface area and pore volume (535 m2 g−1 and 0.33 cm3 g−1) even in a non-surfactant based preparation suggesting that acetic acid catalysed acetate system favours improved textural properties. In vitro SBF tests confirmed the potential of the sample with highest CaO for earlier apatite formation.

Effects of boron oxide substitution on the structure and bioactivity of SrO-containing bioactive glasses

B2O3/SiO2 substitution in 55S4.3 bioactive glasses with 5 mol% of SrO has been synthesized and characterized to understand their structure and bioactivity as a function of composition by combining experimental and computer simulation techniques. Raman spectrometry, X-ray diffraction (XRD) and Fourier transform infrared spectrometry (FTIR) were utilized to characterize the structural changes induced by boron content and to identify the formation of hydroxyapatite (HAp). In vitro bioactivity tests were performed in simulated body fluid with a fixed glass mass to solution volume ratio and a particle size range. Needle-like HAp was found to form on the surface of the 55S4.3 with SrO sample from scanning electron microscopy and confirmed from XRD and FTIR. In addition to the experimental efforts, these glasses were also simulated using classical molecular dynamics simulations with partial charge potentials and recently developed parameters for boron oxide to understand their short- and medium-range structures. The glasses from simulations were analyzed in terms of the local structure around the glass network formers, especially the boron coordination number, and found to agree well with theoretical models. The medium-range structural information such as Q n distribution and network connectivity was also obtained and used to understand the compositional dependence of property and bioactivity. The results show that additional boron oxide increased the network connectivity of the 55S4.3 glass and inhibited or delayed the formation of HAp in vitro.

(FeNaP)<sub>2</sub>O<sub>9</sub> Glasses Doped with Different TM Ions

In an attempt to check the effect of the transition metal ions on the glass network, the following chemical formula was used to prepare some of Iron sodium phosphate glasses doped with different transition metal (TM) ions. 50 mol% P₂O₅ + 20 mol% Na₂O + 15 mol% Fe₂O₃ + 15 mol% M_nO_m, where M_nO_m represents V₂O₅, MnO, Co₃O₄, CuO and ZnO. Mossbauer Effect (ME) spectroscopic analysis showed that, the iron ions are located in two different oxidation states Fe³⁺ and Fe²⁺. A fraction of Fe³⁺ ions act as glass network formers (GNFs), whereas the other in addition to all Fe²⁺ ions act as glass network modifiers (GNMs). The electrical properties for all samples have been measured and then studied as a function of the TMIs atomic number. The D.C. conductivity showed a gradual decreasing with increasing the atomic number of TMIs, while the A.C. conductivity has a similar behavior as predicted by CBH model.