Network Formers Research Articles

Advancing understanding of composition–structure–luminescent properties in laser glass through machine learnings

AbstractRare‐earth (RE)‐doped laser glasses meet urgent needs in national security and scientific fields, and their optimization has garnered extensive attention. However, the design of these laser glasses often relies excessively on trial‐and‐error experimentation, leading to significant costs and a lack of scientific guidance. Herein, we propose an integrated method that combines structural descriptors determined from molecular dynamics simulations, a self‐constructed luminescent database, and a machine learning algorithm to establish the composition–structure–luminescent property (CSLP) relationship. Using an Nd3+‐doped commercial silicate laser glass system as an example, the effectiveness of this approach has been demonstrated. The developed CSLP model enables highly accurate predictions of spectral properties, achieving a determination coefficient (R2) greater than 0.94, based on eight structural descriptors. The importance of different structural descriptors on spectral characteristics is ranked and thoroughly discussed, revealing an intrinsic relationship between the first and second coordination shells around RE ions and luminescent behaviors. Furthermore, the generic structural descriptors identified in the CSLP model can be extrapolated to other systems involving different network formers (e.g., silicate and phosphate) and modifier cations (e.g., Li, Na, K, Ba, and Ca). This capability facilitates the design of laser glasses tailored to specific targets, such as large emission cross‐sections, extended lifetimes, or reduced quenching effects.

Li diffusion in oxygen-chlorine mixed anion borosilicate glasses using a machine-learning simulation.

Lithium-ion conducting borate glasses are suitable for solid-state batteries as an interfacial material between a crystalline electrolyte and an electrode, thanks to their superior formability. Chlorine has been known to improve the electron conductivity of borate glasses as a secondary anion. To examine the impact of chlorine on lithium dynamics, molecular dynamics (MD) simulations were performed with a machine-learning interatomic potential (MLIP). The accuracy of the MLIP in modeling chlorine-doped lithium borate (LBCl) and borosilicate (LBSCl) glasses was verified by comparing with available experimental data on density, neutron diffraction S(q), and glass transition temperatures (Tg). While the MLIP-MD simulations underestimated the density when an isobaric-isothermal (NPT) ensemble was used, the glass models relaxed using the NPT ensemble after a melt-quench simulation employing a canonical (NVT) ensemble possessed reasonable density. The LBCl and LBSCl glass models exhibited increased lithium ion diffusion, and the ions were found to travel longer distances with an increase in the chlorine content. According to the structural analyses, it was observed that chlorine ions primarily interacted with lithium ions rather than the network formers. Consequently, lithium ions that interacted with a higher amount of chlorine showed a moderate increase in mobility. In summary, the MLIP demonstrated reasonable accuracy in modeling chlorine-containing borate glasses and enabled the investigation of the effect of chlorine on electron conductivity. In contrast, the first sharp diffraction peaks in S(q) deviated from the experimental diffractions, suggesting that additional efforts are required to accurately model the middle-range structure of the glasses.

Structural and Dynamical Effects of the CaO/SrO Substitution in Bioactive Glasses.

Silicate glasses containing silicon, sodium, phosphorous, and calcium have the ability to promote bone regeneration and biodegrade as new tissue is generated. Recently, it has been suggested that adding SrO can benefit tissue growth and silicate glass dissolution. Motivated by these recent developments, the effect of SrO/CaO-CaO/SrO substitution on the local structure and dynamics of Si-Na-P-Ca-O oxide glasses has been studied in this work. Differential thermal analysis has been performed to determine the thermal stability of the glasses after the addition of strontium. The local structure has been studied by neutron diffraction augmented by Reverse Monte Carlo simulation, and the local dynamics by neutron Compton scattering and Raman spectroscopy. Differential thermal analysis has shown that SrO-containing glasses have lower glass transition, melting, and crystallisation temperatures. Moreover, the addition of the Sr2+ ions decreased the thermal stability of the glass structure. The total neutron diffraction augmented by the RMC simulation revealed that Sr played a similar role as Ca in the glass structure when substituted on a molar basis. The bond length and the coordination number distributions of the network modifiers and network formers did not change when SrO (x = 0.125, 0.25) was substituted for CaO (25-x). However, the network connectivity increased in glass with 12.5 mol% CaO due to the increased length of the Si-O-Si interconnected chain. The analysis of Raman spectra revealed that substituting CaO with SrO in the glass structure dramatically enhances the intensity of the high-frequency band of 1110-2000 cm-1. For all glasses under investigation, the changes in the relative intensities of Raman bands and the distributions of the bond lengths and coordination numbers upon the SrO substitution were correlated with the values of the widths of nuclear momentum distributions of Si, Na, P, Ca, O, and Sr. The widths of nuclear momentum distributions were observed to soften compared to the values observed and simulated in their parent metal-oxide crystals. The widths of nuclear momentum distributions, obtained from fitting the experimental data to neutron Compton spectra, were related to the amount of disorder of effective force constants acting on individual atomic species in the glasses.

Interpretable machine learning for understanding compositional and testing condition effects on refractive index, density, dielectric constant, and loss tangent of inorganic melts and glasses

Artificial intelligence (AI) and machine learning (ML) have enabled property-targeted design of glasses. Several machine learning models and open-source tools in the literature allow researchers to predict the optical, physical, mechanical, and electrical properties of glasses as a function of their chemical compositions. However, these properties also depend on testing conditions. In this paper, we train machine learning models by considering composition and wavelength, temperature, and frequency to predict the refractive index, density, and the two electrical properties, i.e., dielectric constant and loss tangent of glasses, respectively. The predictions of trained models are explained using SHAP analysis, revealing that testing conditions, such as wavelength and temperature, interact majorly with network formers while predicting refractive index and density. In the case of electrical properties, network formers and frequency have the highest interactions, followed by network modifiers and intermediates, and hence govern predictions of dielectric constant and loss tangent. Overall, AI/ML models that can predict the properties of glasses as a function of their composition and testing conditions, coupled with SHAP plots, provide a practical tool to develop a range of glasses for application under varying conditions.

Biocompatibility and antimicrobial efficacy of silver-doped borosilicate bioactive glass for tissue engineering application

Borate bioactive glasses are an auspicious material for tissue engineering applications due to their enhanced dissolution rate, bioactivity, and capacity to integrate therapeutic ions. In this study, borate-based S49B4 bioactive glass doped with silver at mass fraction of 0.5, 1, and 3 wt% were studied for bioactivity, degradation, antibacterial, and cytocompatibility. Thermogravimetric analysis revealed that the bioactive glasses were thermally stable between 600 and 700 °C. Fourier transform infrared spectroscopy and X-ray diffraction confirmed the successful synthesis of an amorphous phase of the doped borosilicate bioactive glasses and the incorporation of silver ion crystals within the structure, as well as associated contributions from borate and silicate network formers in the borosilicate bioactive glass. Morphological evaluation revealed that the borosilicate bioactive glasses exhibit a uniform and spherical shape across all formulations, with the mean particle size varying from 65 to 76 nm. An in-vitro acellular bioactivity in simulated body fluid medium showed that increasing the silver content increased the degradation rate and pH. Besides, scanning electron microscopy and Energy dispersive X-ray spectroscopy analysis revealed an upsurge in apatite production on the BBGs' surfaces as well as incremental Calcium-Phosphate ratio values of 1.50, 1.65 and 1.70 as the silver content increases. The antibacterial effect was tested against Escherichia coli and Staphylococcus aureus, while cytocompatibility was tested against human gingival epithelial cells. Silver integration at 1 wt percent yielded the most promising outcomes, which were particularly bactericidal at 79.8 % for Escherichia coli and 93.41 % for Staphylococcus aureus. Similarly, its Lactate Dehydrogenase percentage is significantly similar to the negative control employed in the study, indicating its biocompatibility. In contrast, 3 wt% silver exhibited the maximum bactericidal activity while also exhibiting mild cytotoxicity. In summary, our research indicates that elevated silver concentration enhances the bioactivity and antimicrobial characteristics of borosilicate bioactive glasses; nevertheless, a higher silver weight percent in this study also increases the possibility of cytotoxicity. It is therefore essential to carefully regulate the amount of silver doping at lower concentrations in order to maximize antibacterial action and minimize toxicity to human cells. The results presented here contribute to our understanding of the prospective use of silver doped borosilicate bioactive glasses as a possible material for tissue engineering applications.

Chaotic Mixing Experiments: Unravelling Contamination Processes on Dacitic Melts

Magmas are the ultimate source of volcanism on Earth. At high-temperatures these complex silicate melts may easily chaotically mix, on their way towards the surface of the planet.The Paraná-Etendeka Magmatic Province (PEMP), one of the largest volcanic provinces of our planet, serves as the focus of this experimental study. The investigation simulates the contamination of high-Ti dacites passing through the continental crust. Our final aim is to contribute to the origin of the high-Ti Chapecó dacites from PEMP, with particular attention to the genesis of Chapecó-Ourinhos dacites (COD).The experimental apparatus is based on the Journal Bearing System. All experimental runs have been operated at atmospheric pressure and a temperature of 1500 °C. A dacitic magma chamber under the assimilation of crustal material has been simulated. The resulting experimental products (dry/bubble free glasses) exhibit concentric folded and stretched filaments of contrasting compositions. The calculated fractal dimension for a representative section is Dbox = 1.60(3), confirming the achievement of chaotic dynamics. Electron Microprobe Analysis (EMPA) from the experimental glasses clearly shows SiO2-contamination, while Al2O3-data indicate lower contamination levels. As a consequence, different elements depict dissimilar curves in chemical transects. We used the parameter σn2 (normalized variance) to quantify the mixing efficiency and differential elemental mobilities. In addition, our data reproduced the chemical behaviour of some elements in COD- dacites, especially the network formers such as Fe, Al, Ti and Si. EMPA reveals clear deviations from the linear mixing model. Our experiments and data replicate a selective contamination process. Differential elemental mobilities could be calculated. Comparisons with natural data depict how the mixing involving Chapecó-Guarapuava (CGD) and Chapecó-Ourinhos (COD) dacitic end-members may have contributed to the generation of more evolved COD from the interaction of CGD pre-existing melts with crustal rocks from the PEMP basement via chaotic dynamics.

Enhancing glass-forming ability and mechanical properties of barium-calcium-aluminate glasses through ZnO inclusion

Calcium aluminate (CA) glasses have garnered attention in the field of infrared photonics due to their low phonon energy. Nonetheless, the poor glass-forming ability (GFA) and strong crystallization tendency have hindered their utilization in various technological applications. Therefore, we demonstrate here that the substitution of ZnO for CaO enhances the GFA of 29Al2O3–(66X)CaO–5BaO–(X)ZnO (X = 0,7,10,15,20,25) glasses and improves their mechanical properties. The structural characterization using Raman, 27Al MAS-NMR spectroscopy and MD simulations reveal that, Zn2+ ions adopt tetrahedral coordination and contribute as network formers along with Al3+ ions. Notably, MD simulations indicate a preference of ZnO4 units for the CaO6 sites to convert non-bridging oxygens to bridging oxygens. The decrease in glass transition temperature and the increase in elastic modulus is noticed which correlated with the structural changes in the studied glasses. These findings provide valuable insights into the design and development of stable multicomponent CA glasses for photonic applications.

Development of a ReaxFF reactive force field for ternary phosphate-based bioactive glasses.

Phosphate-based glasses (PBGs) in the CaO-Na2O-P2O5 system have diverse applications as biomaterials due to their unique dissolution properties. A reactive force field (ReaxFF) has been developed to simulate these materials at the atomic level. The ReaxFF parameters of PBGs, including the interaction between phosphorus and calcium atoms, have been developed using a published code based on genetic algorithms. The training data, including the atomic charges, atomic forces, bond and angle parameters, and different differential energies, are chosen and measured from static quantum-mechanical calculations and abinitio molecular dynamics of PBGs. We did different short- and medium-range structural analyses on the bulk simulated PBGs with different compositions to validate the developed potential. Radial and angular distribution functions and coordination numbers of network formers and modifiers, as well as the network connectivity of the glass, are in agreement with experimental and previous simulations using both shell-model classical force fields and abinitio simulated data; for example, the coordination number of phosphorus is 4.0. This successful development of ReaxFF parameters being able to describe the bulk PBGs enables us to work on the dissolution behavior of the glasses, including the interaction of water molecules with PBGs, in future works.

Investigating the role of network former interactions on charge carrier diffusivity in glasses

Ionic transport is a critical property for the glass industry, since emerging applications such as sensors, batteries, and electric melting are based on the phenomenon. Short-range interactions (anion-charge carrier) have not been able to explain the total activation barrier observed experimentally, and, as such, it is critical to understand the larger role of all ions in a glass, not just the carrier and the ‘site’ ions. This research focuses on the role of network formers and their impact on diffusion in glasses, something that current models lack an explicit explanation of. Atomistic simulations with randomly generated parameters for the cation potentials and classical simulations were used to determine the diffusion coefficients and activation energies for synthetic network formers. Using this database, explainable machine learning algorithms were employed to explore network former interactions and determine which parameters are the most influential for ion diffusion. Results suggest that the bond length of the cations changes the geometry of the structure contributing the greatest to cation-modifier interactions.

Spray-dried ternary bioactive glass microspheres: Direct and indirect structural effects of copper-doping on acellular degradation behavior

Silicate-based bioactive glass nano/microspheres hold significant promise for bone substitution by facilitating osteointegration through the release of biologically active ions and the formation of a biomimetic apatite layer. Cu-doping enhances properties such as pro-angiogenic and antibacterial behavior. While sol-gel methods usually yield homogeneous spherical particles for pure silica or binary glasses, synthesizing poorly aggregated Cu-doped ternary glass nano/microparticles without a secondary CuO crystalline phase remains challenging. This article introduces an alternative method for fabricating Cu-doped ternary microparticles using sol-gel chemistry combined with spray-drying. The resulting microspheres exhibit well-defined, poorly aggregated particles with spherical shapes and diameters of a few microns. Copper primarily integrates into the microspheres as Cu0 nanoparticles and as Cu2+ within the amorphous network. This doping affects silica network connectivity, as calcium and phosphorus are preferentially distributed in the glass network (respectively as network modifiers and formers) or involved in amorphous calcium phosphate nano-domains depending on the doping rate. These differences affect the interaction with simulated body fluid. Network depolymerization, ion release (SiO44−, Ca2+, PO43−, Cu2+), and apatite nanocrystal layer formation are impacted, as well as copper release. The latter is mainly provided by the copper involved in the silica network and not from metal nanoparticles, most of which remain in the microspheres after interaction. This understanding holds promising implications for potential therapeutic applications, offering possibilities for both short-term and long-term delivery of a tunable copper dose. Statement of significanceA novel methodology, scalable to industrial levels, enables the synthesis of copper-doped ternary bioactive glass microparticles by combining spray-drying and sol-gel chemistry. It provides precise control over the copper percentage in microspheres. This study explores the influence of synthesis conditions on the copper environment, notably Cu0 and Cu2+ ratios, characterized by EPR spectroscopy, an aspect poorly described for copper-doped bioactive glass. Additionally, copper indirectly affects silica network connectivity and calcium/phosphorus distribution, as revealed by SSNMR. Multiscale characterization illustrates how these features impact acellular degradation in simulated body fluid, highlighting the therapeutic potential for customizable copper dosing to address short- and long-term needs.

Advancing mechanical durability and radiation shielding properties in Silicon dioxide (SiO2) glasses through various incorporations: A comparative analysis

Silicon dioxide (SiO2) glasses, known for their high thermal stability, excellent optical transparency, and substantial mechanical strength, are crucial in numerous technological applications, including radiation shielding. This research explores the impact of compositional variations in SiO2-based glasses on their mechanical and radiation shielding properties, particularly focusing on the inclusion of heavy metal oxides (HMO) and rare earth elements (REE) like neodymium (Nd). Through the systematic investigation of fifteen distinct glass samples with varying concentrations of specific oxides and elements, we investigate the compositional changes and their influence on physical properties and their effectiveness in attenuating radiation. Our findings demonstrate that the incorporation of Nd significantly enhances the glass's radiation shielding capabilities. Glasses doped with Nd exhibited higher effective atomic numbers and electron densities, which translate to superior attenuation characteristics at lower photon energies. This is highlighted by the exceptional performance of the 20Nd sample, showing the lowest exposure build-up factors (EBF) at 10 mean free paths (mfp), indicating its potential as a premier candidate for shielding applications against various energy levels of radiation. Moreover, the variation in the Elastic Modulus of the glass samples underscores the significant impact of the glass matrix composition on its mechanical properties, suggesting a delicate balance between network formers and modifiers in determining the glass properties. It can be concluded that the neodymium-doped SiO2-based glasses may be considered as targeted compositions in fine-tuning material properties to meet specific application requirements. As the demand for efficient radiation shielding materials grows across medical, industrial, and space exploration sectors, our findings provide a solid foundation for the development of new glass formulations tailored for enhanced mechanical properties and superior radiation protection levels.

An experimental study on the role of F−, PO43−, Cl− and SO42− ligands in the natrocarbonatite-nephelinite system at 850 °C and 0.1 GPa

Carbonatites and their comagmatic silicate rocks related deposit provide significant resources of rare earth elements (REEs), niobium (Nb) and other elements such as U, Th, Mo, V, Ba, Sr, etc. However, the genesis of mineralization, especially for REEs and Nb, in carbonatite remains enigmatic. Previous liquid immiscibility experiments have demonstrated that both REEs and Nb are preferentially enriched in the silicate conjugate instead of carbonate melts under anhydrous conditions. Nevertheless, ligands other than carbonate ion appear to be abundant due to ubiquity of apatite, baryte, celestine, fluorite and sodalite in carbonate–silicate magmatic systems. Here, we experimentally investigate the trace element partitioning between natrocarbonate and silicate (nephelinite) melts in systems doped with varying amounts of additional F−, PO43−, Cl−, and SO42− ligands (0, 2, 4 and 6 wt%) to understand and constrain the role of ligands.The experiments were conducted at 850 °C and 0.1 GPa using rapid quench cold-seal pressure vessels (CSPVs). A comparison of experimental partition coefficients in this study reveals that the significant amounts F− and PO43− incorporated in the silicate melts can increase the D values for REE by influencing melt structure (DLaCM/SM = 0.85–7.42). In contrast, irrespective of the amount of added Cl− and SO42−, DCM/SM is not affected significantly by these species and the DREECM/SM values remain always lower than 1 (DLaCM/SM = 0.12–0.40). Notably, the DNbCM/SM values are all <1, with only one exception containing 6 wt% F. Besides, in all the investigated systems, Ba, Sr, Mo, V, Cs, Rb and Li preferentially partition into the conjugate carbonate melt. All the high field strength elements (Pb, Th, U, Zr, Hf, Nb, Ta), transition metals (Mn, Co, Cu, Zn) and common network formers (Ga, Ge) essentially partition into the silicate melt.

Preparation of ZrP2O7-based fiber composites by in situ synthesis method

ZrP2O7-based fiber composites were prepared by in situ synthesis and their microstructure, thermal conductivity, mechanical and dielectric properties were determined. The chemical reaction with BPO4 as the phosphorus source and nano-ZrO2 as the zirconium source was initiated at 900°C, which promotes liquid-phase sintering and reduces the sintering densification temperature of the ZrP2O7-based fiber composites by generating small ZrP2O7 grains and low-melting B2O3. The lower sintering densification temperature and the appropriate amount of network formers effectively suppressed the high-temperature crystallization phenomenon of the high-silica-oxygen fibers, strengthened the interfacial bonding between the fibers and the matrix, and improved the interfacial debonding problem of the ZrP2O7-based fiber composites. It is found that the ZrP2O7-based fiber composites possess low dielectric constant, low dielectric loss, good thermal conductivity, and acceptable mechanical properties, which can meet the relevant application requirements of centimeter-wave technology.

Pickering stabilization of water-in-crude oil emulsions by paraffin wax crystals: Insights from X-ray scattering

Previous studies suggest asphaltenes are active materials at the oil-water interface, affecting the formation and stability of crude oil emulsions. However, even oils of low asphaltene content generate stable emulsions, indicating the involvement of other oil fractions. Due to the role of paraffin waxes as Pickering stabilizers or gel network formers in emulsions from other applications, this study explores their stabilization capacity in water-in-oil (W/O) emulsions and their interaction with other fractions with interfacial activity. The extraction and physicochemical characterization of paraffin waxes from two Brazilian crude oils allowed us to correlate their properties with the emulsification of both crude and model oils. Removal of asphaltenes enhances emulsion stability. Emulsion preparation with crude oils without waxes and asphaltenes demonstrates the participation of other amphiphilic components in emulsion formation, whereas waxes are necessary for their stabilization. Experiments with emulsions formed by a model oil confirmed the combined action of waxes and an amphiphilic material in the formation and stabilization of the interfacial film. However, the combination of waxes and asphaltenes are ineffective. Small-angle X-ray scattering (SAXS) analysis revealed that waxes only form a lamellar structure when highly purified, suggesting Pickering stabilization rather than the formation of a gel network. In conclusion, polar oil fractions other than asphaltene play a crucial role in emulsion formation, whereas paraffin wax provides Pickering stabilization, even beyond the wax appearance temperature (WAT). This study enhances our understanding of the mechanisms governing waxy Brazilian crude oil emulsions.

Uncovering the Network Modifier for Highly Disordered Amorphous Li-Garnet Glass-Ceramics.

Highly disordered amorphous Li7La3Zr2O12 (aLLZO) is a promising class of electrolyte separators and protective layers for hybrid or all-solid-state batteries due to its grain-boundary-free nature and wide electrochemical stability window. Unlike low-entropy ionic glasses such as LixPOyNz (LiPON), these medium-entropy non-Zachariasen aLLZO phases offer a higher number of stable structure arrangements over a wide range of tunable synthesis temperatures, providing the potential to tune the LBU-Li+ transport relation. It is revealed that lanthanum is the active "network modifier" for this new class of highly disordered Li+ conductors, whereas zirconium and lithium serve as "network formers". Specifically, within the solubility limit of La in aLLZO, increasing the La concentration can result in longer bond distances between the first nearest neighbors of Zr─O and La─O within the same local building unit (LBU) and the second nearest neighbors of Zr─La across two adjacent network-former and network-modifier LBUs, suggesting a more disordered medium- and long-range order structure in LLZO. These findings open new avenues for future designs of amorphous Li+ electrolytes and the selection of network-modifier dopants. Moreover, the wide yet relatively low synthesis temperatures of these glass-ceramics make them attractive candidates for low-cost and more sustainable hybrid- or all-solid-state batteries for energy storage.

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.

An investigation on 45S5 nanobioactive glass using FTIR and Raman spectroscopy

Bioactive materials are those that cause a number of interactions at the biomaterial-living tissue inter-face that result in the evolution of a mechanically strong association between them. For this reason, an implantable material’s bioactive behavior is highly advantageous. Silicate glasses are encouraged to be used as bioactive glasses due to their great biocompatibility and beneficial biological effects. The sol-gel method is the most effective for preparing silicate glasses because it increases the material’s bioactivity by creating pores. Glass densities are altered by the internal network connectivity between network formers and network modifiers. The increase in the composition of alkali or alkaline oxides reduces the number of bridging oxygens and increases the number of non-bridging oxygens by retaining the overall charge neutrality between the alkali or alkaline cation and oxygen anion. Higher drying temperatures increase pore densities, while the melt-quenching approach encourages the creation of higher density glasses. Band assignments for the BAG structure can be explained in detail using Fourier Transform Infrared (FTIR) and Raman spectroscopic investigations. Raman spectroscopy makes it simple to measure the concentration of the non-bridging oxygens in the silica matrix.

Effect of enhanced pozzolanic activity in nickel slag modified with Al2O3 on mechanical properties of cemented fine tailings backfill

Cemented tailings backfill has gained widespread acceptance in mining industries due to its stable performance and environmental advantages. However, Ordinary Portland cement (OPC), based on engineering experience, falls short in meeting the requirements of cost-effectiveness and environmental protection criteria for cemented fine tailings (median size d50 <20 µm) backfill. Nickel slag (NS), an industrial solid waste with potential reactivity derived from nickel manufacturing processes, is currently employed as a concrete additive at a low rate. In this work, a modification was conducted by melting-quenching the NS-Al2O3 mixtures, followed by a physicochemical analysis of the resulting granulated samples (GAN) using BET and X-ray fluorescence. The mineralogy and structural properties were examined for the GAN samples using X-ray diffraction and Fourier transform infrared spectroscopy. Each of the T-CGAN pastes was formulated by replacing 40 wt% of OPC with the GAN, and then blended with fine tailings at 1:4. The flowability and compressive strength were measured for the T-CGAN pastes, while the hydration products and microstructures of the paste samples were analyzed by derivative thermogravimetry and scanning electron microscope, respectively. The results indicate that the addition of Al2O3 not only provides abundant network formers to GAN glass, but also facilitates the conversion of [SiO4] tetrahedrons from Q4 with strong bond energy to Q3 and Q2 with lower ones, thereby significantly enhancing the pozzolanic activity of the original NS. The T-CGAN slurries exhibit slight decreases in slump values from 228.8 to 224.9 mm compared to T-OPC slurry (236.5 mm), attributed mainly to the strong water absorption of GAN. T-CGAN pastes with higher Al2O3 addition acquired greater compressive strengths during the whole curing ages. After 90 days of curing, T-CGAN20 paste achieves the maximum compressive strength (5.14 MPa), higher than that of the T-OPC by 1.03 MPa. The T-CGAN pastes richer in Al2O3 release more reactive Si and Al to participate in the pozzolanic reaction with calcium hydroxide, contributing to additional formations of C-S-H gel and C-A-H, with SEM micrographs showing a compact microstructure with elevated ratios of Ca/Si, Al/Si, and Fe/Si. This study suggests an effective and environmental way to enhance the pozzolanic activity of the original NS by incorporating Al2O3. The modified NS can then be utilized as a high-performance cement substitute for cemented fine tailings backfill, which also significantly enhances the sustainability for both mining and building industries.

Ionic Conductivity of K-ion Glassy Solid Electrolytes of K2S-P2S5-KOTf System

Ternary glassy electrolytes containing K2S as a glass modifier and P2S5 as a network former are synthesized by introducing a new type of complex and asymmetric salt, potassium triflate (KOTf), to obtain unprecedented K+ ion conductivity at ambient temperature. The glasses are synthesized using a conventional quenching technique at a low temperature. In general, alkali ionic glassy electrolytes of ternary systems, specifically for Li+ and Na+ ion conductivity, have been studied with the addition of halide salts or oxysalts such as M2SO4, M2SiO4, M3PO4 (M = Li or Na), etc. We introduce a distinct and complex salt, potassium triflate (KOTf) with asymmetric anion, to the conventional glass modifier and former to synthesize K+-ion-conducting glassy electrolytes. Two series of glassy electrolytes with a ternary system of (0.9–x)K2S-xP2S5-0.1KOTf (x = 0.15, 0.30, 0.45, 0.60, and 0.75) and z(K2S-2P2S5)-yKOTf (y = 0.05, 0.10, 0.15, 0.20, and 0.25) on a straight line of z(K2S-2P2S5) are studied for their K+ ionic conductivities by using electrochemical impedance spectroscopy (EIS). The composition 0.3K2S-0.6P2S5-0.1KOTf is found to have the highest conductivity among the studied glassy electrolytes at ambient temperature with the value of 1.06 × 10−7 S cm−1, which is the highest of all pure K+-ion-conducting glasses reported to date. Since the glass transition temperatures of the glasses are near 100 °C, as demonstrated by DSC, temperature-dependent conductivities are studied within the range of 25 to 100 °C to determine the activation energies. A Raman spectroscopic study shows the variation in the structural units PS43−, P2S74−, and P2S64− of the network former for different glassy electrolytes. It seems that there is a role of P2S74− and P2S64− in K+-ion conductivity in the glassy electrolytes because the spectroscopic results are compatible with the composition-dependent, room-temperature conductivity trend.