Glass Content Research Articles

A low-temperature molten salt synthesis strategy of Eu2Ti2O7 ceramic enabling ultra-durable glass-ceramic waste forms

The conventional solid-phase sintering method for the preparation of Ln2Ti2O7 ceramics using oxides as reactants generally requires higher temperature, larger pressure, and greater energy consumption. In this paper, we synthesize a Eu2Ti2O7 ceramic powder in relatively low-temperature molten salt (KCl–NaCl) using Eu2O3 powder and TiO2 powder as reactants at 1000 °C. The results of XRD, SEM, and element mapping indicate that the product have high phase purity, good crystal morphology and uniform chemical composition. Moreover, Eu2Ti2O7-based glass-ceramics are obtained by sintering with different contents of borosilicate glass. The SEM images of glass-ceramic show that almost no obvious defects or voids are found on the surface of the samples. The values of water absorption for all glass-ceramic waste forms are less than 0.5 %. With the increase of ceramic embedding rate, the hardness of the glass-ceramics first increases and then decreases, while the density gradually increases. When the embedding rate increased to 30 wt%, the hardness of glass-ceramic reaches a maximum of 19.53 GPa. The glass-ceramic waste form embedded with 30 wt% Eu2Ti2O7 exhibits very stable chemical durability with a low leaching rate of 1.42 × 10−8 g m−2 d−1 at 90 °C even after 28 days.

Facile Synthesis of Surface-Modified Hollow-Silica (SiO2) Aerogel Particles via Oil-Water-Oil Double Emulsion Method.

Due to their high surface area and low weight, silica aerogels are ideally suited for several uses, including drug delivery, catalysis, and insulation. Oil-water-oil (OWO) double emulsion is a simple and regulated technique for encasing a volatile oil phase in a silica shell to produce hollow silica (SiO2) aerogel particles by using hydrophilic and hydrophobic emulsifiers. In this study, the oil-water-oil (OWO) double emulsion method was implemented to synthesize surface-modified hollow silica (SiO2) aerogel particles in a facile and effective way. This investigation mainly focused on the influence of the N-hexane-to-water glass (OW) ratio (r) in the first emulsion, silica (water glass) content concentration (x), and surfactant concentration (s) variations. Furthermore, surface modification techniques were utilized to customize the aerogel's characteristics. The X-ray diffraction (XRD) patterns showed no imprints of impurities except SiO2. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images highlight the hollow microstructure of silica particles. Zeta potential was used to determine particle size analysis of hollow silica aerogel particles. The oil-water-oil (OWO) double emulsion approach was successfully employed to synthesize surface-modified hollow silica (SiO2) aerogel particles, providing precise control over the particle characteristics. By the influence of the optimization condition, this approach improves the aerogel's potential applications in drug delivery, catalysis, and insulation by enabling surface modifications.

Synthesis, structural, and optical behavior of erbium-doped silicophosphate glasses for photonics applications.

Erbium-incorporated silicophosphate glasses are very desirable in principal sectors such as photonics, optoelectronics, lasers, and illuminating diodes. The focus of the current investigation has been on determining how the erbium dopant affects the optical, physical, and structural characteristics of the silicophosphate-based glasses. The pure silicophosphate glasses and doped with various contents of erbium were prepared by the sol-gel process in this work. The noncrystalline character of the glasses synthesized was confirmed by the XRD patterns that were obtained. The optical measurement showed that the addition of trivalent erbium ions resulted in an increase in the refractive index of the samples and a decrease in their energy band gap values. It demonstrated the presence of P-O-P linkage stretching vibration modes that were both symmetrical and asymmetrical, P-O in PO4 bending vibration modes, OH group elongating and flexure vibrations, and P-O-H water absorption in glasses. The theoretical values of the optical basicity (Ʌth) increased from 0.465 to 0.472, while the values of the interaction parameter (A) decreased from 0.218 to 0.214 . Silicophosphate glasses doped with trivalent erbium ions show promise as optoelectronic and optical filter system materials.

Recycled cathode ray tube waste glasses for radiation shielding applications: Role of Na2CO3

The aim of the study is to evaluate the ability of cathode-ray tube funnel waste glasses (CRT-F) to shield photons (gamma and X-ray) and other forms of radiation with rest masses (i.e., neutrons and charged particles) after their Pb content was reclaimed. The lead (Pb) content of cathode-ray tube funnel waste glasses (CRT-F) was reduced using Na2CO3 as the reducing agent CRT-F(Na2CO3). CRT-F and CRT-F(Na2CO3) were produced using the melt and quench processes using the powder of pristine funnel glass from discarded cathode ray tube glass and the reduced glass powder, respectively, as the starting materials. The X-ray fluorescence technique was adopted for determining the chemical composition of CRT-F and CRT-F(Na2CO3) glasses. The parameters relating to the gamma photon, fissile neutron, moderated neutron, slow neutron, and charged radiation (β, H+, He2+, and C6+) attenuation abilities of pristine CRT-F and CRT-F(Na2CO3) were evaluated. The FLUKA simulation code and XCOM were used to estimate the mass attenuation coefficient of the glasses. The stopping power (Sp) and range (R) of β, H+, and He2+ were evaluated by using the NIST data-based calculators (ESTAR for β, PSTAR for H+, and ASTAR for He2+) while Sp and R data for C6+ was determined using SRIM. The cross section for fast, thermal (25 meV), and slow neutrons (0.1–10 meV) was also estimated. The Pb reclamation from the CRT-F drastically increased the half value layer of photons by at least a factor of 4 at 0.1 MeV and by more than 90 % at 10 MeV. The CRT-F interacts more with fissile and thermal neutrons compared to CRT-F(Na2CO3). Although, CRT-F showed a better ability to attenuate all the radiation types considered, both glasses are better absorbers of radiation (especially photons) than some common shields. The reduction of Pb weight in CRT-F resulted in a drastic reduction in the ability of the glass to attenuate radiation; the resulting glass (CRT-F(Na2CO3)) is however, an environmentally safer glass shield.

Compositional Characterization of Glassy Volcanic Material From VSWIR and MIR Spectra Using Partial Least Squares Regression Models

AbstractThe glass phase in volcanic rocks presents a challenge to obtaining compositional data from visible and short‐wave‐infrared (VSWIR) and mid‐infrared (MIR) spectral data of remote surfaces due to its amorphous structure and variable composition. Nonetheless, glass is a common phase in volcanic materials because it forms via the rapid quench of magma and can constitute up to the entirety of a volcanic deposit. Use of partial least squares regression (PLS) to predict glass contents creates models that are insensitive to viewing geometry and sample conditions such as grain size and spectrally inactive compositional variables, enhancing the ability to detect glasses with remote sensing. PLS models are used here to predict crystallinity and oxide composition of samples from VSWIR and MIR spectral data using training spectra from natural volcanic rocks and geologically relevant synthetic samples. Three spectral resolutions of VSWIR and MIR spectra (1, 10, and 100 nm/band, and 1.9, 19, and 190 cm−1/band, respectively) were tested to assess the effects of collection configuration on different spectrometers. PLS models trained on 1 nm and 1.9 cm−1 data sets have the lowest uncertainties of glass modal abundance for VSWIR and MIR, respectively. MIR models predicting sample wt. % SiO2 and FeO, and VSWIR models of wt. % FeO provide accurate estimates (e.g., RMSE‐P of 3.4 wt. % FeO) at all spectral resolutions. Results are based on training data sets skewed to mafic compositions, which affects model accuracies.

The Performance of Modified Asphalt Mixtures with Different Lengths of Glass Fiber

AbstractOne practical option for modifying an asphalt mixture’s performance is to use additives. This will help the mixture perform better against the damaging effects of traffic, loads, and climatic variations. In this regard, glass fiber (GF) has drawn much interest because of its positive effect. Therefore, this paper attempts to study the effect of glass fiber length and content on the performance and strength of asphalt mixtures. It also aims to determine the optimum glass fiber content and the best glass fiber length of modified asphalt mixtures. An experimental program is carried out, which includes the Marshall test, volumetric properties, freeze-thaw splitting test, immersion Marshall test, and wheel tracking test to characterize related properties of glass fiber incorporated in asphalt mixtures. Seven different percentages (0, 0.25, 0.5, 0.75, 1, 1.25, and 1.5) of glass fiber by total weight of aggregates in three various lengths are used to design 19 asphalt mixtures. Based on the results obtained, the performance of the asphalt mixture was enhanced remarkably after adding glass fiber. The use of various lengths of glass fiber led to a better-quality asphalt mixture in terms of volumetric properties, moisture damage resistance, and permanent deformation resistance. Specifically, asphalt mixtures made with (0.5%) glass fiber illustrated the highest quality, and adding (20 mm) length of glass fiber was better than (10 mm and 30 mm) glass fiber lengths. The results also show that adding (10 mm and 30 mm) lengths of glass fiber can improve the resistance of asphalt mixtures to water damage and permanent deformation compared with the control mixture (M0). The findings indicate the applicability of 20 mm glass fiber length in asphalt mixtures to achieve better resistance against moisture and reduce the chance of irreparable permanent deformation under growing traffic loads and hot climate changes. Although the inclusion of glass fiber in asphalt mixtures led to a modest increase (6%) in overall cost, the effective improvement in performance and extension of the service life of the asphalt pavement constitute a convincing argument for this approach, making it an attractive option. Finally, it was concluded that a higher amount of glass fiber (i.e., > 0.5%) and a length greater than (20 mm) could diminish the positive effect of glass fiber to improve the properties of glass fiber asphalt mixtures.

Gelatin-containing functionally graded calcium sulfate/bioactive glass bone tissue engineering scaffold

One of the challenges and limitations of bone tissue engineering includes fast degradation rates, reduced bioactivity, donor site morbidity, and unresolved risks of pathogen transmission. In the field of bone tissue engineering, gradient materials are promising for treating bone defects because they can create graded structures and compositions similar to natural bone. By controlling the amount of components in the structure, the degradation rate, bioactivity, and osteogenic capacity can be manipulated. In the current study, a gradient, multilayer, porous nanocomposite of calcium sulfate/glass (Gn CS/BG) with a gelatin coating (Gn CS/BG-Gel) was prepared using rotational casting technique. The SEM results showed an average pore size of approximately 400 μm within the Gn CS/BG-Gel nanocomposite. An elastic modulus (E) of around 240 MPa and an ultimate tensile strength (σ) of approximately 5.5 MPa were achieved for Gn CS/BG-Gel nanocomposite. The degradation analysis in a dynamic tris-buffer environment revealed a degradation rate of 68 % over a 63-day period, with a decrease in degradation rate as the bioactive glass (BG) content increased in each layer, indicating the influence of BG on the degradation process. The bioactivity results in a dynamic simulated body fluid suggested that increased BG content in each layer promoted hydroxyapatite formation, indicating improved bioactive behavior. The evaluation of ion release with ICP-OES, MTT and Acridine Orange assays using human bone marrow-derived mesenchymal stem cells (hBMSCs) confirmed the non-toxic nature of Gn CS/BG-Gel. Assessments of alkaline phosphatase (ALP) activity, calcium content, Alizarin Red staining and cell attachment behavior substantiated the osteogenic potential of Gn CS/BG-Gel. Collectively, the three-dimensional structure along with the Gn CS/BG-Gel composition contributed to the enhanced cellular responses. These findings hold significant promise for the development of biomaterials with potential applications in bone tissue engineering, and they contribute valuable insights to the field.

Physical, Thermal, and Optical Properties of Mn2+ and Nd3+ Containing Barium Phosphate Glasses.

This work reports on various properties and analysis of optical interactions in phosphate glasses containing red-emitting Mn2+ and near-infrared (NIR)-emitting Nd3+ ions, which are of interest for energy applications and solar spectral converters. The glasses were made by melting with 50P2O5-(48 - x)BaO-2MnO-xNd2O3 (x = 0, 0.5, 1.0, and 2.0 mol %) nominal compositions and characterized by X-ray diffraction, density and related physical properties, differential scanning calorimetry, dilatometry, UV-vis-NIR optical absorption, and photoluminescence spectroscopy with decay kinetics analysis. The glasses were X-ray amorphous, wherein the physical and thermal properties of the Mn2+/Nd3+-codoped glasses were largely impacted by Nd2O3 contents. The optical absorption spectra supported the occurrence of Mn2+ ions and the lack of Mn3+ in the codoped glasses, while the absorption due to Nd3+ ions increased steadily with Nd2O3 contents. Analyzing the glass absorption edges via Tauc and Urbach plots was further pursued for a comparison. The photoluminescence evaluation showed a consistent suppression of the emission from Mn2+ ions with increasing Nd3+ concentration, while the decay kinetics revealed shorter lifetimes in connection with increased Mn2+ → Nd3+ transfer efficiencies. Excitation of Mn2+ at 410 nm, however, led to the Nd3+ NIR emission being most intense for 1.0 mol % Nd2O3, despite the 4F3/2 emission decay analysis showing lifetime shortening throughout. Considering the compromise between red and NIR emissions, the Mn-containing glass doped with 0.5 mol % Nd2O3 is put in perspective with the concept of solar spectral conversion.

Effect of TeO2 on sintering behavior and properties of B2O3-BaO-ZnO-SiO2-Al2O3 glass

The research on low-temperature lead-free glass is of great significance for the miniaturization, integration and intelligence of current electronic products, as well as environmental protection. In this article, we report the preparation of low-temperature lead-free B2O3-BaO-ZnO-SiO2-Al2O3-TeO2 glasses by a melt-quenching technique. With the increase of TeO2 content in glass, the glass transition temperature and melting temperature of sintered glass powder decrease, while its wettability and acid corrosion resistance show an increasing trend. The application of glass powder in the sintering experiment of terminal electrode slurry further proves this viewpoint. Compared with the poor sintering performance of the slurry with TeO2-free glass powder, the slurry containing TeO2 glass powder forms a very dense sintered solid, and the sintered slurry is tightly bonded to the ceramic substrate.

Exploring structural compatibility and energy storage performances enhancement in lead-free BNT dielectric ceramics with NBTP glass integration

An innovative approach was adopted to improve the energy storage and dielectric properties of Bi0.5Na0.5TiO3 (BNT) ceramics by incorporating a glass additive. The chosen Na2O–Bi2O3–TiO2–P2O5 (NBTP) glass shares a similar atomic composition to minimize any alteration of the crystalline structure and the build-up of impurities. Simultaneously, we investigate the feasibility of offsetting Bi and Na losses during the synthesis process. XRD and Rietveld refinement analysis confirmed the formation of pure BNT phases with no secondary phases. Dielectric parameters were evaluated in the frequency range of 1 Hz to 1 MHz, over a wide temperature range of 30 °C–270 °C, showing minimal variation in their values for the composites with lower glass content. Our findings indicate a notable reduction in grain size and the sintering temperature with improved relative density, leading to enhanced energy storage and efficiency in BNT-based ceramics. The composite with 2.5 wt% glass content shows the highest recovered energy of 154.9 mJ/cm3 with an energy efficiency of 88.64 %, making it particularly promising for advanced capacitor technology.

Melt inclusions in spinel from a composite mantle xenolith

Composite mantle xenoliths from the Cima Volcanic Field (CA, USA) contain a variety of melt (now glassy) inclusions hosted within mantle phases. The compositions and textures of these melt inclusions have the potential to constrain their trapping processes, melt sources, and the rates of ascent of their parent xenoliths. Here we focus on unusual spinel-hosted melt inclusions from one composite xenolith, reporting glass and daughter mineral compositions and textures and attempting to reconstruct inclusion bulk compositions. The xenolith contains spinel-hosted melt inclusions in its harzburgite, olivine-websterite and lherzolite layers; there are none in its orthopyroxenite layer.The glass compositions and reconstructed bulk compositions of the partly-crystallized inclusions correspond to alkaline intermediate melts, mostly trachyandesites. Such melts are most likely to be generated and trapped by vapor-undersaturated phlogopite or amphibole dehydration melting to an assemblage of liquid + spinel + olivine ± pyroxenes. We modeled the near-liquidus phase relations of the inclusion bulk compositions and noted the closest approach of each inclusion to simultaneous saturation with spinel and either phlogopite or amphibole, resulting in estimated trapping pressures of ∼0.5–1.5 GPa and temperatures of ∼1000–1100 °C. The large size of the hosting spinel grains suggests a slow process associated with these breakdown reactions, probably thinning of the lithosphere and steepening of the geotherm during regional extension.A linear correlation between the vesicle area and inclusion area (as proxies for volume) suggests an in-situ exsolution process from melts of relatively uniform volatile initial contents, consistent with trapping of vapor-undersaturated melts that later exsolve vapor during cooling and daughter crystal growth. A negative correlation between the glass content in melt inclusions and the size of the inclusion itself suggests a control on the degree of crystallinity with the size. There appears to be a two-stage cooling history captured by the inclusions, forming first prismatic daughter crystals and large round vesicles at the wall of the inclusion, followed by quenching to form a mat of fine crystallites and small vesicles in most inclusions. We connect the final quench to rapid ascent of the xenolith in its host melt, which also triggered partial breakdown of remaining amphibole to fine glassy symplectites.

Polyurethane modified asphalt mixture incorporating waste glass with a wide particle size range: Preparation and performance evaluation

Increasing the utilisation rate of waste glass in asphalt mixtures, especially that with a wide range of particle sizes, is of great importance to resource recycling, while it may bring drawbacks to the engineering performance of asphalt mixtures. Incorporating polyurethane (PU) as a modifier can enhance asphalt mixture's performance, but there is limited research considering the usage of waste glass as aggregates. In this study, PU modified asphalt mixtures were prepared, incorporating waste glass particles ranging in size from 2.36 mm to 9.5 mm as a portion of the aggregates. Optimal preparation methods and mix designs for the PU-modified asphalt binder were determined through a series of tests designed based on Orthogonal method. The performances of the PU-modified asphalt binders were then evaluated to guide the selection of the optimal preparation method and mix design. PU-modified waste glass asphalt mixtures were then prepared and their engineering performances were assessed at various glass-to-aggregate ratios. The results show that scheme PU-1 with a shearing temperature of 140°C, a shearing time of 10 min, a PU content of 10% and a compatibiliser content of 2% is suggested for preparing the PU-modified asphalt binder, which shows the best performances due to superior chemical modification and compatibility. Higher glass content decreases the high/low-temperature performance, but it can be improved by adding silane coupling agent or hydrated lime, with the latter showing better results. The incorporation of glass particles has little impact on anti-sliding performance, and asphalt mixtures maintain excellent anti-sliding properties up to a 20% replacement rate. Overall, the performance of the asphalt with waste glass up to 15% can meet the specification requirements. This novel approach offers a potential solution to enhance the incorporation of waste materials in asphalt construction, contributing to sustainable and environmentally-friendly road construction.

The relationship between iron redox states and H2O contents in back-arc basin basaltic glasses from the North Fiji Basin

Island-arc basalts (IAB) from convergent plate margins tend to have both higher iron oxidation states (higher Fe3+/Fe2+) and higher H2O contents than the mid-ocean ridge basalts (MORB) produced by seafloor spreading, which raises the question of whether these two characteristics are causally related. Back-arc basin basalts (BABB) may help with this question, in that they are products of seafloor spreading, like MORB, but sourced from supra-subduction mantle, like IAB. Here we examine the relationship between Fe3+/Fe2+ (determined by XANES spectroscopy) and H2O contents in BABB glasses from the North Fiji Basin (NFB). The glasses cover a range of compositions from 6.1 to 8.5 wt% MgO, and from 0.16 to 1.6 wt% H2O, and have also been analysed for trace elements and Sr-Nd-Pb-isotopes. Measured Fe3+/Fe2+ range from MORB-like to slightly higher values and are positively correlated with H2O and heavy-halogen contents (Cl, Br and I). The correlation is due to lower Fe2+ rather than higher Fe3+ compared to the MORB array. This suite of BABBs is not significantly enriched in trace elements other than H2O and the heavy halogens, with MORB-like Ba/Th and other incompatible-element ratios, suggesting that the H2O and halogens may have come from dehydration of subducted lithospheric serpentinites under subsolidus conditions. Na2O is unusually variable for a suite of samples from such a limited area, and is not correlated with H2O, precluding a relationship between H2O and degree of melting. The link between H2O and low Fe2+ may be explained by H2O-rich fluids entering the transcrustal magma plumbing system, where they increase the proportion of olivine and augite to plagioclase crystallizing during the crustal evolution of the magmas. In this situation, relatively small additions of H2O can have an enhanced effect on major-element chemistry if the crustal evolution proceeds by cycles of replenish-mix-tap-crystallize (RMTX) rather than by simple fractional crystallization without repeated replenishment and tapping. The absence of any increase in Fe3+ with H2O, together with the lack of any correlation between H2O and Fe3+/Fe2+ in MORB glasses generally, suggest that various mechanisms, including more extensive olivine fractionation, were responsible for elevating Fe3+/Fe2+ in H2O-rich basalts from convergent margin settings. Proxy methods based on concentrations of elements with redox-variable partition coefficients (V, Eu) are not sensitive enough to record the subtle variations in Fe3+/Fe2+ observable by XANES spectroscopy.

The influence of sodium silicate water glass content on the structure and properties of silicate thermal insulation coating

Thermal insulation slurry was fabricated using sodium silicate water glass (SSWG) as the film-forming material and hollow glass microspheres (HGM) as thermal insulation fillers. The thermal insulation slurry was coated on 316L stainless steel to fabricate a silicate thermal insulation coating. The results show that SiO2 phase is formed by SSWG in the thermal insulation coating after sintering at 680 ℃. Through polymerization and dehydration reactions between Si-OH groups, the Si-O three-dimensional network structure develops at 680 ℃. The optimal value of SSWG to aggregate mass ratios is 2.00. Under this condition, the silicate thermal insulation coating exhibitssmoothsurface, continuous and dense microstructure, high Shore hardness of50.1 HSD,remarkablethermal insulation efficiency of21 %at260 ℃, andexcellentresistance to drop and thermal shock tests without anynoticeablecracks or detachment.

Thermal Sintering Matchability between Low‐Temperature Cofired Ceramic Substrate and Silver Pastes and the Effect of CuO on Silver Diffusion Inhibition

Low‐temperature cofired ceramic (LTCC) materials are a promising material for heat dissipation substrates due to their excellent thermal conductivity and thermal expansion coefficient similar to that of silicon. However, the difficulties in surface metallization techniques limit its application. This work uses Bi–B–Si–Zn–Al glass/ceramic composite as the substrate and Bi–B–Si–Zn–Al glass powder as the inorganic binder for silver pastes. The silver thick film with a glass content of 3 wt% is sintered at 800 °C for 30 min, and the samples have excellent electrical conductivity (surface square resistance of 0.29 mΩ £−1) and mechanical properties (interface bonding force of 17.56 MPa). In addition, the introduction of CuO into the glass phase can inhibit the silver diffusion phenomenon during the sintering process and improve the conductive performance of the material. The results are beneficial for the preparation and application stability of LTCC devices.

Valence state conversion of Mn ions in Li2O–ZnO-GeO2 glass-ceramics: Spectral, structural, ESR and XRF studies

Lithium-zinc-germanate glass-ceramics doped with Mn ions are synthesized by volume crystallization method. Structural studies show nucleation of different forms of lithium germanate crystals depending on the isothermal treatment regime of the initial glass. With the increase of the heat treatment temperature and the lithium content in the initial glass, the [GeO4] /[GeO6] ratio in the nucleated crystalline phases increases. The initial distribution of Mn2+/Mn3+/Mn4+ is defined by the Li2O/ZnO ratio in the glass composition: the ratio growth increases the contribution of Mn4+ over the Mn2+ and Mn3+. Low-temperature heat treatment of initial glass leads to uprise of intense red emission of Mn4+ ions in the octahedral environment. High-temperature heat treatment leads to occurrence of intense green emission related to Mn2+ ions in a tetrahedral environment. Discussions on all transformations of symmetry, the crystal field strength of Mn ions’ environment and their valence state based on the results of optical spectroscopy, ESR and XRF studies are provided. The maximum quantum yield of red luminescence is 61%, and of green luminescence is 23%. The synthesized glass-ceramics can be used as a luminescent converter of the UV LED radiation with the maximum energy efficiency of 20%.

Impact of mixed heavy metal cations (Ba and Bi) on the structure, optical and ionizing radiation shielding parameters of Bi2O3–BaO–Fe2O3–SrO–B2O3 glass matrix

The impacts of the Bi2O3/BaO ratio on the microstructure, optical, ligand field, and radiation shielding features of BSrFeBaBi glass matrix. The Bi2O3 content of the BSrFeBaBi glasses was increased from 0 to 20 mol%. The density increased from 3.77 g/cm3 to 5.00 g/cm3 and the molar volume increased from 24.74 cm3/mol to 31.17 cm3/mol with increasing Bi2O3/BaO ratio. The optical analysis confirmed that the transparency of BSrFeBaBi glasses in the visible region is high. Moreover, the presence of Fe cations in the octahedral coordination (FeO6 units) was confirmed. Furthermore, the fundamental absorption edge of BSrFeBaBi glasses shifts towards lower energies with additional Bi2O3/BaO concentrations, confirming the reduced behavior of the optical band gap. Also, ligand field splitting values decreased while Racah parameters increased. The obtained results demonstrate a tendency of the bonds between the Fe ions and their surroundings towards higher degree of ionic nature. Furthermore, the Bi2O3/BaO ratio demonstrated an enhanced radiation shielding behavior. Finally, BSrFeBaBi glasses exhibit favorable attributes for use in the radiation shielding domain due to their efficient radiation shielding features and transparency.

Bioprinting with adipose stem cells and hydrogel modified with bioactive glass

Bioprinting research is focused on utilizing growth factors and multiple cell types to create clinically relevant three-dimensional (3D) tissue models using hydrogels. Rheological and biological challenges are two main factors that limit the creation of extrudable bioactive hydrogels. In this study, we investigate incorporation of fast dissolving and bioactive borate glass in different weight to volume percentages (0.075 to 0.6%) to alginate-gelatin (1:1) hydrogel to improve rheological properties and enable bioprinting with bioactive glass. The addition of glass improved the stiffness of the hydrogel. Human adipose-derived mesenchymal stem cells (ASCs) were uniformly mixed in this bioink at 1 × 106 cells/mL concentration, and spheroid specimens were cultured in both static and dynamic culture conditions. Grid-shaped scaffolds measuring ~18 × 18 × 1 mm3 were fabricated with the viable glass concentrations, and ASC viability was evaluated using Live/Dead assay. Despite immediate toxicity, an increased viability after 7 days with 0.15 w/v % or less borate glass content demonstrated the potential in utilizing highly resorbable calcium-releasing biomaterials such as bioactive glasses to modify hydrogels suitable for bioprinting cellularized 3D structures.

Mössbauer, optical and structural properties of [formula omitted] ion in borate glass

Lanthanum-bearing iron lithium borate glass is a quaternary system for oxide glasses and was prepared via the melt-quenching method. The present article correlates the structure, optical, ligand field and Mössbauer data on iron lithium borate glass containing La3+. The density was measured, while the molar volume was calculated. Other physical parameters are well-described. With increasing the La2O3 content within the glass network, infrared spectra analysis reveals structural modifications such as the increase in BO4 units and the decline in both BO3 units and NBO bonds content. Furthermore, optical absorption spectra were measured. The absorption spectra disclose a plethora of electronic transitions that are related to Fe3+ in tetrahedral and octahedral sites, however, Fe2+ phase is not observed in optical spectra, but it has a clear signature in Mössbauer spectra. Besides, the glass absorption edges undergo a clear blue shift, reflecting an increased band gap energy (1.96–2.28 eV). The decline in NBO bonds justifies this trend. Bewitchingly, the values of crystal field splitting are increased, while the values of Racah parameters are decreased. This trend is justified by the decline in NBO bonds and increases electron localization around Fe cations. Mössbauer spectra confirm the existence of Fe3+ in tetrahedral and octahedral sites, while Fe2+ exists in only a tetrahedral state. With increasing La2O3 content, the isomer shift of Fe3+ in tetrahedral sites changes to be 0.312–0.329 mm/s, while the isomer shift of octahedral Fe3+ is 0.424–0.456 mm/s. These findings coincide with optical data. While the isomer shift of tetrahedral Fe2+ is 0.902–0.911 mm/s. Our results of structural, optical and ligand field associated with Mössbauer spectra open more vistas toward the utility of these samples in the optics realm.

Dielectric and mechanical properties of porous Si3N4–Kovar composites prepared by low‐temperature oxidation sintering

AbstractThe aim of this study is to investigate the impact of the Kovar glass content on the mechanical and electrical properties of Si3N4–Kovar composites sintering at air atmosphere. To achieve this, Si3N4–Kovar composites were prepared using molding technology with the Kovar glass powder ranging from 20 to 70 wt%. The phase composition, morphology, bulk density, apparent porosity, flexural strength at room temperature, dielectric constant, and dielectric loss of the composites were all examined in relation to changing the Kovar glass content. During the sintering process, the α‐quartz on the surface of Si3N4 particles acted as the crystal nucleus, inducing the crystallization of the glass at the wetting position that the Kovar glass and the surface of the Si3N4 particles. A small amount of the β‐quartz phase was crystallized at 750–850°C, followed by a large amount of the β‐quartz phase crystallizing above 900°C. Additionally, some β‐quartz phase transformed into the metastable β‐cristobalite phase that could exist below 1470°C. During the cooling process, the β‐cristobalite phase transformed into a low‐temperature α‐cristobalite phase, while the β‐quartz phase transformed into a low‐temperature α‐quartz phase. The results indicate that the Si3N4–Kovar glass composite with 60 wt% the Kovar glass content sintered at 900°C exhibits higher density (1.88 g/cm3), lower porosity (25.4%), higher flexural strength (55.34 MPa), lower dielectric constant (3.46), and lower dielectric loss (4.26 × 10−3).