The dissolution behavior in alkaline solutions of a borosilicate glass with and without P2O5

There are a variety of applications for glasses in alkaline environments, including glass fibers and glass‐coated steel to reinforce concrete structures. To understand how a simple glass reacts in such environments, the dissolution behavior of a 25Na₂O–25B₂O₃–50SiO₂ (mol%) glass, doped with and without 3 mol% P₂O₅, in pH 12 KOH and pH 12 KOH saturated with Ca²⁺ ions was studied. Ca²⁺ ions in the solution significantly reduce the glass dissolution rate by forming a passivating calcium silicate hydrate (C–S–H) gel layer on the glass surface. When these corroded glasses were then exposed to Ca‐free KOH, the C–S–H layer redissolves into the undersaturated solution and the glass dissolution rate increases. For phosphate‐doped borosilicate glass, PO₄^3? units released from the dissolving glass react with Ca²⁺ ions in saturated solutions to form crystalline hydroxylapatite on the glass surface, but this layer does not protect the glass from corrosion as well as the C–S–H does. The nature of the C–S–H layer was characterized by Raman spectroscopy, which reveals a gel layer constituted mainly of silicate anions.     

Fast Ce3+-activated borosilicate glass scintillators prepared in air atmosphere

We report a simple synthesis method of a transparent and colorless Ce³⁺-activated borosilicate glass scintillator by conventional melt-quenching method in air atmosphere. The optical transmittance and X-ray absorption near edge spectroscopy (XANES) spectra imply that ceric ions (Ce⁴⁺) can be effectively reduced to cerous one (Ce³⁺) in borosilicate glass scintillator by substituting 40–60 mol% SiC for SiO₂. Compared to the x=0 glass scintillator, both the photo- and radioluminescence intensity of the optimized borosilicate glass scintillator (x=15 C) are enhanced by a factor of 6.5 and 7.7, respectively. The integral radioluminescence intensity of the x=15 C borosilicate glass scintillator resulted from the combined reduction effect of both SiC and graphite powder is about that of 14% bismuth germinate (BGO) crystal.     

Role of Al3+ on tuning optical properties of Ce3+‐activated borosilicate scintillating glasses prepared in air

A colorless Ce³⁺‐activated borosilicate scintillating glass enriched with Gd₂O₃ is successfully synthesized in air atmosphere for the first time. The full replacement of 10 mol% BaO by Al₂O₃, and the partial substitution of 3 mol% SiO₂ by Si₃N₄ in the designed glass composition are crucial for this success. The role of Al³⁺ on tuning the optical properties of Ce³⁺‐activated borosilicate scintillating glass synthesized in air are analyzed by optical transmittance, X‐ray absorption near edge spectroscopy (XANES) spectra, photoluminescence (PL) and radioluminescence (RL) spectra. The results suggest that the stable Ce⁴⁺ ions can be effectively reduced to stable Ce³⁺ ions by the full replacement of BaO by Al₂O₃, and both the PL andRL intensity of the designed borosilicate scintillating glass are enhanced by a factor of 6.7 and 5.2, respectively. The integral RL intensity of the synthesized Ce³⁺‐activated borosilicate scintillating glass is ~17.2%BGO, with a light output of about 1180 ph/MeV. The strategy of substituting BaO by Al₂O₃ will trigger more scientific and technological considerations in designing novel fast scintillating glasses.     

Chemical durability of borosilicate pharmaceutical glasses: Mixed alkaline earth effect with varying [MgO]/[CaO] ratio

Glass for pharmaceutical packaging requires high chemical durability for the safe storage and distribution of newly developed medicines. In borosilicate pharmaceutical glasses which typically contain a mixture of different modifier ions (alkali or alkaline earth), the dependence of the chemical durability on alkaline earth oxide concentrations is not well understood. Here, we have designed a series of borosilicate glasses with systematic substitutions of CaO with MgO while keeping their total concentrations at 13 mol% and a fixed Na₂O concentration of 12.7 mol%. We used these glasses to investigate the influence of R = [MgO]/([MgO] + [CaO]) on the resistance to aqueous corrosion at 80°C for 40 days. It was found that this type of borosilicate glass undergoes both leaching of modifier ions through an ion exchange process and etching of the glass network, leading to dissolution of the glass surface. Based on the concentration analysis of the Si and B species dissolved into the solution phase, the dissolved layer thickness was found to increase from ~100 to ~170 nm as R increases from 0 to 1. The depth profiling analysis of the glasses retrieved from the solution showed that the concentration of modifier ions (Na⁺, Ca²⁺, and Mg²⁺) at the interface between the solution and the corroded glass surface decreased to around 40%–60% of the corresponding bulk concentrations, regardless of R and the leaching of modifier cations resulted in a silica-rich layer in the surface. The leaching of Ca²⁺ and Mg²⁺ ions occurred within ~50 and <25 nm, respectively, from the glass surface and this thickness was not a strong function of R. The leaching of Na⁺ ions varied monotonically; the thickness of the Na⁺ depletion layer increased from ~100 nm at R = 0 to ~200 nm at R = 1. Vibrational spectroscopy analysis suggested that the partial depletion of the ions may have caused some degree of the network re-arrangement or re-polymerization in the corroded layer. Overall, these results suggested that for the borosilicate glass, replacing [CaO] with [MgO] deteriorates the chemical durability in aqueous solution.     

Corrosion and Infrared Study of Some γ-Irradiated Lead-Phosphate Glasses Doped with MoO3

In this study we compared the effect of three different concentrations of MoO₃ on the corrosion of sodium phosphate glass containing lead and aluminum oxides to develop its durability. The corrosion was studied in deionized water and acidic solution of 0.1 N HCl. The dissolution mechanism is interpreted depending on the glass weight loss versus time and change in the glass surface. MoO₃ had a stabilizing effect on the glass, causing a decrease in the glass dissolution rate. Acidic medium was found to strongly enhance the glass dissolution. The pH decrease in water with increase in acidic solution gives evidence of the release of some phosphorous ions to form phosphoric acid. The consequent enhancement of the glass durability was influenced by the presence of MoO₃ and showed a remarkable advance by doping with 3 wt% of MoO₃. FT-infrared absorption spectra of the studied glasses show IR vibrational bands due to phosphate groups mainly of the metaphosphate and pyrophosphate units together with the sharing and interference of IR vibrations due to Pb–O bonds. Gamma irradiation produces a minor effect on the IR spectra, and enhances the base glass durability at the beginning of the corrosion process, which can be related to the shielding behavior of the high lead glass. However, glass containing 3% MoO₃ has the best durability and is the least affected by irradiation. The glass durability corresponding to its structure is verified by IR spectroscopy.

     

Oxygen diffusion mechanisms during high‐temperature oxidation of ZrB2‐SiC

Oxygen diffusion mechanisms during oxidation of ZrB₂‐30 vol% SiC were explored at temperatures of 1500°C and 1650°C using an ¹⁸O tracer technique. Double oxidation experiments in ¹⁶O₂ and ¹⁸O₂ were performed using a modified resistive heating system. A combination of scanning electron microscopy, energy‐dispersive spectroscopy, and time‐of‐flight secondary ion mass spectrometry was used to characterize the borosilicate and ZrO₂ oxidation products. Oxygen exchange with the borosilicate network was observed to occur quickly at the oxygen‐borosilicate surface at both 1500°C and 1650°C, while evidence of oxygen permeation was only observed at 1650°C for short time (<1 min) exposures. At longer times, >5‐9 min, complete oxygen exchange throughout both the borosilicate glass and ZrO₂ was observed at both temperatures preventing identification of the oxygen transport mechanisms, but demonstrating that oxygen transport is rapid in both oxide phases.     

Structural features of iron‐phosphate glass

This paper reports a study and discusses the role of Fe ions in the inhibition of corrosion of iron phosphate glasses. The structure of the 40Fe₂O₃–60P₂O₅ (mol%) glass, having a confirmed dissolution rate in aqueous solution at 90°C superior to borosilicate glasses, was investigated. Samples were crystallized at characteristic temperatures defined by differential thermal analysis and analyzed by X‐ray diffraction. Crystalline phases of Fe₂Fe[P₂O₇]₂ and Fe₄[P₂O₇]₃ were detected. The hyperfine parameters from the Mössbauer spectrum indicate that both Fe²⁺ and Fe³⁺ ions are in octahedral coordination, and 18% of the Fe³⁺ ions in the starting batch are reduced to Fe²⁺ ions after melting. The broad and symmetric spectra centered in g≈2.0 from the EPR measurements indicate the presence of two or more Fe interacting ions occupying sites of relatively high local symmetry.     

Lightweight glass–ceramic tiles from the sintering of mining tailings

Modern thermally-insulating building façades comprise lightweight structural panels, in turn mostly composed of porcelain stoneware with engineered porosity. Sintered glass–ceramics may represent a valid alternative, mainly considering layered articles, with a dense surface layer on a highly porous body that could be manufactured by double pressing. In this paper we present a low cost route to lightweight tiles, developed starting from mining tailings, such as waste from the mining of boron-rich minerals and basalt rock, and recycled glasses, such as common soda-lime glass and pharmaceutical borosilicate glass. A highly porous body was obtained by direct sintering of mixtures of mining tailings and soda-lime glass; despite the homogeneity of porosity and the formation of new crystal phases (at only 1000 °C), favorable to good mechanical properties, the water absorption remained far above the limits (>2 wt%). The water absorption was minimized by introduction of a dense glaze, associated to the firing of mixtures coated by a thin layer of recycled borosilicate glass powders; both color and shrinkage were optimized by the mixing of borosilicate glass with powders of zircon mineral and vitrified boron waste/basalt/soda-lime mixture.     

Impact of bismuth oxide on the structure,optical features and ligand field parameters of borosilicate glasses doped with nickel oxide

Understanding the impact of bismuth cations on the optical properties of borosilicate glass is significant for manipulating borate glass applications. In this paper, the influence of bismuth cations on both structural and optical properties of borosilicate glass doped with NiO was investigated. Different glass samples, containing different amounts of Bi₂O₃ and a constant amount of NiO, were prepared and studied. Infrared (IR) analysis was carried out to study the internal structure within the investigated glass samples. Optical absorption studies were performed to investigate the impact of Bi₂O₃ content on optical properties of the BiBaNiB-glasses. Astonishingly, with Bi₂O₃ addition, an absorption band at 380 nm has appeared. Moreover, this band is overlapped with the Urbach edge; which regularly produced an artificial edge-like feature at ~450 nm. A detailed deconvolution protocol has been implemented for an appropriate understanding of these spectra and unraveling the hidden Urbach edge. Optical band gap energy, linear and nonlinear refractive index for each BiBaNiB sample were calculated. Furthermore, the metallization criterion was calculated to examine the metallic or insulating nature of the BiBaNiB-glasses. The values of the nonlinear third-order susceptibility and nonlinear refractive index were increased with Bi₂O₃ doping. The BiBaNiB-glasses exhibited outstanding stability and optical band gap than the pristine glass sample, which makes it possible for practical applications.     

Determination of Retained B2O3 Content in ZrB2‐30 vol% SiC Oxide Scales

The composition of the borosilicate glass layer formed during oxidation of ZrB₂‐30 vol% SiC was determined to elucidate the extent of B₂O₃ retention in the oxide during high‐temperature oxidation. Oxidation was conducted in stagnant air at 1300°C, 1400°C, and 1500°C for times between 100 and 221 min. Specimens were characterized using mass change and scanning electron microscopy. After oxidation, the borosilicate glass layer was dissolved from the specimens sequentially with deionized H₂O and HF acid, to analyze the glass composition using inductively coupled plasma optical emission spectrometry. It was found that the average B₂O₃ content in the glass scale ranged from 23 to 47 mol%. Retained B₂O₃ content in the bulk of the glass decreased with increasing temperature, confirming increased volatility with temperature. Boron depth profiles were also obtained in the near surface region using X‐ray photoelectron spectroscopy and energy dispersive spectroscopy. The measured B concentrations were used to estimate the B₂O₃ concentration profile and B diffusion coefficients in the borosilicate glass. Implications for the ZrB₂‐SiC oxidation process are discussed.     

Self-healing behavior in MoSi2/borosilicate glass composite

The self-healing behavior of MoSi₂/borosilicate glass composite was investigated by comparing the flexure strength of pre-scratched specimens before and after healing treatment. The post-healing strength partially recovered when healing temperature was higher than 800 °C, and the healing of the scratch was observed after healing treatment at 900 °C and 1400 °C. Two kinds of possible mechanisms were proposed on the basis of morphology and elemental analyses of healing areas. The specimen treated at 900 °C showed a porous healing area and the strength recovered 28.6% resulted from the oxidation of MoSi₂ into MoO₃ and SiO₂. By contrast, the specimen treated at 1400 °C had a dense healing area and the strength recovered 86.9% due to the viscous flow of borosilicate glass.     

Synthesis and Spectral Properties of Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>-Doped Sodium Silicophosphate Glass

Combined UV-visible and FTIR spectral studies of undoped and Nd₂O₃ –doped sodium silicophosphate glasses were carried out to characterize the optical and structural properties of such glasses. The base undoped silicophosphate glass exhibits strong UV absorption which is due to the presence of unavoidable trace iron impurities (mainly Fe³⁺ ions) present contaminated within the raw materials used for the preparation of such glasses. Nd₂O₃ –doped glasses show characteristic absorption bands extending in the entire visible region which are attributed to the contribution of Nd³⁺ ions with distinct peaks which are almost constant with the increase of dopant. This comes from the combined compact glass structure containing two glass forming units and the shielding of the rare-earth ions. Infrared absorption spectra of the studied glasses reveal characteristic IR bands due to the combination of both silicate and phosphate groups. The introduction of Nd₂O₃ within the dopant level (2 %) produces no variations in the IR vibrational bands due to the presence of the two structural silicate and phosphate groups giving compactness of the network structure. The deconvoluted spectra reveal the presence of phosphate groups in a slightly high ratio due to the high content of P₂O₅ in the composition.     

Properties and vibrational spectra of magnesium phosphate glasses for nuclear waste immobilization

The leaching behavior and structure of magnesium phosphate glasses containing 45–55 mol% MgO incorporated with simulated high level nuclear wastes (HLW) were studied. The leach rate of the waste glasses decrease with increasing of the simulated HLW content. The gross leach rate of the glass waste form containing 50 mol% MgO and 45 mass% simulated HLW is of the order of 10⁻⁶ g/cm² day at 90 °C, which is small enough as compared with the corresponding release from a currently used borosilicate glass waste form. The isolated ions such as dimeric (P₂O₇)⁴⁻ and monomeric (PO₄)³⁻ ions increase upon as increasing the incorporating amount of the simulated HLW. The changes in properties can be attributed to the structure changes owing to the incorporation of the simulated HLW.     

Synthesis and properties of UV-curable hyperbranched polyurethane acrylate oligomers containing carboxyl groups

Using step by step polymerization process, the first- and second-generation hyperbranched polyesters were synthesized with N,N-diethylol-3-amine methylpropionate as branched monomer and pentaerythrite as a core molecule. The second-generation hyperbranched polyurethane acrylate oligomers containing carboxyl groups were obtained by further reacting with semiadduct urethane monoacrylate and maleic anhydride. The structures of the oligomers were investigated with elemental analysis, FT–IR, and NMR. UV–Vis spectra results showed that the oligomers had sharp absorption bands at about 207 nm. The glass transition temperatures were investigated by differential scanning calorimetry and showed in the range of −44.96 to −19.83 °C. Gel permeation chromatograph was used to observe the molecular weights and polydispersities of the oligomers. UV-curing properties were characterized by FT–IR with different curing time. In addition, the solubilities and viscosity of the oligomers were also examined.     

Effect of MgF2 addition on sinterability and mechanical properties of fluorapatite ceramic composites fabricated by wollastonite and phosphate glass

In this paper, we successfully report the design and synthesis of fluorapatite ceramic composites using phosphate glass and wollastonite as raw materials via a simple sintering method. The effects of MgF₂ additives in phase composition, microstructure, densification, and mechanical properties are investigated at various temperatures from 600 °C to 900 °C, and characterized by SEM/EDS, XRD, FTIR, linear shrinkage and water absorption, flexural strength analysis. It shows that the densification and mechanical behavior of composites increase with both the sintering temperature and MgF₂ content. Especially, the sample SCPF-7 exhibits the highest densification and optimal mechanical properties at 900 °C. At these conditions, the water absorption of fluorapatite ceramic composite is less than 0.20%, and the flexural strength is over 70 MPa. For the microstructure analysis, the formation of fluorapatite with a rod-like microstructure is enhanced with the increase of MgF₂ content. The amelioration of these properties is due to the formation of a new phase which helps to the formation of compact microstructure. The findings in this work provide a feasible strategy for the preparation of fluorapatite ceramic composites from available phosphate glass and wollastonite at a lower temperature.     

Ce3+‐ and Dy3+‐Doped Oxyfluoride Borosilicate Glasses with Near White Luminescence

A series of Ce³⁺/Dy³⁺‐doped oxyfluoride borosilicate glasses prepared by melt‐quenching method are investigated for light‐emitting diodes applications. These glasses are studied via X‐ray diffraction (XRD), optical absorption, photoluminescence (PL), color coordinate, and Fourier transform infrared (FT‐IR) spectra. We find that the absorption and emission bands of Ce³⁺ ions move to the longer wavelengths with increasing Ce³⁺ concentrations and decreasing B₂O₃ and Al₂O₃ contents in the glass compositions. We also discover the emission behavior of Ce³⁺ ions is dependent on the excitation wavelengths. The glass structure variations with changing glass compositions are examined using the FT‐IR spectra. The influence of glass network structure on the luminescence of Ce³⁺/Dy³⁺ codoped glasses is studied. Furthermore, the near‐ideal white light emission (color coordinate x = 0.32, y = 0.32) from the Ce³⁺/Dy³⁺ codoped glasses excited at 350 nm UV light is realized.     

Effects of glass additions on the microstructure and dielectric properties of barium strontium titanate (BST) ceramics

Commercial glass frits (lead borosilicate glasses) were employed as the sintering aids to reduce the sintering temperatures of BST ceramics. The effects of the glass content and the sintering temperature on the microstructures, dielectric properties and tunabilities of BST ceramics have been investigated. Densification of BST ceramics of 5 wt% glass content becomes significant from sintering temperature of 1000 °C. The glass content shows a strong influence on the Curie temperature T_c, permittivity and the diffuse transition. X-ray results show all BST ceramics exhibit a perovskite structure and also the formation of a secondary phase, Ba₂TiSi₂O₈. The shift of BST diffraction peaks towards higher angle with increasing the glass content indicates the substitution of Pb²⁺ in Ba²⁺ site, which mainly accounts for the diffuse transition observed in these BST ceramics. BST ceramics with 10 wt% glass additives possess the highest tunability at all four sintering temperatures. A tunability of 12.2% at a bias field of 1 kV/mm was achieved for BST ceramics with 10 wt% glass content sintered at 900 °C.     

Oxidation treatments for SiC particles and its compatibility with glass

Different thermal treatments were performed to produce a protective coating on the surface of SiC particles in order to allow their incorporation in a glass matrix. These oxidation treatments were carried out in air at different temperatures ranging from 800 °C to 1500 °C and different times at 1200 °C (10 min–48 h). The oxidation kinetics followed the Deal–Grove model and the thickness of the protective coating increased with temperature and SiC particle size. Protected SiC particles with different particle sizes were incorporated in a borosilicate glass. With small particles sizes foam glasses were obtained, whereas particles with higher grain size, i.e., higher coating thickness, were stable in the glass matrix and a smooth glass was obtained.     

Thermal stability of [B]ZSM-5 molecular sieve

The thermal stability of [BJZSM-5 (boronsilicalite) has been examined by IR, XRD,¹¹B MAS NMR and XPS techniques. [B]ZSM-5 and amorphous borosilicate were converted to α-cristobalite at high temperatures (=750C). However, Na-free amorphous borosilicate was not converted to a-cristobalite at 750C. Therefore, the presence of Na ions in [BJZSM-5 would determine whether this transition occurred or not. When the phase transition to α-cristobalite occurred, most of B atoms tetrahedrally coordinated were released from the ZSM-5 structure and migrated to the exterior surface as a boron compound having trigonal BO₃ units and oxidation states of 3.     

Initial Stages of ZrB2–30 vol% SiC Oxidation at 1500°C

The initial oxidation behavior of ZrB₂–30 vol% SiC was analyzed with the goal of understanding any relationship to the variable oxidation performance observed at longer times. A box furnace was used to oxidize samples for times as short as 10 s and up to 100 min at 1500°C in air. The samples were characterized using mass change, scanning electron microscopy, energy dispersive spectroscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy to explore the oxidation behavior. The presence of borosilicate glass and ZrO₂ was observed on the surface at times as early as 10 s. Bubble formation in the borosilicate glass was observed after 30 s of oxidation and is attributed to uneven distribution of the glass. The impact of surface roughness on oxidation was also explored and found to be negligible for times greater than 30 s.