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Microstructural evolution of borosilicate glass–sulfate (BaSO4 or Na2SO4) mixture was observed in situ using a high‐temperature confocal scanning laser microscope. The phase compositions and sulfate retention of the mixture at different temperatures were also examined. The results indicate that for the glass–BaSO4 sample (abbreviated as BS), the borosilicate glass begins to melt at about 900°C, and the triangular BaSO4 crystals grow obviously between 900°C and 1100°C. At temperatures above 1100°C, the BaSO4 crystals gradually melt and decompose. For the glass–Na2SO4 sample (abbreviated as NS), strip‐shaped BaSO4 crystals begin to form at about 820°C after the borosilicate glass melting, and then gradually melt with further increasing temperature. When the temperature increases to 1000°C, the upper layer of the NS sample possesses Na2SO4, LiNaSO4, and BaSO4 phases, while the lower layer possesses an amorphous phase. Moreover, the SO3 retention in the BS sample remains almost unchanged with temperature increases from 900°C to 1100°C, and then decreases with further increasing temperature. The SO3 retention retained in the NS sample decreases rapidly at temperatures above 900°C. These findings can provide a guidance for vitrifying sulfur‐rich high‐level liquid waste. [ABSTRACT FROM AUTHOR]

As a fission product in high‐level radioactive nuclear waste, Mo has low solubility in borosilicate glass. Fe2O3 is not only a prevalent transition metal element but also a major corrosion product in high‐level radioactive nuclear waste. Against this backdrop, the effect of Fe2O3 content on the structure and chemical durability of typical molybdenum‐containing sodium borosilicate glasses for nuclear waste immobilization are studied. The results show that the samples containing more than 3.85 mol% Fe2O3, a completely homogenous amorphous glass sample is obtained. Moreover, the mechanism of the effect of Fe2O3 on the solubility of Mo is discussed in detail. In this work, a portion of Fe3+ is reduced to Fe2+ and enters into the glasses as a charge compensation ion as Fe2+O6. Concurrently, Fe3+ ions contribute to the formation of the glass networks as Fe3+O4. Iron incorporation can improve the chemical durability of the sample. [ABSTRACT FROM AUTHOR]

The stress distribution in sealing glass is one of the most concerning issues for glass‐to‐metal (GtM) seals. In this study, photoluminescence spectroscopy was applied by exploiting the piezospectroscopic effect of Cr‐doped α‐Al2O3 (ruby), and the overall stress distribution along the radius of a concentric seal was detected and analyzed. It was discovered that the compressive stress first increased and then decreased at the edge of the seal. The maximum compressive stress of 91 MPa was detected at ∼20 µm from the interface and was ascribed to the interaction between the glass and surface oxide film of the metal. Stress distributions in pore regions were also investigated and obvious stress fluctuations were observed clustering around pores. A circle of compressive stress was observed around the pores in a single glass without a metal housing; for the pores in the center of the concentric seal, the stress distribution was dominated by the inner contraction of the metal housing; and for the pores near the edge of the seal, the concentration of tensile stress located perpendicular to that of the compressive stress. This study demonstrates a high‐resolved and nondestructive method to detect the stress field and explores the potential for future tailorability of stress distribution in GtM seals. [ABSTRACT FROM AUTHOR]

Knowledge of the structural organization of nuclear waste glasses at the atomic scale is the basis for further studies of macroscopic properties (e.g., fracture toughness, chemical durability, and leaching rate). Recent studies have focused on the iodine dissolution mechanism in oxide‐based glasses synthesized under high‐pressure conditions, but there is still a lack of key information on the extent of the modifications caused by iodine entering the glass network. We therefore decided to conduct an in‐depth study by nuclear magnetic resonance on two series of aluminoborosilicate glasses synthetized under high pressure conditions and doped with either I2 or I2O5. The obtained 11B, 23Na, and 27Al nuclear magnetic resonance (NMR) spectra were fitted and correlated with the iodine content in order to find possible relationships with the local environment change for the probed cations. These data showed that iodine has no effect on the coordination of aluminum and very little effects on that of boron. In contrast, we found an expected relationship of the I content with the 23Na NMR parameters. In comparison with previous studies on the non‐bridging oxygen (NBO) distribution in aluminoborosilicate, we suggest that Na+ is mainly scavenged from silica tetrahedra with one or two NBO (Q3${Q}^3$ or Q2${Q}^2$) as no boron planar triangles with one NBO are expected for such compositions. From those information, we establish a model for iodine dissolution in nuclear waste glass that is consistent with previous studies. [ABSTRACT FROM AUTHOR]

One major factor impeding the design of nuclear waste glasses with enhanced waste loadings is our insufficient understanding of their composition–structure–durability relationships, specifically in the environments the waste form is expected to encounter in a geological repository. In particular, the high field‐strength cations (HFSCs) are an integral component of most waste streams. However, their impact on the long‐term performance of the glassy waste form remains mostly undeciphered. In this context, the present study aims to understand the impact of some HFSCs (i.e., Nb5+, Zr4+, Ti4+, and La3+) on the dissolution behavior of alkali/alkaline‐earth aluminoborosilicate‐based model nuclear waste glasses in hyper‐alkaline media. At pH = 13, the studied glasses dissolve through the dissolution–reprecipitation mechanism, with Ca precipitation being the most vital step to passivation. In Ca‐free glasses, although the HFSCs slow down the forward rate, they do not seem to impact the residual rate behavior of glasses. The presence of Ca2+, however, initiates the rapid precipitation of network polymerizing HFSCs (i.e., Nb5+, Zr4+, and Ti4+) into a Ca2+/HFSCs‐based passivating layer, thus suggesting a synergy between Ca2+ and HFSCs that contributes to the enhanced long‐term durability of the glasses. Such synergy is not strongly evident for La3+, but instead, a potential La/Si affinity is observed upon the formation of the alteration layer. [ABSTRACT FROM AUTHOR]

At present, doping of different alkaline-earth metal ions is mainly used to tune the emission peak of europium (Eu) ions in glasses. However, the optimization of Eu-doped glasses is hindered due to limited discussion on the relationship between local glass network structure, concentration of Eu ion dopants, and visible light emission by Eu ions. In this study,we prepared two series of borosilicate glasses doped with Eu ions, by varying the ratio of SiO2 to B2O3 and adjusting the concentration of Eu ion dopants to obtain cyan emission. The optical properties, structure, and differential scanning calorimetry (DSC) of the investigated glasses were systematically studied. With gradual increase in the content of SiO2, red shifting from 471 nm to 492 nm was observed under excitation at 410 nm, with the introduction of Eu2O3 also causing a redshift from 471 nm to 488 nm. The spectral results also revealed that under excitation at 410 nm all the glass samples exhibited cyan emission, with the optimal cyan peak at 492 nm (Si-45) and the strongest cyan emission at Eu-0.4 (480 nm). By adjusting the concentration ratios of Si to B in europium-doped borosilicate glass, it was observed that by altering the [SiO4] tetrahedra, [BO4] tetrahedra, and [BO3] triangles within the glass ultimately cyan emission can be achieved. By varying the doping concentration of Eu ion to change the degree of local Eu ion clustering in the glass system, cyan emission can be achieved by tuning the emission peak. [ABSTRACT FROM AUTHOR]

Evaluating the corrosion behavior of borosilicate glass after irradiation holds vital importance for the safe geological disposal of high‐level radioactive waste. This study examined the leaching properties of three kinds of sodium‐borosilicate (RNa2O‒B2O3‒KSiO2, denoted as "NBS") glasses with the same R but varying K under 5 MeV Xe‐ion radiation to decipher the correlation between the corrosion mechanism and glass composition. After Xe‐ion radiation, an increase in [BO3] units was observed, indicative of the glass network depolymerization. Irradiated glasses exhibited a more significant change in [BO3] units over the leaching time compared to their pristine counterparts. There is a strong correlation between the initial dissolution rates of pristine glasses, the K value, and the proportion of Na. Additionally, the initial Si dissolution rate of the NBS glasses has been accelerated by heavy ion irradiation. For the same R value over the glass series, the initial Si dissolution rates in ternary borosilicate glasses change at similar rates after irradiation. This study concluded that the variation trend in the initial dissolution rate of Si and Na differs under ion radiation. [ABSTRACT FROM AUTHOR]

Here, we report on core–clad bioactive borosilicate fibers, that we have prepared both with round and rectangular cross‐section profile. The exposed approach, which relies on the stacking and drawing of glass slabs, demonstrates our ability to develop bioactive‐based glass fibers with tailored cross‐section profiles. Tens‐of‐meters‐long fibers were successfully drawn, although suffering from elevated losses in the case of the rectangular ones. The response of the fibers in simulated body fluid was studied for both geometries. We found that a round cladding can act as protective layer, tempering effects of the corrosion. We also noticed that rectangular fibers are more prone to degradation, the enhanced corrosion beginning from their sharp corners as they accumulated residual tensile stress during drawing. To the best of our knowledge, this is the first report on the effect of residual tensile stresses from surface tension deformations applied to the corrosion of rectangular fibers. As geometry plays a critical role on the biodegradation behavior of the fiberglass, we believe the enclosed results could lead to the design of fiber devices with tailored cross‐section profile in order to tune their rate of degradation on solely based geometrical effects. [ABSTRACT FROM AUTHOR]

We examine the impact of the glass network‐modifier cation field strength (CFS) on ion irradiation‐induced mechanical property changes in borosilicate (BS) glasses for the ternary M2O–B2O3–SiO2 systems with M = {Na, K, Rb} and the quaternary [0.5M(2)O–0.5Na2O]–B2O3–SiO2 systems with M = {Li, Na, K, Rb Mg, Ca, Sr, Ba}. 11B nuclear magnetic resonance (NMR) experiments on the as‐prepared BS glasses yielded the fractional population of four‐coordinated B species (B[4]) out of all {B[3], B[4]} groups in the glass network, along with the fraction of B[4]–O–Si linkages out of all B[4]–O–Si/B bonds. Both parameters correlated linearly with the (average) CFS of the M+ and/or {M(2)+, Na+} cations. Both the nanoindentation‐derived hardness and Young's modulus values of the glasses reduced upon their irradiation by Si2+ ions, with the property deterioration decreasing linearly with increasing Mz+ CFS, that is, for higher Mz+⋅⋅⋅O interaction strength. The irradiation damage of the glass network also increased linearly with the fraction of B[4]–O–Si linkages, which are the second weakest in the structure after the Mz+⋅⋅⋅O bonds. Our results underscore the advantages of employing BS glasses with high‐CFS cations for enhancing the radiation resistance for nuclear waste storage. [ABSTRACT FROM AUTHOR]

Classical molecular dynamics simulations have been used to investigate the structural role of Mg and its effect when it is incorporated in sodium aluminoborosilicate glasses. The simulations have been performed using three interatomic potentials; one is based on the rigid ionic model parameterized by Wang et al. (2018) and two slightly different parameterization of the core–shell model provided by Stevensson et al. (2018) and Pedone et al. (2020) The accuracies of these models have been assessed by detailed structural analysis and comparing the simulated nuclear magnetic resonance (NMR) spectra for spin active nuclei (29Si, 27Al, 11B, 17O, 25Mg, and 23Na) with the experimental counterparts collected in a previous work. Our simulations reveal that the core–shell parameterizations provide better structural models. In fact, they better reproduce the NMR spectra of all the investigated nuclei and give better agreement with known experimental data. Magnesium is found to be five coordinated on average with distances with oxygen in between a network modifier (like Na) and an intermediate network formed (like Al). It prefers to lay closer to three‐coordinated B atoms, forming B–NBO bonds, with respect to Si and especially Al. This can explain the formation of AlO5 and AlO6 units in the investigated Na‐free glass, together with a Si clusterization. [ABSTRACT FROM AUTHOR]

Borosilicate glass has been extensively studied due to its unique properties of solidifying high‐level radioactive waste (HLW). However, the responses of borosilicate glass under γ irradiation are not fully understood. In this work, NBS9 and NBS10 glass were irradiated by γ‐rays at absorbed doses of 8 kGy and 800 kGy, respectively. Scanning electronic microscopy, energy dispersive X‐ray, and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) were used to observe the surface morphology and elemental distributions. The results show that the borosilicate glass remains stable until the absorbed dose was up to 800 kGy. At 800 kGy, the samples precipitate particles composed of Na and O on the surface. Na and B near the surface are significantly reduced under γ‐rays irradiation. The results indicate that the effects of γ irradiation on glass vitrification are obvious with certain accumulated doses. The changes of glass structures and elemental distributions by γ‐ray irradiation are also dependent on glass compositions. [ABSTRACT FROM AUTHOR]

Optimizing the concentration of molybdenum incorporated in a borosilicate glass matrix is essential in the vitrification of high‐level radioactive waste. However, the incorporation limit of MoO3 in fundamental borosilicate systems has been rarely correlated with the local structure of the molybdenum cations. This study investigates the variations in the incorporation limit of MoO3 in ternary sodium borosilicate glass upon varying the B2O3/(SiO2 + B2O3) ratio (i.e., B). The incorporation limit of MoO3 was less than 3 mol% in the low‐B region (B < 0.7), where molybdenum cations mainly existed as [MoO4]2−. However, when B was higher than 0.85, the incorporation limit was higher than 6 mol%, and the Raman spectra indicated the presence of octahedrally coordinated molybdenum cations, essential to stabilize the Mo–O–Mo linkage. The variation in the local structure of molybdenum cations can be explained by the available amount of non‐framework cations compensating for the negative charge near [MoO4]2−. These results allow the development of glass compositions with a high incorporation limit of MoO3 simply by controlling the local structure near the molybdenum cations. [ABSTRACT FROM AUTHOR]

Iron oxide is commonly found in natural or industrial glass compositions and can exist as ferrous (Fe2+) or ferric (Fe3+) species, with their ratios depending on glass composition, temperature, pressure and the redox reactions during the glass forming process. The iron redox ratio plays an important role on silicate glass structures and consequently various properties. This work aims to study the effect of iron oxide, and particularly the iron redox ratio, on the structures of borosilicate and boroaluminosilicate glasses using molecular dynamics simulations with newly developed iron potential parameters that are compatible with the borosilicate potentials. The results provide detailed cation coordination states of both iron species and the effect of redox ratio on boron coordination and other structural features. Particularly, competition for charge compensating modifier cations (such as Na+) among the fourfold‐coordinated cations such as B3+, Al3+, and Fe3+ is investigated by calculating the cation–cation pair distribution functions and coordination preferential ratios. The results show that the trivalent ferric ions, with a shorter Fe–O bond distance and better defined first coordiation shell with mainly four‐fold coordination, act as a glass former whereas the divalent ferrous ions mainly play the role of glass modifier. The ferrous/ferric ratio (Fe2+/Fe3+) was found to affect the glass chemistry and hence glass properties by regulating the amount of four‐coordinated boron, the fraction of non‐briding oxygen and other features. The results are compared with available experimental data to gain insights of the complex structures and charge compensation schemes of the glass system. [ABSTRACT FROM AUTHOR]

A new self‐consistent empirical potential model based on the BMP potential [Bertani et al., Phys. Rev. Mat. 5 (2021) 045602] has been developed for the simulation of multicomponent borate and borosilicate glasses. We exploited the Bayesian optimization approach to create a set of parameters for the B–O interaction, which depends on the glass composition, and in particular on the R = ([A2O]+[AEO])/[B2O3] (A = alkaline and AE alkaline‐earth ions) and K = [SiO2]/[B2O3] ratios. The obtained force field (FF) has been applied to several borate and borosilicate glass series containing, as modifier oxide, Na2O, Li2O, CaO, and MgO and tested on experimental data, such as the fraction of BO4 (N4), density, non‐bridging oxygen speciation, neutron diffraction spectra, 11B, 29Si, and 17O magic angle spinning nuclear magnetic resonance. A comparison with other interatomic potentials available in literature has also been performed. The results show that the FF reproduces well almost all the abovementioned properties, showing excellent agreement with experimental data in a wide range of compositions. [ABSTRACT FROM AUTHOR]

Lanthanide borosilicate glasses containing Pu and the nonradioactive analog element Ce were subjects of an x‐ray absorption spectroscopy investigation to quantify the +3/+4 ratio of these redox‐sensitive elements. The data show that the dominant oxidation states are +4 for Pu and +3 for Ce. The data also indicate that the reductive potential of glasses can be quantified from a solution chemistry method adapted to glass chemistry, although allowances must be made for glass composition. These data can therefore be used to formulate glass compositions and processing schedules that lead to a controlled oxidation state of Pu in melts. Furthermore, the data show that Ce is a poor analog for Pu behavior in melts and that the suitability of surrogates can be assessed by the evaluation approach presented here. The method demonstrated in this paper can be used to estimate the oxidation states of a range of multi‐valent elements as functions of temperature and composition with data from only a single redox couple. [ABSTRACT FROM AUTHOR]

Aim: To assess in vitro the effect of two novel phase separated borosilicate glasses (PSBS) in the system SiO2‐B2O3‐K2O‐CaO‐Al2O3 on dental pulp cells; and to compare their bioactivity and mechanical properties to a conventional fluoroaluminosilicate glass ionomer cement namely FUJI IX. Methodology: The cytocompatibility assessment of the two novel borosilicate glasses, one without alumina (PSBS8) and one containing alumina (PSBS16), was performed on cultured primary human pulp cells. Alamar blue assay was used to assess cell metabolic activity and cell morphology was evaluated by confocal imaging. The bioactivity in Stimulated Body Fluid was also evaluated after 1 and 3 weeks of immersion using SEM‐EDX analysis. Vickers microhardness and flexural strength were assessed after incorporating the glass particles into a commercial glass ionomer cement (GIC) liquid containing both polyacrylic and polybasic carboxylic acid. Results: The data revealed that the two borosilicate glasses enhanced cell viability ratios at all‐time points in both direct and indirect contact assays. After 3 days of contact, PSBS8 without alumina showed higher viability rate (152%) compared to the PSBS16 containing alumina (145%) and the conventional glass ionomer particles (117%). EDX analysis confirmed an initial Ca/P ratio of 2.1 for 45S5K and 2.08 for PSBS8 without alumina after 3 weeks of immersion. The cement prepared using PSBS8 showed significantly higher Vickers hardness values (p =.001) than that prepared using PSBS16 (46.6 vs. 36.7 MPa). After 24 h of maturation, PSBS8 (without alumina) exhibited a flexural strength of 12.9 MPa compared to a value of 16.4 MPa for the commercial control. PSBS8 without alumina had a higher strength than PSBS16 with alumina, after 1 and 7 days of maturation (p =.001). Conclusions: The present in vitro results demonstrated that the borosilicate bioactive glass without alumina enhanced pulp cell viability, spreading and acellular bioactivity better than the conventional GIC and the experimental borosilicate glass containing alumina. [ABSTRACT FROM AUTHOR]

Borosilicate glasses are used ubiquitously for a wide range of applications, where their mechanical properties play a critical role. However, the deformation mechanisms governing the sharp contact response of these glasses remain poorly understood. Herein, we analyze the role of elastoplastic response in determining the indentation deformation mechanisms for a range of borosilicate glass compositions. The series of glasses were made by varying the SiO2‐to‐B2O3 molar ratio while maintaining a constant content of network modifying alkali and alkaline earth oxides. We employed nanoindentation followed by annealing below the glass transition temperature to quantify the contribution of densification and shear flow as a function of glass composition. Interestingly, we observe that the volume recovery upon annealing is inversely proportional to the hardness of the glasses. This suggests that the resistance to permanent deformation is closely related to the network connectivity of the glasses, which in turn governs the mechanism of deformation under sharp contact loading. Overall, we show the important role of alkali and alkaline earth modifiers in governing the composition‐dependent indentation behavior of borosilicate glass series. [ABSTRACT FROM AUTHOR]

The chemical composition and surface structure of glass affect its wettability and can thus lead to the formation of various functional surfaces. This study examined the influence of the structural changes induced by the heat treatment of sodium borosilicate glass on its wettability. Specifically, 15Na2O‐40B2O3‐45SiO2 glass was prepared through melt‐quenching. The obtained glass was subjected to heat treatment at 600°C for 3 h. The heat‐treated glass exhibited a higher hydrophilicity and surface free energy than the nontreated glass. The heat treatment led to a variation in the relative ratio associated with the boron coordination number and nonbridging oxygen. Therefore, the heat‐treatment‐induced changes in the glass structure considerably enhanced the wettability of the glass. [ABSTRACT FROM AUTHOR]

Vitrification is a kind of glass that can solidify high‐level radioactive waste (HLW). As the basic material of vitrification, borosilicate glass was studied extensively. To keep HLW away from the biosphere, the tolerance of borosilicate glass to irradiation is important. In this work, various samples of borosilicate glass with different compositions were irradiated with gamma rays at ambient temperature to study their stability. The hardness, moduli, and microscopic changes on surfaces of the borosilicate glasses were measured at specific absorbed doses. Upon the gamma irradiation, the structural changes on surfaces of borosilicate glasses were identified, which were strongly influenced by the composition of borosilicate glasses. The results demonstrate that gamma irradiation, as well as beta irradiation, might strongly influence the properties of vitrification. The irradiation effects on vitrification induced by gamma irradiation should be paid more attention to than before. [ABSTRACT FROM AUTHOR]

Borosilicate glass has been adopted internationally for the treatment of nuclear waste with the object of long‐term stabilization through vitrification. Aiming to facilitate experimental comparisons across laboratories, the six‐component international simple glass (ISG) was developed as benchmark. The original ISG produced by Mo‐SCI Corporation (Rolla, MO) was distributed and characterized for different physical properties thus serving as reference for further studies. Still, photoluminescence (PL) properties, which may be useful for scrutinizing radiation‐induced damage, have not been reported. Further, the original ISG contained significant iron impurities, which may present interference in various studies (e.g., optical). Consequently, two new ISG analogs lacking iron impurities (labeled ISG‐1 [closest composition to original ISG] and ISG‐2 [some MgO added at expense of CaO]) were synthesized by Corning Inc. (Corning, NY) (also doped with lanthanum for subsequent corrosion tests involving atom probe tomography), which remain to be fully characterized. Accordingly, this work was undertaken to perform a comprehensive study comparing the three ISG specimens. Various characterizations were then performed on the pristine glasses: X‐ray diffraction and vibrational spectroscopy (structural properties); static‐leach product consistency test (PCT, dissolution behavior); dilatometry and calorimetry measurements (thermal properties); and optical absorption with Tauc and Urbach plots analysis, followed by PL spectroscopy with decay kinetics assessment (optical properties). While the general structural features appeared similar among the glasses, the deconvolution of Raman spectra suggested a lower degree of connectivity in the silica network for ISG‐2. In addition, some differences were indicated from the PCT results and thermal properties assessed, which were discussed based on compositional variations. Further on, the optical properties were shown to be the most distinct. The optical absorption of the original ISG was characterized by Fe2+/Fe3+ impurities not detected for ISG‐1 and ISG‐2. The glasses all exhibited two main PL features (∼1.8 and 2.5 eV) with multiexponential decay behavior apparently of intrinsic origin. In addition, ISG‐1 and ISG‐2 showed a third high‐energy (∼3.4 eV) fast‐decaying contribution tentatively credited to tin impurities, which appeared most significantly for ISG‐1. The results are expected to serve as baseline for future studies simulating the effects of radioactive element decay. [ABSTRACT FROM AUTHOR]

In this study, hot‐compression is applied to two multicomponent borosilicate glasses, Borofloat33 (Boro33) and N‐BK7, using molecular dynamics simulations. The effects of pressure on elastic properties, surface energy, and fracture toughness (KIC)${K_{IC}})$ are investigated. It is found that the impact on KIC${K_{IC}}$ is mainly dominated by the change of Young's modulus under pressure, which is proportional to the relative change in density. Between the two glasses under investigation, KIC${K_{IC}}$ can be improved more effectively by the hot‐compression process for Boro33, due to its higher concentration of 3‐coordinated boron (B3), which facilitates densification via B3 to B4 conversion under compression. [ABSTRACT FROM AUTHOR]

This work deals with the preliminary design of glass containers to be deposited on the seabed at 2000 m depth after being filled with liquefied carbon dioxide (CO2) at a pressure of 10 MPa. The specific purpose is to provide preliminary structural analyses of the containers to be employed in a novel patent CO2 storage method called confined submarine carbon storage (CSCS). The core steps of the CSCS technology are the container manufacturing and filling with high‐pressure liquid CO2. Consequently, the container geometry, material properties and structural response are the most critical aspects in the container design. Due to the low cost and to the high stability in salty environment, glass has been identified as a suitable material for the CSCS technology. Furthermore, the high compressive resistance allows glass containers to be deposited on the seabed where the external water pressure exceeds the internal pressure of liquefied carbon dioxide. On the other hand, the limited tensile resistance of glass requires a careful shape design. The glass containers have to be designed to withstand stresses generated during their entire working life. This includes CO2 filling, the launching, the impact with the seabed and the final piling up and stacking of a huge number of containers. Finite element analyses have been performed in order to define the container shape, conjugating an acceptable storage capacity with a safe mechanical response during both the filling and deposition phases. [ABSTRACT FROM AUTHOR]

Borosilicate glasses incorporating high‐level nuclear waste are exposed to high‐energy radiations during their storage in the deep geological repositories. However, the effect of radiation on the atomic structure of borosilicate glasses remains poorly understood. Herein, using molecular dynamics simulations, we study the irradiation‐induced structural changes of a series of calcium‐sodium borosilicate glasses with varying Si/B molar ratios—ranging from pure silicate to pure borate glasses. We observe that irradiation leads to an increase in disorder, both in the short‐ and medium‐range, as evidenced by the enthalpy, coordination number, and ring distribution. In particular, the impact of the change in the atomic structure (due to radiation) on the glass volume is investigated. Interestingly, we observe a composition‐dependent transition in the volumetric response of borosilicate glasses under irradiation—wherein borate‐rich compositions tend to swell, whereas silica‐rich glasses tend to densify. Through a detailed analysis of the structure, we demonstrate two competing mechanisms contributing to the volume change, i.e., a decrease in the coordination number of boron atoms and a reduction in the average silicon inter‐polytope angle. We also show that the increase in the disorder in the medium‐range order may play a major role in governing the volumetric changes in the irradiated structure in a non‐trivial fashion. Altogether, the present study highlights that irradiation has a non‐trivial effect on borosilicate glasses, which, in turn, could impact their corrosion kinetics. [ABSTRACT FROM AUTHOR]

If the direct feed approach to vitrify the Hanford's tank waste is implemented, the low activity waste (LAW) will comprise higher concentrations of alkali/alkaline‐earth sulfates than expected under the previously proposed vitrification scheme. To ensure a minimal impact of higher sulfate concentrations on the downstream operations and overall cost of vitrification, advanced glass formulations with enhanced sulfate loadings (solubility) are needed. While, the current sulfate solubility predictive models have been successful in designing LAW glasses with sulfate loadings <2 wt.%, it will be difficult for them to design glass compositions with enhanced loadings due to our limited understanding of the fundamental science governing these processes. In this pursuit, this article unearths the underlying compositional and structural drivers controlling the sulfate solubility in model LAW glasses. It has been shown that the SO42‐ preferentially removes non‐framework cations from the modifier sites in the silicate network, thus, leading to the polymerization in the glass network via the formation of ring‐structured borosilicate units. Furthermore, though the sulfate solubility slightly decreases with increasing Li+/Na+ in the glasses, the SO42‐ prefers to be charge compensated by Na+, as it is easier for SO42‐ to break Na–O bonds instead of Li–O bonds. [ABSTRACT FROM AUTHOR]

Seven magnesium‐containing aluminoborosilicate glasses, with three to five oxides, have been studied through comprehensive multinuclear solid‐state NMR (11B, 27Al, 29Si, 23Na, 17O, and 25Mg) and Raman spectroscopy. The progressive addition of cations and the substitution of sodium and calcium by magnesium illuminate the impact of magnesium on the glass structure. The proportion of tri‐coordinated boron drastically increased with magnesium addition, demonstrating the poor charge‐compensating capabilities of magnesium in tetrahedral boron units. Oxygen‐17 NMR showed the formation of mixing sites containing both Na and Mg near nonbridging oxygen sites. Furthermore, a high magnesium content appears to result in the formation of two subnetworks (boron and silicon rich) with different polymerization degrees as well as to promote the formation of high‐coordination aluminum sites (Al[V] and Al[VI]). Finally, magnesium coordination ranging from 4 to 6, with a mean value shifting from 5 to 6 along the series, suggests that magnesium might endorse an intermediate role in these glasses. [ABSTRACT FROM AUTHOR]

Quantitative Structure Property Relationship (QSPR) analysis based on molecular dynamics (MD) simulations is a promising approach for establishing the composition‐property relationships of glasses and other materials with complex structures. A series of 20 borosilicate, aluminosilicate, and boroaluminosilicate glasses have been modeled using MD simulations with recently developed effective potentials. Short‐ and medium‐range structures of these glasses were analyzed and, based on the structural information, QSPR analysis of the initial dissolution rates (r0) of these glasses that were measured at 90°C and pH 9 by using various structural descriptors such as percentage of bridging oxygen species, network connectivity, and average ring size. The structural descriptor, Fnet, which contains both energetic information such as single bond strength and structural information such as cation coordination number and Qn distribution, was also used. It was found that while the overall network connectivity, average ring size and Fnet provide reasonable correlations with r0 of studied glasses, Fnet gives the best correlation among the descriptors. For glasses that show incongruent dissolution, it was found that modification of glass compositions to account for preferential release of modifier cations is necessary to achieve best correlations. The findings were discussed with results of recent studies on evaluating the compositional dependence of glass dissolution behavior using the topological‐constraints‐based models. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The dissolution rate of some glasses accelerates after prolonged time spent at a slow, residual dissolution rate. This phenomenon is referred to as Stage III behavior. The acceleration in glass dissolution rate linked to Stage III behavior is significant and may be the most impactful behavior to long‐term performance of glass in a repository. This work is aimed at understanding the effect of glass composition on Stage III behavior to add a level of technical defensibility to glass disposal. To this end, a set of 24 glass compositions were statistically designed, where eight glass components (SiO2, B2O3, Al2O3, CaO, Na2O, SnO2, ZrO2, and Others) have been independently varied in order to study the individual effects of each glass component. These glasses have been subjected to static dissolution tests at 90°C in deionized water and then seeded with zeolite Na‐P2 28 days into the testing to induce Stage III behavior. The response of the glasses to the zeolite seeds fell into four primary types: (1) no response to seeds; (2) an immediate linear sustained acceleration in the rate; (3) an immediate linear acceleration in the rate followed by a decrease; and (4) a progressive acceleration in the rate that is concurrent with the addition of the seeds. The main glass components observed to influence these behaviors were CaO, Al2O3, B2O3, and ZrO2, where (1) CaO influenced which glasses showed a Stage III response to seeds (high CaO: types 2, 3, and 4) or did not respond to seeds (low CaO: type 1), (2) Al2O3 and B2O3 influenced which glasses showed a sustainable Stage III response (high Al2O3: types 2 and 4) versus transitory response (low Al2O3 and high B2O3: type 3), and (3) ZrO2 concentration influenced whether glasses showed a linear (high ZrO2: type 2) versus progressive (low ZrO2: type 4) response to seeds. [ABSTRACT FROM AUTHOR]

Thermal strengthening remains the primary method for enhancing the practical strength of commodity glass products, however, the process is limited in terms of applicable glass thickness and coefficient of thermal expansion. The primary reasons for this limitation are the achievable heat transfer coefficient when using conventional gas cooling, and the occurrence of transient surface tension in the early stages of rapid quenching. We revisit this problem for the case of thin borosilicate glass sheet. Using liquid gallium as the cooling medium, ultra‐fast heat extraction is achieved, with a heat transfer coefficient exceeding 5000 Wm−2 K−1. The low vapor pressure of gallium even at high temperatures enables preheating to a wide range of sheet entrant temperatures. We demonstrate thermal strengthening of low‐expansion borosilicate glass with persistent surface compression of up to 85 MPa, and quenching to a fictive temperature of ~190 K above the glass transition temperature. Glass sheet obtained in this way exhibits notably enhanced surface defect resistance to sharp indentation. In addition to thermal strengthening, the extraordinarily high heat extraction rates achieved by liquid metal immersion enable exploitation of high‐Tf glass properties beyond small and thin sample geometry. [ABSTRACT FROM AUTHOR]

The aim of this paper was to assess factors affecting primary and secondary phase separation in simplified calcium borosilicate glasses studied for nuclear waste applications. Several glasses with varying [MoO3] and [B2O3] were synthesized and exposed to Au‐irradiation to examine compositional effects on glass structure and domain size of separated phases induced by accumulated radiation damage resulting from α‐decay over a ~1000 year timeframe. The produced glasses fell within the immiscibility dome of CaO−SiO2−B2O3 and showed a unique microstructure of embedded immiscibility with three identifiable amorphous phases according to electron microscopy, Raman spectroscopy, and diffraction. These glasses were then bombarded with 7 MeV Au3+ ions to a dose of 3 × 1014 ions/cm2 creating an estimated ~1 dpa of damage. Several changes to the morphology, spatial distribution, and size of secondary phases were observed, indicative of significant structural reorganization and changes to the chemical composition of each phase. A general mechanism of coalescence to form larger particles was observed for [MoO3] < 2.5 mol%, whereas segregation to form smaller more evenly distributed particles was seen for [B2O3] ≤ 15 mol% and [MoO3] ≥ 2.5 mol%. These microscopic changes were concurrent to surface‐bulk diffusion of Ca and/or Mo ions, where the direction of diffusion was dependent on [B2O3] with a barrier identified at ~20 mol%, as well as cross‐phase diffusion of said ions. These modifications occurred in part through the formation of distorted ring structures within the borosilicate network, which enabled the increased dissolution of isolated (MoO4)2− units. Au‐irradiation was therefore able to increase the solubility of molybdenum and alter the structure and composition of secondary phases with the extent of modification varying with [MoO3] and [B2O3]/[SiO2], though glasses notably remained heterogeneous. The collective results suggest that radiation and composition can both be used as design tools to modulate the domain size and distribution of separated phases in heterogeneous glasses. [ABSTRACT FROM AUTHOR]

The shear behaviors of two multicomponent borosilicate glasses, Borofloat®33 (Boro33) and N‐BK7® (N‐BK7), under different pressures are investigated using molecular dynamics simulations. The addition of alkali ions lowers the yield stress and changes the pressure dependence of shear modulus. Shear‐induced densification is observed in both glasses. It is found that the decreases of the oxygen‐centered bond angle and the coordination number change of B are responsible for the density changes at low pressures, and the increase of 5‐coordinated Si is the dominant mechanism for densification at high pressures. The average shear stresses experienced by Si and B decrease with pressure except that the flow stress of Si at the end of shear deformation in N‐BK7. Moreover, the average shear stress of B is more sensitive to the applied pressures compared to Si, suggesting that B is able to relax mechanical stress more easily under pressurized‐shear. By analyzing the nonaffine displacement of atoms, it is found that N‐BK7 exhibits more localized plastic deformation compared to Boro33 at low pressures and the local rearrangements in both glasses become more homogeneous with increasing pressure. The mean squared nonaffine displacement curves show that alkali ions have the highest mobility induced by shear compared to the network formers and B is more mobile than Si for both glasses. We also observed that plastic deformation tends to take place around boron atoms for Boro33, whereas it occurs in the alkali‐rich regions for N‐BK7, indicating that these two glasses have different atomic‐scale deformation mechanisms. [ABSTRACT FROM AUTHOR]

Several different ways of measuring the energy resolution for meV‐resolved inelastic X‐ray scattering (IXS) are compared: using scattering from poly(methyl methacrylate), PMMA, using scattering from borosilicate glass (Tempax), and using powder diffraction from aluminium. All of these methods provide a reasonable first approximation to the energy resolution, but, also, in all cases, inelastic contributions appear over some range of energy transfers. Over a range of ±15 meV energy transfer there is good agreement between the measurements of PMMA and Tempax at low temperature, and room‐temperature powder diffraction from aluminium, so we consider this to be a good indication of the true resolution of our ∼1.3 meV spectrometer. The resolution over a wider energy range is self‐consistently determined using the temperature, momentum and sample dependence of the measured response. The inelastic contributions from the PMMA and Tempax, and their dependence on momentum transfer and temperature, are then quantitatively investigated. The resulting data allow us to determine the resolution of our multi‐analyzer array efficiently using a single scan. The importance of this procedure is demonstrated by showing that the results of the analysis of a spectrum from a glass are changed by using the properly deconvolved resolution function. The impact of radiation damage on the scattering from PMMA and Tempax is also discussed. [ABSTRACT FROM AUTHOR]

The glass transition temperature (Tg) is a key parameter to investigate for application in nuclear waste immobilization in borosilicate glasses. Tg for several glasses containing iodine (I) has been measured in order to determine the I effect on Tg. Two series of glass composition (ISG and NH) containing up to 2.5 mol% I and synthesized under high pressure (0.5 to 1.5 GPa) have been investigated using differential scanning calorimetry (DSC). The I local environment in glasses has been determined using X‐ray photoelectron spectroscopy and revealed that I is dissolved under its iodide form (I−). Results show that Tg is decreased with the I addition in the glass in agreement with previous results. We also observed that this Tg decrease is a strong function of glass composition. For NH, 2.5 mol% I induces a decrease of 24°C in Tg, whereas for ISG, 1.2 mol% decreases the Tg by 64°C. We interpret this difference as the result of the I dissolution mechanism and its effect on the polymerization of the boron network. The I dissolution in ISG is accompanied by a depolymerization of the boron network, whereas it is the opposite in NH. Although ISG corresponds to a standardized glass, for the particular case of I immobilization it appears less adequate than NH considering that the decrease in Tg for NH is small in comparison to ISG. [ABSTRACT FROM AUTHOR]

The temperature dependence of glass relaxation has been intensively studied; however, the effect of an imposed pressure history on relaxation behavior is poorly understood. In this study, we subjected SCHOTT N‐BK7® borosilicate glasses to isostatic compression in a Paterson press (PP) and a gas pressure chamber (GPC). The pressure ranged from 0.1 GPa to 2 GPa for various dwell temperatures and times near the glass transition region. Comparison with our recent results on the same glass using the piston‐cylinder apparatus (PC, 0.5‐1.5 GPa) reveals that the density of a glass, which has been quenched from the equilibrium state under high pressure at 2 K/min (pressure quench), increases approximately linearly with increasing pressure up to 2 GPa. Considering the volume recovery results at ambient pressure, we assert that the preceding high‐pressure treatment in PC (uniaxial loading) generates a similar isostatic pressure effect on N‐BK7 glass as those of PP and GPC treatments. Finally, we verify the previously proposed two‐internal‐parameter relaxation model on the volume recovery data using the three different compression methods. With a new set of parameters in the model, we can account for the pressure and temperature dependence of volume relaxation even for the samples quenched from nonequilibrium states at high pressure. [ABSTRACT FROM AUTHOR]

High‐alumina containing high‐level waste (HLW) will be vitrified at the Waste Treatment Plant at the Hanford Site. The resulting glasses, high in alumina, will have distinct composition‐structure‐property (C‐S‐P) relationships compared to previously studied HLW glasses. These C‐S‐P relationships determine the processability and product durability of glasses and therefore must be understood. The main purpose of this study is to understand the detailed structural changes caused by Al:Si and (Al + Na):Si substitutions in a simplified nuclear waste model glass (ISG, international simple glass) by combining experimental structural characterizations and molecular dynamics (MD) simulations. The structures of these two series of glasses were characterized by neutron total scattering and 27Al, 23Na, 29Si, and 11B solid‐state nuclear magnetic resonance (NMR) spectroscopy. Additionally, MD simulations were used to generate atomistic structural models of the borosilicate glasses and simulation results were validated by the experimental structural data. Short‐range (eg, bond distance, coordination number, etc) and medium‐range (eg, oxygen speciation, network connectivity, polyhedral linkages) structural features of the borosilicate glasses were systematically investigated as a function of the degree of substitution. The results show that bond distance and coordination number of the cation‐oxygen pairs are relatively insensitive to Al:Si and (Al + Na):Si substitutions with the exception of the B‐O pair. Additionally, the Al:Si substitution results in an increase in tri‐bridging oxygen species, whereas (Al + Na):Si substitution creates nonbridging oxygen species. Charge compensator preferences were found for Si‐[NBO] (Na+), [3]B‐[NBO] (Na+), [4]B (mostly Ca2+), [4]Al (nearly equally split Na+ and Ca2+), and [6]Zr (mostly Ca2+). The network former‐BO‐network former linkages preferences were also tabulated; Si‐O‐Al and Al‐O‐Al were preferred at the expense of lower Si‐O‐[3]B and [3]B‐O‐[3]B linkages. These results provide insights on the structural origins of property changes such as glass‐transition temperature caused by the substitutions, providing a basis for future improvements of theoretical and computer simulation models. [ABSTRACT FROM AUTHOR]

Understanding composition‐structure‐property relationships of high‐alumina nuclear waste glasses are important for vitrification of nuclear waste at the Hanford Site. Two series of glasses were designed, one with varying Al:Si ratios and the other with (Al + Na):Si ratios based on the international simple glass (ISG, a simplified nuclear waste model glass), with Al2O3 ranging from 0 to 23 mol% (0 to 32 wt%). The glasses were synthesized and characterized using electron probe microanalysis, X‐ray photoelectron spectroscopy, small angle X‐ray scattering, high‐temperature oxide melt solution calorimetry, and infrared spectroscopy. Glasses were crystal free, and the lowest Na2O and Al2O3 glass formed an immiscible glass phase. Evolution of various properties—glass‐transition temperature, percentage of 4‐coordinated B, enthalpy of glass formation—and infrared spectroscopy results indicate that structural effects differ based on the glass series. [ABSTRACT FROM AUTHOR]

Erratum for a new self-consistent empirical potential model for multicomponent borate and borosilicate glasses Keywords: borates; borosilicate glass; molecular dynamics; structure EN borates borosilicate glass molecular dynamics structure 5104 5105 2 06/05/23 20230801 NES 230801 B Abstract b The manuscript contains a mistake in Equation (6) and an erroneous value of the B SB ij sb term of B-O interaction in Table 2. Borates, borosilicate glass, molecular dynamics, structure. [Extracted from the article]

The thermal stability of sol‐gel‐derived silica and borosilicate glasses exposed to dry O2 at 800 and 1200°C for 100 hours was characterized by weight change, thermal transitions, morphology, structure, and composition to investigate suitability as models for thermally grown oxides. Rapid weight loss was observed in the first few hours of isothermal exposure for borosilicate glasses, followed by constant weight loss at a low rate for the balance of the exposure. Weight loss resulted from loss of residual hydroxyl species retained from the sol‐gel synthesis, and from oxidation of carbon retained from thermal decomposition of the organic precursors by pyrolysis. Characterization of the sol‐gel‐derived glasses showed structural similarities to silica and binary borosilicate glasses synthesized by melt or vapor deposition methods, and to thermally grown oxides. Oxygen transport mechanisms through the sol‐gel‐derived glasses is not thought to be affected by the retained carbon. However, a silica‐enriched glass surface resulting from boria volatility, observed from a borosilicate glass exposed dry O2 at 1200°C, will slow O2 transport rates. The results show that sol‐gel‐derived silica and borosilicate glasses can be used as models for thermally grown oxides. [ABSTRACT FROM AUTHOR]

Borosilicate glasses have been in widespread use for over a century; however, a detailed understanding of the structural response to densification is still lacking. In this work, two commercial borosilicate glasses, viz., SCHOTT N‐BK7® (N‐BK7) and Borofloat33® (Boro33), are hot compressed up to 2 GPa with nitrogen gas, and the structural response to this densification is explored via 11B solid‐state nuclear magnetic resonance (NMR) spectroscopy and classical molecular dynamics (MD) simulations. The molar volume (Vm) of N‐BK7 and Boro33 decreases ~5% and ~10%, respectively, as a result of hot compression at 2 GPa. The NMR results demonstrate the presence of three different types of fourfold coordinated boron species (B[4]), which are confirmed in MD simulations to be B14(0B,4Si[4]), B24(1B[3],3Si[4]), and B34(1B[4],3Si[4]) (where subscripts represent different B[4] types and brackets indicate the next nearest neighbors (NNN)). The NMR results also show that the fraction of B[4] increases by ~13% in N‐BK7 glass upon hot compression at 2 GPa via the trigonal boron to tetrahedral boron (B[3] to B[4]) conversion, while the fraction of B[4] in Boro33 glass only increases by ~2% at the same pressure, despite the fact that the Vm decrease in N‐BK7 is double that of Boro33. The MD simulations capture the experimental trends in B[4] populations, despite an underestimation of the B[4] increase of N‐BK7 (only ~6%) at 2 GPa. Moreover, the MD simulations suggest that the Vm reduction is a linear function of bond angle change and the fraction of Si‐O‐Si and B[4]‐O‐Si. The modifiers and boron coordination conversion also influence the volume densification of borosilicate glasses by increasing the difficulty of bond bending, decreasing the bond lengths, and increasing the population of B[4]‐O‐Si linkages. Finally, the B[4] to B[4] conversion, that is, B24(1B[3],3Si[4]) and B34(1B[4],3Si[4]) to B14(0B,4Si[4]), is observed in hot compressed N‐BK7 and Boro33 from NMR and qualitatively confirmed in MD. [ABSTRACT FROM AUTHOR]

Sulfur trioxide (SO3) additions, up to 3.0 mass%, were systematically investigated for effects on the physical properties of sodium borosilicate glass melted in air, with a sulfur‐free composition of 50SiO2–10Al2O3–12B2O3–21Na2O–7CaO (mass%). Solubility measurements, using electron microscopy chemical analysis, determined the maximum loading to be ~1.2 mass% SO3. It was found that measured sulfur (here as sulfate) additions up to 1.18 mass% increased the glass transition temperature by 3%, thermal diffusivity by 11%, heat capacity by 10%, and thermal conductivity by 20%, and decreased the mass density by 1%. Structural analysis, performed with Raman spectroscopy, indicated that the borosilicate network polymerized with sulfur additions up to 3.0 mass%, presumably due to Na2O being required to charge compensate the ionic SO42- additions, thus becoming unavailable to form non‐bridging oxygen in the silicate network. It is postulated that this increased cross‐linking of the borosilicate backbone led to a structure with higher dimensionality and average bond energy. This increased the mean free paths and vibration frequency of the phonons, which resulted in the observed increase in thermal properties. [ABSTRACT FROM AUTHOR]

This work aims to study the mechanisms of oxygen bubble formation coming from redox reaction of a polyvalent element incorporated in a glass melt. Borosilicate glass composition is selected for its use as a glass matrix for nuclear waste conditioning. Cerium is selected as a polyvalent element as it may be found in nuclear waste. The chosen material is characterized in terms of physical properties which influence bubble formation and growth. A postmortem optical microscope approach is used to observe bubbles in the investigated material after thermal treatment for varying temperatures (900°C‐1100°C) and durations. To support the understanding of oxygen bubble formation, cerium speciation by X‐ray absorption near‐edge structure (XANES) and bubble gas composition are experimentally evaluated. In this article, we indicate how bubbles are formed in the investigated glass melt system. It is also demonstrated that the mechanisms that govern bubble evolution are fundamentally the same and that the plot's optimum points are strongly influenced by the temperature. These last statements are confirmed by considering some bubble features, such as bubble mean density and bubble mean diameter evolutions, and normalizing the experimental time using a characteristic residence time (tη) obtaining thereafter a dimensionless time, which is a function of the glass melt properties obtained by the physical characterizations. The impact of temperature and time on bubble formation is described. [ABSTRACT FROM AUTHOR]

A new, in situ hermeticity testing apparatus has been developed to allow helium leak evaluation of ceramic tubes, including nuclear‐grade SiC/SiC fuel cladding ceramic matrix composites (CMC), during four‐point bending with simultaneous monitoring of local deformation and damage, using stereoscopic digital image correlation (DIC) and acoustic emissions. The capabilities of the experimental apparatus are demonstrated using alumina, borosilicate glass, and 4130 steel tubes with representative cladding dimensions and then applied to study the deformation‐hermeticity relationship of SiC/SiC CMCs. Results of three CMCs appear to indicate that matrix cracking occurs near the deviation from linearity strain at strains ranging from 0.04% to 0.06% and is shortly followed by an initial loss of gas tightness by 0.09% bending strain. Leaking increased in distinct steps over 0.1%‐0.2% bending strain, and within this range, results indicate that prior to fiber fracture, it is likely possible to regain gas tightness upon unloading. This technique and uncovered hermetic failure behavior are intended to progress the standardization of a test methodology for nuclear reactor components and to begin to resolve the mechanisms controlling distinct steps of ceramic matrix composite failure. [ABSTRACT FROM AUTHOR]

Three kinds of borosilicate glass‐ceramics Low temperature co‐fired ceramics (LTCC) substrate materials, Ca‐B‐Si‐O (CBS), Ca‐Al‐B‐Si‐O (CABS), and Ca‐Mg‐B‐Si‐O (CMBS), have been prepared, and the biocompatibility of these materials was evaluated. Compared with CBS and CMBS samples, the CABS sample presented the lowest crystallinity and dissolution in the bioleaching experiments. The direct and indirect cell culturing results showed that the CABS sample also possessed the best biocompatibility to the bone mesenchymal stem cells (BMSCs) due to its good bio‐stability and surface micro‐pore structure. The effects of surface topography and released ions on cytocompatibility were analyzed. These results were expected to offer some guideline information for developing LTCC substrate materials used in the microfluidic biosensors for the future biological and medical application. [ABSTRACT FROM AUTHOR]

Borates and borosilicates are potential candidates for the design and development of glass formulations with important industrial and technological applications. A major challenge that retards the pace of development of borate/borosilicate based glasses using predictive modeling is the lack of reliable computational models to predict the structure‐property relationships in these glasses over a wide compositional space. A major hindrance in this pursuit has been the complexity of boron‐oxygen bonding due to which it has been difficult to develop adequate B–O interatomic potentials. In this article, we have evaluated the performance of three B–O interatomic potential models recently developed by Bauchy et al [J. Non‐Cryst. Solids, 2018, 498, 294–304], Du et al [J. Am. Ceram. Soc. https://doi.org/10.1111/jace.16082] and Edèn et al [Phys. Chem. Chem. Phys., 2018, 20, 8192–8209] aiming to reproduce the short‐to‐medium range structures of sodium borosilicate glasses in the system 25 Na2O x B2O3 (75 − x) SiO2 (x = 0‐75 mol%). To evaluate the different force fields, we have computed at the density functional theory level the NMR parameters of 11B, 23Na, and 29Si of the models generated with the three potentials and the simulated MAS NMR spectra compared with the experimental counterparts. It was observed that the rigid ionic models proposed by Bauchy and Du can both reliably reproduce the partitioning between BO3 and BO4 species of the investigated glasses, along with the local environment around sodium in the glass structure. However, they do not accurately reproduce the second coordination sphere of silicon ions and the Si–O–T (T = Si, B) and B‐O‐T distribution angles in the investigated compositional space which strongly affect the NMR parameters and final spectral shape. On the other hand, the core‐shell parameterization model proposed by Edén underestimates the fraction of BO4 species of the glass with composition 25Na2O 18.4B2O3 56.6SiO2 but can accurately reproduce the shape of the 11B and 29Si MAS‐NMR spectra of the glasses investigations due to the narrower B–O–T and Si‐O‐T bond angle distributions. Finally, the effect of the number of boron atoms (also distinguishing the BO3 and BO4 units) in the second coordination sphere of the network former cations on the NMR parameters have been evaluated. [ABSTRACT FROM AUTHOR]

Corrosion of glass in silica‐saturated solution has been performed with the assumption that dissolution of silicate species from the glass network would not occur. Using surface‐sensitive analytical techniques, we report experimental evidence suggesting the dissolution of silicate network species from a model nuclear waste glass, called international simple glass (ISG), in an aqueous solution initially saturated with soluble silica species. Results from low energy ion scattering and X‐ray photoelectron spectroscopy reveal a complete depletion of mobile element species (B, Na) from the ISG surface and an enrichment of Zr on the outmost surface. In support of spectroscopic analyses, results from topographic imaging with atomic force microscopy show a stochastic dissolution of glass surface resulting in a higher surface roughness with increasing corrosion time in aqueous solution. This study shows that a true equilibrium between soluble silica species in the solution phase and silicate species in the glass network could not be warranted by performing corrosion experiments in the solution where dissolved silica species are initially equilibrated with amorphous silica in the presence of KOH. The leaching of mobile species (B, Na) could affect the saturation level of aqueous solution and induce further dissolution of the glass surface. [ABSTRACT FROM AUTHOR]

Compression creep tests (CCTs) have been widely used in phenomenological characterization of viscoelastic materials such as glasses. However, disturbed by specimen‐tool interface friction, the real stress‐strain data regarding the pure viscoelastic deformation are frequently misestimated in conventional CCTs, causing decreased accuracies of the derived viscoelastic parameters. This study proposes a comprehensive CCT‐based approach to develop a viscoelastic model with weakened frictional disturbance and enhanced predictive accuracy. An integrated calculation procedure is first built to mathematically characterize the frictional and viscoelastic behaviors of glass during compression. Uniaxial CCTs of a typical borosilicate glass (L‐BAL42) are then performed at varied frictional conditions. The quantified coefficients of interface friction indicate that a minor frictional disturbance is achieved when Nickel foils are used as interfacial layers, whereby a more realistic viscoelastic constitutive relation of the glass is derived. The obtained frictional and viscoelastic constants are further incorporated into computational modeling of the CCT and precision molding processes. The demonstrated consistencies between the simulated and measured results (creep displacement and molding force) suggest that, by technically slashing the interface friction and theoretically correcting the friction‐involved stress in CCTs, the frictional disturbance to experimental stress‐strain data can be effectively weakened, and a viscoelastic model of enhanced predictive accuracy can be thus developed. [ABSTRACT FROM AUTHOR]

Molecular dynamics and related atomistic computer simulations are effective ways in studying the structures and structure–property relations of glass materials. However, simulations of boron oxide (B2O3)‐containing oxide glasses pose a challenge due to the lack of reliable empirical potentials. This paper reports development of a set of partial charge pairwise composition‐dependent potentials for boron‐related interactions that enable simulations of multicomponent borosilicate glasses, together with some of the existing parameters. This set of potentials was tested in sodium borate glasses and sodium borosilicate glasses and it is shown capable to describe boron coordination change with glass composition in wide composition ranges. Structure features such as boron N4 value, density, Qn species distribution, fraction of non‐bridging oxygen around boron and silicon, total correlation function, and bond angle distribution function were calculated and compared with available experimental data. Mechanical properties of the simulated glasses calculated with the new potential also show good agreement with experiments. Therefore, this new set of potential can be used to simulate boron oxide‐containing multicomponent glasses including those with wide industrial and technology applications. [ABSTRACT FROM AUTHOR]

Abstract: The oxidation behavior of Sylramic SiC fibers without a boron nitride surface layer was compared to Sylramic iBN SiC fibers with a boron nitride surface layer by conducting thermogravimetric analysis in dry O2 at temperatures ranging from 800 to 1300°C for times up to 100 hours. Sylramic fibers followed the Deal and Grove oxidation kinetic model. A transient period of accelerated oxidation kinetics was observed with Sylramic iBN fibers. Raman spectroscopic analysis of oxidized fibers provided evidence for a borosilicate glass structure. The boron concentrations in the oxides, quantified by inductively coupled plasma‐optical emission spectrometry, were correlated with the weight change behavior, oxide thickness, and fiber recession of the oxidized fibers. Oxides formed from Sylramic iBN fibers were typically higher in boron concentration, which led to initial rapid oxidation rates that were 3‐10 times faster than observed for pure SiC. Slower oxidation rates followed as the oxide surface became increasingly enriched with SiO2 due to boria volatilization, thus limiting boria effects on SiC fiber oxidation kinetics. The accelerated high‐temperature oxidation of SiC fibers due to the presence of BN are discussed in terms of the borosilicate glass structure and composition. [ABSTRACT FROM AUTHOR]

A one‐step method to obtain boron emitters for n‐type solar cells based on the use of boron tribromide (BBr3) as a dopant source is developed. During this study several experimental parameters are varied. It is observed that besides the diffusion temperature, the nitrogen gas flux and the BBr3 bubbler temperature have a significant impact on the obtained emitter properties. Using the adequate experimental conditions a homogenous boron emitter without boron rich layer (BRL), a sheet resistance of 77 Ω sq−1 and a dark saturation current <100 fA cm−2 is obtained. [ABSTRACT FROM AUTHOR]

Abstract: Optical fibers possessing a crystalline oxide core have significant potential for novel and useful electro‐ or nonlinear‐optic waveguides. Presently, however, their utility suffers from the slow speed and limited cladding materials afforded by conventional crystal‐fiber‐growth techniques. Described herein is the development of single phase bismuth germanium oxide crystalline core fibers using conventional glass fiber drawing. More specifically, fibers were fabricated and evaluated based on 2 embodiments of the molten core method. In a first approach, a Bi4Ge3O12 single crystal was employed as the precursor and sleeved inside a borosilicate glass cladding. In the second approach, additional Bi2O3 was included along with the Bi4Ge3O12 precursor single crystal. Glass clad fibers drawn from the precursor Bi4Ge3O12 single crystal resulted in a polycrystalline core with various crystal morphologies (line‐like, dendrite‐like, and uniform grains) as will be discussed, while fibers drawn from the Bi4Ge3O12 single crystal surrounded by Bi2O3 resulted in a more homogeneous microstructure. The eulytine crystal structure was crystallized using both approaches, with the formation of a secondary crystal phase using the second approach. More particularly, this work aims at showing that single phase and phase pure crystalline oxide core optical fibers can be achieved using conventional glass fiber draw processes, although further optimization is necessary for obtaining single crystalline core fibers. [ABSTRACT FROM AUTHOR]