Glass Chemistry Research Articles

Insights into the mechanism and kinetics of dissolution of aluminoborosilicate glasses in acidic media: Impact of high ionic field strength cations

Achieving thinner and higher performance display/substrate glasses and transparent glass-ceramics with tunable properties requires a precise control of acid-etching process, thus necessitating a comprehensive understanding of glass composition–structure–dissolution behavior relationships in acidic medium. Unfortunately, the literature on this subject has been focused only on a narrow set of glass chemistries. Therefore, consensus on the mechanisms that govern the acidic dissolution of multicomponent silicate glasses over a broad compositional space is still lacking. The present work employs a suite of state-of-the-art spectroscopic techniques, including 1D and 2D NMR, TEM-EELS, ICP-OES, and XPS, to provide an insight into the mechanism and kinetics of corrosion of alkali/alkaline-earth aluminoborosilicate glasses (comprising high field strength cations – HFSCs, i.e., La3+, Ti4+, Zr4+ and Nb5+) in acidic media (HCl; pH = 2). Incorporating the HFSCs into the glasses induces significant structural changes in their network, thus, impacting the forward rate dissolution kinetics. Based on the results, we hypothesize that the glasses dissolve at pH = 2 through an ‘interfacial dissolution – re-precipitation mechanism (IDPM)’ and ‘in-situ recondensation’ coupled pattern, wherein the IDPM results in a Si-rich alteration layer, followed by local recondensation occurring due to limited kinetics near the interfacial solution between the uncorroded glass surface and the outer alteration layer.

Hydrogen isotope behavior during rhyolite glass hydration under hydrothermal conditions

The diffusion of molecular water (H2Om) from the environment into volcanic glass can hydrate the glass up to several wt% at low temperature over long timescales. During this process, the water imprints its hydrogen isotope composition (δDH2O) to the glass (δDgl) offset by a glass-H2O fractionation factor (ΔDgl-H2O = δDgl – δDH2O) which is approximately −33‰ at Earth surface temperatures. Glasses hydrate much more rapidly at higher, sub-magmatic temperatures as they interact with H2O during eruption, transport, and emplacement. To aid in the interpretation of δDgl in natural samples, we present hydrogen isotope results from vapor hydration experiments conducted at 175–375 °C for durations of hours to months using natural volcanic glasses. The results can be divided into two thermal regimes: above 250 °C and below 250 °C. Lower temperature experiments yield raw ΔDgl-H2O values in the range of −33 ± 11‰. Experiments at 225 °C using both positive and negative initial ΔDgl-H2O values converge on this range of values, suggesting this range represents the approximate equilibrium fractionation for H isotopes between glass and H2O vapor (103lnαgl-H2O) below 250 °C. Variation in ΔDgl-H2O (−33 ± 11‰) between different experiments and glasses may arise from incomplete hydration, analytical uncertainty, differences in glass chemistry, and/or subordinate kinetic isotope effects. Experiments above 250 °C yield unexpectedly low δDgl values with ΔDgl-H2O values of ≤–85‰. While alteration alone is incapable of explaining the data, these run products have more extensive surface alteration and are not interpreted to reflect equilibrium fractionation between glass and H2O vapor. Fourier transform infrared spectroscopy (FTIR) shows that glass can hydrate with as much as 5.9 wt% H2Om and 1.0 wt% hydroxl (OH−) in the highest P-T experiment at 375 °C and 21.1 MPa. Therefore, we employ a 1D isotope diffusion–reaction model of glass hydration to evaluate the roles of equilibrium fractionation, isotope diffusion, water speciation reactions internal to the glass, and changing boundary conditions (e.g. alteration and dissolution). At lower temperatures, the best fitting model results to experimental data for low silica rhyolite (LSR) glasses require only an equilibrium fractionation factor and yield 103lnαgl-H2O values of −33‰ ± 5‰ and −25‰ ± 5‰ at 175 °C and 225 °C, respectively. At higher temperatures, ΔDgl-H2O is dominated by boundary layer effects during glass hydration and glass surface alteration. The modeled bulk δDgl value is highly responsive to changes in the δDgl boundary condition regardless of the magnitude of other kinetic effects. Observed glass dissolution and surficial secondary mineral formation are likely to impose a disequilibrium boundary layer that drives extreme δDgl fractionation with progressive glass hydration. These results indicate that the observed ΔDgl-H2O of ∼−33 ± 11‰ can be cautiously applied as an equilibrium 103lnαgl-H2O value to natural silicic glasses hydrated below 250 °C to identify hydration sources. This approximate ΔDgl-H2O may be applicable to even higher temperature glasses hydrated on short timescales (of seconds to minutes) in phreatomagmatic or submarine eruptions before H2O in the glass is primarily affected by boundary layer effects associated with alteration on the glass surface.

Assessment of rhenium as a surrogate for technetium in Hanford low activity waste borosilicate glasses: Speciation, solubility, and redox effects

AbstractRe is often used as a nonradioactive surrogate for Tc in borosilicate melts because both elements have similar valences, ionic radii, and coordination environments. Re solubility in high sodium borosilicate waste glasses is sensitive to melter redox conditions; at 1150°C the solubility is ∼4130 ppm under oxidizing atmospheres. Raman, X‐ray absorption spectroscopy, and X‐ray diffraction show that Re dissolved in waste glasses under oxidizing conditions is in perrhenate tetrahedra; under more reducing conditions, Re0 separates from the melt. From air to ∼ 10−4 atm, both Re7+ and Tc7+ are dominant species in borosilicate melts. However, Tc and Re behaviors deviate between < 10−4 atm and > 10−8 atm, where Tc4+ becomes dominant, whereas Re7+ remains stable. Unlike Tc4+, Re4+ is not observed in borosilicate melts at 1150°C and associated glasses. Near = 10−8 atm, Tc4+ reduces to Tc0, whereas below = 10−8 atm, Re7+ reduces to Re0. Re is found to be a good surrogate for Tc under oxidizing conditions (> 10−4 atm) and under highly reducing conditions (< 10−9 atm). Redox and solubility behaviors of Tc and Re are also sensitive to glass chemistry, such that the fair assessment of Re modeling Tc behavior should be glass specific.

Tailoring the Hydroxyl Density of Glass Surface for Anionic Ring-Opening Polymerization of Polyamide 6 to Manufacture Thermoplastic Composites.

Reactive thermoplastics matrices offer ease of processing using well-known molding techniques (such as Resin Transfer Molding) due to their initially low viscosity. For Polyamide 6 (PA6)/glass composites, the hydroxyl groups on the glass surface slow down the anionic ring-opening polymerization (AROP) reaction, and can ultimately inhibit it. This work aims to thoroughly control the hydroxyl groups and the surface chemistry of glass particulates to facilitate in situ AROP-an aspect that has been barely explored until now. A model system composed of a PA6 matrix synthesized by AROP is reinforced with calcinated and silanized glass microparticles. We systematically quantify, by TGA and FTIR, the complete particle surface modification sequence, from the dehydration, dehydroxylation and rehydroxylation processes, to the silanization step. Finally, the impact of the particle surface chemistry on the polymerization and crystallization of the PA6/glass composites was quantified by DSC. The results confirm that a careful balance is required between the dehydroxylation process, the simultaneous rehydroxylation and silane grafting, and the residual hydroxyl groups, in order to maintain fast polymerization and crystallization kinetics and to prevent reaction inhibition. Specifically, a hydroxyl concentration above 0.2 mmol OH·g−1 leads to a slowdown of the PA6 polymerization reaction. This reaction can be completely inhibited when the hydroxyl concentration reaches 0.77 mmol OH·g−1 as in the case of fully rehydroxylated particles or pristine raw particles. Furthermore, both the rehydroxylation and silanization processes can be realized simultaneously without any negative impact on the polymerization. This can be achieved with a silanization time of 2 h under the treatment conditions of the study. In this case, the silane agent gradually replaces the regenerated hydroxyls. This work provides a roadmap for the preparation of reinforced reactive thermoplastic materials.

A high-throughput ab-initio study of diverse glasses: Accuracy of the atomic structure and refractive index

A high-throughput method to predict the spectral refractive index of glasses from a purely ab-initio approach is presented. Atomic structures for 34 different and diverse glass chemistries are generated using high-throughput simulation framework that can quickly generate data. Predicted mechanical properties ensure the generated structures are the representative atomistic model, and we suggest a scaling factor to match the experimental refractive index (RI) using high-throughput values. Calculated RI in this work aligns with experimentally measured values, with an average error of < 0.9%. On the other hand, the predicted absorption coefficient is limited to comparing qualitative trends across different glass chemistries.

Forecasting and communicating the dispersion and fallout of ash during volcanic eruptions: lessons from the September 20, 2020 eruptive pulse at Sangay volcano, Ecuador

Volcanic ash is a hazard to human health and activities. Accurate and timely forecasts coupled with effective communication about the dispersion and fallout of volcanic ash during explosive events are essential to reduce impacts on local communities and limit economic losses. In this study, we present the first detailed description of an eruptive pulse at Sangay volcano and its eruption source parameters. The eruptive pulse on September 20, 2020, started at about 9:20 UTC and lasted between 90 and 100 min, producing an eruptive column that rapidly separated into (1) a higher (15.2 km above sea level, asl), gas-rich cloud moving east-southeast and (2) a lower (12.2 km asl), ash-rich cloud moving west and causing ash fallout up to 280 km from the volcano. Field data collected immediately after the event allow estimating the volume of bulk tephra to be between 1.5 and 5.0 × 106 m3, corresponding to a volcanic explosivity index of 2. The eruptive pulse, identified as violent Strombolian, emitted andesitic ash that was more mafic than products ejected by Sangay volcano in recent decades. Component analysis and glass chemistry of juvenile particles support the hypothesis that this event excavated deeper into the upper conduit compared to typical Strombolian activity at Sangay volcano, while grain-size analysis allows reconstruction of the total grain-size distribution of the fallout deposit. The discrepancies between the ash fallout simulations performed with the Ash3D online tool and the actual deposit are mainly the result of inaccurate pre- and syn-eruptive configurations and highlight the importance of additional processes such as aggregation. Communication products issued during the event included (1) several standard short reports, (2) volcano observatory notices for aviation, (3) social media posts, and (4) a special report providing the results of the ash fallout simulation. Although communication was effective with the authorities and the connected population, an effort must be made to reach the most vulnerable isolated communities for future events. This study shows that forecasting ash dispersion and fallout during volcanic eruptions can guide early warnings and trigger humanitarian actions, and should become a standard in volcano observatories worldwide.

Effect of iron redox ratio on the structures of boroaluminosilicate glasses

AbstractIron 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.

Influence of V2O5 on the optical properties and radiation shielding performance of borate glass system containing Li2O and ZnO

It is significant to investigate the photon transmission resilience of different glasses in order to identify the role played by each chemical unit therein and identify the radiation protection functionality of such glass systems. The role of V2O5 in dictating the optical and radiation transmission ability of (15-x)Li2O-70B2O3-15ZnO-xV2O5 glasses is investigated in this report. Extensive optical parameters which include: molar refractivity (Rmol.), metallization criterion (M), molar polarizability (αMol.), optical transmission (TOpt.), static dielectric constant, εstatic, reflection loss (RLoss), and optical dielectric constant, εoptical of the studied glasses were theoretically calculated. The mass attenuation coefficient MACg of the investigated glasses for 15 keV to 15 MeV photons was simulated through the FLUKA Monte Carlo simulation code and XCOM. Also, the fissile neutron removal cross section ΣR was estimated theoretically using the partial density method. Obtained results indicated that he Rmol. and αMol. of the LBZV glasses were enhanced with increment in V2O5 concentration; increasing from 16.892 to 19.869 cm2/mol and 6.703 × 10−24 to 7.885 × 10−24 cm3 respectively. Other estimated optical constants showed variations that appear to be strongly dictated by the amount of V2O5 in the glass chemistry. MACgdata from FLUKA simulations and XCOM calculations resonate well with each other. The MACg lies in the limits of 0.02–13.418 cm2/g, 0.018–13.848 cm2/g, 0.020–14.182 cm2/g, 0.02–14.367 cm2/g, and 0.019–14.772 cm2/g for increasing V2O5 concentration. The absorption parameters show that the V2O5 plays a positive role in the ability of the glasses to absorb gamma photons.

Experimental Investigation of Trachydacite Magma Storage Prior to the 1257 Eruption of Mt Samalas

Abstract The caldera-forming Samalas eruption of the Samalas–Rinjani volcanic complex on Lombok, Indonesia, in 1257 CE ranks as one of the most explosive and sulphur-rich eruptions of the past thousand years. Along with other significant events (e.g. Tambora 1815, El Chichón 1982), Samalas 1257 forms a class of powerful eruptions of magmas of intermediate alkaline composition, which remain relatively understudied. This study aims to better understand the pre-eruptive magma reservoir conditions and volatile storage capacities of intermediate alkaline systems, using the 1257 Samalas eruption as a case study. Systematic partial-equilibrium experiments were run to constrain potential magma reservoir conditions (25–200 MPa and 850–1000°C) by examining changes in the chemistry and textures of experimental glass and mineral products. Natural trachydacite pumice from the 1257 Samalas eruption was used as the experimental charge for a series of water-saturated experiments run in cold-seal pressure vessels, buffered at an oxygen fugacity ƒO2 of NNO/NNO + 1 log units. Assessing the match between natural and experimental glass compositions and mineral phases and textures reveals that pre-eruptive magma reservoir conditions were between 875°C and 930°C and ca. 100–150 MPa (4.5 ± 1km depth). Breakdown of experimental amphibole at pressures below 75 MPa, and plagioclase instability at 950°C/100 MPa, provide the strongest constraints on phase stabilities that are consistent with the magma storage region. In the observed temperature and pressure range, the natural compositions of plagioclase, amphibole and orthopyroxene are replicated in experimentally precipitated rims. Clinopyroxene and high anorthite plagioclase (An&amp;gt;64) in the natural mineral assemblage could not be replicated in the experiments, implying that these compositions most likely did not grow in the shallow pre-eruptive reservoir of Mt Samalas. The pre-eruptive storage depths of trachydacite magma are significantly shallower than the postulated magma storage at the currently active basaltic-andesite magmatic system at Rinjani, and thus monitoring magma storage depth may be a useful indicator of changing magma composition in the future. Our findings show that highly explosive VEI 7 eruptions of intermediate alkaline magma can be fed from a relatively limited range of storage pressures (100–150 MPa), suggesting accumulation of magma in one place, rather than the rapid extraction of magma from a vertically extensive, transcrustal magma system.

Redox chemistry of plutonium and plutonium surrogates in vitrified nuclear wastes

AbstractLanthanide 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.

Broadband NIR-emitting Te cluster-doped glass for smart light source towards night-vision and NIR spectroscopy applications

Broadband near-infrared (NIR)-emitting materials are crucial components of the next generation of smart NIR light sources based on blue light-emitting diodes (LEDs). Here, we report a Te cluster-doped borate glass, which exhibits ultra-broadband emission around 980 nm with a full-width at half-maximum (FWHM) of 306 nm under blue light excitation. We propose adjustments of glass chemistry and processing condition as a means for topo-chemical tailoring of the NIR photoemission characteristics in such materials. Through implementing strongly reducing conditions during glass melting, Te clusters with broad NIR photoluminescence can be generated and stabilized once the melt is vitrified to the glassy state. Tunability of the NIR emission peak over the wavelength range of 904 to 1026 nm is possible in this way, allowing for fine adjustments of spectral properties relative to the stretching vibrations of common chemical bonds, for example, in water, proteins, and fats. This potentially enables high sensitivity in NIR spectroscopy. We further demonstrate potential application of glass-converted LEDs in night vision.

Olivine and glass chemistry record cycles of plumbing system recovery after summit collapse events at Kīlauea Volcano, Hawai‘i

The eruptive activity of Kīlauea Volcano (Hawai‘i) in the past 2500 years has alternated between centuries-long periods dominated either by explosive or effusive eruptions. The onset of explosive periods appears to be marked by caldera collapse events at the volcano's summit accompanied by draining of Kīlauea's magmatic plumbing system. Here we leverage >1800 olivine forsterite (Fo) contents, >900 glass MgO contents, and estimated magma supply rates from the past six centuries to describe the relationships between summit collapse and the composition of erupted material. On a first order basis, the major element chemistry of the centuries-long eruptive periods largely originates from fundamental differences between fractional crystallization of shallowly stored magmas during high-supply effusive-dominated periods versus little evolution of mafic recharge magmas during low-supply explosive-dominated periods. The modern effusive period (1820s-present) is dominated by relatively evolved olivine forsterite contents (Fo81–82) for Kīlauea, which is interpreted to reflect a buffered crustal reservoir system in which shallow storage and fractional crystallization control the composition of magmas. In contrast, olivine crystals from the explosive Keanakāko‘i Tephra (1500 - early 1800s C.E.) are dominated by higher olivine forsterite contents (Fo89) which are interpreted to reflect more primitive compositions, are correlated with glass MgO compositions extending to high values (e.g.,11.0 wt%), and show signs of magma mixing (zoned olivine, bimodal Fo populations). These signatures reflect a disrupted reservoir system in which high-MgO recharge melts mix with melts left over from draining of the shallow (<5 km) magma plumbing.Superimposed on these explosive-effusive periods are three decades- to centuries long periods of progressively evolving olivine and glass compositions. Eruptions that occur after caldera collapse in ~1500C.E. and smaller scale crater collapse events in 1790 (inferred) and 1924 have heterogeneous olivine populations dominated by ≥Fo88 and typically high MgO glasses. These compositions reflect inefficient mixing of stored and primitive recharge magmas after the disruption of the shallow plumbing system. After these collapses, olivine Fo and glass MgO subsequently evolve to <Fo82 and <7.0 wt% compositions, reflecting the recovery of the crustal plumbing system to an end-member system state characterized by efficient mixing of recharge and stored magmas that serve to buffer the shallow magma reservoirs. These evolved signatures suggest that a mature and buffered reservoir system may be a key condition for significant disruptions of volcanic plumbing systems. Plumbing system recovery is slower following large-scale caldera collapse (hundreds of years) compared to recovery following smaller crater collapse (tens of years), which may be modulated by differences in magma supply rates. Following the 2018 crater collapse olivine populations have high-Fo but glasses are low MgO, suggesting that this collapse might have disrupted shallow magma pathways but not strongly impacted the reservoir(s). Ultimately, olivine and glass major element chemistry record the impacts of caldera and smaller but significant summit crater collapse events at Kīlauea and could be used to provide a framework for better characterizing long-term volcano evolution in Hawai‘i and shield volcanoes elsewhere.

Potential correlation of the hardness of CaO–Al2O3–SiO2 glasses with melting behavior

AbstractIt is proposed that the hardness of aluminosilicate glasses correlates with the melting temperature as predicted by the phase diagram. To evaluate this hypothesis, a broad range of CaO–Al2O3–SiO2 compositions was evaluated, verifying the glass formation region, and allowing for a systematic comparison of Vickers indentation hardness with melting temperature. Candidate glass forming compositions were restricted to the normal glass formation region (SiO2 &gt; CaO) and ranging from SiO2:CaO ratios of 1:1 to 9:1 and Al2O3:CaO ratios ranging from .2:1.0 to 1.3:1.0. Glass forming compositions were X‐ray amorphous. The correlation of hardness was nonlinear but showed reasonable correlation with the melting behavior, with the lowest hardness glass obtained for the eutectic composition. The maximum hardness was obtained in the narrow glass chemistry range of 1.0:1.0:1.5 to 1.0:1.2:1.5 (CaO:Al2O3:SiO2) in the vicinity of anorthite (CaO·Al2O3·2SiO2).

Havre 2012 pink pumice is evidence of a short-lived, deep-sea, magnetite nanolite-driven explosive eruption

The Havre 2012 deep-sea rhyolite eruption went unobserved and was initially recognised from a massive pumice raft at the sea surface. Havre pumices are predominantly white or grey, however pink pumice is common in the raft. In subaerial explosive eruptions, pink pumice is understood to result from high-temperature atmospheric iron-oxidation. The presence of pink pumice questions the effusive eruption model for the Havre raft. Here we report results from X-ray Absorption Near Edge Structure spectroscopy, magnetic measurements, TEM imaging and glass chemistry that collectively show the colour results from increasing amounts of magnetite nanolites in the raft pumice glass oxidizing to hematite. This suggests a short-lived but powerful explosive eruption phase penetrated the water column allowing hot pyroclasts to oxidise in air. Our results therefore challenge the known depth limits for explosive eruptions in the marine realm and suggest pink pumice can be an indicator of magnetite nanolite-driven explosive eruptions.

Developing and expanding the Late-Glacial and Holocene tephrochronological framework of France: A new contribution from the Chaîne des Puys volcanic field in the Massif Central

The aim of this paper is to highlight new occurrences of tephra and cryptotephra layers from three peatbogs located southeastern from the French Massif Central in France. These tephras were evidenced using magnetic susceptibility logging, scanner imagery and chemical analyses by X-Ray Fluorescence, and characterized by their glass chemistry. Originated from the Chaîne des Puys volcanic field, these six new tephras allow for the definition of a more detailed regional tephrostratigraphic framework. Most of these tephras were deposited between ca. 13,500 and 9500 yrs cal. BP, and the last one was deposited between 6400 and 5920 yrs cal. BP. Some tephras of this framework were previously described in the Jura Mountains, the Northern Alps and the Western Swiss Plateau, and allow its correlation to the Northern European context established by previous studies.

Contrast of color-changing metallic glasses reveals the glass properties beneath the surface

Recently, color-changing glasses have been developed from a series of Ce-based metallic alloys. The functionality originates from fast and spontaneous surface oxidation. In most cases, single-color glasses have been obtained, but in a few cases, multicolor glasses that have spatially-dependent color contrast have been found. The natural color contrast mostly results from the interference effects on the oxide layer. The present work investigates factors that influence and control the variable oxidation rate observed at different locations on the surface, and what manufacturing steps and processing history lead to the rate variation. It is found that cooling rate, residual strain, and precipitation in melt-spun ribbons are the effects controlling the oxidation rate giving the enhanced color contrast. Therefore, the final surface color contrast reflects the non-uniform distribution of enthalpy (glassy state), microstructure, and chemistry of the metallic glass beneath the surface. The inspection of natural color contrast also represents technologically useful method for early surface flaw detection in color-changing metallic glasses.

Biomass ashes as potential raw materials for mineral wool manufacture: initial studies of glass structure and chemistry

The energy intensive and CO2-generating nature of commercial mineral wool and glass production necessitates advances and changes in materials and processes. The derivation of raw materials from waste products arising from biomass energy generation offers the possibility of a two-fold environmental benefit: partial replacement of carbonate raw minerals in production, leading to lower CO2 release during melting; and the utilisation and valorisation of byproducts which may otherwise be sent to landfill. Glass samples with a basaltic mineral wool composition were produced with additions to the raw materials of 0, 1, 5 and 10 wt% of a fly ash and a bottom ash arising from biomass combustion. The resulting glasses were analysed by x-ray fluorescence, x-ray diffraction, dilatometry, 57Fe Mössbauer and Raman spectroscopies, and their densities, molar volumes and viscosity–temperature profiles were calculated and compared against benchmark glass samples. All biomass ash-containing glasses were closely similar in both composition and properties to the benchmark glass, with up to 10 wt% ash additions to the raw materials. In addition, the use of the biomass fly ash led to a reduction in batch CO2 content estimated to be 1·5 kg CO2 per tonne of batch for each 1 wt% addition. These initial results provide evidence supporting the further development of these ash materials as potential value-added raw materials for mineral wool manufacture.

Grasping the Lithium hype: Insights into modern dental Lithium Silicate glass-ceramics

ObjectivesLithium-based glass-ceramics are currently dominating the landscape of dental restorative ceramic materials, with new products taking the market by storm in the last years. Though, the difference among all these new and old products is not readily accessible for the practitioner, who faces the dilemma of reaching a blind choice or trusting manufacturers’ marketing brochures. To add confusion, new compositions tend to wear material terminologies inherited from vanguard dental lithium disilicates, disregarding accuracy. Here we aim to characterize such materials for their microstructure, crystalline fraction, glass chemistry and mechanical properties. MethodsEleven commercial dental lithium-based glass ceramics were evaluated: IPS e.max® CAD, IPS e.max® Press, Celtra® Duo, Suprinity® PC, Initial™ LiSi Press, Initial™ LiSi Block, Amber® Mill, Amber® Press, N!CE®, Obsidian® and CEREC Tessera™. The chemical composition of their base glasses was measured by X-Ray Fluorescence Spectroscopy (XRF) and Inductive Coupled Plasma Optical Emission Spectroscopy (ICP-OES), as well as the composition of their residual glass by subtracting the oxides bound in the crystallized fraction, characterized by X-Ray Diffraction (XRD) and Rietveld refinement, and quantified accurately using the G-factor method (QXRD). The crystallization behavior is revealed by differential scanning calorimetry (DSC) curves. Elastic constants are provided from Resonant Ultrasound Spectroscopy (RUS) and the fracture toughness measured by the Ball-on-Three-Balls method (B3B- K Ic). The microstructure is revealed by field-emission scanning electron microscopy (FE-SEM). ResultsThe base glasses showed a wide range of SiO2 /Li2O ratios, from 1.5 to 3.0, with the degree of depolymerization dropping from ½ to 2/3 of the initial connectivity. Materials contained Li2SiO3+Li3PO4, Li2SiO3+Li3PO4+Li2Si2O5, Li2Si2O5+Li3PO4+ Cristobalite and/or Quartz and Li2Si2O5+Li3 PO4+LiAlSi2O6, in crystallinity degrees from 45 to 80 vol%. Crystalline phases could be traced to their crystallization peaks on the DSC curves. Pressable materials and IPS e.max® CAD were the only material showing micrometric phases, with N!CE® and Initial™ LiSi Block showing solely nanometric crystals, with the rest presenting a mixture of submicrometric and nanometric particles. Fracture toughness from 1.45 to 2.30 MPa√m were measured, with the linear correlation to crystalline fraction breaking down for submicrometric and nanometric crystal phases. SignificanceDental lithium-based silicate glass-ceramics cannot be all put in the same bag, as differences exist in chemical composition, microstructure, crystallinity and mechanical properties. Pressable materials still perform better mechanically than CAM/CAM blocks, which loose resistance to fracture when crystal phases enter the submicrometric and nanometric range

Structural dependence of crystallization in phosphorus‐containing sodium aluminoborosilicate glasses

AbstractThe article reports on the structural dependence of crystallization in Na2O–Al2O3–B2O3–P2O5–SiO2‐based glasses over a broad compositional space. The structure of melt‐quenched glasses has been investigated using 11B, 27Al, 29Si, and 31P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, while the crystallization behavior has been followed using X‐ray diffraction and scanning electron microscopy combined with energy dispersive spectroscopy. In general, the integration of phosphate into the sodium aluminoborosilicate network is mainly accomplished via the formation of Al–O–P and B–O–P linkages with the possibility of formation of Si–O–P linkages playing only a minor role. In terms of crystallization, at low concentrations (≤5 mol.%), P2O5 promotes the crystallization of nepheline (NaAlSiO4), while at higher concentrations (≥10 mol.%), it tends to suppress (completely or incompletely depending on the glass chemistry) the crystallization in glasses. When correlating the structure of glasses with their crystallization behavior, the MAS NMR results highlight the importance of the substitution/replacement of Si–O–Al linkages by Al–O–P, Si–O–B, and B–O–P linkages in the suppression of nepheline crystallization in glasses. The results have been discussed in the context of (1) the problem of nepheline crystallization in Hanford high‐level waste glasses and (2) designing vitreous waste forms for the immobilization of phosphate‐rich dehalogenated Echem salt waste.

Establishing Genetic Relationships between the Takidani Pluton and Two Large Silicic Eruptions in the Northern Japan Alps

AbstractThe Takidani pluton (1·1–1·6 Ma) represents a shallow magmatic reservoir at the base of an exhumed caldera floor. The deposits of two large caldera-forming eruptions, the Nyukawa Pyroclastic Flow Deposit (1·76 Ma; crystal-rich dacite) and the Chayano Tuff and Ebisutoge Pyroclastic Deposits (1·75 Ma; a sequence of crystal-poor rhyolite), are distributed concentrically around the pluton. We use major and trace element chemistry of whole-rock, glass and minerals to show that (1) the crystal-rich dacite (&amp;gt;400 km3 DRE; dense rock equivalent) is the erupted portion of a shallow mush zone constituting the Takidani pluton and (2) the crystal-poor rhyolite (&amp;gt;100 km3 DRE) was extracted from a deeper part of this vertically extended magmatic plumbing system. Whole-rock geochemistry indicates that the Nyukawa and Takidani compositions were produced dominantly through crystal fractionation of amphibole, pyroxene and plagioclase in the mid to lower crust and subsequently emplaced in the upper crust prior to eruption and solidification, respectively. The crystal-poor Chayano–Ebisutoge rhyolite (&amp;gt;100 km3 DRE) is compositionally distinct from the Nyukawa and Takidani magmas and its generation is associated with a substantial contribution of crustal melts. However, plagioclase and orthopyroxene textures and chemistry provide strong evidence that the ascending rhyolite percolated through the upper Takidani–Nyukawa mush zone prior to eruption. Overgrowth of ‘rhyolitic plagioclase’ on ‘xenocrystic dacitic plagioclase’ typical of the Takidani–Nyukawa magmas indicates that the extraction and accumulation of the rhyolitic melts could have occurred in less than 10 kyr (i.e. the time between eruptions) prior to eruption, providing maximum timescales for pre-eruption storage. Overall, our findings show a progressive growth and thermal maturation of a vertically extended magmatic plumbing system over hundreds of thousands of years and imply that large volcanic eruptions can occur in relatively short succession without dramatic changes in the plumbing system, thus complicating the identification of signs of an impending large eruption.