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At least 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Fluorescent security glass

A tamper-evident glass and methods of using the tamper-evident glass are provided herein. The tamper-evident glass comprising at least a first plurality of tamper-evident elements, which may be unique or near unique to each manufacturing of tam per-evident glass. The initial state of tamper-evident glass and positioning of the plurality of tamper-evident elements may be mapped through digital scanning to create a digital file of the current state of the tamper-evident glass. The tamper-evident glass may be scanned again to create a new digital file for comparison and to determine if a tampering event has occurred. The tamper-evident elements may include any combination of inorganic fluorescent material, crystals grown through nucleation and crystallization, or added colorants.

Grodsky, Rachel Leigh↗
DOE OSTI2026

Rotation of Crystal Seed During Early Stages of Growth Reveals the Anisotropy of Glass Matrix

Glass-ceramics are a highly valuable class of materials that are needed for realizing many high-tech as well as consumer products. They are made by controlling crystallization of glass. Theoretical atomistic insights obtained using molecular dynamics simulations in this work reveal that crystal seeds can spontaneously rotate within glass at high temperatures due to anisotropic forces at the glass-crystal interface. This rotation challenges the long‐held view of glass as isotropic solid, and highlights how atomic‐scale inhomogeneities influence crystal growth and microstructure, hence the physical properties glass‐ceramics.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Behavior of B in passivating gels formed on International Simple Glass in acid and basic pH

International Simple Glass altered for years in silica saturated conditions develops a passivating gel, which retains some mobile elements such as B and Ca in its inner region. It has been suggested that the retention of these elements impacts the dissolution rate of the glass. However, the elements' retention mechanism, speciation, and diffusion properties are still unknown. This study finds that simultaneous presence of B and Ca in the solution can dramatically slow down glass alteration. However, splitting the B and Ca into two different solutions with other glass elements did not give similar protection against glass alteration. These experiments along with other experiments conducted in basic or acid pH, in which isotopically tagged B can diffuse in gels revealed that (i) water diffusion is not dramatically affected by the retention of B and Ca in passivating gels, and (ii) slow diffusion and high retention of B is observed only in gels developed in basic pH during the tracing experiments. Finally, this last mechanism therefore appears as one of the many mechanisms controlling the glass dissolution rate in the residual regime.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Surface modified, collapsible controlled pore glass materials for sequestration and immobilization of trivalent metal ions.

We report a one-pot method for sequestration, containment, and immobilization of lanthanide (Ln) ions from dilute aqueous waste streams. The approach is based on the use of collapsible, surface modified controlled pore glass (CPG) nanomaterials. We present several approaches for a single-step chemical modification of 3-propylaminated CPGs that yield highly efficient Ln-extracting materials with distribution coefficients exceeding 10000 mL/g. The resulting Ln complexes were studied using X-ray absorption, magnetic resonance, and time-resolved luminescence spectroscopies. One of these CPG materials involving an imidodi(methanediphosphate) moiety demonstrated high extraction efficacy, significant ionic radius sensitivity, and exceptional tolerance to masking agents, which is conducive to its use for removal of traces of radionuclide ions from aqueous TALSPEAK raffinate (trivalent actinide-lanthanide separation by phosphorus reagent extraction from aqueous complexes process used in processing of spent nuclear fuel). The glass loaded with the extracted metal ions can be calcined and sintered at 1100 C, yielding fused material that buries Ln ions in the vitreous matrix. This processing temperature is significantly lower than 1700 C that is required for direct vitrification of lanthanide oxides in high-silica glass. X-ray absorption spectroscopy and acid leaching tests indicate that the immobilized ions are isolated and dispersed in the fused glass matrix. Thus, the method integrates Ln ions into the glass network. The resulting glass can be used for temporary storage or as the source of silica for production of borosilicate waste forms that are used for long-term disposal of high level radioactive waste.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

Structure and Chemistry in Halide Lead-Tellurite Glasses

A series of TeO2-PbO glasses were fabricated with increasing fractions of mixed alkali, alkaline earth, and lanthanide chlorides. The glass and crystal structure was studied with Raman spectroscopy, nuclear magnetic resonance (NMR), X-ray diffraction, and electron microscopy. As the chloride fraction increased, the medium-range order in the glass decreased up to a critical point (~14 mass% of mixed chlorides), above which the glasses became phase-separated. Resulting phases are a TeO2/PbO-rich phase and a crystalline phase rich in alkali chlorides. The 125Te NMR indicates, contrary to previous studies, that Te site distribution did not change with increased concentrations of M+, M2+, and M3+ cations, but rather is controlled by the Te/Pb molar ratio. The 207Pb NMR shows that two Pb species exist and their relative concentration changes nearly linearly with addition of the mixed chlorides, indicating that the additives to the TeO2-PbO glass are accommodated by changing the Pb species. The 23Na and 35Cl NMR indicate that Na and Cl are distributed in the single-phase glass phase up to the critical point, and at higher concentrations partition to crystalline phases. Transmission electron microscopy shows that the sample at the critical point contains ~10 nm seed nuclei that increase in size and concentration with exposure to the electron beam.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2024

Unveiling the effect of composition on nuclear waste immobilization glasses’ durability by nonparametric machine learning

Abstract Ensuring the long-term chemical durability of glasses is critical for nuclear waste immobilization operations. Durable glasses usually undergo qualification for disposal based on their response to standardized tests such as the product consistency test or the vapor hydration test (VHT). The VHT uses elevated temperature and water vapor to accelerate glass alteration and the formation of secondary phases. Understanding the relationship between glass composition and VHT response is of fundamental and practical interest. However, this relationship is complex, non-linear, and sometimes fairly variable, posing challenges in identifying the distinct effect of individual oxides on VHT response. Here, we leverage a dataset comprising 654 Hanford low-activity waste (LAW) glasses across a wide compositional envelope and employ various machine learning techniques to explore this relationship. We find that Gaussian process regression (GPR), a nonparametric regression method, yields the highest predictive accuracy. By utilizing the trained model, we discern the influence of each oxide on the glasses’ VHT response. Moreover, we discuss the trade-off between underfitting and overfitting for extrapolating the material performance in the context of sparse and heterogeneous datasets.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Reactive cluster model of metallic glasses

Though discovered more than a half century ago metallic glasses remain a scientific enigma. Unlike crystalline metals, characterized by short, medium, and long-range order, in metallic glasses short and medium-range order persist, though long-range order is absent. This fact has prompted research to develop structural descriptions of metallic glasses. Among these are cluster-based models that attribute amorphous structure to the existence of clusters that are incommensurate with crystalline periodicity. Not addressed, however, are the chemical factors stabilizing these clusters and promoting their interconnections. We have found that glass formers are characterized by a rich cluster chemistry that above the glass transformation temperature promotes exchange as well as static and vibronic sharing of atoms between clusters. The vibronic mechanism induces correlated motions between neighboring clusters and we hypothesize that the distance over which these motions are correlated mediates metallic glass stability and influences critical cooling rates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Thermal and Gamma-ray induced relaxation in As-S glasses: modeling and experiment

Enthalpy relaxation is measured in a series of As-S glasses irradiated with gamma rays and these samples are compared with a set of identical control samples kept in the dark. It is shown that gamma irradiation lifts the kinetic barrier for relaxation at room temperature and speeds up the enthalpy release. The measured values of thermal relaxation in the dark agree closely with modeling results obtained by fitting differential scanning calorimetry curves with the TNM equations. The measured values of activation energy for enthalpy relaxation are also in close agreement with that predicted by the TNM model therefore lending credence to the fitting results. These measurements permit extraction of the effect of gamma irradiation on the glass structure for a series of As-S glasses with increasing structural coordination, and gamma irradiation is shown to reduce the structural relaxation time. It is also shown that lower coordination glasses exhibit greater radiation sensitivity but also greater thermal relaxation due to their lower Tg. On the other end, over-coordinated glasses show lower relaxation and almost no radiation sensitivity. This behavior is similar to the glass response under sub-bandgap light irradiation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Gamma Radiation Effects on Physical, Optical, and Structural Properties of Binary As-S glasses

Gamma radiation induces changes in physical, optical, and structural properties in chalcogenide glasses., Previous research has focused on As{sub 2}S{sub 3} and families of glasses containing Ge. For the first time, we present composition and dose dependent data on the As-S binary glass series. Binary As{sub x}S{sub 100-x} (x = 30, 33, 36, 40, and 42) glasses were irradiated with gamma radiation using a {sup 60}Co source at 2.8 Gy/s to accumulated doses of 1, 2, 3, and 4 MGy. The irradiated samples were characterized at each dose level for density, refractive index, x-ray diffraction, and Raman spectrum. These results are compared to those of as-made and 1 year aged samples. We report an initial increase in density followed by a decrease as a function of dose that contradicts the expected compositional dependence of molar volume of these glasses. This unusual behavior is explained based on microvoid formation and nanoscale phase-separation induced by the irradiation in these glasses. XRD, Raman, and EPR data provide supporting evidence, underscoring the importance of optimally- or overly-constrained structures for stability under aging or irradiation.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Synthesis of Nanoceria with Varied Ratios of Ce3+/Ce4+ Utilizing Soluble Borate Glass

Mixed-valence cerium oxide nanoparticles (nanoceria) have been investigated with pronounced interest due to a wide range of biomedical and industrial applications that arises from its remarkable redox catalytic properties. However, there is no understanding of how to control the formation of these two types of nanoceria to obtain Ce3+/Ce4+ ratios required in various applications. In this work, using a soluble borate glass, nanoceria with specific ratios of Ce3+/Ce4+ are created and extracted via controlled glass-melting parameters. Glass embedded with nanoceria as well as nanoceria extracted from the glass were studied via XANES and fitted with the Multivariate Curve Resolution (MCR) technique to calculate the ratio of Ce3+/Ce4+. Results show that mixed-valence nanoceria with specific ratios are hermetically sealed within the glass for long durations. When the glass dissolves, the mixed-valence nanoceria are released, and the extracted nanoceria have unchanged Ce3+/Ce4+ ratios. Furthermore, TEM investigation on released nanoceria show that the nanoceria consist of several different structures. Although nanocrystal structures of Ce7O12, Ce11O20, and Ce2O3 contribute to the reduced state, a new quasi-stable phase of CeO1.66 has been observed as well.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Glass Formulation for Next Generation Cold Crucible Induction Melter

Transformational melter technologies are being considered to support mission acceleration within the U.S. Department of Energy (DOE) complex. New glass formulations are required to take full advantage of the next generation melters, for example, the cold crucible induction melter (CCIM). The key advantage of CCIM technology over current reference technologies is its capability to provide higher processing temperatures, which can lead to an increased waste throughput rate by achieving higher waste loadings and by increasing the feed processing rate. Various waste compositions within the DOE complex were evaluated to determine their potential for successfully demonstrating the unique advantages of the CCIM technology. Glass formulations that satisfy a set of constraints for product quality and assumed CCIM processing conditions were developed for two Hanford waste streams, AZ-101 high-level waste (HLW) and AN-105 low-activity waste (LAW). Three glasses selected for AZ-101 HLW have waste loadings of 40, 42.5, and 45 wt%. The 45-wt% waste loading corresponds to a 22% increase from 37 wt%, which is the maximum expected waste loading based on the current reference formulation. One glass selected for AN-105 LAW has a waste loading of 31.3 wt% at 24 wt% Na2O in glass, which is a 14% increase from the current reference formulation maximum of 21 wt% Na2O. These four glasses are planned for scaled melter tests for initial demonstration of the CCIM technologies for Hanford wastes.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2012

Changes in the Atomic Structure through Glass Transition Observed by X-Ray Scattering

The glass transition involves a minor change in the internal energy, and yet the physical and mechanical properties of a glass change dramatically. In order to determine the evolution of the atomic structure through the glass transition, we employed in-situ synchrotron X-ray scattering measurements as a function of temperature on a model material: Zr-Cu-Al metallic glass. We found that the thermal expansion at the atomic level is smaller than the macroscopic thermal expansion, and significantly increases above the glass transition temperature. The observed changes in the pair-distribution function (PDF) are explained in terms of the fluctuations in the local atomic volume and their change through the glass transition.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Raman Analysis of Perrhenate and Pertechnetate in Alkali Salts and Borosilicate Glasses

Sodium borosilicate glasses containing various concentrations of rhenium or technetium were fabricated, and their vibrational spectra studied using a Raman microscope. Spectra were interpreted with reference to new high resolution measurements of alkali pertechnetates and perrhenates NaReO4, KReO4, NaTcO4, and KTcO4. At low concentrations of ReO4- or TcO4-, glass spectra show weak peaks superimposed on a dominant spectrum of glass characteristic of silicate and borate network vibrations. At high concentrations, sharp peaks characteristic of crystal field splitting and C4h symmetry dominate the spectra of glasses, indicating alkali nearby tetrahedral Re or Tc. Often peaks indicative of both the K and Na pertechnetates/ perrhenates are evident in the Raman spectrum, with the latter being favored at high additions of the source chemical, since Na is more prevalent in the glass and ion exchange takes place. These results have significance to immobilization of nuclear waste containing radioactive 99Tc in glass for ultimate disposal.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2018

Glass-Fiber Reinforcement as a Means of Recycling Polymers from Post-Consumer Applications

A major barrier to the recycling of post-consumer plastics is the commingled nature of these materials with consequent poor and variable mechanical, thermal and flow properties. Using polymers from end-of-life electronics, this comprehensive study demonstrates that glass-reinforcement is a viable method for reusing post-consumer plastics. In this work, a twin screw extruder was used to incorporate short glass fibers into polycarbonate containing varying amounts of polymeric impurities. The mechanical and melt flow properties of the compounded polycarbonate, having as much as 50% impurity, were studied. It was observed that, in the presence of 15 wt% short glass fibers, the measured mechanical and flow properties of the glass-reinforced material containing 25% impurity in the matrix phase, were indistinguishable from the corresponding properties of the virgin polymer and containing the same amount of glass reinforcement but no impurities. The effectiveness of this approach was confirmed by obtaining similar mechanical property data on a variety of other glass-filled thermoplastics.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Compliant alkali silicate sealing glass for solid oxide fuel cell applications: the effect of protective alumina coating on electrical stability in dual environment

An alkali-containing silicate glass was recently proposed as a potential sealant for solid oxide fuel cells (SOFC). The glass contains appreciable amount of alkalis and retains its glassy microstructure at elevated temperatures over time. It is more compliant as compared to conventional glass-ceramics sealants and could potentially heal cracks during thermal cycling. In previous papers the thermal cycle stability, thermal stability and chemical compatibility were reported with yttria-stabilized zirconia (YSZ) electrolyte and YSZ-coated ferritic stainless steel interconnect. In this paper, we report the electrical stability of the compliant glass with aluminized AISI441 interconnect material under DC load in dual environment at 700-800oC. Apparent electrical resistivity was measured with a 4-point method for the glass sealed between two aluminized AISI441 metal coupons as well as plain AISI441 substrates. The results showed good electrical stability with the aluminized AISI441 substrate, while unstable behavior was observed for un-coated substrates. In addition, interfacial microstructure was examined with scanning electron microscopy and correlated with the measured resistivity results. Overall, the alumina coating demonstrated good chemical stability with the alkali-containing silicate sealing glass under DC loading.

aluminization↗
DOE OSTI2017

Reduced alkali-silica reaction damage in recycled glass mortar samples with supplementary cementitious materials

Recycling waste glass aggregate into concrete can reduce environmental impacts but also may lead to serious alkali silica reaction (ASR) damage. This study aims to characterize ASR damage development in the mortar samples containing reactive glass aggregates and investigate the damage reduction effect of the waste supplementary cementitious materials (SCMs), including recycled glass powders and fly ash. The recycled glass aggregate mortar samples with/without SCMs were prepared in this study. The length change tests were first conducted with the prepared mortar samples based on the ASTM C1260 standard. The results demonstrated the added SCMs can largely decrease early-age ASR expansion rate. The optical microscope and Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectroscopy (EDS) were further conducted to characterize the ASR damage in mortar samples and investigate the damage mitigation mechanism with added SCMs. The combined SEM imaging and chemical analysis indicated added SCMs can decrease both the alkali and calcium content of the generated ASR gel. In addition, the ASR damage development inside mortar samples were monitored with dynamic micron X-ray CT (μCT) over a reaction period of 63 hour at the temperature of 80°C. The scanning patterns demonstrated the ASR damage can be easily developed from the area with initial cracks and sharp corners. In conclusion, the images of glass power and fly ash samples showed significantly reduced ASR damage. This study showed that adding of SCMs can largely reduce ASR deterioration and thus facilitate the recycling glass particles into concrete.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

A comparative study of the effectiveness of empirical potentials for molecular dynamics simulations of borosilicate glasses

Despite their practical importance, atomistic modeling of B 2 O 3 containing glasses have been challenging due to the lack of reliable empirical potentials. Fortunately, a few recent developments have shown promises to simulate these glasses where the boron coordination has complex and non-linear dependence on glass composition. This work aims to provide an evaluation of the effectiveness of three recently developed potentials by a systematic study of a series (~20) of sodium borosilicate glasses with constant K (ratio of [SiO 2 ]/[B 2 O 3 ]) =2 and varying R (ratio of [Na 2 O]/[B 2 O 3 ] ranging from 0.1 to 4) values and several sodium boroaluminosilicate glasses. A comparative assessment was established on the basis of the short- and medium-range structure features, such as boron N 4 values, total correlation functions, bond angle distribution, oxygen speciation, and mechanical properties using experimental or well-established models as criteria. Furthermore, this work provides insights on the choices of empirical potentials for MD simulations of borosilicate glasses and gives directions of future potential development and refining.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

Kinetic model for quartz and spinel dissolution during melting of high-level-waste glass batch

The dissolution of quartz particles and the growth and dissolution of crystalline phases during the conversion of batch to glass potentially affects both the glass melting process and product quality. Crystals of spinel exiting the cold cap to molten glass below can be troublesome during the vitrification of iron-containing high-level wastes. To estimate the distribution of quartz and spinel fractions within the cold cap, we used kinetic models that relate fractions of these phases to temperature and heating rate. Fitting the model equations to data showed that the heating rate, apart from affecting quartz and spinel behavior directly, also affects them indirectly via concurrent processes, such as the formation and motion of bubbles. Because of these indirect effects, it was necessary to allow one kinetic parameter (the pre-exponential factor) to vary with the heating rate. The resulting kinetic equations are sufficiently simple for the detailed modeling of batch-to-glass conversion as it occurs in glass melters. The estimated fractions and sizes of quartz and spinel particles as they leave the cold cap, determined in this study, will provide the source terms needed for modeling the behavior of these solid particles within the flow of molten glass in the melter.

Batch melting, Cold cap, Quartz, Spinel, Waste gla↗