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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Reaction cured glass and glass coatings

The invention relates to reaction cured glass and glass coatings prepared by reacting a compound selected from the group consisting of silicon tetraboride, silicon hexaboride, other boron silicides, boron and mixtures with a reactive glass frit composed of a porous high silica borosilicate glass and boron oxide. The glassy composites of the present invention are useful as coatings on low density fibrous porous silica insulations used as heat shields and for articles such as reaction vessels that are subjected to high temperatures with rapid heating and cooling and that require resistance to temperature and repeated thermal shock at temperatures up to about 1482C (2700PF).

Goldstein, H. E.↗
NASA NTRS1986

Are gel-derived glasses different from ordinary glasses?

A review is presented of some of the previously reported differences and similarities between comparable gel glasses (and gels) and ordinary glasses. In this regard, considerations are made with respect to such factors as structure, physical and thermal properties, and phase transformation behavior. A variety of silicate glass compositions are used for illustrative purposes. The discussion is roughly divided into two sections: low and high temperature behavior. At low temperatures one anticipates that differences between gel and conventional glasses will exist, but such dissimilarities are not expected to persist to high temperatures. However, experimental evidence is presented which indicates the perpetuation of such differences to very high temperatures. A partial resolution for this anomalous behavior is offered.

Weinberg, M. C.↗
NASA NTRS1991

Glass formation and crystallization in high-temperature glass-ceramics and Si3N4

The softening of glassy grain boundaries in ceramic matrix composites and Si3N4 at high temperatures reduces mechanical strength and the upper-use temperature. By crystallizing this glass to a more refractory crystalline phase, a material which performs at higher temperatures may result. Three systems were examined: a cordierite composition with ZrO2 as a nucleating agent; celsian compositions; and yttrium silicate glasses both in bulk and intergranular in Si3N4. For the cordierite compositions, a series of metastable phases was obtained. The crystallization of these compositions was summarized in terms of metastable ternary isothermal sections. Zircon formed at the expense of ZrO2 and spinel. In SiC composites, the transformations were slower. In celsian, two polymorphs were crystallized. One phase, hexacelsian, which always crystallized, even when metastable, had an undesirable volume change. The other phase, celsian, was very difficult to crystallize. In yttrium silicate bulk glasses, similar in composition to the intergranular glass in Si3N4, a number of polymorphs of Y2Si2O7 were crystallized. The conditions under which these polymorphs formed are compared with crystallization in Si3N4.

Drummond, Charles H., III↗
NASA NTRS1992

Elastic modulus measurements of LDEF glasses and glass-ceramics using a speckle technique

Elastic moduli of five glass types and the glass-ceramic Zerodur, exposed to a near-earth orbit environment on the Long Duration Exposure Facility (LDEF), were compared to that of unexposed samples. A double exposure speckle photography technique utilizing 633 nm laser light was used in the production of the speckle pattern. Subsequent illumination of a double exposed negative using the same wavelength radiation produces Young's fringes from which the in-plane displacements are measured. Stresses imposed by compressive loading produced measurable strains in the glasses and glass-ceramic.

Wiedlocher, D. E.↗
DOE OSTI2023

Potential induced degradation in c-Si glass-glass modules after extended damp heat stress

Traditional Glass-Backsheet (GB) photovoltaic (PV) modules have been the industry standard for a long time, but the Glass-Glass (GG) modules are quickly rising in popularity. PV modules installed in hot-humid climates with high string voltages can undergo potential induced degradation (PID). So far, to the best of our knowledge, only fresh modules with strong interfacial adhesion have been investigated for PID. However, in reality, the PV modules have weak interfacial adhesion after a few years of field exposure. Therefore, it is essential to evaluate PV modules with weakened interfaces. In this study, we investigated the PID susceptibility of PV modules with weakened interfaces after subjecting them to 2000 hours of damp heat (DH2000) at 85°C/85% relative humidity (RH) in an accelerated environmental chamber. Fresh GG modules were also stressed for PID to compare with PID degradation of DH-stressed modules. Pre- and post-characterization tests were done before, between, and after each stress method to determine the changes in electrical performance, cell metallization properties, and hotspot properties. It is observed that fresh GG modules showed little/no degradation (less than 1%) in maximum power (Pmax), whereas the GG modules that underwent sequential DH and PID degraded by 11% to 12%. Potential mechanisms for these degradations are also presented. Furthermore, the results presented in this study are critical for the industry, considering that the bifacial modules with GG construction will be dominant in the next 10 years.

14 SOLAR ENERGY↗
DOE OSTI2015

Comparative study of local atomic structures in Zr{sub 2}Cu{sub x}Ni{sub 1−x} (x = 0, 0.5, 1) metallic glasses

Extensive analysis has been performed to understand the key structural motifs accounting for the difference in glass forming ability in the Zr-Cu and Zr-Ni binary alloy systems. Here, the reliable atomic structure models of Zr{sub 2}Cu{sub x}Ni{sub 1−x} (x = 0, 0.5, 1) are constructed using the combination of X-ray diffraction experiments, ab initio molecular dynamics simulations and a constrained reverse Monte Carlo method. We observe a systematic variation of the interatomic distance of different atomic pairs with respect to the alloy composition. The ideal icosahedral content in all samples is limited, despite the high content of five-fold symmetry motifs. We also demonstrate that the population of Z-clusters in Zr{sub 2}Cu glass is much higher than that in the Zr{sub 2}Ni and Zr{sub 2}Cu{sub 0.5}Ni{sub 0.5} samples. And Z12 〈0, 0, 12, 0〉 Voronoi polyhedra clusters prefer to form around Cu atoms, while Ni-centered clusters are more like Z11 〈0, 2, 8, 1〉 clusters, which is less energetically stable compared to Z12 clusters. These two different structural properties may account for the higher glass forming ability of Zr{sub 2}Cu alloy than that of Zr{sub 2}Ni alloy.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Comparative Analysis of Hotspot Stress Endurance in Pristine and Thermal Cycled Prestressed Glass–Glass Photovoltaic Modules

Hotspots pose a significant long-term reliability challenge in photovoltaic (PV) modules that can have a detrimental impact on the efficiency, safety, and financial viability of a PV system. This paper aims to evaluate the endurance of hotspot stress in pristine and prestressed glass–glass (GG) modules. The accelerated prestressing was conducted for 600 thermal cycles (TC600) to represent decades of field exposure. GG modules are quickly becoming an alternative to the traditional glass–backsheet (GB) modules that have been the industry standard. Unlike other conventional studies that subject only pristine modules to hotspot stress, this paper evaluates the performance of an accelerated/simulated field-aged GG module (using TC600) and a pristine GG module. Pre- and post-characterizations were performed before and after each test to determine changes in electrical performance and observe any defects in GG modules. During the hotspot test, an approximately 200 °C maximum cell temperature was observed with a cell shading of 25% (the worst-case shading ratio). After the hotspot test, electroluminescence imaging indicated that most cells in the prestressed GG module exhibited severe damage whereas no significant defects were evident in the pristine GG module where the prestressed GG module degraded 8.2% and the pristine GG module degraded 1.5% in maximum power. These findings are critical for the industry, considering that GG bifacial modules will dominate the market.

14 SOLAR ENERGY↗
DOE OSTI2016

Nanoscale imaging of Li and B in nuclear waste glass, a comparison of ToF-SIMS, NanoSIMS, and APT: Nanoscale imaging of Li and B in nuclear waste glass

It has been very difficult to use popular elemental imaging techniques to image Li and B distribution in glass samples with nanoscale resolution. In this study, atom probe tomography (APT), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and nanoscale secondary ion mass spectrometry (NanoSIMS) were used to image the distribution of Li and B in two representative glass samples. APT can provide three-dimensional Li and B imaging with very high spatial resolution (≤ 2 nm). In addition, absolute quantification of Li and B is possible, though room remains to improve accuracy. However, the major drawbacks of APT include limited field of view (normally ≤ 100 × 100 × 500 nm 3 ) and poor sample compatibility. As a comparison, ToF-SIMS and NanoSIMS are sample-friendly with flexible field of view (up to 500 × 500 μm 2 and image stitching is feasible); however, lateral resolution is limited to only about 100 nm. Therefore, SIMS and APT can be regarded as complementary techniques for nanoscale imaging Li and B in glass and other novel materials.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

Glass formulation and lab-scale testing of glasses designed for in-can Melter and in-container Vitrification of high-assay low-enriched uranium aqueous polishing Raffinate waste

Glasses were designed for processing a nuclear waste from aqueous polishing of high-assay low-enriched uranium using either In-Can Melter (ICM) or GeoMelt® In-Container Vitrification™ (ICV) technologies, which operate at temperatures of T p ≤ 1100 °C and T p ≤ 1450 °C, respectively. Due to the different operating conditions, the melt and glass properties were optimized differently for each technology. Each glass was designed to optimize for maximum waste loading while simultaneously satisfying processing (e.g., crystallization, viscosity, and conductivity) and product quality (e.g., durability, hazard characteristic, and crystal content) constraints. Here, the raffinate waste contains high nitric acid (4 M) and low total solids (9 g·L -1 ) concentrations. Feed preparation processes were tested to facilitate concentration and nitrate destruction/removal while controlling redox of the melter feed. A successful feed process including sugar addition and spray-drying was performed to generate an adequate melter feed for ICV processing.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

Correlation between medium-range order structure and glass-forming ability for Al-based metallic glasses

To clarify the correlation of medium-range order (MRO) structure with glass forming ability (GFA) of Al-based metallic glasses, Al{sub 86}Ni{sub 14-a}Y{sub a} (a = 2∼9 at. %) metallic glasses were analyzed by x-ray diffraction in detail and further verified by synchrotron high-energy x-ray diffraction. The prepeak that reflects the MRO structural evolution was found to be much sensitive to alloy composition. We have proposed an icosahedral supercluster MRO structure model in Al-TM (transition metal)-RE (rare earth metal) system, which consists of 12 RE(TM)-centered clusters on the vertex of icosahedral supercluster, one RE(TM)-centered clusters in the center, and TM(RE) atoms located at RE(TM)-centered cluster tetrahedral interstices in the icosahedral supercluster. It was indicated that the MRO structural stability mainly depends on the interaction of efficient dense packing and electrochemical potential equalization principle. The Al{sub 86}Ni{sub 9}Y(La){sub 5} alloys present good GFA due to the combination of the two structural factors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Striking role of non-bridging oxygen on glass transition temperature of calcium aluminosilicate glass-formers

Molecular dynamics simulations are used to study the structural and dynamic properties of calcium aluminosilicate, (CaO-Al{sub 2}O{sub 3}){sub 1−x}(SiO{sub 2}){sub x}, glass formers along three joins, namely, R = 1, 1.57, and 3, in which the silica content x can vary from 0 to 1. For all compositions, we determined the glass-transition temperature, the abundances of the non-bridging oxygen, triclusters, and AlO{sub 5} structural units, as well as the fragility from the temperature evolution of the α-relaxation times. We clearly evidence the role played by the non-bridging oxygen linked either to Al atoms or Si atoms in the evolution of the glass-transition temperature as well as of the fragility as a function of silica content along the three joins.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Structure and constitution of glass and steel compound in glass-metal composite

The research using methods of optical and scanning electronic microscopy was conducted and it discovered common factors on structures and diffusing zone forming after welding glass C49-1 and steel Ct3sp in technological process of creating new glass-metal composite. Different technological modes of steel surface preliminary oxidation welded with and without glass were investigated. The time of welding was varied from minimum encountering time to the time of stabilizing width of diffusion zone.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Ductility and work hardening in nano-sized metallic glasses

In-situ nano-tensile experiments on 70 nm-diameter free-standing electroplated NiP metallic glass nanostructures reveal tensile true strains of ∼18%, an amount comparable to compositionally identical 100 nm-diameter focused ion beam samples and ∼3 times greater than 100 nm-diameter electroplated samples. Simultaneous in-situ observations and stress-strain data during post-elastic deformation reveal necking and work hardening, features uncharacteristic for metallic glasses. The evolution of free volume within molecular dynamics-simulated samples suggests a free surface-mediated relaxation mechanism in nano-sized metallic glasses.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Analysis of Potential-Induced Degradation in Soda-Lime Glass and Borosilicate-Glass Cu(In,Ga)Se 2 Samples

In this study, potential-induced degradation (PID) is investigated in small-size Cu(In,Ga)Se 2 (CIGS) submodules of individual cells. Samples with conventional soda-lime glass (SLG) and low-alkaline glass (borosilicate glass, BSG) were analyzed applying positive and negative 1000 V bias at 85 degrees C and low relative humidity after a heat-soaking phase. During the heat-soaking phase, BSG samples showed degradation, with variations in their dark current-voltage (I-V) curve parameters compared with the stability of SLG samples. During the PID stress phase, back-grounded SLG samples with -1000 V applied to the cell experienced fast degradation, with complete failure in 25 h, whereas, BSG samples only showed changes because of the dark heat environment. When grounded on their front face, SLG samples remained stable during more than 150 h of PID testing, beginning degradation after longer applications of stress. The analysis of the dark I-V curves of SLG samples through the single-diode model showed that an increase in saturation current J 0 occurs first, attributed to Na + ions migrating into the CdS/ZnO layer; later, a decrease in shunt resistance occurs. Lastly, the application of the model in BSG samples showed an increase in series resistance evaluated at 25 degrees C. When the bias is reversed, SLG samples gradually recover their performance.

14 SOLAR ENERGY↗
DOE OSTI2017

X-ray tomography of feed-to-glass transition of simulated borosilicate waste glasses

The feed composition of a high level nuclear waste (HLW) glass melter affects the overall melting rate by influencing the chemical, thermophysical, and morphological properties of a relatively insulating cold cap layer over the molten phase where the primary feed vitrification reactions occur. Data from X ray computed tomography imaging of melting pellets comprised of a simulated high-aluminum HLW feed heated at a rate of 10°C/min reveal the distribution and morphology of bubbles, collectively known as primary foam, within this layer for various SiO 2 /(Li 2 CO 3 +H 3 BO 3 +Na 2 CO 3 ) mass fractions at temperatures between 600°C and 1040°C. To track melting dynamics, cross-sections obtained through the central profile of the pellet were digitally segmented into primary foam and a condensed phase. Pellet dimensions were extracted using Photoshop CS6 tools while the DREAM.3D software package was used to calculate pellet profile area, average and maximum bubble areas, and two-dimensional void fraction. The measured linear increase in the pellet area expansion rates – and therefore the increase in batch gas evolution rates – with SiO 2 /(Li 2 CO 3 +H 3 BO 3 +Na 2 CO 3 ) mass fraction despite an exponential increase in viscosity of the final waste glass at 1050°C and a lower total amount of gas-evolving species suggest that the retention of primary foam with large average bubble size at higher temperatures results from faster reaction kinetics rather than increased viscosity. However, viscosity does affect the initial foam collapse temperature by supporting the growth of larger bubbles. Because the maximum bubble size is limited by the pellet dimensions, larger scale studies are needed to understand primary foam morphology at high temperatures. This temperature-dependent morphological data can be used in future investigations to synthetically generate cold cap structures for use in models of heat transfer within a HLW glass melter.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Glass Transition Characteristics and Thermodynamic Functions of (1–x)(0.75TeO{sub 2}–0.25WO{sub 3}) + xLa{sub 2}O{sub 3} Glasses

The temperature-dependent heat capacity of three high-purity (1–x)(0.75TeO{sub 2}–0.25WO{sub 3}) + xLa{sub 2}O{sub 3} tellurite glass samples (x = 0.02, 0.04, and 0.06) has been determined by dynamic calorimetry in the range 320–1000 K. The experimental devitrification and heat capacity data have been used to evaluate standard thermodynamic functions: C{sub p}{sup o}(T), enthalpy, entropy, and Gibbs energy in glassy and supercooled liquid states. We have demonstrated model-parameter similarity of properties in a statistical approach and found correlation relationships for parameters as functions of composition, which make it possible to predict the thermodynamic functions of unexplored glasses of this series. We have identified crystallization-resistant compositions of (1–x)(0.75TeO{sub 2}–0.25WO{sub 3}) + xLa{sub 2}O{sub 3} glasses as a basis for the development of optically active elements.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Chemical Composition Analysis and Product Consistency Tests to Support Enhanced Hanford Waste Glass Models: Results for the August and October 2014 LAW Glasses

In this report, the Savannah River National Laboratory provides chemical analyses and Product Consistency Test (PCT) results for several simulated low activity waste (LAW) glasses (designated as the August and October 2014 LAW glasses) fabricated by the Pacific Northwest National Laboratory. The results of these analyses will be used as part of efforts to revise or extend the validation regions of the current Hanford Waste Treatment and Immobilization Plant glass property models to cover a broader span of waste compositions.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗