Vapor-deposited organic glasses exhibit enhanced stability against photodegradation
This work shows the first demonstration that amorphous packing arrangements can significantly modulate photodegradation in organic glasses.
Chemistry↗
SEARCH · Engineering Papers
Results for “Glass”
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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Improved neutron-gamma discrimination for a {sup 6}Li-glass neutron detector using digital signal analysis methods
A {sup 6}Li-glass scintillator (GS20) based neutron Anger camera was developed for time-of-flight single-crystal diffraction instruments at Spallation Neutron Source. Traditional Pulse-Height Analysis (PHA) for Neutron-Gamma Discrimination (NGD) resulted in the neutron-gamma efficiency ratio (defined as NGD ratio) on the order of 10{sup 4}. The NGD ratios of Anger cameras need to be improved for broader applications including neutron reflectometers. For this purpose, six digital signal analysis methods of individual waveforms acquired from photomultiplier tubes were proposed using (i) charge integration, (ii) pulse-amplitude histograms, (iii) power spectrum analysis combined with the maximum pulse-amplitude, (iv) two event parameters (a{sub 1}, b{sub 0}) obtained from a Wiener filter, (v) an effective amplitude (m) obtained from an adaptive least-mean-square filter, and (vi) a cross-correlation coefficient between individual and reference waveforms. The NGD ratios are about 70 times those from the traditional PHA method. Our results indicate the NGD capabilities of neutron Anger cameras based on GS20 scintillators can be significantly improved with digital signal analysis methods.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Numerical study of the temperature dependence of the NMR relaxation rate across the superfluid–Bose glass transition in one dimension
Here, we study the nuclear magnetic resonance (NMR) spin-lattice relaxation rate 1/ T 1 1 in random one-dimensional spin chains as a function of the temperature and disorder strength. In the zero temperature limit, the system displays a disorder-induced quantum phase transition between a critical Tomonaga-Luttinger liquid (TLL) phase and a localized Bose glass phase. The 1/ T 1 is investigated across this transition using large-scale simulations based on matrix product state techniques. We find that this quantity can detect the transition and probe the value of the dimensionless TLL parameter K . We also compute the NMR relaxation rate distributions for each temperature and disorder strength considered. In particular, we discuss the applicability of the stretched exponential fit to the return-to-equilibrium function to extract the 1/ T 1 experimentally. The results presented here should provide valuable insights in regards of future NMR experiments in realistic disordered spin compounds.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
High Chrome Refractory Characterization: Part II . Accumulation of Spinel Corrosion Deposits in Radioactive Waste Glass Melters
High Cr 2 O 3 containing Monofrax ™ K‐3 is a robust refractory that is used in radioactive waste glass melters worldwide. Monofrax ™ K‐3 contains highly reduced phases. Conversely, many of the radioactive feeds being processed are highly oxidizing. The K‐3 refractory corrosion rates in oxidizing (high nitrate) feeds were ~1.8–2.8 times higher than the rates determined using reducing feeds. The corrosion product formed is a mixture of spinel and glass (slag) that can accumulate on the melter floor. A methodology to calculate the depth of slag deposits from refractory corrosion is presented and verified with slag measurements from the Defense Waste Processing Facility ( DWPF ) melter after it had processed oxidized feeds for 1.75 years. The calculations show that had the facility continued to process oxidized feeds the melter lifetime (based on when the deposits could have reached and blocked the pour spout riser) would have been ~4.5 years. The DWPF changed to a reducing flow sheet after ~3 years of operation. The lifetimes of Melter #1 and Melter #2, assuming a failure due to pour spout blockage, are calculated as 7.7–12 years based on corrosion rates measured with reducing feeds. Lifetimes of 9 and >11 years have actually been achieved.
Jantzen, Carol M.↗
Signatures of the Martian regolith components entrained in some impact-melt glasses in shergottites
Abstract not provided
Rao, M. N.↗
Comparison of HLW Glass Melting Rate Between Frit and Glass Forming Chemicals Using X-Ray Computed Tomography
Efforts are being made to increase the loading of Hanford tank wastes in glass while meeting melter lifetime expectancies, as well as requirements for processing, regulatory compliance, and product quality. To achieve these goals, the Department of Energy – Office of River Protection (DOE-ORP) has requested that the Savannah River National Laboratory (SRNL) support the advancement of glass formulations and process control strategies in various key technical areas, which include melting rate studies. Numerous parameters influence cold cap melting and it is important to identify laboratory test methods to discern changes in melting rate. One of the primary screening tools being used at SRNL for melting rate comparisons is the dry-fed melt rate furnace (MRF). The MRF has been very effective in ranking relative melting rates of candidate frits for the Defense Waste Processing Facility (DWPF) on the laboratory-scale, which has successfully translated to facility operations.
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
M-Area Mixed Waste Glasses: II: Durability and Viscosity Testing of High Aluminum and Uranium Containing Borosilicate Waste Glasses
Radioactive waste sludges that were high in A l2 O 3 (14.17 to 29.02 wt%) and U 3 O 8 (2.93 to 5.66 wt%) while being simultaneously low in Fe 2 O 3 (1.26 to 2.01 wt%) were vitrified into borosilicate glass in the Savannah River Site’s (SRS) M-Area. The overall Na 2 O concentrations of borosilicate and soda-lime-silica (SLS) glasses studied at the Savannah River National Laboratory (then the Savannah River Technology Center) prior to startup of the M-Area melter ranged from 6.80 to 27.09 wt%, while the B 2 O 3 concentrations ranged from 0.04 to 32.62 wt%.
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
Final report: Understanding influence of thermal history and glass chemistry on kinetics of phase separation and crystallization in borosilicate glass-ceramic waste forms for aqueous reprocessed high level waste
This report provides an overview of the research activities conducted over the three-year period, October 1, 2015 to September 30, 2018. The project consisted of the US DOE component and a parallel project funded by the UK’s EPSRC. The US project is reported here, with some overview of the UK project results. The project was designed to be highly collaborative, including work in the US by Washington State University and Rutgers University, and in the UK by the University of Sheffield and the University of Warwick. Pacific Northwest National Laboratory supported the US project with some synthesis and some characterization. The overall program had two aims: (Aim 1) Understand fundamental mechanisms of the phase transitions leading to the conversion of melt to multiphase glass-ceramic as a function of composition and cooling rate; (Aim 2) Understand influence of glass chemistry on kinetics of phase separation and crystallization. This report includes the summary of the project objectives, approaches, results and deliverables.
36 MATERIALS SCIENCE↗
Fluidization of Group A Glass Particles: Experiments and Preliminary Validation
This work is aimed at providing reliable high-quality data from fluidization experiments. Geldart Group A glass beads are used as bed material. The fluidizing medium is air at atmospheric pressure which enters the system at 40% relative humidity. The air inlet velocity is varied over a broad range from 2 U mf to 26 U mf , where the minimum fluidization velocity, U mf , is 0.608 cm/s. There is not a significant change in the mean values of differential pressure; however, there are noticeable trends in their standard deviation values. Preliminary validation studies are performed using the open-source software Multiphase Flow with Interphase eXchanges (MFiX) developed by the National Energy Technology Laboratory (NETL). The results from Eulerian-Eulerian (MFiX-TFM, two-fluid model) and Eulerian-Lagrangian (MFiX-PIC, particle-in-cell) formulations are compared. The work presented in this report highlights the applicability of MFiX-PIC for large-scale applications, and reveals that PIC simulation offers a suitable alternative to TFM simulation when effects due to multiple components or polydispersity are significant. PIC modeling provides a readily extendible framework for such systems. However, PIC models do rely on an empirical closure for inter-particle stress. Some solution discrepancies were evident in MFiX-PIC predictions which require further analysis. As such, the study underlines the need for a systematic approach to quantify the sources of numerical uncertainty within the PIC model. However, even with known empiricism, MFiX-PIC has demonstrated considerable potential in analyzing gas-solid systems. The results obtained are encouraging and warrant further investigation to improve the predictive capability of MFiX-PIC.
36 MATERIALS SCIENCE↗
Ages of Darwin glass, Macedon glass, and Far Eastern tektites
Age determination of Darwin glass, Macedon glass, and Far Eastern tektites
Fleischer, R. L.↗
Glass matrix composites. I - Graphite fiber reinforced glass
An experimental program is described in which graphite fibers of Hercules HMS and HTS, Thornel 300, and Celanese DG-12 were used to reinforce, both uniaxially and biaxially, borosilicate pyrex glass. Composite flexural strength distribution, strength as a function of test temperature, fracture toughness and oxidative stability were determined and shown to be primarily a function of fiber type and the quality of fiber-matrix bond formed during composite fabrication. It is demonstrated that the graphite fiber reinforced glass system offers unique possibilities as a high performance structural material.
Prewo, K. M.↗
Fiber reinforced glasses and glass-ceramics for high performance applications
The development of fiber reinforced glass and glass-ceramic matrix composites is described. The general concepts involved in composite fabrication and resultant composite properties are given for a broad range of fiber and matrix combinations. It is shown that composite materials can be tailored to achieve high levels of toughness, strength, and elastic stiffness, as well as wear resistance and dimensional stability.
Prewo, K. M.↗
Apollo 15 yellow-brown volcanic glass - Chemistry and petrogenetic relations to green volcanic glass and olivine-normative mare basalts
Electron microprobe and INAA were used to analyze forty spherules of Apollo 15 yellow-brown glass for major and trace elements. The glass is one of twenty-five high-Mg primary magmas emplaced on the lunar surface in pyroclastic eruptions. The abundances show that the magma was produced by partial melting of differentiated cumulates in the lunar mantle. Models to explain the possible source-regions of several Apollo 15 and Apollo 12 low-Ti mare magmas are presented.
Hughes, S. S.↗
Leaching behavior of microtektite glass compositions in sea water and the effect of precipitation on glass leaching
The present study attempts to account for the slow corrosion rates of microtektite glass in nature by comparing the leach rates of synthetic microtektite glass samples in deionized water and in sea-water, respectively. In order to obtain systematic data about leachant composition effects, leach tests were also carried out with synthetic leachant compositions enriched with respect to silica or depleted with respect to certain major components of sea-water (Mg, Ca).
Source record↗
Anomalous structural recovery in the near glass transition range in a polymer glass: Data revisited in light of temperature variability in vacuum oven‐based experiments*
Abstract There is considerable interest in data reported by Cangialosi et al. [Cangialosi, D., Boucher, V. M., Alegría, A., & Colmenero, J. (2013). Physical Review Letters , 111 (9), 095701] that purportedly showed unusual irregular responses in the isothermal structural recovery behavior of glasses because the observation challenges the general view of the dynamics being smooth functions of time as observed in extensive dilatometric experiments by Kovacs [Kovacs, A. J. (1964). In Fortschritte der Hochpolymeren‐Forschung , 3 , 394–507. Springer, Berlin, Heidelberg.] in the 1960s. The reported data show an apparent two mechanism structural (enthalpy) recovery at aging temperatures ranging from 6 to 17 K below which is also controversial as it could not be reproduced in work from Koh and Simon [Koh, Y. P., & Simon, S. L. (2013). Macromolecules , 46(14), 5815–5821.] where a second plateau observed in the enthalpy loss curve was not reproduced in nearly 1‐year‐long experiments at 15 K below . Therefore, it is important to determine what might be possible reasons for the apparent non‐smooth relaxations. Here, we examine the possibility that the poor temperature control of a typical vacuum oven could explain the anomalous results. We used the Tool–Narayanaswamy–Moynihan (TNM) model of structural recovery to calculate the effect of typical vacuum oven temperature variation on the structural recovery of polystyrene and find that we can reproduce the reported experimental results. The issue of temperature control using a vacuum oven is discussed, and data from thermocouple measurements of temperature at various locations inside a vacuum oven are shown.
36 MATERIALS SCIENCE↗
Evolution of residual stress, free volume, and hardness in the laser shock peened Ti-based metallic glass
Laser shock peening (LSP) with different cycles was performed on the Ti-based bulk metallic glasses (BMGs). The sub-surface residual stress of the LSPed specimens was measured by high-energy X-ray diffraction (HEXRD) and the near-surface residual stress was measured by scanning electron microscope/focused ion beam (SEM/FIB) instrument. The sub-surface residual stress in the LSP impact direction (about-170MPa) is much lower than that perpendicular to the impact direction (about -350 MPa), exhibiting anisotropy. The depth of the compressive stress zone increases from 400 mu m to 500 mu m with increasing LSP cycles. The highest near-surface residual stress is about -750 MPa. LSP caused the free volume to increase and the maximum increase appeared after the first LSP process. Compared with the hardness (567 +/- 7 HV) of the as-cast BMG, the hardness (590 +/- 9 HV) on the shocked surface shows a hardening effect due to the hardening mechanism of compressive residual stress; and the hardness (420 +/- 9 HV) on the longitudinal section shows a softening effect due to the softening mechanism of free volume.
bulk metallic glasses↗
Pressure-induced densification in GeO{sub 2} glass: A transmission x-ray microscopy study
Nanoscale transmission x-ray microscopy measurements have been performed to determine the effect of pressure (P) on the volume (V) change in GeO{sub 2} glass up to 38.5 GPa. The P-V data show a continuous increase upon compression, indicating that the density-driven structural transformation is a gradual process. Over the pressure range studied, a transition is observed at approximately 10–13 GPa, where the material displays distinct compression behaviors. The pressure-induced densification that involves the coordination number change has been discussed. Using this newly developed high-pressure imaging technique with tens of nanometer resolution, we have provided a direct and unequivocal way for measuring density of amorphous materials to much higher pressures with accuracy rivaling x-ray diffraction of crystalline solids.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗