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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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657 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Unusual superparamagnetic behavior in bulk Ba 0.198 La 0.784 Ti 0.096 Fe 0.8 O 3-δ

Here, we report the observation of superparamgnetic behavior induced by the substitution La 3+ by Ba 2+ at A-sites and Fe +3 by Ti 4+ at B-sites. Ba 0.198 La 0.784 Ti 0.096 Fe 0.8 O 3-δ was synthesized via solid state reaction. The Rietveld refinements revealed an orthorhombic (Pbnm). The low-mag STEM results showed that the particles were found to exhibit square like shape and formed in single crystal with high degree of crystallinity. The particle size ranges of 50 300 nm. Element mapping demonstrates a complementary distribution between Ba and La, while homogenous distribution is found for Fe and O. The optical band gap determined from UV-vis analysis is equal to 1.93 eV which is smaller than the reported one for LaFeO 3 and BaTiO 3 . The hysteresis loops at 300 K and 10 K show superparamagnetic behavior, which deviate extremely from the antiferromagnetic nature of LaFeO 3 perovskite. The temperature dependent magnetization demonstrates that the material kept a net magnetization of 12.29 (emu/g) at very low temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Loss characterization of Mo-doped FeNi flake for DC-to-DC converter and MHz frequency applications

Magnetic core materials with low loss, high magnetic induction, large permeability, and high working frequencies above 1 MHz are in high demand in the next generation of miniaturized power electronic devices. Magnetic flake based composite materials have been developed to take advantage of high operating frequency ranges, low eddy current losses, high magnetic induction, and low cost fabrication methods. In this study, Mo-doped FeNi flakes with thicknesses of 0.4 +/- 0.2 mu m to 1.6 +/- 0.5 mu m have been successfully fabricated with high energy ball milling. The lateral size of the flake is around 100 mu m. After being hot-pressed with polymers, all of the samples show initial permeability higher than 40 in the frequency range up to 10 MHz and a loss tangent lower than 0.1. At high excitations, the composite materials show core losses 5 times lower than that of Fe flakes at 800 kHz. (C) 2012 American Institute of Physics. [doi:10.1063/1.3677310]

Zhou, Y↗
DOE OSTI2015

Suppression of conformational heterogeneity at a protein–protein interface

Staphylococcal protein A (SpA) is an important virulence factor from Staphylococcus aureus responsible for the bacterium’s evasion of the host immune system. SpA includes five small three-helix–bundle domains that can each bind with high affinity to many host proteins such as antibodies. The interaction between a SpA domain and the F c fragment of IgG was partially elucidated previously in the crystal structure 1FC2. Although informative, the previous structure was not properly folded and left many substantial questions unanswered, such as a detailed description of the tertiary structure of SpA domains in complex with F c and the structural changes that take place upon binding. Here we report the 2.3-Å structure of a fully folded SpA domain in complex with F c . Our structure indicates that there are extensive structural rearrangements necessary for binding F c , including a general reduction in SpA conformational heterogeneity, freezing out of polyrotameric interfacial residues, and displacement of a SpA side chain by an F c side chain in a molecular-recognition pocket. Such a loss of conformational heterogeneity upon formation of the protein–protein interface may occur when SpA binds its multiple binding partners. As a result, suppression of conformational heterogeneity may be an important structural paradigm in functionally plastic proteins.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

CD23 is a glycan-binding receptor in some mammalian species

CD23, the low-affinity IgE receptor found on B lymphocytes and other cells, contains a C-terminal lectin-like domain that resembles C-type carbohydrate-recognition domains (CRDs) found in many glycan-binding receptors. In most mammalian species, the CD23 residues required to form a sugar-binding site are present, although binding of CD23 to IgE does not involve sugars. Solid-phase binding competition assays, glycoprotein blotting experiments, and glycan array analysis employing the lectin-like domains of cow and mouse CD23 demonstrate that they bind to mannose, GlcNAc, glucose, and fucose and to glycoproteins that bear these sugars in nonreducing terminal positions. Crystal structures of the cow CRD in the presence of α-methyl mannoside and GlcNAcβ1–2Man reveal that a range of oligosaccharide ligands can be accommodated in an open binding site in which most interactions are with a single terminal sugar residue. Although mouse CD23 shows a pattern of monosaccharide and glycoprotein binding similar to cow CD23, the binding is weaker. In contrast, no sugar binding was observed in similar experiments with human CD23. The absence of sugar-binding activity correlates with accumulation of mutations in the gene for CD23 in the primate lineage leading to humans, resulting in loss of key sugar-binding residues. These results are consistent with a role for CD23 in many species as a receptor for potentially pathogenic microorganisms as well as IgE. However, the ability of CD23 to bind several different ligands varies between species, suggesting that it has distinct functions in different organisms.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Advancements in Anion Exchange Membrane Cations

Anion-exchange membrane fuel cells (AME-FCs) are of increasingly popular interest as they enable the use of non-Pt fuel cell catalysts, the primary cost limitation of proton exchange membrane fuel cells. Benzyltrimethyl ammonium (BTMA) is the standard cation that has historically been utilized as the hydroxide conductor in AEMs. Herein we approach AEMs from two directions. First and foremost we study the stability of several different cations in a hydroxide solution at elevated temperatures. We specifically targeted BTMA and methoxy and nitro substituted BTMA. We've also studied the effects of adding an akyl spacer units between the ammonium cation and the phenyl group. In the second approach we use computational studies to predict stable ammonium cations, which are then synthesized and tested for stability. Our unique method to study cation stability in caustic conditions at elevated temperatures utilizes Teflon Parr reactors suitable for use under various temperatures and cation concentrations. NMR analysis was used to determine remaining cation concentrations at specific time points with GCMS analysis verifying product distribution. We then compare the experimental results with calculated modeling stabilities. Our studies show that the electron donating methoxy groups slightly increase stability (compared to that of BTMA), while the electron withdrawing nitro groups greatly decrease stability in base. These results give insight into possible linking strategies to be employed when tethering a BTMA like ammonium cation to a polymeric backbone; thus synthesizing an anion exchange membrane.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Improved Accelerated Stress Tests Based on Fuel Cell Vehicle Data

UTC will led a top-tier team of industry and national laboratory participants to update and improve DOE’s Accelerated Stress Tests (AST’s) for hydrogen fuel cells. This in-depth investigation will focused on critical fuel cell components (e.g. membrane electrode assemblies - MEA) whose durability represented barriers for widespread commercialization of hydrogen fuel cell technology. UTC had access to MEA materials that had accrued significant load time under real-world conditions in PureMotion® 120 power plant used in transit buses. These materials are referred to as end-of-life (EOL) components in the rest of this document. Advanced characterization techniques were used to evaluate degradation mode progress using these critical cell components extracted from both bus power plants and corresponding materials tested using the DOE AST’s. These techniques were applied to samples at beginning-of-life (BOL) to serve as a baseline. These comparisons advised the progress of the various failure modes that these critical components were subjected to, such as membrane degradation, catalyst support corrosion, platinum group metal dissolution, and others. Gaps in the existing ASTs predicted the degradation observed in the field in terms of these modes were outlined. Using the gaps, new AST’s were recommended and tested to better reflect the degradation modes seen in field operation. Also, BOL components were degraded in a test vehicle at UTC designed to accelerate the bus field operation.

08 HYDROGEN↗
DOE OSTI2011

Solid Acid Fuel Cell Stack for APU Applications

Solid acid fuel cell technology affords the opportunity to operate at the 200-300 degree centigrade regime that would allow for more fuel flexibility, compared to polymer electrode membrane fuel cell, while avoiding the relatively more expensive and complex system components required by solid oxide fuel cell. This project addresses many factors such as MEA size scalability, fuel robustness, stability, etc., that are essential for successful commercialization of the technology.

08 HYDROGEN↗
DOE OSTI2025

Performance and Durability Investigation of Thin, Low Crossover Proton Exchange Membranes for Water Electrolyzers

The goal of this project was to fabricate and study the performance and durability implications of thin, mechanically reinforced membranes containing gas recombination catalysts (GRCs) for advanced proton exchange membrane water electrolysis (PEMWE) systems. The thinner membranes, optimized for a PEMWE environment, dramatically reduced the proton transport resistance across the membrane, improving the overall efficiency of the PEMWE system. At the same time, the GRC technology was deployed to recombine crossover hydrogen from the cathode with oxygen from the anode to form water within the membrane. This reaction mitigated the buildup of hydrogen in the oxygen stream, ensuring safe operation of the PEMWE system. Capabilities to measure the gas crossover in both an ex-situ screening cell and in operando application testing were developed over the course of the project to track membrane progress and quantify deliverables. State of the art roll to roll manufacturing technologies were leveraged to fabricate the membranes on a commercial scale, where the membrane structure was precisely tuned and GRC distributed within the membrane structure.

08 HYDROGEN↗