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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Comment on “Investigations on ion irradiation induced modifications in Th 5f occupancy in thoria,” by P. Jegadeesan, S. Amirthapandian, Gurpreet Kaur, D. Sanjay Kumar, Arindam Das, D.K. Avasthi, K. Ananthasivan, B.K. Panigrahi

The primary purpose of this letter is to address some issues raised in the paper by Jegadeesan et al. There are three salient points. (1) The Branching Ratio (BR) analysis of thorium dioxide is complicated by peaks from Extended X-Ray Absorption Fine Structure (EXAFS). (2) Uranium metal is not an LS coupling but rather a delocalized 5f case. (3) Radiation damage effects in the BR measurements are small but strong effects can be seen in Resonant Photoemission.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Occupant-driven end use load models for demand response and flexibility service participation of residential grid-interactive buildings

As demand response becomes increasingly used as a tool to support improved grid flexibility, it is important to consider that there are many potential types of energy end uses that may be used to support such flexibility. Residential appliances, often accounting for 30 % or more of residential energy use, are a currently untapped source of demand flexibility, particularly when aggregated together across homes. To date there has been very limited analysis of residential appliances for use as grid-interactive loads. As such, this research uses disaggregated energy end use data for 564 households, to model the electricity demand flexibility potential of the use of residential dishwashers, clothes washers, clothes dryers, ovens, and ranges (oven + stovetop) on both weekdays and weekends. This includes both at the building level, as well as aggregated to the grid level, specifically the Midcontinent Independent System Operator (MISO) region. This study was divided into two parts. Part 1 focuses on determining appliance-level loads, and Part 2, which involves aggregation to the grid. Findings suggest that among the studied appliances, clothes dryers provide the greatest demand reduction potential for most times of the day, followed by dishwashers and clothes washers. The maximum potential reduction for clothes dryers is found to be approximately at 11:00 a.m. and this potential sustains throughout most of the daytime period. When considering the willingness of households to participate, based on a survey of households in the Midwest region, clothes dryers still have the most potential for demand reduction. The availability of appliances for load modulation on weekdays and weekends indicates similar load reduction potential for all appliances. Overall, the results of this study suggest that there is an opportunity for shifting appliance usage to optimize grid efficiency and enhance demand response strategies.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2016

Different site occupancies in substitution variants of Mo{sub 3}Sb{sub 7}

A series of samples with the initial formula Mo{sub 3–x}Fe{sub x}Sb{sub 7} and Mo{sub 3–x}Ni{sub x}Sb{sub 7} have been prepared by solid state reaction at 873 K, starting from the elements in the stoichiometric ratios. The materials were compressed via hot-pressing, and their thermoelectric properties determined. Single crystal data show that Ni atoms in part occupy the cubic voids of the Mo{sub 3}Sb{sub 7} structure, as well as replace some Mo atoms, in contrast to the Fe analogues, where we found no evidence for Fe in the cubic voids. Supported by electronic structure calculations, replacing Mo with Fe or Ni increases the valence-electron count, thus decreases the numbers of p-type carriers of Mo{sub 3}Sb{sub 7}. On the other hand, filling the holes with Ni atoms appears to have no such effect. As a consequence, the Ni containing samples exhibit higher electrical conductivity than the Fe analogues, and ultimately lower thermoelectric figure-of-merit, as the p-type carrier concentration remains too high. - Graphical abstract: Trying to substitute Ni atoms for Mo in Mo{sub 3}Sb{sub 7} resulted in partial filling of the cubic voids, in contrast to Mo{sub 3–x}Fe{sub x}Sb{sub 7}. Since the Ni atoms in the Sb{sub 8} cubes do not act as electron donors, the Ni-containing materials exhibit very high carrier concentration, and thus high electric conductivity and low Seebeck coefficient. - Highlights: • Various substitution variants of Mo{sub 3}Sb{sub 7} with Fe and Ni were characterized. • While the Fe atoms replace the Mo atoms, the Ni atoms also fill the cubic voids. • Higher Fe/Ni amount on the Mo sites causes a decrease of the charge carriers. • The Ni atoms on the cubic sites do not decrease the charge carriers. • The lower the carrier concentration, the better the thermoelectric properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Consequences of Ca multisite occupation for the conducting properties of BaTiO{sub 3}

In combination with the dielectric modulus formalism and theoretical calculations, a newly developed defect incorporation mode, which is a combination of the standard A- and B-site doping mechanisms, is used to explain the conducting properties in 5 mol% Ca-doped BaTiO{sub 3}. Simulation results for Ca solution energies in the BaTiO{sub 3} lattice show that the new oxygen vacancy inducing mixed mode exhibits low defect energies. A reduction in dc conductivity compared with undoped BaTiO{sub 3} is witnessed for the incorporation of Ca. The conducting properties of 5 mol% Ca-doped BaTiO{sub 3} are analyzed using molecular dynamics and impedance spectroscopy. The ionic conductivity activation energies for each incorporation mode are calculated and good agreement with experimental data for oxygen migration is observed. The likely existence of the proposed defect configuration is also analyzed on the basis of these methods. - Graphical abstract: Oxygen vacancy formation as a result of self-compensation in Ca-doped BaTiO{sub 3}.

36 MATERIALS SCIENCE↗
DOE OSTI2014

The site occupation and valence of Mn ions in the crystal lattice of Sr{sub 4}Al{sub 14}O{sub 25} and its deep red emission for high color-rendering white light-emitting diodes

Highlights: • Different valences of Mn ions in Sr{sub 4}Al{sub 14}O{sub 25} were identified using XANES and EPR. • Red luminescence was attributed to Mn{sup 4+} occupying the center of AlO{sub 6} octahedron. • The Mn{sup 3+} incorporated in the center of AlO{sub 4} tetrahedron was non-luminescent. • The bond-valence theory was used to analyze the effective valences of cations. • A white LED device with CRI up to Ra 93.23 was packaged by using the red phosphor. - Abstract: The synthesis and component of red phosphor, Sr{sub 4}Al{sub 14}O{sub 25}: Mn, were optimized for application in white light-emitting diodes. The microstructure and morphology were investigated by the X-ray diffraction and scanning electron microscopy. Different valences of Mn ions in Sr{sub 4}Al{sub 14}O{sub 25} were discriminated using the electron paramagnetic resonance and X-ray absorption near-edge structure spectroscopy techniques. The bond-valence theory was used to analyze the effective valences of Sr{sup 2+} and Al{sup 3+} in Sr{sub 4}Al{sub 14}O{sub 25}. As a result, the strong covalence of Al{sup 3+} in the AlO{sub 4} tetrahedron other than in the AlO{sub 6} octahedron is disclosed. The deep red emission is attributed to Mn{sup 4+} occupying the center of AlO{sub 6} octahedron. The mechanism of energy transfer is mainly through dipole–dipole interaction, revealed by the analyses of critical distance and concentration quench. A high color rendering white LED prototype with color-rendering index up to Ra 93.23 packaged by using the red phosphor demonstrates its applicability.

36 MATERIALS SCIENCE↗