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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 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Kinetic study of the azo – Hydrazone photoinduced mechanism in complexes with a -Re(CO) 3 L 0/+ core by flash photolysis

The photoprocesses of three rhenium(I) tricarbonyl complexes, fac-Re(NN)(CO) 3 L 0/+ , bearing an azo/hydrazone ligand, NN, and L = Cl, Br or CH 3 CN as axial ligand, were studied by time-resolved spectroscopic techniques. Flash irradiation of deaerated solutions of the complexes in acetonitrile photogenerated intermediates with intense optical absorptions in the UV–vis spectral region of the hydrazone ligand. The decay of the intermediates photogenerated with the Cl, Br and CH 3 CN ligands in the axial position proceeds by three different mechanisms. For the fac-Re(NN)(CO) 3 Cl, a three-step mechanism involving isomerization, tautomerization and rotation accounts for the spectroscopic transformations. In contrast to the flash photolysis result, the continuous photolysis of the complex in acetonitrile does not show spectroscopic changes associated with the generation of a stable product, i.e., the complex exhibits a photoreversible behavior. The first step observed in the flash irradiation of fac-Re(NN)(CO) 3 Cl, is missing in the decay of the photogenerated intermediates with fac-Re(NN)(CO) 3 Br and fac-[Re(NN)(CO) 3 CH 3 CN] + . A possible reason for this absence is that the process is too fast for the time-response of the flash photolysis set-up. Time-resolved spectra and associated reaction rate data for the Re(I) complexes are communicated and discussed. Finally, DFT calculations support a plausible E → Z mechanism with thermal back-isomerization mediated by tautomerization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

(CrMnCoNiZn) 3 O 4 @PPy core-shell nanocomposite with excellent electrochemical performance as lithium-ion battery anode

High entropy oxides (HEOs) have an excellent potential for use as electrode materials in lithium-ion batteries (LIBs) due to their high theoretical specific capacity. In this work, spinel-structured (CrMnCoNiZn) 3 O 4 HEO nanoparticles with five elements in equal molar ratio is first generated by solution combustion method. (CrMnCoNiZn) 3 O 4 @polypyrrole (PPy) nanocomposites are prepared by in-situ polymerization method. As an anode for lithium-ion batteries, the electrochemical performance of the (CrMnCoNiZn) 3 O 4 @PPy composite outperforms that of (CrMnCoNiZn) 3 O 4 nanoparticles. The capacity is 802 mAh/g after 100 cycles at a current density of 100 mA/g, 416 mAh/g after 1000 cycles at a high current density of 1 A/g, and 360 mAh/g rate capacity at 2 A/g. The excellent electrochemical performance of the composites is mainly due to the fact that the conductive and flexible PPy is encapsulated on the high-entropy oxides, which can alleviate the volume change triggered by extraction-insertion of lithium ions process, as well as enhance the electrical conductivity and reduce the occurrence of some side reactions. Finally, this method of compositing materials can also be used in other HEOs and conductive polymers, providing a new idea to enhance the electrochemical properties of HEOs.

25 ENERGY STORAGE↗
DOE OSTI2024

Integration of layered group IV selenides: From SnSe–SnSe 2-x S x core-shell crystals to complex (SnSe–SnSe 2-x S x )-GeSe van der waals heterostructures

The layered semiconductor tin selenide (SnSe) has received extensive interest due to its promising thermoelectric and ferroelectric properties. Integrating SnSe with other layered crystals in heterostructures can enable the modification of charge- and thermal transport, electrical polarization, and other properties such as chemical stability, optoelectronics, and photonics. Here, we demonstrate the vapor transport synthesis of single-crystalline SnSe monochalcogenide flakes that are spontaneously encapsulated in a thin layered SnSe 2-x S x dichalcogenide shell. In a second growth step, such SnSe-SnSe 2-x S x heterostructures are integrated with the monochalcogenide GeSe, which is laterally stitched to the SnSe side facets while preserving the dichalcogenide shell across the basal facets. This architecture is confirmed by optical microscopy, electron microscopy and diffraction, energy dispersive X-ray and Raman spectroscopies, as well as cathodoluminescence spectroscopy. Furthermore, the results extend our capabilities for materials integration by forming complex heterostructures with both vertical van der Waals interfaces and covalent lateral interfaces between layered semiconductors.

2D layered crystals↗
DOE OSTI2023

SiC as a core-edge integrated wall solution in DIII-D

Silicon carbide (SiC) is a promising material for use in a fusion reactor due to its low hydrogenic diffusivity, high temperature strength and resilience under neutron irradiation. To assess SiC as a main wall material in DIII-D, simulations with TRIM.SP and DIVIMP are performed on a well-diagnosed L-mode discharge. The effective charge, Z eff , across the separatrix is used as a figure of merit in comparing SiC to the current graphite walls. It is found that SiC is expected to reduce Z eff , potentially by as much as ~50%. It is discussed how SiC may be expected to "self-condition" and create wall conditions similar to siliconization, further lowering Z eff due to efficient oxygen gettering. Furthermore, the potential benefits are reviewed and a path towards SiC walls in DIII-D is presented.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Experimental studies on metallic fuel relocation in a pin bundle core structure of a sodium-cooled fast reactor

Understanding the relocation behavior of metallic fuel in severe accident scenarios is one of the most important factors in the safety assessment of sodium-cooled fast reactors (SFRs). In the present study, the relocation behavior of uranium metallic fuel was investigated by conducting metallic fuel relocation experiments using 19-pin bundle test sections in the Argonne's Metallic Uranium Safety Experiment (MUSE) facility. Post-test radiographic images were taken to characterize the uranium fuel relocation within the pin bundle test section. In addition, the pressure drop in the test sections was measured after the relocation experiments to evaluate the blockage of the sodium coolant channel. The pressure drop in the pin bundle test sections was also analytically calculated by varying the porosity and the pore size of the relocated fuel. The porosity and pore size of the relocated fuel in the pin bundle test sections were estimated by comparing those calculated pressure drop values with the measured pressure drop values from the pressure drop tests. In this work, the experimental results showed that the more formation of the eutectics could lead to more fuel dispersion and less blockage due to the lower freezing point of the eutectics.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗