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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Dielectric and Structural Properties of the Hybrid Material Polyvinylidene Fluoride-Bacterial Nanocellulose-Based Composite

In the search for environmentally friendly materials with a wide range of properties, polymer composites have emerged as a promising alternative due to their multifunctional properties. This study focuses on the synthesis of composite materials consisting of four components: bacterial nanocellulose (BNC) modified with magnetic Fe 3 O 4 , and a mixture of BaTiO 3 (BT) and polyvinylidene fluoride (PVDF). The BT powder was mechanically activated prior to mixing with PVDF. The influence of BT mechanical activation and BNC with magnetic particles on the PVDF matrix was investigated. The obtained composite films’ structural characteristics, morphology, and dielectric properties are presented. This research provides insights into the relationship between mechanical activation of the filler and structural and dielectric properties in the PVDF/BT/BNC/Fe 3 O 4 system, creating the way for the development of materials with a wide range of diverse properties that support the concept of green technologies.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Deciphering when Metal Corrosion is Spontaneous in Molten Fluorides Using Potential-Activity Diagrams

The work identifies the conditions for thermodynamically favored spontaneous metal corrosion using potential-activity diagrams tailored for high-temperature molten fluorides. These diagrams provide insights into the thermodynamic phase stability of both solid and dissolved metal species, such as Cr, Cr(II), Cr(III), Ni, Ni(II), Fe, and Fe(II), along with their potential primary oxidizers, including Eu(III), O2, and HF, over a broad range of theoretical F− anion activities. The work further examines the practical implications, prospects, and challenges associated with the construction of these diagrams. The key objective of this project is to pinpoint crucial thermodynamic variables that substantially affect metal corrosion electrochemistry in the context of molten salt nuclear reactor applications.

Materials Science↗
DOE OSTI2023

Molten Salt Tritium Transport Experiment: A Versatile Fluoride Salt Loop for Validation of Tritium Transport Phenomena

Tritium is generated in Molten Salt Reactors (MSRs) from neutron capture by lithium and other constituents of the molten salt FLiBe. Tritium is a unique radionuclide as it readily permeates through hot structural materials. Thus, any material in contact with tritium laden molten salt is a potential pathway for release. Understanding tritium transport and devising adequate control strategies is necessary for the safe operation of MSRs. The Molten Salt Tritium Transport Experiment (MSTTE) is a forced-convection fluoride salt loop with the capability to inject hydrogen isotopes into flowing molten salt and to measure transport phenomena such as permeation through metals and evolution from free-surfaces. MSTTE is designed to be versatile to test potential control technology in future campaigns. This report focuses on the current design and analysis of MSTTE. Custom designed and fabricated experiment components such as the hydrogen injection system, permeation test section, diagnostics, and gas distribution system are discussed in detail. System-level tritium transport modeling using the System Analysis Module investigates experiment parameters such as hydrogen source terms, salt flow rate, and salt temperature. Computational fluid dynamics of the salt flow in the permeation test section informs design choices to establish fully developed flow in the measured permeation zone.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2022

Neutronic design and fuel cycle analysis of a fluoride salt-cooled High Temperature Reactor (FHR)

The Fluoride salt-cooled High temperature Reactor (FHR) is a new Gen IV reactor concept that can operate under near atmospheric pressure circumstances and further enhance the inherent safety. In this study, an FHR core design with 165 megawatts of thermal output (MWth) is proposed. The reactor core employs tri-structural-isotropic (TRISO) particle fuel within prismatic graphite blocks as the basic fuel form, FLiBe (2 {sup 7}LiF-BeF{sub 2}) as the primary coolant, and a three-batch fuel cycle scheme. Sensitivity analyses on various parameters were performed to optimize the cycle length and neutronic parameters. The fuel cycle of this core design was evaluated in detail from 4 aspects: cycle length, power peaking factor (PPF), discharge burnup, and temperature coefficient. It was found that larger fuel channel pitch (FCP) would have a relatively harder neutron spectrum, and yield relatively longer cycle length, lower, better fuel temperature coefficient (FTC), and moderator temperature coefficient (MTC). In addition, burnable poison (BP), Er{sub 2}O{sub 3}, can effectively reduce PPF, hold down the multiplication factor, and more importantly it can improve the MTC. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2022

The Role of Electrolyte Composition in Enabling Li Metal‐Iron Fluoride Full‐Cell Batteries

Abstract FeF 3 conversion cathodes, paired with Li metal, are promising for use in next‐generation secondary batteries and offer a remarkable theoretical energy density of 1947 Wh kg −1 compared to 690 Wh kg −1 for LiNi 0.5 Mn 1.5 O 4 ; however, many successful studies on FeF 3 cathodes are performed in cells with a large (>90‐fold) excess of Li that disguises the effects of tested variables on the anode and decreases the practical energy density of the battery. Herein, it is demonstrated that for full‐cell compatibility, the electrolyte must produce both a protective solid‐electrolyte interphase and cathode‐electrolyte interphase and that an electrolyte composed of 1:1.3:3 (m/m) LiFSI, 1,2‐dimethoxyethane, and 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether fulfills both these requirements. This work demonstrates the importance of verifying electrode level solutions on the full‐cell level when developing new battery chemistries and represents the first full cell demonstration of a Li/FeF 3 cell, with both limited Li and high capacity FeF 3 utilization.

25 ENERGY STORAGE↗
DOE OSTI2022

Separations of U/Pu and Np/Pu using fluoride volatility

Here the importance of uranium/plutonium and neptunium/plutonium separations at large scale or at environmental levels is such that the reactivity of nitrogen trifluoride (NF 3 ) with respect to other fluorinating reagents warranted investigation. We show that NF 3 does not convert PuO 2 or PuF 4 to PuF 6 , during separations of U/Pu and Np/Pu, even under forcing conditions. Herein, this is analytically demonstrated to trace level. This rather exclusive behavior has been reported for only one other reagent: BrF 3 . Confidence in this result now allows for rapid and selective separations of volatile UF 6 and NpF 6 from plutonium. Preliminary data concerning the separation of 233 Pa from 237 Np is also described.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Optical properties of differing nanolayered structures of divalent europium doped barium fluoride thin films synthesized by pulsed laser deposition

Optically-active thin films are employed in a variety of applications, such as LEDs and photovoltaics, due to their ability to act as up- or down-photon energy converters. Their performance depends critically on their composition and structure; thus, the use of novel synthesis techniques that allow for their control at the nanoscale level can result in improved efficiency and practicality. Here, layered thin films consisting of Eu 2+ - doped BaF 2 nanocrystalline layers separated by amorphous Al 2 O 3 were synthesized via sequential pulsed laser deposition using three separate targets for the different components; this synthesis technique provides precise control of layer thickness at the nanoscale along with dopant distribution within the film. Cross-sectional transmission electron microscopy analysis verified the desired nano-layering. Post-deposition heat treatments in a nitrogen atmosphere resulted in samples exhibiting steady emission with a broad peak ranging from 400 to 600 nm and a shoulder at 410 nm. The CIE 1931 chromaticity coordinates are x = 0.26-0.29 and y = 0.32-0.35 and vary as a function of the sample configuration. Because the chromaticity coordinates are close to those of a pure white light (x = 0.33, y = 0.33), these films demonstrate advantageous properties for applications with UV-pumped white light LEDs.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Solvent‐Phobic and Ionophilic Carboxylated Polythiophene Layer for Fluoride‐Rich Cathode Electrolyte Interphase

Abstract One focal area of contemporary organic mixed ionic‐electronic conductor (OMIEC) research relates to utilization of dual‐conductive properties to enhance the ion/electron transfer kinetics for energy storage applications. Insight regarding OMIEC response toward the electrolyte anion and solvent used in lithium‐ion batteries (LIBs), however, is limited. Here, for the first time, the solvent‐phobic and ionophilic (SP‐IP) properties of the OMIEC, poly[3‐(potassium‐4‐butanoate)thiophene‐2,5‐diyl] (P3KBT), are revealed through comprehensive evaluation and characterization. The solvent‐phobic characteristics arise from the cooperation of dispersive interaction, polar interaction, and hydrogen‐bonding between P3KBT and electrolyte solvent. The ionophilic nature is driven by electrostatic interactions between P3KBT side chain carboxylate groups and LiPF 6 , and the reversible electrochemical doping/de‐doping of the polythiophene backbone with PF 6 ⁻ . The SP‐IP properties induce formation of a LiF‐ rich , Li 2 CO 3 ‐ limited cathode electrolyte interphase (CEI) layer when a P3KBT coating layer is applied to the active material surface, significantly improving half‐cell life to over 1500 cycles at 2C.

Ren, Haoze [Department of Chemical and Bimolecular↗
DOE OSTI2020

Vapor‐ and liquid‐phase adsorption of alcohol and water in silicalite‐1 synthesized in fluoride media

Abstract In this work, batch‐adsorption experiments and molecular simulations are employed to probe the adsorption of binary mixtures containing ethanol or a linear alkane‐1, n ‐diol solvated in water or ethanol onto silicalite‐1. Since the batch‐adsorption experiments require an additional relationship to determine the amount of solute (and solvent) adsorbed, as only the bulk liquid reservoir can be probed directly, molecular simulations are used to provide a relationship between solute and solvent adsorption for input to the experimental bulk measurements. The combination of bulk experimental measurements and simulated solute–solvent relationship yields solvent and solute loadings that are self‐consistent with simulation alone, and allow for an assessment of the various assumptions made in the literature. At low solution concentrations, the solute loading calculated is independent of the assumption made. At high concentrations, a negligent choice of assumption can lead to systematic overestimation or underestimation of calculated solute loading.

DeJaco, Robert F.↗
DOE OSTI2020

Interfacial Speciation Determines Interfacial Chemistry: X-ray-Induced Lithium Fluoride Formation from Water-in-salt Electrolytes on Solid Surfaces

Using synchrotron X-rays the LiTFSI/H 2 O electrolyte interfacial decomposition pathways in the „water-in-salt“ and „salt-in-water“ regimes are investigated. The resultant photoelectron-induced reduction was revealed to be concentration-dependent interfacial chemistry that only occurs among closely contact ion-pairs, which constitutes the rationale behind the „water-in-salt“ concept.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗