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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Comparison of AlF 3 thin films grown by thermal and plasma enhanced atomic layer deposition

Films of aluminum fluoride (AlF 3 ) deposited by thermal and plasma enhanced atomic layer deposition (PEALD) have been compared using in situ multiwavelength ellipsometry (MWE) and monochromatic x-ray photoelectron spectroscopy (XPS). The AlF 3 films were grown using cyclic exposures of trimethylaluminum, hydrogen fluoride, and H radicals from a remote H 2 inductively coupled plasma. Films were characterized in situ using MWE and XPS for growth rate, film composition, and impurity incorporation. The MWE showed a growth rate of 1.1 and 0.7 Å per cycle, at 100 °C, for thermal and plasma enhanced ALD AlF 3 films, respectively. Carbon incorporation was below the XPS detection limit. The plasma enhanced ALD AlF 3 film showed the presence of Al-Al chemical states, in the Al 2p scans, suggesting the presence of Al-rich clusters with a concentration of 14%. The Al-rich clusters are thought to originate during the hydrogen plasma step of the PEALD process. Finally, the Al-rich clusters were not detected in thermal ALD AlF 3 films using the same precursors and substrate temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Engineering Solid Electrolyte Interphase Composition by Assessing Decomposition Pathways of Fluorinated Organic Solvents in Lithium Metal Batteries

Studies have shown fluorinated electrolyte solvents can form desirable solid electrolyte interphase (SEI) in lithium metal batteries. In this study, we develop a detailed mechanistic understanding of two high performing electrolytes, Fluoroethylene Carbonate (FEC) and Difluoroethylene Carbonate (DFEC) to demonstrate minimal structural variations can lead to different decomposition products, and thereby the nature of the SEI. Using density functional theory (DFT) calculations, we find different initial bond-breaking mechanisms between FEC and DFEC. We develop free energy diagrams for the decomposition pathways including both electrochemical and chemical steps. Using the computational Li electrode, we identify the largest limiting potential of 1.77 V for FEC decomposition, associated with the formation of lithium fluoride, lithium oxide and FEC oligomers, and 1.53 V for DFEC, which correspond to the formation of polymerized vinylene carbonate and lithium fluoride. We suggest the formation of oligomers in the case of FEC instead of long polymers may lead to better SEI compactness. We also demonstrate the SEI components of FEC and DFEC are not stable on typical cathode voltage (3.87 V). This study presents a unified electrocatalytic perspective on SEI formation and decomposition.

25 ENERGY STORAGE↗
DOE OSTI2023

Application of the Solute-Solvent EMF Cell to Measure Activity of NiF 2 in Molten FLiNaK

Electromotive force (emf) measurements made using a combination of solute- and solvent-based electrodes were used to determine the activity of NiF 2 in molten FLiNaK eutectic at 823 K across a concentration range of x NiF2 = 5.2 × 10 –4 –1.0 × 10 –2 . The solute emf values were measured using electrodes consisting of Ni wires immersed in FLiNaK with dissolved NiF 2 contained in graphite crucibles. The measured emf values were then converted to the FLiNaK Eutectic Potassium Electrode (FEKE) potential and used to quantify the activity of dissolved NiF 2 . This quantification was based upon comparative measurements of a reference solvent electrode consisting of a K-Bi alloy immersed in pure FLiNaK contained in a boron nitride crucible and a solute electrode. Short cell lives were characteristic of the measurements due to the corrosive nature of the fluoride salts. Quantifying the activity of NiF 2 will improve the utility of Ni 2+ /Ni reference electrodes in molten fluoride salts, which are notoriously difficult electrolytes to work with because of their reactivity. In conclusion, this work demonstrates the general nature of the solute-solvent approach as a repeatable, easily employed method for measuring the activity values of electroactive species in a variety of molten salts to improve understanding of the electroactive species behavior in these systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Electrochemical Characterization of Dissolved Oxides in Molten FLiNaK

Molten fluoride salts have long been the subject of investigation given their application in a variety of industrial processes. Oxides are a common exogeneous impurity within these systems, and can lead to many operational and regulatory concerns. In recent studies, the electro-oxidation of dissolved metallic oxides has been attributed to a single step oxygen evolution reaction despite voltametric evidence suggesting otherwise. Here, we first use square wave voltammetry to confirm that the oxidation of dissolved oxides in fluorides proceeds via a two-electron transfer reaction and then demonstrate that the presence of a peroxide-mediated redox reaction better explains the electrochemical data. Numerical simulations were then used to support the determination of improved diffusion coefficients to enable electroanalytical measurements of the oxide concentration across at a variety of temperatures. A linear Arrhenius relationship was observed when the experimental data was corrected for ohmic resistance effects. Concentration measurements using the corrected square wave voltammetry data demonstrated high accuracy across a large range of concentrations, while the uncorrected data showed plateauing and high errors. In total, this work serves to rectify previously misconstrued electrochemical data of oxides in molten salts and demonstrate how accurate, in situ concentration measurements can be achieved in real-world systems.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Materials Data on H5NF2 by Materials Project

NH4HF2 is High Pressure (4-7GPa) Tellurium structured and crystallizes in the orthorhombic Pmna space group. The structure is zero-dimensional and consists of four ammonium molecules and four hydrogen fluoride hydrogen fluoride molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H13C4NF2 by Materials Project

N(CH3)4HF2 is Silicon tetrafluoride-derived structured and crystallizes in the orthorhombic Pmmn space group. The structure is zero-dimensional and consists of two hydrogen fluoride hydrogen fluoride molecules and two tetramethylammonium molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KH(IF6)2 by Materials Project

K(IF5)2HF2 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional and consists of four hydrogen fluoride hydrogen fluoride molecules and one K(IF5)2 framework. In the K(IF5)2 framework, K1+ is bonded in a 8-coordinate geometry to eight equivalent F1- atoms. All K–F bond lengths are 2.69 Å. I5+ is bonded in a 5-coordinate geometry to five F1- atoms. There is one shorter (1.88 Å) and four longer (1.95 Å) I–F bond length. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one I5+ atom. In the second F1- site, F1- is bonded in a distorted linear geometry to one K1+ and one I5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TeH14C3S3(N3F2)2 by Materials Project

C3H13TeS3(N3F)2HF2 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of four hydrogen fluoride hydrogen fluoride molecules and two C3H13TeS3(N3F)2 clusters. In each C3H13TeS3(N3F)2 cluster, there are three inequivalent C+3.33+ sites. In the first C+3.33+ site, C+3.33+ is bonded in a distorted bent 120 degrees geometry to two N3- and one S2- atom. Both C–N bond lengths are 1.33 Å. The C–S bond length is 1.75 Å. In the second C+3.33+ site, C+3.33+ is bonded in a distorted trigonal planar geometry to two N3- and one S2- atom. Both C–N bond lengths are 1.33 Å. The C–S bond length is 1.74 Å. In the third C+3.33+ site, C+3.33+ is bonded in a distorted trigonal planar geometry to two N3- and one S2- atom. There is one shorter (1.30 Å) and one longer (1.34 Å) C–N bond length. The C–S bond length is 1.79 Å. There are six inequivalent N3- sites. In the first N3- site, N3- is bonded in a trigonal planar geometry to one C+3.33+ and two H1+ atoms. Both N–H bond lengths are 1.03 Å. In the second N3- site, N3- is bonded in a trigonal planar geometry to one C+3.33+ and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the third N3- site, N3- is bonded in a trigonal planar geometry to one C+3.33+ and two H1+ atoms. Both N–H bond lengths are 1.03 Å. In the fourth N3- site, N3- is bonded in a trigonal planar geometry to one C+3.33+ and two H1+ atoms. There is one shorter (1.01 Å) and one longer (1.02 Å) N–H bond length. In the fifth N3- site, N3- is bonded in a trigonal planar geometry to one C+3.33+ and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the sixth N3- site, N3- is bonded in a trigonal planar geometry to one C+3.33+ and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.25 Å) N–H bond length. There are thirteen inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one S2- and one F1- atom. The H–S bond length is 2.04 Å. The H–F bond length is 0.99 Å. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the tenth H1+ site, H1+ is bonded in a linear geometry to one N3- and one F1- atom. The H–F bond length is 1.17 Å. In the eleventh H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the twelfth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the thirteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. Te4+ is bonded in a distorted rectangular see-saw-like geometry to four S2- atoms. There are a spread of Te–S bond distances ranging from 2.45–3.27 Å. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to one C+3.33+, one H1+, and two equivalent Te4+ atoms. In the second S2- site, S2- is bonded in a water-like geometry to one C+3.33+ and one Te4+ atom. In the third S2- site, S2- is bonded in a distorted T-shaped geometry to one C+3.33+, one Te4+, and one F1- atom. The S–F bond length is 2.77 Å. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one H1+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one H1+ and one S2- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H3F2 by Materials Project

H2(HF)4 crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of one hydrogen molecule and two hydrogen fluoride hydrogen fluoride molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HXe2F15 by Materials Project

(XeF6)4(HF2)2F2 crystallizes in the orthorhombic Pna2_1 space group. The structure is zero-dimensional and consists of four hydrofluoric acid molecules, four hydrogen fluoride hydrogen fluoride molecules, and four XeF6 clusters. In each XeF6 cluster, there are two inequivalent Xe sites. In the first Xe site, Xe is bonded in a 7-coordinate geometry to seven F atoms. There are a spread of Xe–F bond distances ranging from 1.98–2.51 Å. In the second Xe site, Xe is bonded in a 7-coordinate geometry to seven F atoms. There are a spread of Xe–F bond distances ranging from 1.98–2.48 Å. There are twelve inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one Xe atom. In the second F site, F is bonded in a single-bond geometry to one Xe atom. In the third F site, F is bonded in a single-bond geometry to one Xe atom. In the fourth F site, F is bonded in a single-bond geometry to one Xe atom. In the fifth F site, F is bonded in a single-bond geometry to one Xe atom. In the sixth F site, F is bonded in a single-bond geometry to one Xe atom. In the seventh F site, F is bonded in a single-bond geometry to one Xe atom. In the eighth F site, F is bonded in a single-bond geometry to one Xe atom. In the ninth F site, F is bonded in a bent 120 degrees geometry to two Xe atoms. In the tenth F site, F is bonded in a single-bond geometry to one Xe atom. In the eleventh F site, F is bonded in a bent 120 degrees geometry to two Xe atoms. In the twelfth F site, F is bonded in a single-bond geometry to one Xe atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H25C8IN2(OF2)2 by Materials Project

(N(CH3)4)2HF2I(OF)2 is Silicon tetrafluoride-derived structured and crystallizes in the monoclinic C2/m space group. The structure is zero-dimensional and consists of four hydrogen fluoride hydrogen fluoride molecules, eight tetramethylammonium molecules, and four I(OF)2 clusters. In each I(OF)2 cluster, O2- is bonded in a single-bond geometry to one I1- atom. The O–I bond length is 1.80 Å. I1- is bonded in a distorted rectangular see-saw-like geometry to two equivalent O2- and two F1- atoms. Both I–F bond lengths are 2.08 Å. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one I1- atom. In the second F1- site, F1- is bonded in a single-bond geometry to one I1- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H4NF2 by Materials Project

N2(H2)3(HF2)2 crystallizes in the trigonal R-3m space group. The structure is zero-dimensional and consists of six hydrogen fluoride hydrogen fluoride molecules, six molecular hydrogen molecules, and three nitrogen molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te3(OF6)2 by Materials Project

Te3(OF4)2(F2)2 crystallizes in the tetragonal I4_1/a space group. The structure is zero-dimensional and consists of sixteen hydrogen fluoride hydrogen fluoride molecules and eight Te3(OF4)2 clusters. In each Te3(OF4)2 cluster, there are two inequivalent Te+5.33+ sites. In the first Te+5.33+ site, Te+5.33+ is bonded in a trigonal pyramidal geometry to one O2- and three F1- atoms. The Te–O bond length is 2.01 Å. There are a spread of Te–F bond distances ranging from 1.86–1.95 Å. In the second Te+5.33+ site, Te+5.33+ is bonded in a square co-planar geometry to two equivalent O2- and two equivalent F1- atoms. Both Te–O bond lengths are 2.00 Å. Both Te–F bond lengths are 1.98 Å. O2- is bonded in a distorted bent 150 degrees geometry to two Te+5.33+ atoms. There are four inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Te+5.33+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Te+5.33+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one Te+5.33+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one Te+5.33+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sb2HF13 by Materials Project

Sb2F11HF2 is Tungsten Carbide structured and crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of one hydrogen fluoride hydrogen fluoride molecule and one Sb2F11 cluster. In the Sb2F11 cluster, Sb is bonded to six F atoms to form corner-sharing SbF6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Sb–F bond distances ranging from 1.89–2.08 Å. There are six inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one Sb atom. In the second F site, F is bonded in a single-bond geometry to one Sb atom. In the third F site, F is bonded in a single-bond geometry to one Sb atom. In the fourth F site, F is bonded in a single-bond geometry to one Sb atom. In the fifth F site, F is bonded in a single-bond geometry to one Sb atom. In the sixth F site, F is bonded in a linear geometry to two equivalent Sb atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

An Updated Analysis of Clad Degradation

This report provides an analysis of the clad barrier function associated with the direct disposal of dual purpose canisters (DPCs) under hypothetical conditions in a shale repository and in an alluvial repository, including the effect of a postulated criticality event inside a disposed DPC. Should a postulated criticality event occur in a hypothetical shale repository, cladding will primarily degrade by general corrosion. Stress corrosion cracking, hydride cracking, creep failure, pitting and crevice corrosion, rod pressurization, and clad unzipping are calculated to have little impact on cladding persistence. At the higher temperature expected during a postulated criticality event in a saturated shale repository, general corrosion of cladding would be rapid - on the order of 0.034 microns/yr. A few hundred years after onset of a postulated criticality event in a shale repository complete general corrosion of fuel assembly grid spacer walls and guide tubes will likely result in settling of fuel rods upon each other. This rod consolidation should displace the water moderator and possibly terminate a postulated criticality. The primary potential degradation pathway for cladding in a hypothetical alluvial repository is localized corrosion by fluoride, which cannot occur in a shale repository. Fluoride-enhanced corrosion of cladding would be accelerated under the slightly higher (< 100°C) temperatures associated with a postulated criticality event. The impact of criticality in both cases (shale and alluvial) would be to increase the amount of failed cladding. But it would require very specialized transport pathways.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Characterization of the Sulfur-Saturated Melt Versions of the HFG1 Study Glasses

The U.S. Department of Energy (DOE) is responsible for building the Hanford Tank Waste Treatment and Immobilization Plant (WTP) at the Hanford Site in Washington to remediate 55 million gallons of radioactive waste that is temporarily stored in 177 underground tanks. The Office of River Protection (ORP) has requested that the Savannah River National Laboratory (SRNL) contribute to current glass studies to support successful startup of the WTP, due to SRNL’s recognized capabilities and expertise for glass waste form development. As part of this effort, the Pacific Northwest National Laboratory (PNNL) is developing, batching, and fabricating simulated high-level waste (HLW) glasses to generate the associated property data needed to validate or identify areas of potential characterization improvements in the current glass property/ composition models. Currently, the models cover only a small fraction of the waste compositions projected in the Hanford tank farm; therefore, the models must be expanded to include high fluoride compositions to successfully complete the WTP mission. SRNL support of this work is defined in the Task Technical and Quality Assurance Plan (TTQAP). This report provides results from the chemical analyses of a series of sulfur-saturated melt (SSM) versions of simulated nuclear waste glasses fabricated at PNNL. The glasses were selected as part of a broader study of the influence of glass composition on chemical durability, sulfur retention, and other properties. The glasses were designated the High Fluoride Glasses-1 (HLG1).

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Product Consistency Test Results for the HFG1 Glasses

The U.S. Department of Energy (DOE) is responsible for building the Hanford Tank Waste Treatment and Immobilization Plant (WTP) at the Hanford site in Washington to remediate 55 million gallons of radioactive waste that is temporarily stored in 177 underground tanks. The Office of River Protection (ORP) has requested that the Savannah River National Laboratory (SRNL) contribute in areas of recognized capabilities and expertise for glass waste form development to support successful startup of the WTP. As part of this effort, the Pacific Northwest National Laboratory (PNNL) is developing, batching, and fabricating simulated high-level waste (HLW) glasses to generate the associated property data needed to validate or identify areas of potential characterization improvement in the current glass property/composition models. Currently, the models cover only a small fraction of the waste compositions projected in the Hanford tank farm; therefore, the models must be expanded to include high fluoride compositions to successfully complete the WTP mission. SRNL support of this work is defined in the Task Technical and Quality Assurance Plan (TTQAP). This report provides the results of the Product Consistency Test (PCT) leachates from the High Fluoride Glasses-1 (HFG1), a series of simulated nuclear waste glasses fabricated at PNNL. The series included quenched (Q) and canister-centerline cooled (CCC) versions of the glasses. The glasses were selected as part of a broader study of the influence of glass composition on chemical durability, sulfur retention, and other properties. These data will be used to validate or identify areas of potential characterization improvements in the current glass property/composition models.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Predicting thermodynamic and thermophysical properties of molten chloride salts from ab-initio and classical molecular dynamics simulations

Molten salt reactors (MSRs) are among the advanced concepts pursued under the generation IV nuclear energy technology umbrella. However, the basic concept is not new and was first developed as part of the effort to power aircrafts with nuclear energy in the 1950’s. Later in the 1960’s, Oak Ridge National Laboratory (ORNL) built and operated the Molten-Salt Reactor Experiment (MSRE). This reactor used a fluoride salt with uranium as fuel. Fluorides salts are still highly relevant and proposed in several designs. In addition, chloride salts are being considered for MSRs operating in the fast neutron spectrum. This report focuses on chloride salts.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗