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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 OSTI2015

Comparison of topotactic fluorination methods for complex oxide films

We have investigated the synthesis of SrFeO{sub 3−α}F{sub γ} (α and γ ≤ 1) perovskite films using topotactic fluorination reactions utilizing poly(vinylidene fluoride) as a fluorine source. Two different fluorination methods, a spin-coating and a vapor transport approach, were performed on as-grown SrFeO{sub 2.5} films. We highlight differences in the structural, compositional, and optical properties of the oxyfluoride films obtained via the two methods, providing insight into how fluorination reactions can be used to modify electronic and optical behavior in complex oxide heterostructures.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Improved Cycling Performance of Li-Excess Cation-Disordered Cathode Materials upon Fluorine Substitution

We report the recent discovery of Li-excess cation-disordered rock salt cathodes has greatly enlarged the design space of Li-ion cathode materials. Evidence of facile lattice fluorine substitution for oxygen has further provided an important strategy to enhance the cycling performance of this class of materials. Here, a group of Mn 3+ –Nb 5+ -based cation-disordered oxyfluorides, Li 1.2 Mn 3+ 0.6+0.5x Nb 5+ 0.2-0.5x O 2-x F x (x = 0, 0.05, 0.1, 0.15, 0.2) is investigated and it is found that fluorination improves capacity retention in a very significant way. Combining spectroscopic methods and ab initio calculations, it is demonstrated that the increased transition-metal redox (Mn 3+ /Mn 4+ ) capacity that can be accommodated upon fluorination reduces reliance on oxygen redox and leads to less oxygen loss, as evidenced by differential electrochemical mass spectroscopy measurements. Furthermore, it is found that fluorine substitution also decreases the Mn 3+ -induced Jahn–Teller distortion, leading to an orbital rearrangement that further increases the contribution of Mn-redox capacity to the overall capacity.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Synthesizing High-Capacity Oxyfluoride Conversion Anodes by Direct Fluorination of Molybdenum Dioxide (MoO 2 )

High-capacity metal oxide conversion anodes for lithium-ion batteries (LIBs) are primarily limited by their poor reversibility and cycling stability. In this study, a promising approach has been developed to improve the electrochemical performance of a MoO 2 anode by direct fluorination of the prelithiated MoO 2 . The fluorinated anode contains a mixture of crystalline MoO 2 and amorphous molybdenum oxyfluoride phases, as determined from a suite of characterization methods including X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy, and scanning transmission electron microscopy. Electrochemical measurements indicate that fluorination facilitates the conversion reaction kinetics, which leads to increased capacity, higher coulombic efficiency, and better cycling stability as compared to the nonfluorinated samples. Overall, these results suggest that fluorination after prelithiation not only favors formation of the oxyfluoride phase but also improves the lithium-ion diffusivity and reversibility of the conversion reaction, making it an attractive approach to address the problems of conversion electrodes. These findings provide a new route to design high-capacity negative electrodes for LIBs.

25 ENERGY STORAGE↗
DOE OSTI2019

Synergistic Effects of Side-Chain Engineering and Fluorination on Small Molecule Acceptors to Simultaneously Broaden Spectral Response and Minimize Voltage Loss for 13.8% Efficiency Organic Solar Cells

In this paper, three small molecule (SM)-acceptors (POIT-IC, POIT-IC2F, and POIT-IC4F) are developed by combining the side-chain engineering located on the sp 3 -hybridized carbon atoms of the fused-ring core and the fluorination of end groups. From ITIC to POIT-IC, POIT-IC2F, and then to POIT-IC4F, the SM-acceptors show gradually broadened absorption spectra, increased maximum extinction coefficient, crystallinity, and electron mobilities due to the synergistic effects of side-chain engineering and fluorination. Compared with nonfluorinated ITIC and POIT-IC, as fluorination broadens the molecular spectra, POIT-IC2F and POIT-IC4F with alkoxyphenyl side chains show less decreased LUMO levels than IT-IC2F and IT-IC4F with alkylphenyl side chains, which are conducive to both higher V oc and J sc for organic solar cells (OSCs). Combined with polymer donor PM6, the POIT-IC4F-based OSCs achieve a device efficiency of up to 13.8% with a high V oc of 0.91 V and J sc of 20.9 mA cm –2 , which are significantly higher than that of the control OSCs based on ITIC (8.9%), POIT-IC (10.1%), or IT-IC4F (12.2%). An efficiency of 13.8% is one of the highest PCEs reported for the annealing-free OSCs. Our results show that the synergistic effects of side-chain engineering and fluorination on SM-acceptor can simultaneously broaden spectral response and minimize voltage loss of OSCs and ultimately achieve high device efficiency.

14 SOLAR ENERGY↗
DOE OSTI2012

On the Use of Thermal NF3 as the Fluorination and Oxidation Agent in Treatment of Used Nuclear Fuels

This paper presents results of our investigation on the use of nitrogen trifluoride as the fluorination or fluorination/oxidation agent for use in a process for separating valuable constituents from used nuclear fuels by employing the volatility of many transition metal and actinide fluorides. Nitrogen trifluoride is less chemically and reactively hazardous than the hazardous and aggressive fluorinating agents used to prepare uranium hexafluoride and considered for fluoride volatility based nuclear fuels reprocessing. In addition, nitrogen trifluoride’s less aggressive character may be used to separate the volatile fluorides from used fuel and from themselves based on the fluorination reaction’s temperature sensitivity (thermal tunability) rather than relying on differences in sublimation/boiling temperature and sorbents. Our thermodynamic calculations found that nitrogen trifluoride has the potential to produce volatile fission product and actinide fluorides from candidate oxides and metals. Our simultaneous thermogravimetric and differential thermal analyses found that the oxides of lanthanum, cerium, rhodium, and plutonium fluorinated but did not form volatile fluorides and that depending on temperature volatile fluorides formed from the oxides of niobium, molybdenum, ruthenium, tellurium, uranium, and neptunium. We also demonstrated near-quantitative removal of uranium from plutonium in a mixed oxide.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Lithium–sulfur battery with partially fluorinated ether electrolytes: Interplay between capacity, coulombic efficiency and Li anode protection

Seven partially fluorinated ethers (PFE) were explored as co-solvents for lithium-sulfur battery with the goal to understand the interplay between the molecular structure and the electrochemical properties, including capacity, Coulombic efficiency and SEI formation on the Li anode. Electrochemical cycling suggests a loose correlation between the Coulombic efficiency observed over 200 cycles and the fluorination degree of the PFE, which correlates with the computed pKa of the C–H bond of the ethers. PFE with lower pKa (<36) tends to chemically react with lithium anode forming a solid-electrolyte-interphase (SEI) layer thus preventing the shuttling effect of the lithium polysulfides. The cycled lithium anodes with DOL/PFE electrolyte was discovered to produce a protective SEI analyzed by FT-IR and SEM/EDS. Computations of the interactions between the PFEs of interest and a lithium surface suggest the generation of LiF and unsaturated PFE derivatives which are easily reduced and polymerized on the Li surface. The PFE decomposition is more thermodynamically likely with increasing fluorination degree. This research sheds light on the role that fluorine substitution and structure play in the high Coulombic efficiencies observed for Li–S cells.

25 ENERGY STORAGE↗
DOE OSTI2016

Mechanochemical synthesis of low-fluorine doped aluminum hydroxide fluorides

Different aluminum hydroxide fluorides with varying Al/F molar ratios from 1:1.5 up to 1:0.05 were successfully synthesized by mechanochemical reactions. The characterization of the products by XRD, {sup 27}Al and {sup 19}F MAS NMR, thermal analysis, nitrogen adsorption and zeta potential techniques allows a detailed understanding of the structure and surface properties of the products. Using γ-Al(OH){sub 3} and β-AlF{sub 3}·3H{sub 2}O as OH- and F-sources, respectively, strongly disordered products were obtained with an Al: F molar ratio higher than 1:0.25. The fluorination degree has affected the amount of 4- and 5-fold coordinated Al sites, not present in the reactants. An evolution of the sub-coordinated Al-species has been detected also as a consequence of annealing processes. Obviously, these species affect the phase transition to alumina, by decreasing the transition temperature of the formation of α-Al{sub 2}O{sub 3}. Synthesis conditions (milling time, fluorination degree) play a crucial role for the product composition. - Graphical abstract: The impact of the combined action of the milling and the different fluorine doping on the structure of new aluminum hydroxide fluorides was followed by {sup 27}Al and {sup 19}F NMR and by other complementary techniques. - Highlights: • Low F-doped Al-hydroxide fluorides can be successfully prepared by mechanosynthesis. • Both F-doping and mechanochemical synthesis introduce a high number of defects in the structure. • The fluorination degree affects the amount of 4- and 5-fold coordinated Al sites as well as the transition temperature to corundum.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Trap Passivation in Indium-Based Quantum Dots through Surface Fluorination: Mechanism and Applications

Treatment of InP colloidal quantum dots (QDs) with hydrofluoric acid (HF) has been an effective method to improve their photoluminescence quantum yield (PLQY) without growing a shell. Previous work has shown that this can occur through the dissolution of the fluorinated phosphorus and subsequent passivation of indium on the reconstructed surface by excess ligands. In this article, we demonstrate that very significant luminescence enhancements occur at lower HF exposure though a different mechanism. At lower exposure to HF, the main role of the fluoride ions is to directly passivate the surface indium dangling bonds in the form of atomic ligands. The PLQY enhancement in this case is accompanied by red shifts of the emission and absorption peaks rather than blue shifts caused by etching as seen at higher exposures. Density functional theory shows that the surface fluorination is thermodynamically preferred and that the observed spectral characteristics might be due to greater exciton delocalization over the outermost surface layer of the InP QDs as well as alteration of the optical oscillator strength by the highly electronegative fluoride layer. Passivation of surface indium with fluorides can be applied to other indium-based QDs. PLQY of InAs QDs could also be increased by an order of magnitude via fluorination. We fabricated fluorinated InAs QD-based electrical devices exhibiting improved switching and higher mobility than those of 1,2-ethanedithiol cross-linked QD devices. The effective surface passivation eliminates persistent photoconductivity usually found in InAs QD-based solid films.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Specific Fluorine Labeling of the HyHEL10 Antibody Affects Antigen Binding and Dynamics

To more fully understand the molecular mechanisms responsible for variations in binding affinity with antibody maturation, we explored the use of site specific fluorine labeling and {sup 19}F nuclear magnetic resonance (NMR). Several single-chain (scFv) antibodies, derived from an affinity-matured series of anti-hen egg white lysozyme (HEL) mouse IgG1, were constructed with either complete or individual replacement of tryptophan residues with 5-fluorotryptophan ({sup 5F}W). An array of biophysical techniques was used to gain insight into the impact of fluorine substitution on the overall protein structure and antigen binding. SPR measurements indicated that {sup 5F}W incorporation lowered binding affinity for the HEL antigen. The degree of analogue impact was residue-dependent, and the greatest decrease in affinity was observed when {sup 5F}W was substituted for residues near the binding interface. In contrast, corresponding crystal structures in complex with HEL were essentially indistinguishable from the unsubstituted antibody. {sup 19}F NMR analysis showed severe overlap of signals in the free fluorinated protein that was resolved upon binding to antigen, suggesting very distinct chemical environments for each {sup 5F}W in the complex. Preliminary relaxation analysis suggested the presence of chemical exchange in the antibody-antigen complex that could not be observed by X-ray crystallography. These data demonstrate that fluorine NMR can be an extremely useful tool for discerning structural changes in scFv antibody-antigen complexes with altered function that may not be discernible by other biophysical techniques.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Passivation of oxide traps and interface states in GaAs metal-oxide-semiconductor capacitor by LaTaON passivation layer and fluorine incorporation

GaAs metal-oxide-semiconductor capacitor with TaYON/LaTaON gate-oxide stack and fluorine-plasma treatment is fabricated and compared with its counterparts without the LaTaON passivation interlayer or the fluorine treatment. Experimental results show that the sample exhibits better characteristics: low interface-state density (8 × 10{sup 11 }cm{sup −2}/eV), small flatband voltage (0.69 V), good capacitance-voltage behavior, small frequency dispersion, and small gate leakage current (6.35 × 10{sup −6} A/cm{sup 2} at V{sub fb} + 1 V). These should be attributed to the suppressed growth of unstable Ga and As oxides on the GaAs surface during gate-oxide annealing by the LaTaON interlayer and fluorine incorporation, and the passivating effects of fluorine atoms on the acceptor-like interface and near-interface traps.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Suppression of surface charge accumulation on Al{sub 2}O{sub 3}-filled epoxy resin insulator under dc voltage by direct fluorination

Surface charge accumulation on insulators under high dc voltage is a major factor that may lead to the reduction of insulation levels in gas insulated devices. In this paper, disc insulators made of Al{sub 2}O{sub 3}-filled epoxy resin were surface fluorinated using a F{sub 2}/N{sub 2} mixture (12.5% F{sub 2}) at 50 °C and 0.1 MPa for different durations of 15 min, 30 min and 60 min. A dc voltage was applied to the insulator for 30 min and the charge density on its surface was measured by an electrostatic probe. The results revealed significant lower surface charge densities on the fluorinated insulators in comparison with the original one. Surface conductivity measurements indicated a higher surface conductivity by over three orders of magnitude after fluorination, which would allow the charges to transfer along the surface and thus may suppress their accumulation. Further, attenuated total reflection infrared analysis and surface morphology observations of the samples revealed that the introduction of fluoride groups altered the surface physicochemical properties. These structure changes, especially the physical defects reduced the depth of charge traps in the surface layer, which was verified by the measurement of energy distributions of the electron and hole traps based on the isothermal current theory. The results in this paper demonstrate that fluorination can be a promising and effective method to suppress surface charge accumulation on epoxy insulators in gas insulated devices.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Relationship between the defect structure and fluorine-ion conductivity of La{sub 1−y}Sr{sub y}F{sub 3−y} (0 ⩽ y ⩽ 0.15) crystals according to X-ray and neutron diffraction data

The defect structure of crystals of as-grown nonstoichiometric tysonite (LaF{sub 3} type) La{sub 1−y}Sr{sub y}F{sub 3−y} phase (y = 0, 0.05, 0.07, and 0.15) has been investigated by X-ray diffraction and neutron diffraction. A concentration-driven structural transition from the β-La{sub 1−y}Sr{sub y}F{sub 3−y} modification to the α-La{sub 1−y}Sr{sub y}F{sub 3−}y modification in the range y = 0.05–0.10 has been observed for the first time. This transition correlates with the maximum of fluorine-ion conductivity (y = 0.05 ± 0.02) and the maximum in the melting curve (y = 0.07 ± 0.03). β-LaF{sub 3} and β-La{sub 0.95}Sr{sub 0.05}F{sub 2.95} crystals belong to the trigonal system (sp. gr. P3̄c1, Z = 6) and are twinned according to the merohedral twin law. Fine changes in the fluorine sublattice of β-La{sub 0.95}Sr{sub 0.05}F{sub 2.95} increase conductivity σ{sub 293K} to 3 × 10{sup −4} S/cm; hence, these crystals can be used as fluorine-conducting solid electrolytes (FCSEs) in solid-state ionics devices. Additional possibilities of ion transport over twin joints are discussed. In α-La{sub 0.85}Sr{sub 0.15}F{sub 2.85} crystal the symmetry group changes to P6{sub 3}/mmc, Z = 2; it is not twinned and its fluorine-ion conductivity is reduced.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

Change in the electronic properties of an InAs (111)A surface at oxygen and fluorine adsorption

Based on ab initio calculations, the adsorption of oxygen and fluorine on reconstructed (2 Multiplication-Sign 2) and unreconstructed (1 Multiplication-Sign 1) InAs (111)A surfaces is studied. The most stable adsorption positions are determined. It is shown that adsorption of oxygen on both surfaces gives rise to electronic states in the band gap. The preferential positions for oxygen adsorption on an InAs (111)A (2 Multiplication-Sign 2) surface are those where oxygen is bonded both to indium atoms and to arsenic atoms in the surface layer and also the vacant site between three indium atoms (the 'In-hollow position). Adsorption of fluorine brings about a pushing of the surface states out of the band gap; the position above indium atoms (the 'In-top position) is preferential for adsorbed fluorine. Adsorption of fluorine on an InAs (111)A (1 Multiplication-Sign 1) surface leads to the elimination of the surface state formed by indium p orbitals and to an unpinning of the Fermi level.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Fluorinated Electrolytes for Li-S Battery: Suppressing the Self-Discharge with an Electrolyte Containing Fluoroether Solvent

The fluorinated electrolyte containing a fluoroether 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) was investigated as a new electrolyte for lithium-sulfur (Li-S) batteries. The low solubility of lithium polysulfides (LiPS) in the fluorinated electrolyte reduced the parasitic reactions with Li anode and mitigated the self-discharge by limiting their diffusion from the cathode to the anode. The use of fluorinated ether as a co-solvent and LiNO3 as an additive in the electrolyte shows synergetic effect in suppressing the self-discharge of Li-S battery due to the formation of the solid electrolyte interphase (SEI) on both sulfur cathode and the lithium anode. The Li-S cell with the fluorinated electrolyte showed prolonged shelf life at fully charged state.

Fluorinated electrolyte↗
DOE OSTI2025

Extending the operating range and safety of Li-ion batteries with new fluorinated electrolytes

Orbia Fluor and Energy Materials (formerly Koura) has successfully developed a new class of fluorinated electrolyte solvents for lithium-ion batteries. In collaboration with Silatronix and Argonne National Laboratory, the team synthesized and screened over 20 novel fluorinated compounds, optimizing formulations that significantly enhance battery performance across critical metrics such as thermal stability, fast-charging capability, and cycling life at extreme temperatures. Electrolytes with fluorinated molecules developed in this program demonstrated superior performance in 2 Ah pouch cells, achieving over 1000 fast-charge cycles with minimal capacity fade, outperforming conventional carbonate-based electrolytes. Mechanistic studies revealed that the fluorinated electrolytes promote a stable solid electrolyte interphase at the anode and reduce cathode metal dissolution, contributing to improved long-term stability. These advancements mark a significant step toward safer, more efficient batteries for applications ranging from grid storage to defense systems to electric vehicles. We gratefully acknowledge DOE’s financial support through contract DE-EE0009642.

25 ENERGY STORAGE↗
DOE OSTI2011

Synthesis and characterization of the La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}} system and the fluorinated phases La{sub 1-x}Sr{sub x}FeO{sub 3-x}F{sub x}

The oxyfluorides La{sub 1-x}Sr{sub x}FeO{sub 3-x}F{sub x} have been prepared by fluorination of the precursor oxides La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}} via a low temperature route using poly(vinylidene fluoride) (PVDF). The structures of the oxides and oxyfluorides were investigated in detail by the Rietveld analysis of powder diffraction data. The oxyfluorides crystallize in the space group Pnma for 0<x{<=}0.9 (SrFeO{sub 2}F itself is cubic, space group Pm-3m) and show a sort of two-step structural distortion for decreasing x. Furthermore, a structural comparison of the oxyfluorides with the oxides is given, revealing an increase of the volume per La{sub 1-x}Sr{sub x}FeX{sub 3} unit during fluorination, of which the magnitude highly depends on the value of x. - Graphical abstract: The crystal structures of the perovskites La{sub 1-x}Sr{sub x}FeO{sub 3-x}F{sub x} for x=0.8 (a), 0.5 (b) and 0.1 (c). Highlights: > Oxyfluorides La{sub 1-x}Sr{sub x}FeO{sub 3-x}F{sub x} were prepared via low temperature fluorination using PVDF. > A structural investigation of the compounds La{sub 1-x}Sr{sub x}FeO{sub 3-x}F{sub x} is presented in detail. > Differences in structure are discussed in comparison with the precursor oxides La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Stereochemically‐Controlled Fluorinated Copolymers for Selectively Permeable Barrier Applications

Selective oxygen permeability coupled with low water vapor transmission is essential for biomedical and packaging applications requiring controlled oxygen flux under humid conditions. However, most high‐performance barrier polymers depend on perfluoroalkyl substances (PFAS), whose persistence and regulatory restrictions limit their long‐term applicability. We designed a series of stereocontrolled thiol‐yne‐based polyesters, including both fluorinated and non‐fluorinated variants, for selective oxygen permeability with considerable water barrier performance. Tailoring polymer crystallinity and morphology tuned both oxygen transport and mechanical properties. Fluorinated polymers demonstrated enhanced hydrophobicity and water resistance while maintaining oxygen diffusivity within a range relevant to oxygen‐sensing applications. Structure–property relationships were elucidated through small‐ and wide‐angle X‐ray scattering, revealing semi‐crystalline domains influenced by fluorine content and dithiol chain length. Barrier performance was rigorously evaluated via water vapor transmission rate and dynamic vapor sorption, showing reduced water uptake with increasing dithiol monomer length and crystallinity. In conclusion, this work introduces a PFAS‐free alternative to conventional barrier materials and establishes a tunable materials platform with potential relevance for biomedical devices and packaging systems requiring controlled oxygen permeability.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Tuning the surface energy of fluorinated diamond-like carbon coatings via plasma immersion ion implantation plasma-enhanced chemical vapor deposition with 1,1,1,2-tetrafluoroethane

Here, we demonstrate an environmentally friendly and scalable method to create fluorine-doped diamond-like carbon (F-DLC) coatings using plasma immersion ion implantation plasma-enhanced chemical vapor deposition (PIII-PECVD) with 1,1,1,2-tetrafluoroethane. F-DLC films tend to have low wettability and good mechanical flexibility, which make them suitable for applications in biomedical devices and antibiofouling surfaces. We report on the effects of fluorine incorporation on the surface chemistry, surface energy, and morphology of these coatings, showing that our method is effective in increasing the fluorine content in the F-DLC up to 40%. We show that the addition of fluorine leads to a decrease in surface energy, which is consistent with a reduction in surface wettability.

Contact angle↗