Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “FLUORINATION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Fluorinated polythiophenes with ester side chains for boosting the V OC and efficiency in non-fullerene polymer solar cells

As the power conversion efficiency (PCE) of organic photovoltaics (OPVs) approximates the 19 % threshold, wide bandgap (WBG) polythiophenes (PTs) have gained increasing attention due to their simple chemical structures and ease of synthesis, making them promising candidates for large-scale production. However, the benchmark polymer poly(3-hexylthiophene) (P3HT) is limited by its high-lying HOMO energy level, which restricts the open-circuit voltage (V OC ) in solar cells. Here, in this study, we introduce a novel series of PT derivatives (PDC8-T, PDC8-3T, PDC16-3T, and PDC16-3T-2F) featuring ester side chains designed to fine-tune electronic properties through a streamlined three-step synthesis. Additionally, we incorporated a π-spacer to reduce steric hindrance and elongated alkyl side chains to improve solubility and processability. Compared to P3HT, these PT derivatives demonstrate a significant reduction in HOMO energy levels, lowering by approximately 0.3–0.4 eV. Among them, PDC16-3T-2F—with fluorine atom substitution—achieves the lowest HOMO energy level, induces a coplanar molecular conformation, and enhances polymer aggregation behavior. We evaluated these PT derivatives in inverted non-fullerene bulk-heterojunction (NFA BHJ) OPVs. The PDC8-3T device showed a relatively low PCE of 0.69 %, with a V OC of 0.76 V, a short-circuit current density (J SC ) of 3.32 mA/cm 2 , and a fill factor (FF) of 27.3 %. In contrast, the PDC16-3T-2F device achieved an impressive PCE of 7.21 %, with a V OC of 0.85 V, a J SC of 14.60 mA/cm 2 , and an FF of 58.4 %. This remarkable improvement is attributed to the fluorine substitution, which not only enhances molecular orientation but also downshifts the HOMO energy level and further boosts the V OC . Hence, these molecular design strategies have led to a fibrillar bicontinuous interpenetrating network with optimal nanoscale phase separation within the active layer.

14 SOLAR ENERGY↗
DOE OSTI2017

A Fluorinated Ether Electrolyte Enabled High Performance Prelithiated Graphite/Sulfur Batteries

Lithium/sulfur (Li/S) batteries have attracted great attention as a promising energy storage technology, but so far their practical applications are greatly hindered by issues of polysulfide shuttling and unstable lithium/electrolyte interface. To address these issues, a feasible strategy is to construct a rechargeable prelithiated graphite/sulfur batteries. In this study, a fluorinated ether of bis(2,2,2-trifluoroethyl) ether (BTFE) was reported to blend with 1,3-dioxolane (DOL) for making a multifunctional electrolyte of 1.0 M LiTFSI DOL/BTFE (1:1, v/v) to enable high performance prelithiated graphite/S batteries. First, the electrolyte significantly reduces polysulfide solubility to suppress the deleterious polysulfide shuttling and thus improves capacity retention of sulfur cathodes. Second, thanks to the low viscosity and good wettability, the fluorinated electrolyte dramatically enhances the reaction kinetics and sulfur utilization of high-areal-loading sulfur cathodes. More importantly, this electrolyte forms a stable solid-electrolyte interphase (SEI) layer on graphite surface and thus enables remarkable cyclability of graphite anodes. Lastly, by coupling prelithiated graphite anodes with sulfur cathodes with high areal capacity of ~3 mAh cm -2 , we demonstrate prelithiated graphite/sulfur batteries that show high sulfur-specific capacity of ~1000 mAh g -1 and an excellent capacity retention of >65% after 450 cycles at C/10.

25 ENERGY STORAGE↗
DOE OSTI2026

Lithium–Sulfur Batteries Enabled by Fluorine-Free Electrolytes with a Compressed Solvation Structure

In this paper, a fluorine-free aromatic cosolvent strategy is presented to regulate electrolyte solvation chemistry in Li-S batteries with sulfurized polyacrylonitrile (SPAN) cathodes. Assisted by the Uni-ELF AI tool and experimental validation, toluene is identified as an optimal weakly solvating cosolvent. Its incorporation compresses the Li⁺ solvation sheath and induces an anion-dominated solvation structure, thereby enhancing interfacial ion transport and sulfur redox kinetics through controlled π-π interactions with polysulfides. Consequently, Li || Li symmetric cells exhibit stable cycling for over 1,000 cycles at a current density of 1 mA cm⁻². Meanwhile, Li-S cells employing high-loading SPAN cathodes retain more than 75% of their initial capacity after 250 cycles at -10 °C. Additionally, a practical pouch cell with high SPAN loading and a low electrolyte-to-SPAN ratio of 3 µL mg⁻¹ delivers an initial capacity of around 600 mAh gSPAN⁻¹, underscoring the potential of fluorine-free electrolytes for practical metal-sulfur batteries.

25 ENERGY STORAGE↗
DOE OSTI2011

Determining concentration depth profiles in fluorinated networks by means of electric force microscopy

By means of electric force microscopy, composition depth profiles were measured with nanometric resolution for a series of fluorinated networks. By mapping the dielectric permittivity along a line going from the surface to the bulk, we were able to experimentally access to the fluorine concentration profile. Obtained data show composition gradient lengths ranging from 30 nm to 80 nm in the near surface area for samples containing from 0.5 to 5 wt. % F, respectively. In contrast, no gradients of concentration were detected in bulk. This method has several advantages over other techniques because it allows profiling directly on a sectional cut of the sample. By combining the obtained results with x-ray photoelectron spectroscopy measurements, we were also able to quantify F/C ratio as a function of depth with nanoscale resolution.

36 MATERIALS SCIENCE↗
DOE OSTI2012

UV photodissociation dynamics of iodobenzene: Effects of fluorination

The UV photochemistry of various fluorinated iodobenzenes (4-fluoro-, 2,4-difluoro-, 3,5-difluoro-, and perfluoro-iodobenzene) has been investigated at many wavelengths by velocity map imaging, time-resolved near infrared absorption spectroscopy and (spin-orbit resolved) ab initio calculations of the ground and excited state potentials along the C-I stretch coordinate, R{sub C-I}. The textbook description of the near UV photochemistry of CH{sub 3}I, i.e., {sigma}*(leftarrow)n excitation to the {sup 3}Q{sub 0+} state, followed by direct dissociation (to yield spin-orbit excited iodine atom (I*) products) or by non-adiabatic coupling via a conical intersection (CI) with the {sup 1}Q{sub 1} potential (to yield ground state iodine (I) atoms) is shown to provide a good zero-order model for aryl iodide photochemistry also. However, the aryl halides also possess occupied {pi} and low-lying {pi}* orbitals, and have lower (C{sub 2v} or C{sub s}) symmetry than CH{sub 3}I. Both of these factors introduce additional subtleties. For example, excitations to and predissociation of {pi}{pi}* excited states provide additional routes to I products, most obviously at long UV wavelengths. n{sigma}*/{pi}{sigma}* configuration mixing stabilizes the (analogue of the) {sup 3}Q{sub 0+} potential energy surface (PES), to an extent that scales with the degree of fluorination; the corresponding 4A{sub 1} PES in C{sub 6}F{sub 5}I is actually predicted to exhibit a minimum at extended R{sub C-I}. This has the effect of extending the long wavelength threshold for forming I* products. The lowered symmetry enables an additional (sloped) CI with the 5A{sub 2} (9A{sup ''} in 2,4-difluorobenzene) PES, which provides an extra non-adiabatic route to (fast) ground state I atoms when populating the 4A{sub 1} PES at shorter UV excitation wavelengths.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Characteristics of ultra low-k nanoporous and fluorinated silica based films prepared by plasma enhanced chemical vapor deposition

Low dielectric constant (low-k) silica based films were deposited on p-type silicon and polycarbonate substrates by radio frequency (RF) plasma enhanced chemical vapor deposition method at low temperature. A mixture of tetraethoxysilane vapor, oxygen, and tetrafluoromethane (CF{sub 4}) was used for the deposition of the films in forms of two structures called as SiO{sub x}C{sub y} and SiO{sub x}C{sub y}F{sub z}. Properties of the films were controlled by amount of porosity and fluorine content in the film matrix. The influence of RF power and CF{sub 4} flow on the elemental composition, deposition rate, surface roughness, leakage current, refractive index, and dielectric constant of the films were characterized. Moreover, optical emission spectroscopy was applied to monitor the plasma process at the different parameters. Electrical characteristics of SiO{sub x}C{sub y} and SiO{sub x}C{sub y}F{sub z} films with metal-oxide-semiconductor structure were investigated using current-voltage analysis to measure the leakage current and breakdown field, as well as capacitance-voltage analysis to obtain the film's dielectric constant. The results revealed that SiO{sub x}C{sub y} films, which are deposited at lower RF power produce more leakage current, meanwhile the dielectric constant and refractive index of these films decreased mainly due to the more porosity in the film structure. By adding CF{sub 4} in the deposition process, fluorine, the most electronegative and the least polarized atom, doped into the silica film and led to decrease in the refractive index and the dielectric constant. In addition, no breakdown field was observed in the electrical characteristics of SiO{sub x}C{sub y}F{sub z} films and the leakage current of these films reduced by increment of the CF{sub 4} flow.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Impact of fluorine based reactive chemistry on structure and properties of high moment magnetic material

The impact of the fluorine-based reactive ion etch (RIE) process on the structural, electrical, and magnetic properties of NiFe and CoNiFe-plated materials was investigated. Several techniques, including X-ray fluorescence, 4-point-probe, BH looper, transmission electron microscopy (TEM), and electron energy loss spectroscopy (EELS), were utilized to characterize both bulk film properties such as thickness, average composition, Rs, ρ, Bs, Ms, and surface magnetic “dead” layers' properties such as thickness and element concentration. Experimental data showed that the majority of Rs and Bs changes of these bulk films were due to thickness reduction during exposure to the RIE process. ρ and Ms change after taking thickness reduction into account were negligible. The composition of the bulk films, which were not sensitive to surface magnetic dead layers with nano-meter scale, showed minimum change as well. It was found by TEM and EELS analysis that although both before and after RIE there were magnetic dead layers on the top surface of these materials, the thickness and element concentration of the layers were quite different. Prior to RIE, dead layer was actually native oxidation layers (about 2 nm thick), while after RIE dead layer consisted of two sub-layers that were about 6 nm thick in total. Sub-layer on the top was native oxidation layer, while the bottom layer was RIE “damaged” layer with very high fluorine concentration. Two in-situ RIE approaches were also proposed and tested to remove such damaged sub-layers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Investigation of fluorine-doped tin oxide based optically transparent E-shaped patch antenna for terahertz communications

In this paper, a fluorine-doped tin oxide based optically transparent E-shaped patch antenna is designed and its radiation performance is analyzed in the 705 – 804 GHz band. As optically transparent antennas can be mounted on optical display, they facilitate the reduction of overall system size. The proposed antenna design is simulated using electromagnetic solver - Ansys HFSS and its characteristics such as impedance bandwidth, directivity, radiation efficiency and gain are observed. Results show that the fluorine-doped tin oxide based optically transparent patch antenna overcomes the conventional patch antenna limitations and thus the same can be used for solar cell antenna used in satellite systems.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2010

Charge exchange of multiply charged fluorine and lithium ions with Ne atoms

The charge exchange of multiply charged fluorine and lithium ions with Ne atoms in a gas jet was recorded from the line spectra in the 125 - 350 A range, which arise from the radiative decay of the excited states of Li II - III and F III - VIII ions populated in the charge exchange. In the F III - VI ion spectra obtained from the plasma - gas interaction region we observed transitions from levels with an open (partly filled or completely open) 2s-shell, which may be populated in sequential events of single-electron charge exchange as well as in double- and many-electron charge exchange. Partial cross sections were calculated for the single-electron charge exchange of F VIII ions with Ne atoms. By way of Hartree - Fock energy level calculations it was possible to reveal resonances between the ground states of k-fold (k = 1 - 4) ionised donor atoms and the states of k-fold excited multiply charged fluorine ion resulting from the k-fold charge exchange of F VIII ions. These resonances may be responsible for the relatively large cross sections of double- and many-electron charge exchange (laser applications and other topics in quantum electronics)

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2017

Optical properties of heavily ytterbium- and fluorine-doped aluminosilicate core fibres

An improved MCVD process has been proposed which allows one to fabricate ytterbium-doped fibre preforms with a fluorine-doped aluminosilicate glass-based core. Using this process, we have demonstrated the possibility of codoping the glass with high Yb{sup 3+} concentration (about 2 wt %), high fluorine concentration (2 wt %) and aluminium oxide concentration above 1.5 mol % (to ensure high ytterbium solubility), resulting in a record low refractive index of the glass (Δn ≈ 0.000 – 0.003). A series of fibre with a SiO{sub 2} – Al{sub 2}O{sub 3} – GeO{sub 2} – Yb{sub 2}O{sub 3} – F core have been fabricated and their optical characteristics have been investigated. In particular, we have demonstrated the possibility of reaching the highest possible lasing efficiency (82.7 % with respect to absorbed pump power). We have studied the photodarkening level in the fibres as a function of ytterbium concentration and demonstrated the feasibility of making ytterbium-doped fibre amplifiers based on the described fibres, with an extremely low output power degradation rate (less than 20 % after 10 000 h of continuous operation). (paper)

36 MATERIALS SCIENCE↗
DOE OSTI2020

Comparative analysis of characteristics of a supersonic cw chemical HF laser on molecular fluorine and nitrogen trifluoride

We have experimentally studied the characteristics of a supersonic cw chemical HF laser with a flat nozzle array based on a nozzle – nozzle reagent mixing scheme operating with the use of F{sub 2} – D{sub 2} – He and NF{sub 3} – D{sub 2} – He fuel compositions in an atomic fluorine generator. The active medium flow field pattern, its gas-dynamic characteristics, and the laser radiation spectrum are considered. The comparison of these characteristics has made it possible to establish a strong impact on the flow field (lasing zone length) of the chemical composition of the combustion products from the atomic fluorine generator. The gas-dynamic parameters of the active medium formed by using a NF{sub 3} – D{sub 2} – He fuel have turned out to be less acceptable in terms of the gas flow pressure recovery than in the case of F{sub 2} – D{sub 2} – He fuel, while the radiation spectrum was more preferable from the viewpoint of passing through the atmosphere. (paper)

36 MATERIALS SCIENCE↗
DOE OSTI2020

Efficient lasing in mixtures of helium and fluorine in diffuse discharges formed by runaway electrons

The parameters of stimulated lasing in diffuse discharges formed in mixtures of helium and fluorine in a strongly inhomogeneous electric field are investigated. Lasing is obtained in the visible and VUV spectral regions on the transitions of fluorine atoms and molecules. It is shown that lasing in He – F{sub 2} mixtures at a wavelength of 157 nm continues for several half-periods of the discharge current. Due to the homogeneity of the diffuse discharge, the maximum lasing efficiency of the F{sub 2} laser is 0.15 %, which corresponds to the efficiency of this type of lasers pumped by pre-ionised transverse volume discharges. (paper)

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2010

Evaluation of the diffusion coefficient of fluorine during the electropolishing of niobium

Future accelerators require unprecedented cavity performance, which is strongly influenced by interior surface nano-smoothness. Electropolishing (EP) is the technique of choice being developed for high–field SRF cavities. Previous study has shown that the mechanism of Nb electropolishing proceeds by formation and dissolution of a compact salt film under fluorine diffusion-limited mass transport control. We pursue an improved understanding of the microscopic conditions required for optimum surface finishing. The viscosity of the standard electrolyte has been measured using a commercial viscometer, and the diffusion coefficient of fluorine was derived at a variety of temperatures from 0ºC to 50ºC using an Nb rotating disk electrode. In addition, data indicate that electrode kinetics becomes competitive with the mass transfer current limitation and increases dramatically with temperature. These findings are expected to guide the optimization of EP process parameters for achieving controlled, reproducible and uniform nano-smooth surface finishing of SRF cavities.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Tunnel Emission from Nanostructured Field-Emission Array Cathodes with a Fluorine–Carbon Coating

Variations of the morphology and field-emission properties of surface-structured n- and p-type silicon wafers have been studied. The silicon surface has been structured by etching in a fluorine–carbon plasma and depositing subnanodimensional island carbon masks. It has been shown that surface structuring in a fluorine–carbon plasma makes it possible to reach desired field-emission currents in electric fields of different strengths. Physicochemical models of field emission mechanisms and models of destruction of surface-modified multipoint silicon array cathodes have been considered.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Surface Modified Pinecone Shaped Hierarchical Structure Fluorinated Mesocarbon Microbeads for Ultrafast Discharge and Improved Electrochemical Performances

Among all primary lithium batteries, Li/CF x primary battery possesses the highest energy density of 2180 Wh kg -1 . However, a key limitation is its poor rate capability because the cathode material CF x is intrinsically a poor electronic conductor. Here, we developed a so-called “doing subtraction” method to modify the pinecone shaped fluorinated mesocarbon microbead (F-MCMB). The modified fluorinated mesocarbon microbead (MF-MCMB), manifests the advantage of open-framed structure, possesses good electronic conductivity and removes transport barrier for lithium ions. Thus, high capacity performance and excellent rate capability without compromising capacity can be obtained. A capacity of 343 mAhg -1 and a maximum power density of 54600 W kg -1 are realized at an ultrafast rate of 40 C (28A g -1 ). Additionally, the MF-MCMB cathode does not show any voltage delay even at 5C during the discharge, which is a remarkable improvement over the state-of-the-art CF x materials.

25 ENERGY STORAGE↗
DOE OSTI2011

Fluorination of Uranium Metal to UF3 and UF4 by Nitrogen Trifluoride: Evidence for Elusive UF2

We have recently found that uranium and plutonium metals will react with nitrogen trifluoride (NF3) at temperatures below 120?C. These are the first reported instances of such low temperature fluorination reactions using NF3 and implicate metal catalyzed dissociation of the NF3 bond. We additionally present preliminary evidences for a surface mediated product distribution. Reaction of uranium metal with NF3 promotes products that are apparently determined by the concentration of the fluorinating reagent between temperatures of 60 to 120?C.

NF3, Fluorination, U metal, UF4, UF3, UF2↗
DOE OSTI2020

Fluorine Limits and Impacts in High-Level Waste Glass Compositions

The impact of elevated fluorine (F) content on Hanford high-level waste (HLW) glasses has not previously been studied in detail. This effort represents the first systematic study to determine what F concentration limits should be used for the design of alkali-borosilicate-based Hanford Waste Treatment and Immobilization Plant (WTP) HLW glasses, and to document the technical basis for that limit. If alkali borosilicate glass made from Hanford HLW can accommodate a large amount of F, the large capital costs for complex sludge washing facilities may be avoided, as would much of the operational costs and negative schedule impacts associated with handling the large volumes of water required to dissolve these salts. In order to determine a limit for F in likely HLW glass compositions, an evaluation was conducted on glasses with F ≤ 0.90 mass% from previous nuclear waste glass studies. The collected dataset contains 239 glasses (232 HLW glasses and 7 LAW glasses) including 109 glasses with 0.9 ≤ F mass% ≤ 2.5, 116 with 2.5 < F mass% ≤ 8.0, and 14 with F mass% ≥ 8 (max. F mass% = 17.42). The collected composition and property data were analyzed to determine the basis for the F tolerance, i.e. the maximum F concentration that can be processed without potential issues. Fluorine volatility, product consistency test (PCT) response, liquidus temperature (T L ), glass melt viscosity, and crystallinity have been investigated. No limits for F concentration can be made based on F volatility, T L , or glass melt viscosity, because the data show that high F in glasses do not indicate, with high probability, being restricted by those property constrains. However, crystallinity and PCT response were used to estimate the F tolerance. The results show that glasses with high F (≥ 0.90 mass%) are more likely to form large fractions of F-containing crystal phases which may increase PCT responses, i.e. decrease the glass durability. Based on the results of crystallinity and PCT data, the F tolerance of 4.5 mass% is estimated. There is no evidence of other glass components, such as calcium oxides and alkali metal oxides have combined impacts with F on the glass properties. Overall, the available high-F glass data is limited, especially in the designed HLW glass composition regions. Future work on formulation and testing of HLW glasses with F ≥ 0.9 mass% will close the data gaps and expand operational flexibility with respect to the fluoride tolerances. Volatility of F from melters and corrosion of materials in contact with glass melts are important for processing of high-F wastes; yet no test data are currently available. It is recommended tests be conducted to address these two potential issues.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗