Amount Of Fluorine Research Articles

Influence of fluoroalkyl chains on structural, morphological, and optical properties of silica-based coatings on flexible substrate

The presented work aimed to investigate the dependence of the fluoroalkyl precursors, used in the sol–gel synthesis of silica-based materials, on the structural and optical properties of the final coating deposited on polyethylene terephthalate foil. The structural properties of the fabricated coatings were analyzed using Raman Spectroscopy, X-ray Photoelectron Spectroscopy, and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS). The morphology of the samples was investigated using SEM and Atomic Force Microscopy methods. Optical properties were analyzed using ellipsometry and reflectometry. Additionally, the wettability properties with the surface free energy were determined. The cracks-free layers were obtained on the elastic substrate as proved by microscopic observations. The expected chemical structure was confirmed using spectroscopic studies that showed fluoroalkyl chains build into the final structure. The coatings (except the one obtained from the precursor with the longest fluoroalkyl chain) exhibited smooth surfaces and high transparency with a transmittance of 92% in the visible range. They had low refractive indices, which could be tuned in a wide range from 1.435 down to 1.347 (at 633 nm) by changing the fluorinated precursors and increasing the amount of fluorine in the material. A longer fluoroalkyl chain also improved the hydrophobic character of the coating. Such materials have great potential application in flexible photonic structures (for example in photovoltaics). Highlights, Influence of fluoroalkyl chains on structural, morphological, and optical properties of silica-based coatings on flexible substrate . • Fluorinated silica-based hybrid coatings deposited on polymeric foil were reported • The structural properties of the fabricated coatings were analyzed • The wettability properties with the surface free energy and optical properties were determined • The modification of properties depending on the content of fluorinated carbons was shown

Facile fabrication of robust, biomimetic and superhydrophobic polymer/graphene-based coatings with self-cleaning, oil-water separation, anti-icing and corrosion resistance properties

In this paper, a robust, biomimetic and superhydrophobic polymer/graphene-based coatings have been successfully prepared on different substrates by spraying and thermal treatment method. The aim for this design was to obtain the robust superhydrophobic coatings with versatility, such as self-cleaning, oil-water separation, anti-icing and corrosion resistance. The tests have demonstrated that water contact angle (WCA) and water sliding angle (WSA) values of as-prepared coatings reached 159.2° and 4° when the content of graphene in coatings was 6 mg/mL. The formation of superhydrophobic effect with low adhesion could be ascribed to micro- and nano-scaled “radial-like” fibrous-network morphology with a great amount of fluorine and silicon concentrated on the surface of coatings, which have been well accorded with the formative factors of natural superhydrophobic phenomenon. Except that, the mechanical stability tests have illustrated the friction-abrasion for coatings could maintain superhydrophobicity after 100 cycles. Along with scratch and adhesive tests, the results have also revealed the as-prepared superhydrophobic coatings possessed good mechanical strength, heat resistance and chemical stability. Moreover, the self-cleaning behavior for the coatings was also found. Most of all, the as-prepared coatings can also accomplish oil-water separation, anti-icing and corrosion resistance and their possible action mechanism were primarily proposed. Based on these facts, the superhydrophobic robust polymer/graphene coatings have been expected to be used in agricultural machinery, automobiles and national defense industry in future.

Estimation of recoverable resources used in lithium-ion batteries from portable electronic devices in Japan

Lithium-ion batteries (LIBs) are commonly used in portable electronic devices and are becoming increasingly popular worldwide in recent years. As LIBs are composed of several metals, secondary material recovery is vital in promoting sustainable resource use, but a statistical database on the amount and material information of LIBs consumed in Japan is not available. To develop a globally harmonized strategy for LIB recycling, this study estimates the recoverable resources used in LIBs from portable electronic devices in Japan. An analysis of LIB samples and estimated consumption amounts reveals that cobalt has been the most utilized resource of obsolete LIBs, but its usage has gradually decreased in recent years. Instead, nickel usage has increased in both obsolete and in-use LIBs, corresponding to the trend changes of cathode materials. Moreover, the amounts of copper, lithium, manganese, and fluorine steadily increased with the increase in LIB usage. Our results also illustrate the effectiveness of environmental labels in collecting LIBs and separating them into cobalt-rich or nickel-rich groups. We applied a vacuum heat treatment to the LIBs and found that this pretreatment is effective in inactivating LIBs. This study evaluates the LIB waste collection rate in Japan and discuss the challenges behind it. As the demand for sustainable resource use from discarded LIBs will increase in the future, this study will contribute to the development of strategies to continuously improve LIB recycling and resource recovery.

Existing form and distribution of fluorine and phosphorus in phosphate rock acid-insoluble residue.

The phosphorus-sulfur two-step production process was developed in the wet-process phosphoric acid industry to solve phosphogypsum pollution. However, phosphate rock acid-insoluble residue is produced during this process as a new type of solid waste, which had a high potential for recycling. For process reasons, this type of residue still contains a certain amount of fluorine and phosphorus, which has a massive impact on the potential uses of phosphate rock acid-insoluble residue. Therefore, X-ray photoelectron spectroscopy, Raman, electron probe spectroscopy, and scanning electron microscopy were used to examine the existing form and distribution of fluorine and phosphorus in phosphate rock acid-insoluble residue. The mass fraction of F and P2O5 were 9.407% and 11.862%, respectively. Fluorine existed mainly in the form of fluorite, fluorapatite and metal fluoride. Phosphorus existed mainly in the form of fluoroapatite, phosphate, hydrogen phosphate, and dihydrogen phosphate. The total phosphate, hydrogen phosphate and dihydrogen phosphate contents were much higher than that of fluoroapatite, whereas the fluoroapatite content was higher than that of fluorite and metal fluoride. Fluorine and phosphorus were distributed in the form of agglomerates in the phosphate rock acid-insoluble residue. Fluorine and phosphorus were partially correlated, showing a weak relationship in the high phosphorus area.

Structure, Magnetism, and Thermal Stability of La2NiO2.5F3: A Ruddlesden-Popper Oxyfluoride Crystallizing in Space Group P42/nnm.

We report on the new Ruddlesden-Popper (RP) oxyfluoride La2NiO2.5F3 containing an unprecedented high amount of fluorine and Ni2+. This oxyfluoride was prepared by topochemical low-temperature fluorination of La2NiO4, which was obtained by a soft chemistry synthesis, with poly(vinylidene difluoride) (PVDF) as fluorinating agent. La2NiO2.5F3 is the first n = 1 RP compound crystallizing in the tetragonal space group P42/nnm (a = 5.7297(6) Å and c = 13.0106(2) Å). The crystal structure shows a unique tilting scheme of the NiO4F2 octahedra that has so far been only theoretically predicted. Combined neutron and X-ray powder diffraction experiments together with bond-valence-sum and DFT+U calculations reveal an unusual anion ordering with fluoride being located on the apical anion sites of the NiO4F2 octahedra. Excess fluorine ions were found to populate two of the four interstitial anion sites in an ordered fashion. A third interstitial anion position is occupied by oxygen ions while the fourth site remains unoccupied. This hitherto unobserved ordering scenario in RP oxyfluorides promotes a strong layerwise alternating tilting of the NiO4F2 octahedra. Magnetic measurements show strong antiferromagnetic interactions with a high Néel temperature of about 225 K and a pronounced ZFC/FC splitting most likely as the result of a small ferromagnetic moment arising from spin canting. The electronic structure was characterized by DFT and UV-vis spectroscopy, and a strong increase of Eg was found compared to La2NiO4 (3.4 eV vs 1.3 eV).

Synthesis and optical analyses of fluorine doped tin oxide (SnO2) nanoparticles

The study was focused on to synthesis of pure and fluorine-doped SnO2 (FTO) nanoparticles by sol-gel method combining with low temperature, 300 °C, annealing process, immediately after gelation. The relationship between the structural and optical properties of FTO was investigated to understand the effects of fluorine amount on the optical transmittance ratio and configuration of electronic energy levels. Homogeneous distribution of fluorine in SnO2 lattice was observed at all synthesized FTO powders. In addition, the change in electronic energy configuration was investigated by the fluctuation from 3.85 eV to 3.64 eV in band gap energy values according to the amount of fluorine in SnO2. The optical transmittance values were observed in the range of ∼90% and 95%. Optical analysis proved that the amount of fluorine had no specific effect on the high optical transmittance performances of SnO2 particles in the visible region, however the F amount had high impact on band gap energy values due to due to varying defect intensity.

Antibacterial Properties of a Honeycomb-like Pattern with Cellulose Acetate and Silver Nanoparticles.

This study involved the preparation and characterization of structures with a honeycomb-like pattern (HCP) formed using the phase separation method using a solution mixture of chloroform and methanol together with cellulose acetate. Fluorinated ethylene propylene modified by plasma treatment was used as a suitable substrate for the formation of the HCP structures. Further, we modified the HCP structures using silver sputtering (discontinuous Ag nanoparticles) or by adding Ag nanoparticles in PEG into the cellulose acetate solution. The material morphology was then determined using atomic force microscopy (AFM) and scanning electron microscopy (SEM), while the material surface chemistry was studied using energy dispersive spectroscopy (EDS) and wettability was analyzed with goniometry. The AFM and SEM results revealed that the surface morphology of pristine HCP with hexagonal pores changed after additional sample modification with Ag, both via the addition of nanoparticles and sputtering, accompanied with an increase in the roughness of the PEG-doped samples, which was caused by the high molecular weight of PEG and its gel-like structure. The highest amount (approx. 25 at %) of fluorine was detected using the EDS method on the sample with an HCP-like structure, while the lowest amount (0.08%) was measured on the PEG + Ag sample, which revealed the covering of the substrate with biopolymer (the greater fluorine extent means more of the fluorinated substrate is exposed). As expected, the thickness of the Ag layer on the HCP surface depended on the length of sputtering (either 150 s or 500 s). The sputtering times for Ag (150 s and 500 s) corresponded to layers with heights of about 8 nm (3.9 at % of Ag) and 22 nm (10.8 at % of Ag), respectively. In addition, we evaluated the antibacterial potential of the prepared substrate using two bacterial strains, one Gram-positive of S. epidermidis and one Gram-negative of E. coli. The most effective method for the construction of antibacterial surfaces was determined to be sputtering (150 s) of a silver nanolayer onto a HCP-like cellulose structure, which proved to have excellent antibacterial properties against both G+ and G− bacterial strains.

Fluoroethylamine Engineering for Effective Passivation to Attain 23.4% Efficiency Perovskite Solar Cells with Superior Stability

AbstractDefects in perovskite layers usually cause nonradiative recombination, impairing device performance and stability. Here, fluoroethylamine (FC2H4NH3, FEA) is integrated into the perovskite film to passivate defects. By engineering of different amounts of fluorine in the molecule, it is found that when 2‐fluoroethylamine (1FEA), in which one F bonds to the first carbon atom at the end of the molecule's structure, is used, the F atoms appear to be distributed throughout the bulk to the very surface. When 2,2‐difluoroethylamine (2FEA) and 2, 2, 2‐trifluoroethylamine (3FEA) are used, F is prone to distribution in the bulk of the perovskite film, while there appears to be no detectable F content on the surface. With the FEA passivation, the nonradiative recombination is suppressed, the carrier‐lifetime is improved to 840.01 ns, and the film‐air interface offers greater hydrophobicity, especially in the case of 1FEA, where because it is distributed throughout the film thickness, it passivates more defects and delivers the highest efficiency, as much as 23.40%. The device with 3FEA shows the best environmental stability; specifically, the bare cell without any encapsulation maintains 87% of its initial efficiency after exposure to the ambient environment for 1200 h.

Towards Better Stability and Reversibility of Mn2+/Mn4+ Double Redox Activity in Disordered Rocksalt Oxyfluoride Cathode Materials

Recently discovered cation disordered rocksalt (DRS) materials have shown high reversibility towards Li ions due to facile insertion and extraction in the structure. Nonetheless, issues with manganese containing compounds have been identified due to instabilities of the structure and/or solubility of manganese in the electrolyte. In our study, we combined the use of high-valent cations with partial substitution of fluorine for oxygen anions in DRS-structure phase to achieve optimal Mn2+/Mn4+ double-redox reaction in the composition system Li2MnxTi1-xO2F (1/3 ≤ x ≤ 1). Four different compositions (Li2MnIIIO2F, Li2MnII 1/3MnIII 1/3TiIV 1/3O2F, Li2MnII 1/2TiIV 1/2O2F and Li2MnII 1/3TiIII 1/3TiIV 1/3O2F) have been synthesized and optimized according to the starting precursors and their oxidation states. By studying the electrochemical behavior of different compounds, we found that Ti+4 keeps Mn at the second state of charge in the structure which lead to double redox reaction of Mn2+/Mn4+. Galvanostatic cycling and rate capability tests of the sample with the composition Li2Mn2/3Ti1/3O2F showed notable electrochemical kinetics and cycling performance, with initial high discharge capacity of 227 mAh g-1 in the voltage window of 1.5-4.3 V and 82% coulombic efficiency after 100 cycles.In a further study, synthesis related issues and limitations due to fluorination were examined. In fact, lithium diffusion can be impeded due to preferable strong Li-F bonds. Thus, two more samples based on the Li2Mn2/3Ti1/3O2F composition were synthesized and their properties were investigated (Li1.5MnII 1/3MnIII 1/3TiIV 1/3O2F0.5 and Li1.25MnII 1/3MnIII 1/3TiIV 1/3O2F0.25), in order to find the proper amount of fluorine which compromises the structural/chemical stability and electrochemical storage against Li-ions.We will present and discuss the structural characteristics of these selected DRS materials using XRD-Rietveld refinement analysis, energy-dispersive X-ray spectroscopy and scanning electron microscopy. The oxidation states and charge transfer mechanism using a combination of CV and XPS will be also addressed, in which the results approve the double redox mechanism of Mn2+/Mn4+ in agreement with Mn-Ti structural charge compensation. The findings pave the way for designing high capacity electrode materials with multi-electron redox reactions. Figure 1

Optimization of hydrogen evolution reaction catalytic activity of Ti2CO2 via surface engineering with an isolated fluorine effect: An ab-initio density functional theory study

MXenes have potential as a hydrogen evolution reaction (HER) catalyst based on their large surface area and excellent electrical properties. In this study, the change in HER catalytic properties according to the surface state of Ti2C-based MXene was analyzed theoretically based on first principles calculation. It was confirmed that the reactivity of the surrounding active sites is enhanced by the influence of isolated fluorine. The mechanism of this phenomenon was investigated, focusing on the electron migration and structural changes. In the MXene family, the Ti2C-based MXene best utilized the isolated fluorine effect. It was found that Ti2CO2 functionalized with a small amount of fluorine was superior as a HER catalyst to Ti2CO2 fully functionalized with oxygen, and the optimal proportion of fluorine was 1.5 to 3%.

Enhancement of Volumetric Capacitance of Binder-Free Single-Walled Carbon Nanotube Film via Fluorination.

Robust electrode materials without the addition of binders allow increasing efficiency of electrical storage devices. We demonstrate the fabrication of binder-free electrodes from modified single-walled carbon nanotubes (SWCNTs) for electrochemical double-layer capacitors (EDLCs). Modification of SWCNTs included a sonication in 1,2-dichlorobenzene and/or fluorination with gaseous BrF3 at room temperature. The sonication caused the shortening of SWCNTs and the splitting of their bundles. As a result, the film prepared from such SWCNTs had a higher density and attached a larger amount of fluorine as compared to the film from non-sonicated SWCNTs. In EDLCs with 1M H2SO4 electrolyte, the fluorinated films were gradually defluorinated, which lead to an increase of the specific capacitance by 2.5–4 times in comparison with the initial values. Although the highest gravimetric capacitance (29 F g−1 at 100 mV s−1) was observed for the binder-free film from non-modified SWCNT, the fluorinated film from the sonicated SWCNTs had an enhanced volumetric capacitance (44 F cm−3 at 100 mV s−1). Initial SWCNT films and defluorinated films showed stable work in EDLCs during several thousand cycles.

Optical properties of novel oxyfluoride glasses on the systems of LaF3–LaO3/2–NbO5/2 and LaF3–LaO3/2–NbO5/2–AlO3/2

AbstractOxyfluoride glasses of xLaF3–(60 − x)LaO3/2–40NbO5/2 (x = 0, 5, 10, 35) and xLaF3–(60 − x)LaO3/2–30NbO5/2–10AlO3/2 (x = 0, 10, 20, 30) were prepared using a levitation technique. Both the glass‐transition temperature, Tg, and onset crystallization temperature, Tc, were lowered by substituting a part of the oxygen with fluorine in the glasses. An appropriate amount of fluorine maximized the difference between the temperatures, ΔT (= Tc − Tg), indicating the improvement in the glass‐forming ability. The atomic packing densities of the glasses were approximately 60%, which gradually increased with the fluorine content. The absorption edge of the glasses shifted toward the shorter wavelength region in the ultraviolet spectra and toward the longer region in the infrared spectra by fluorine substitution. In addition, in one of the oxyfluoride glasses, a wide transparency from 307 nm to 9.2 µm was realized. Furthermore, the glass exhibited superior optical properties, with a combination of a high refractive index, nd, of 2.020 and low wavelength dispersion, vd, of 30.1. The effect of fluorine substitution on the nd and its vd was analyzed using the Lorentz–Lorenz dispersion formula.

Molecular dynamics study on the co‐doping effect of Al2O3 and fluorine to reduce Rayleigh scattering of silica glass

AbstractFurther attenuation of Rayleigh scattering of silica glass is required to extend the capacity of long‐distance optical fiber communication. To theoretically examine the effect of aluminum and fluorine co‐doping on the density fluctuations of silica glass, which is related to Rayleigh scattering, a set of force‐matching potentials (FMP) for simulating F‐doped aluminosilicates was developed using Bayesian optimization based on density functional theory calculations. Molecular dynamics (MD) simulations with the new FMP could evaluate the densities of silica glasses to which a small amount of fluorine was doped and those of aluminosilicate glasses with a wide range of aluminum contents within reasonable accuracy. The FMP successfully represents the changing role of aluminum from a network former without a compensating cation (threefold coordination) to that with a compensating cation and a charge compensator in the aluminosilicates. Indeed, relative concentrations of four, five, and sixfold‐coordinated aluminum observed by NMR measurements were reproduced better than the original Teter potential at a high aluminum content. At an aluminum content lower than 1 mol%, threefold‐coordinated aluminum was observed, which is consistent with ESR measurements. After careful validations of the FMP, the effect of the co‐doping of alumina and fluorine on the density fluctuations of silica glass was computationally examined. Consequently, it was expected that the co‐doping might not sufficiently attenuate the Rayleigh scattering, even though 1 wt% fluorine would be able to reduce the density fluctuations of aluminosilicate glasses for some extent. This is because more alumina‐doping increases density fluctuations of silica glass if the drawing temperature and procedure are the same with those for silica glass fiber. Thereby, a possible fabrication process to sufficiently attenuate the Rayleigh scattering of the F‐doped aluminosilicate glass was proposed, according to the density fluctuation analysis at high temperature.

DEVELOPMENT OFTHE PRECISION DEVICE FOR TARGETED DELIVERY OF MEDICATION AND CREATION OFISOLATED RESERVOIRS IN THE WEDGE-SHAPED L

— This study proves the necessity of using new minimum intervention tooth-preserving technologies and their implementation methods in hard dental tissue pathology treatment, in particular, wedge-shaped defects within enamel. Personalized approach to choosing the treatment method for this type of pathology is updated. The study prioritizes the pathogenetic mechanisms of this process, taking into account morphofunctional changes in enamel. Changes in architectonics of tooth enamel and its elemental composition are studied and discussed. A method of delivering the medication directly into the lesion is suggested. The objective of this study was to develop a precision device for targeted delivery of medication and creation of isolated reservoirs in the wedge-shaped lesion. Materials: slices of teeth removed due to orthodontic indications. Methods: experimental, analytical, statistical, sociological, electron microscopy. The scientific basis and principles of the research concept are based on the data on microstructural transformations, changes in the elemental composition of the tooth with a wedge-shaped defect. It is proved that oxygenation increases in a wedge-shaped lesion while the amount of fluorine and carbon compounds decreases, leading to the presence of such non-specific microelements as sulfur. The results obtained are the basis for the application of a targeted and personalized algorithm for treating this pathology, using additive technologies and 3D printing.

Real Time Observation of Lithium Insertion into Pre-Cycled Conversion-Type Materials.

Conversion-type electrode materials for lithium-ion batteries experience significant structural changes during the first discharge–charge cycle, where a single particle is taken apart into a number of nanoparticles. This structural evolution may affect the following lithium insertion reactions; however, how lithiation occurs in pre-cycled electrode materials is elusive. In this work, in situ transmission electron microscopy was employed to see the lithium-induced structural and chemical evolutions in pre-cycled nickel oxide as a model system. The introduction of lithium ions induced the evolution of metallic nickel, with volume expansion as a result of a conversion reaction. After pre-cycling, the phase evolutions occurred in two separate areas almost at the same time. This is different from the first lithiation, where the phase change takes place successively, with a boundary dividing the reacted and unreacted areas. Structural changes were restricted at the areas having large amount of fluorine, implying the residuals from the decomposition of electrolytes may have hindered the electrochemical reactions. This work provides insights into phase and chemical evolutions in pre-cycled conversion-type materials, which govern electrochemical properties during operation.

Factors governing the fluorination of hydroxyapatite by an ionic liquid

Fluorapatite exhibits improved bone-bonding and chemical durability under neutral and acidic conditions compared with hydroxyapatite. Typically, an aqueous fluoride solution is used for F− incorporation into the hydroxyapatite. Use of an ionic liquid as F− source provides highly-concentrated ionic environment and can lead to more effective fluorination. In this study, two ionic liquids were added during the synthesis of hydroxyapatite under various conditions, and the differences in the crystalline structure and chemical durability of the resulting fluorapatites were investigated. 1-ethyl-3-methylimidazolium tetrafluoroborate was quite effective for F− incorporation, but not 1-ethyl-3-methylimidazolium hexafluorophosphate. When the temperature was increased to 80 °C, not only the hydroxyapatite or fluorapatite but also CaF2 was generated as a by-product. When the initial pH was decreased to 7, the formed product fully converted to CaF2. The solubility of the product tended to be suppressed in acidic conditions with increase in amount of fluorine substituted in the crystal lattice.

Influence of LiBF4 sintering aid on the microstructure and conductivity of LATP solid electrolyte

To improve sintering performance, LiBF4, as a novel sintering aid, was added to a NASICON-type solid electrolyte LATP, which was synthesized by the sol-gel method. The microstructure, crystallinity and lithium-ion conductivity of the obtained LATP was measured by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Raman spectroscopy, MAS NMR and impedance spectroscopy (IS). Results indicate that during sintering, LiBF4 not only forms liquid phase to promote the growth of grains, but also forms a replacement solid solution with LATP. A small amount of boron and fluorine substitutes phosphorus and oxygen, thus entering the LATP lattice and forming a channel that is more suitable for Li-ion migration. The formation of the solid solution phase of LiBF4 and LATP also leads to the gradual disappearance of grain boundaries, which further promotes the improvement in ionic conductivity. The highest ionic conductivity of the LATP sintered pellet obtained with 3 wt% LiBF4 is 0.85 mScm−1.

Anion Reactivity in Cation-Disordered Rocksalt Cathode Materials: The Influence of Fluorine Substitution

The global demand for energy storage technology has created a tremendous need for Li-ion batteries that are lightweight, low cost, and sustainable. Research in the field of lithium-rich cathode materials has led to the development a new class of lithium-excess, cation-disordered rocksalt (DRX) materials. DRX materials display exciting promise as potential cathodes in lithium-ion batteries, owing to their high capacity and resource-friendly composition. Despite these exciting characteristics, these materials suffer from capacity loss over extended cycling due to deleterious side reactions that occur at high potentials, such as O2 loss. It has been shown that oxygen loss can be suppressed by partial substitution of the lattice oxygen for fluorine, but the role of fluorine in the material remains unclear. In this study, we examine the impact of fluorination on the anionic reactivity of DRX materials. We first use Differential Electrochemical Mass Spectrometry (DEMS) and Titration Mass Spectrometry to map first-charge electrochemistry in DRX cathodes. Comparing the results of this analysis for a DRX oxide and a DRX oxyfluoride, we observe that fluorination increases the transition metal capacity and reduces the oxygen redox capacity. These two effects influence the total material capacity in opposite ways, shifting the balance between transition metal redox and oxygen redox without strongly affecting the total charge capacity. We also adapt an existing technique that couples DEMS with a fluoride-scavenging additive, using it for the first time to show that small amounts of fluorine dissolve from DRX oxyfluorides during charging to high potentials. Finally, we extend these techniques over the first several cycles to study the reversibility of the redox processes and the stability of the materials during cycling. We demonstrate that while oxygen redox remains mostly reversible from cycle to cycle, electrolyte degradation and fluoride dissolution also continue to occur to a diminishing extent during cycling. These conclusions motivate surface passivation to control interfacial reactivity as an important direction to improve cycling stability.

Pseudomonas sp. Strain 273 Degrades Fluorinated Alkanes.

Fluorinated organic compounds have emerged as environmental constituents of concern. We demonstrate that the alkane degrader Pseudomonas sp. strain 273 utilizes terminally monofluorinated C7-C10 alkanes and 1,10-difluorodecane (DFD) as the sole carbon and energy sources in the presence of oxygen. Strain 273 degraded 1-fluorodecane (FD) (5.97 ± 0.22 mM, nominal) and DFD (5.62 ± 0.13 mM, nominal) within 7 days of incubation, and 92.7 ± 3.8 and 90.1 ± 1.9% of the theoretical maximum amounts of fluorine were recovered as inorganic fluoride, respectively. With n-decane, strain 273 attained (3.24 ± 0.14) × 107 cells per μmol of carbon consumed, while lower biomass yields of (2.48 ± 0.15) × 107 and (1.62 ± 0.23) × 107 cells were measured with FD or DFD as electron donors, respectively. The organism coupled decanol and decanoate oxidation to denitrification, but the utilization of (fluoro)alkanes was strictly oxygen-dependent, presumably because the initial attack on the terminal carbon requires oxygen. Fluorohexanoate was detected as an intermediate in cultures grown with FD or DFD, suggesting that the initial attack on the fluoroalkanes can occur on the terminal methyl or fluoromethyl groups. The findings indicate that specialized bacteria such as Pseudomonas sp. strain 273 can break carbon-fluorine bonds most likely with oxygenolytic enzyme systems and that terminally monofluorinated alkanes are susceptible to microbial degradation. The findings have implications for the fate of components associated with aqueous film-forming foam (AFFF) mixtures.

Regularities of fluorine leaching from the rocks by organic acids

Experiments on fluorine leaching from the rocks (alkaline agpaitic granite, dacite, and feldspathic-quartzy aleurite) by 0.005 M solutions of acetic, tartaric, citric, and oxalic acids were carried out. The previously revealed fact of decrease in the fluorine leaching by organic acids as compared with that by distilled water with an increase in acidity of solutions in the pH range from 6.3 to 3.5 is confirmed. According to the leaching ability in relation to distilled water, organic acids are formed a number: oxalic > citric > acetic ≈ tartaric. It is assumed that decrease in pH leads to sorption of fluorides as a result of the replacement of adsorbed hydroxyl ions. From this point of view, less intensive (compared with distilled water) fluorine leaching in acidic medium can be associated with sorption immobilization of fluoride ions in the solid phase. A positive correlation between amounts of leached fluorine and magnesium indicates the existence of a certain common, as well as not established mechanism for transition of these elements from minerals to aqueous solution.