Reaction Of Fluorine Research Articles

PTFE-modified Al through bridging approach to enhance combustion reaction and energetic performance

Aluminum/Polytetrafluoroethylene (Al/PTFE) composites have attracted a great deal of attention due to their remarkable energy density and wide range of applications. Unfortunately, the inert oxide layer (Al2O3) on the surface of Al and the interfacial contact area between PTFE and Al seriously impact the combustion reaction kinetics and energy output efficiency. Here, an approach is utilized to significantly enhance the interfacial contact area between Al and PTFE through F2601 serving as the bridging agent. The ignition, combustion reaction, and energetic performance (pressure and combustion heat) can be adjusted by varying the particle size of Al and PTFE content. The energy release efficiency of bridging Al/PTFE has been improved significantly as PTFE content increases and the particle size of Al decreases. The bridging Al/PTFE with 10 μm Al and nano Al exhibit a bright and wide flame, and a fierce flame propagation process, as well as much high pressure output (167.73 kPa and 199.92 kPa) and heat release (11879 J/g and 12322 J/g). Furthermore, the critical mass ratio (approximately 88/12) of bridging Al/PTFE for self-sustained combustion has been obtained for the first time. The improvement of energy output performance is attributed to the interfacial contact between PTFE and Al and the reaction of fluorine and Al2O3 resulted from bridging Al/PTFE through F2601. The prepared bridging Al/PTFE with high energy output characteristics holds great potential in solid propellants, reactive materials, and other high-energy fuels.

Reaction of Atomic Fluorine with Benzene

Reaction of Atomic Fluorine with Benzene

Bimetal Organic Framework–Ti3C2Tx MXene with Metalloporphyrin Electrocatalyst for Lithium–Oxygen Batteries

AbstractThe gravest oxidation of MXenes has become a critical problem due to the formation of metal oxides, leading to the loss of their intrinsic properties. Herein, bimetallic cobalt–manganese organic framework (CMT) directly grown on a Ti3C2Tx MXene sheet via solvothermal treatment to obtain strong oxidation resistance in an open structured application and to enhance electrocatalytic properties for oxygen evolution and reduction reaction is reported. Inspired by ligand chemistry, the carboxyl acids in tetrakis(4–carboxyphenyl)porphyrin acting as an organic linker are grafted with the surface terminators of Ti3C2Tx MXene through the Fischer esterification and substitution reaction of fluorine, thereby greatly enhancing the antioxidation stability. Furthermore, the as‐formed metalloporphyrin structure and unpaired electrons, produced between CMT and Ti3C2Tx MXene during solvothermal treatment, improve their electrocatalytic activity, durability, and electrical conductivity through an electron hopping mechanism. Consequently, the CMT@MXene demonstrates high stability as a bifunctional electrocatalyst at a fixed specific capacity of 1000 mAh g−1 and a current density of 500 mA g−1 for 247 cycles in lithium–oxygen (LiO2) battery. This approach suggests new strategies for the synergistic coupling of MXenes and MOFs for future open structured applications.

An effective strategy to improve combustion and pressure output performance of HMX/Al

To improve and adjust the combustion and energy output of HMX/Al, graphite fluoride (CF) as oxidizer was introduced in HMX/Al and gradient structured HMX/Al/CF was prepared by additive manufacturing technology. For HMX/Al added with CF, a significantly exothermic peak is observed ranging from 860 to 950 °C due to the reaction of Al and fluorine derived from CF decomposition, and the heat release increases by 106.63% compared to that of HMX/Al. The fourth exothermic heat increases from 161.48 to 955.25 J/g with the increased Al content from 10 to 30 wt%. Moreover, the combustion rate and pressure output of HMX/Al have been improved by introducing CF. For HMX/Al added with CF, the combustion time decreases from 10.3 to 2.5 s, which is dependent on the Al content from 10 to 30 wt%. And the highest peak pressure is 1712.2 kPa when Al content is 20 wt% in HMX/Al/CF composites. Furthermore, gradient structured HMX/Al/CF consisting of three layers with Al content of 10, 20 and 30 wt% was prepared to improve combustion and pressure output. The combustion rate and peak pressure of gradient structured HMX/Al/CF are higher than those of single structured HMX/Al/CF. The highest peak pressure (∼2.24 MPa) is obtained when the Al content of the middle layer and outer layer is 30 wt% and 20 wt% in the gradient structured HMX/Al/CF cylinder, respectively. Finally, the reaction intermediates and combustion reaction products were fully characterized to understand the enhanced effect of CF in HMX/Al. This work provides a promoting way to improve and regulate the combustion reaction performance and pressure output of HMX/Al.

The reaction between the bromine atom and the water trimer: high level theoretical studies.

Three different reaction pathways are found for the reaction of bromine atom (Br) with the lowest-energy structure of the water trimer [uud-(H2O)3], initially using the MPW1K-DFT method. The three bromine pathways have closely related geometries and energetics, analogous to those found for the fluorine and chlorine reactions. The lowest-energy pathway of the Br + uud-(H2O)3 reaction was further investigated using the "gold standard" CCSD(T) method and the correlation-consistent basis sets up to cc-pVQZ(-PP). Based on the CCSD(T)/cc-pVQZ(-PP)//CCSD(T)/cc-pVTZ(-PP) results, the Br + (H2O)3 reaction is endothermic by 33.3 kcal mol-1. The classical barrier height is 29.0 kcal mol-1 between the reactants and the exit complex, and there is no barrier for the reverse reaction. The Br⋯(H2O)3 entrance complex is found to lie 4.7 kcal mol-1 below the separated reactants, and the HBr⋯(H2O)2OH exit complex is bound by 6.4 kcal mol-1 relative to the separated products. This potential energy profile is further corrected by the zero point energies and spin-orbit coupling effects. Structurally, the Br + (H2O)3 stationary points can be derived from those of the simpler Br + (H2O)2 reaction by judiciously appending a H2O molecule. The Br + (H2O)3 potential energy profile is compared with the Br + (H2O)2 and Br + H2O reactions, as well as to the valence isoelectronic Cl + (H2O)3 and F + (H2O)3 systems. It is reasonable to expect that the reactions between the bromine atom and larger water clusters would be similar to the Br + (H2O)3 reaction.

Matrix Isolation Spectroscopic and Relativistic Quantum Chemical Study of Molecular Platinum Fluorides PtFn (n=1-6) Reveals Magnetic Bistability of PtF4.

Molecular platinum fluorides PtF n , n=1–6, are prepared by two different routes, photo‐initiated fluorine elimination from PtF6 embedded in solid noble‐gas matrices, and the reaction of elemental fluorine with laser‐ablated platinum atoms. IR spectra of the reaction products isolated in rare‐gas matrices under cryogenic conditions provide, for the first time, experimental vibrational frequencies of molecular PtF3, PtF4 and PtF5. Photolysis of PtF6 enabled a highly efficient and almost quantitative formation of molecular PtF4, whereas both PtF5 and PtF3 were formed simultaneously by subsequent UV irradiation of PtF4. The vibrational spectra of these molecular platinum fluorides were assigned with the help of one‐ and two‐component quasirelativistic DFT computation to account for scalar relativistic and spin–orbit coupling effects. Competing Jahn‐Teller and spin–orbit coupling effects result in a magnetic bistability of PtF4, for which a spin‐triplet (3B2g, D 2h) coexists with an electronic singlet state (1A1g, D 4h) in solid neon matrices.

Differential cross section measurements of the 6.13 MeV gamma ray from proton-induced reaction of fluorine

Fundamental cross section measurements are essential for particle-induced gamma emission (PIGE) analysis. 19F(p,αγ2-0)16O can be utilized in PIGE analysis; however, differential cross section measurements for this reaction do not exist due to the difficulty in deconvolving overlapping peaks in the gamma spectrum. Although gamma yield measurements for this reaction exist (Dababneh et al., 1993), these can only be used for relative measurements. This work presents the 6.13 MeV gamma production differential cross sections for the 19F(p,αγ2-0)16O reaction in the incident proton kinetic energy range of 837 to 1517 keV. The yield of the 6.13 MeV gamma was obtained by subtracting the contribution of the 7.12 MeV double escape peak using the experimentally-determined ratio of the escape peaks. The corrected yields were converted to differential cross sections, which are presented here for the first time, as a contribution to the current knowledge and utilization of PIGE techniques.

F/OH ratio in a rare fluorine-poor blue topaz from Padre Para\xedso (Minas Gerais, Brazil) to unravel topaz\u2019s ambient of formation

Topaz [Al2SiO4(F,OH)2] is one of the main fluorine-bearing silicates occurring in environments where variably acidic (F)/aqueous (OH) fluids saturate the silicate system. In this work we fully characterized blue topaz from Padre Paraíso (Minas Gerais, Brazil) by means of in situ synchrotron X-Ray and neutron powder diffraction measurements (temperature range 298–1273 K) combined with EDS microanalyses. Understanding the role of OH/F substitution in topaz is important in order to determine the hydrophilicity and the exchange reactions of fluorine by hydroxyl groups, and ultimately to characterize the environmental redox conditions (H2O/F) required for mineral formation. The fluorine content estimated from neutron diffraction data is ~ 1.03 a.f.u (10.34 wt%), in agreement with the chemical data (on average 10.0 wt%). The XOH [OH/(OH + F)] (0.484) is close to the maximum XOH value (0.5), and represents the OH- richest topaz composition so far analysed in the Minas Gerais district. Topaz crystallinity and fluorine content sharply decrease at 1170 K, while mullite phase starts growing. On the basis of this behaviour, we suggest that this temperature may represent the potential initial topaz’s crystallization temperature from supercritical fluids in a pegmatite system. The log(fH2O/fHF)fluid (1.27 (0.06)) is coherent with the fluorine activity calculated for hydrothermal fluids (pegmatitic stage) in equilibrium with the forming mineral (log(fH2O/fHF)fluid = 1.2–6.5) and clearly different from pure magmatic (granitic) residual melts [log(fH2O/fHF)fluid < 1]. The modelled H2O saturated fluids with the F content not exceeding 1 wt% may represent an anomalous water-dominant / fluorine-poor pegmatite lens of the Padre Paraíso Pegmatite Field.

Etching of Si3N4 by SF6/H2 and SF6/D2 plasmas

Selective plasma etching of silicon nitride (Si3N4) over silicon oxide (SiO2) is one of critical steps in the nanofabrication processes, where a direct plasma etching of Si3N4 is required for some applications. It was reported recently that Si3N4 etching by remote plasma source can be initiated by the vibrationally excited HF(v) molecules at the low concentration of atomic fluorine. Generally, the main source of HF(v) in plasma is reaction of atomic fluorine with H2 molecule. Due to this fact, the kinetic isotope effect should be observed during Si3N4 etching if replace the H2 source gas on deuterium gas (D2). The data presented here are the Si3N4 and SiO2 etching by the SF6/H2 and SF6/D2 plasmas. A different amount of H2 and D2 have been added to the SF6 discharge during the Si3N4 and SiO2 etching. It was shown that at low H2/D2 flow rate the Si3N4 etch rate is lower in the SF6/D2 discharge. This one confirms the hypothesis about Si3N4 etching by HF(v) and indicates on the fact that HF(v) gives contribution to Si3N4 etching by the direct plasma (not only by the remote plasma) at relatively high concentration of atomic fluorine.

Influences of substrate temperatures on etch rates of PECVD-SiN thin films with a CF4/H2 plasma

The dependence of substrate temperatures (50 to −20 °C) on etch rate in two kinds of PECVD SiN films were investigated by a CF4/H2 mixture plasma. The XRR and XPS results indicate that the chemical composition and film density were almost identical for the films. The FTIR shows that the ratio of NH and SiH groups were found to be significantly different in the SiN films. The NH rich films exhibited a lower etch rate at −20 °C than that observed at room temperature or higher, whereas the SiH rich films showed a higher etch rate at −20 °C. We found that the fluorocarbon thickness was thicker in the SiH rich samples than NH rich samples. The fact suggests that hydrogen originated from the broken SiH bonds enhanced the polymerization, which causes the decrease of etch rate. A thinner fluorocarbon thickness was found in the SiH rich samples at low temperature, which results in the higher etch rate. Angular-resolved XPS indicates that NH bonding formed easier on film surface at −20 °C. These results indicate that the bonding structure and substrate temperature affected the fluorocarbon thickness, fluorine reaction probability and hydrogen dissociation during the SiN etching.

Manipulation of cellular behaviour on surface-modified polyvinylidene difluoride using wet chemistry

The surface modification of polyvinylidene difluoride (PVDF) for various biomedical uses is notoriously hampered by the chemical inertness of the polymer. A wet chemical approach aiming at covalently grafting biomolecules was demonstrated by means of an elimination reaction of fluorine from the polymer backbone followed by subsequent modification steps. Exemplified as a possible biological application, the coupling of the peptide REDV rendered the material adhesive for endothelial cells while adhesion of thrombocytes was dramatically reduced.

Elemental Analysis of Polychlorotrifluoroethylene Bombarded with Accelerated MeV Protons and the Composition of Gaseous Products

The action of accelerated 1–4-MeV protons on polychlorotrifluoroethylene in vacuum was accompanied by a preferential rupture of the main polymer chain with the release of more than 30 gaseous products, most of which were tetrafluoroethylene and chlorine- and fluorine-containing compounds. As a result of proton bombardment, the concentration of carbon on the polymer surface decreased and the concentrations of fluorine and chlorine increased. It has been shown that the incorporation of chlorine atoms into the structure of a perfluoropolymer changes the mechanism of its proton bombardment and helps to protect its macromolecule from the reaction of fluorine abstraction by accelerated protons with the formation of hydrogen fluoride. It has been found that irradiation with accelerated protons leads to changes in surface energy characteristics.

Non-adiabatic transitions in the reaction of fluorine with methane.

Reactions of methane with different atoms are benchmark examples of elementary reaction processes intensively studied by theory and experiment. Due to the presence of conical intersections and spin-orbit coupling, non-adiabatic transitions can occur in reactions with F, Cl, or O atoms. Extending detailed quantum theory beyond the Born-Oppenheimer approximation for polyatomic reaction processes, non-adiabatic wave packet dynamics calculations studying the F(2P3/2)/F*(2P1/2) + CHD3 → HF + CD3 reaction on accurate vibronically and spin-orbit coupled diabatic potential energy surfaces are presented. Non-adiabatic transitions are found to increase the reactivity compared to Born-Oppenheimer theory and are more prominent than in triatomic reactions previously studied. Furthermore, the lifetimes of reactive resonances are reduced. The reactivity of F(2P3/2) is found to exceed the one of F*(2P1/2) even at low collision energies.

Double-activated nucleophilic aromatic substitution polymerization by bis-ortho-trifluoromethyl groups to soluble para-poly(biphenylene oxide)

Poly(biphenylene oxide)s (PBPOs) containing two pendent trifluoromethyl groups were synthesized from AB-type monomers, 4ʹ-hydroxy-4-fluoro-3,5-bis(trifluoromethyl)biphenyl and its 3ʹ-hydroxyl isomer. The displacement reaction of fluorine leaving group activated by the two trifluoromethyl groups at the ortho-positions produced high-molecular-weight polymers with Mn up to 101,000 g/mol, indicating the nucleophilic aromatic substitution reaction proceeded effectively. PBPOs with para-, meta-, and mixed ether linkages were obtained and well characterized by FTIR and 1H/19F NMR spectroscopies. All PBPOs were amorphous and soluble in a wide range of organic solvents, and exhibited even more enhanced thermal stability than the previously reported two meta-trifluoromethyl substituted analogues. Increasing the para-linkage fraction in the polymer generally improved solubility and increased Tg in contrast to the meta-trifluoromethyl case, where para-linked polymer was poorly soluble and semicrystalline. This suggests that the ortho-trifluoromethyl substituents are more effective for the synthesis of para-linked PBPOs. They also showed low refractive indices and birefringence values.

RGO‐SO3H Catalysed Green Synthesis of Fluoro‐Substituted Aminomethylene Bisphosphonates and their Anticancer, Molecular Docking studies

AbstractA facile and green synthetic protocol was aimed for the synthesis of aminomethylene bisphosphonates via one‐pot reaction of fluorine bearing anilines, triethyl orthoformate and dialkyl phosphite in presence of rGO‐SO3H as catalyst under microwave irradiation and solvent‐free conditions. All the title compounds were evaluated for their anticancer activity against human breast cancer cell lines (MCF‐7) by MTT assay method using exemestane as standard drug. Molecular docking studies were carried out against Human estrogen receptor alpha (ERα). Both in vitro and in silico studies revealed that compounds tetramethyl (((3‐(trifluoromethyl) phenyl) aminomethylene)bisphosphonate) (4e), tetramethyl (((2‐methoxy(5‐trifluoromethyl) phenyl) amino) methylene)bis (phosphonate) (4m) and tetraethyl (((4‐bromo‐2‐fluorophenyl) amino)methylene)bis(phosphonate) (4l) exhibited remarkable higher anticancer activity than that of standard.

Fluorine saturation on thermally reduced graphene

Fluorographene is a wide band-gap insulator with high photoluminescence and hydrophobicity. In the past, fluorographene was considered to be chemically inert similarly to Teflon. However, it has been recently reported that fluorographene can undergo several chemical modifications such as nucleophilic or radical substitutions. Fluorinated graphene is typically prepared by top-down synthesis based on sonochemical exfoliation of fluorographite. This method does not allow any control over the graphene fluorination degree. On the other hand, methods based on reaction of fluorine with graphene can be used for synthesis of fluorographene with control of the fluorine content. In this work, we have demonstrated the synthesis of fluorinated graphene with composition in the range from (C1F0.05)n up to (C1F0.6)n at room temperature. A detailed mapping of experimental conditions allows synthesis with tailored fluorine concentration. The influence of fluorination degree on graphene structure, surface functional group composition and electrochemical properties was studied in detail. Moreover, partially fluorinated graphene exhibited enhanced bio-sensing activity towards nucleobases.

Side-On Sulfur Monoxide Complexes of Tantalum, Niobium, and Vanadium Oxyfluorides.

Side-on sulfur monoxide complexes of tantalum, niobium, and vanadium oxyfluorides OMF2(η2-SO) were prepared via the reactions of metal atoms and SO2F2 upon UV-vis irradiation in a cryogenic matrix. The product structures were identified by the characteristic infrared absorptions and isotopic frequency ratios of terminal M-O, F-M-F, and M-(SO) stretches, which were further supported by density functional theory calculations at the B3LYP level. All of the three complexes were predicted to have doublet ground states with the S-O bond nearly perpendicular to the terminal metal-oxygen bond. Although end-on bonded isomers with either M-OS or M-SO geometry are stable as well, they are higher in energy than the side-on isomers, and their vibrational frequencies do not match the experimental values. For the OMF2(η2-SO) complexes, the S-O bond length approaches that of SO-, but it is longer than that of neutral SO due to the electron transfer from the metal d orbital to the in-plane π* orbital of SO. The metal-SO bonding in the side-on complex is mainly ionic, but covalent interactions play some role between the two parts. On the basis of the calculation results, the OMF2(η2-SO) complexes can be considered as (OMF2)+(SO)- in which the unpaired electron is mainly located in the out-of-plane π* orbital of SO. In addition to the complexes containing SO ligand, a series of other stable isomers were obtained by the B3LYP calculations, and they were proposed as intermediates involved in the formation of the OMF2(η2-SO) products via fluorine and oxygen transfer reactions between metal atoms and SO2F2 under UV-vis irradiation.

Base‐Promoted Oxidative C(sp3)–S Bond Cross‐Coupling of Inactive Fluorenes and Thiols for the Synthesis of 9‐Monothiolated Fluorenes

The highly efficient and selective C(sp3)–S bond cross‐coupling method for the synthesis of 9‐thiolated fluorenes through a direct thiolation at 9‐C(sp3)–H of fluorenes with thiols is described. This reaction occurs at ambient conditions and shows good tolerance of functional groups including arylthiols and alkylthiols. A wide range of products is obtained in moderate to good yields. Besides, the reaction of benzothiophenol and fluorine generates unexpected 9‐benzylidene‐9H‐fluorene by eliminating hydrogen sulfide.

Fluorine speciation in soil and the remediation of fluorine contaminated soil

In China, fluoride pollution in soil is severe and poses a serious threat to human health and ecological security. However, how to control fluorine-contaminated soil has not received widespread attention. Here, we summarized fluorine speciation in soil and its main chemical reactions in water-soil system and reviewed the research progress on the remediation of fluorine-contaminated soils. Then, we proposed the focus of future research on fluorine-contaminated soil remediation. The aim of this review was providing the reference for the remediation of fluoride-contaminated soil. There are five forms of fluorine in soils, with the proportion of residual fluorine being over 90%. The reactions of fluorine in the soil solution mainly include precipitation-dissolution, complexation-dissociation, and adsorption-desorption. At present, the remediation technology of fluorine contaminated soil mainly focused on chemo-immobilization, chemical leaching, electrokinetic remediation, and phytoremediation. Clarifying the combined forms of fluorine in soil, screening functional microorga-nisms and plants, developing the combined remediation technology will be the focus of future research. Ultimately, on site fluorine-contaminated soil remediation could be implemented.

Forensic Aspects of Fluorine Poisoning

In medical literature, existing studies show the opportunity to use fluorine for one�s health. The presence of this substance in the normal composition of all tissues and organs of the human body as well as deficiencies highlighted under certain circumstances support this aspect. They show both the positive effects of fluorine, such as the role of fluorine in increased calcium storing in the bones and teeth, and the negative effects, for example inhibition of phosphatases, (enzymes used in many metabolic processes). The double effect also appears in the use of fluorine in treatments, because when overcoming a critical threshold for the body it may produce adverse effects, sometimes leading to death. The present article analyzes these effects, the primary purpose being to raise awareness and identify the reactions of fluorine on the body.