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In order to prepare self-standing and flexible slow neutron reflectors made of graphite fluoride (GF) with high contents of (C2F)n structural phase, graphite foils of different thicknesses were used as starting materials for gas (F2)/solid fluorination. The maximal interlayer distance of GF was obtained with this phase thanks to the stacking sequence FCCF/FCCF; this is mandatory for the efficient reflection of slow neutrons. 71 and 77% of the (C2F)n phase were achieved for graphite foils with thicknesses of 1.0 and 0.1 mm, respectively. The interlayer distances were 8.6 Å as expected. The fluorination conditions (static mode, a long duration of 24 h, annealing in pure F2 gas for 24 h, and temperatures in the 390–460 °C range) were adapted to large pieces of graphite foils (7 × 7 cm2) in order to both avoid exfoliation and achieve a homogeneous dispersion of fluorine atoms. This process was also efficient for thinner (0.01 mm thick) graphitized graphene oxide foil. 56% of the (C2F)n phase and an interlayer of 8.6 Å were achieved for this foil when fluorination was performed at 430 °C. Whatever the nature and the thickness of the foil, their flexibilities are maintained. [ABSTRACT FROM AUTHOR]

A new solid-state 19 F magic-angle spinning NMR signal at an isotropic 19 F chemical shift of −53 ppm is measured from graphite fluoride synthesized by reaction of graphite with F 2 at temperatures above 750 K with no catalyst. Two-dimensional NMR suggests the −53 ppm 19 F NMR signal originates from covalent fluoromethanetriyl groups belonging to ordered (C y F) n bulk domains composited with the major (CF) n domains. Quantitative 19 F and 13 C NMR find y = 4.32 ± 0.64 . DFT calculations of NMR chemical shifts for unsaturated fluorographene models show that a (C 4 F) n phase with fluorine bound covalently to a single side of the carbon layer best explains the observed NMR chemical shifts. We assign the new phase to this (C 4 F) n structure, which constitutes up to 15% of the carbon in our graphite fluoride composites. The (C 4 F) n content of the composite affects bulk electrochemical properties in a manner similar to graphite fluorides produced by conventional, catalyzed fluorination processes. [ABSTRACT FROM AUTHOR]

Fluorinated single-layer diamond ("F-diamond") is a new form of two-dimensional (2D) carbon allotrope. Herein, poly(dicarbon monofluoride) (C 2 F) n which is essentially made of stacked layers of "F-diamane" has been synthesized and exfoliated in a variety of solvents to yield well-dispersed ultrathin sheets. Microscopic and spectroscopic analyses revealed that the exfoliated nanosheets retained the "F-diamane"-like structure. The experimental results are also supported by density functional theory (DFT) calculations. Image 1 • Poly(dicarbon monofluoride) (C 2 F) n was synthesized by the fluorination of graphite. • The (C 2 F) n is essentially made of stacked layers of "F-diamane". • Liquid-phase exfoliation of (C 2 F) n yielded ultrathin nanosheets. • The "F-diamane"-like structure was retained after exfoliation. • Density functional theory calculations support the experimental results. [ABSTRACT FROM AUTHOR]

In the present paper, graphite fluoride compounds C x F with various degrees of fluorination (x = 4, 2 and 1), i.e., with different C-F bonding characteristics, were systematically investigated using X-ray Raman Spectroscopy (XRS) and X-ray and neutron diffraction by means of Pair Distribution Function (PDF) analysis. For both techniques, ab-initio calculations allow the experimental results and structural/bonding assignments to be explained and/or confirmed. Presented here for the three stoichiometries are results for the carbon and fluorine first-neighbour distances, the evolution of the electronic band structure due to the change of the carbon hybridization upon fluorination, and also the nature of the final states for 1s core-electron excitations. Since fluorination is limited by the diffusion of fluorine in the carbon lattice, the process is less effective in the bulk, where a graphitic core remains. The cross-checked XRS, PDF data and Density Functional Theory (DFT) simulations appear also to be a powerful method to highlight the presence of a residual graphitic core, even at the highest fluorine content, in such semi-disordered and structurally complex compounds. Image 1 [ABSTRACT FROM AUTHOR]

Abstract Fluorine Graphite Intercalation Compounds are one of the most common cathode used in primary lithium batteries, mainly for their high delivering potential. Nevertheless, to increase their capacities, fluorine can be partially substituted by oxygen. Oxifluorides offer then versatility to design cathode materials delivering the upmost performances. Combining the choice of the precursor (either graphite oxide or sub-fluorinated graphite fluoride) and two-step synthesis processes, which include Hummers' oxidation and direct fluorination, allow the tuning of the fluorine and oxygen atoms distribution. According to the sequence, i.e. fluorination/oxidation or oxidation/fluorination, several oxifluorides were then prepared. On one hand, direct fluorination using F 2 gas resulted in homogeneous fluorine dispersion when precursor was graphite oxide. On the other hand, Hummers' oxidation was modulated according to the temperature parameter. C OH, C O C, COOH, CF, CF 2 and CF 3 were identified through multinuclear solid-state MAS-NMR. Covalence and environment, especially in-plane organization of those chemical groups, were assessed. When oxifluorides are then used as cathode in primary lithium battery, the better performances are obtained for 3 phases compounds where fluorinated part insured high potential whereas oxygenated part allowed durability to be reached; carbonaceous region providing conductivity. A maximum of about 2400 Wh/kg of energy density is attempted. Graphical abstract High performances of cathode materials for primary lithium battery have been obtained through bifunctionalization by fluorine and oxygen of graphite. Two steps synthesis: gas solid fluorination/Hummer's oxidation or oxidation/fluorination allow to get various functional groups and their repartition in graphite structure. Image 1 [ABSTRACT FROM AUTHOR]

The fluorination of two types of graphene oxides conducted by an easy and scalable deoxyfluorination reaction is reported. This reaction was carried out using diethylaminodifluorosulfinium tetrafluoroborate, a stable compound and an efficient reagent for replacing oxygenated functional groups of graphene oxide by fluoride. The graphene oxide produced by the Hummers’ method (GOH) showed lower reactivity than that produced by the Brodie’s method (GOB). X-ray photoelectron spectroscopy indicated that the highest fluorination degree achieved was 4.7 at.% when GOB was used, and the C F character corresponds to semi-ionic bonds. Additionally, a partial reduction of GO was concomitant with the functionalization reaction. The deoxyfluorination reaction changed the crystalline structure of GO, favoring the reconstruction of Csp 2 structure of the graphene lattice and reducing the number of stacked layers. The fluorination led to the modification of the electronic band structure of this material, increasing the band gap from 2.05 eV for GOB to 3.88 eV for fluorinated GOB, while for GOH the low flurionation led to a slight increase of the band gap, from 3.48 eV to 3.57 eV. [ABSTRACT FROM AUTHOR]

Fluorinated graphene (FG) has been obtained by a fluorination of thermally exfoliated graphite fluoride C2F layers using a gaseous mixture of BrF3 and Br2 at room temperature. Comparative study of electromagnetic (EM) response of thin FG films after recovering their conductivity via different methods is presented in microwave (GHz) and terahertz (THz) frequency ranges. We discovered that fluorination can be used as promising tool for producing tunable EM interference (EMI) shielding materials, combining reflective and absorptive layers. [ABSTRACT FROM AUTHOR]

The effect of the amount of sp3 defects in graphene on the graphene enhanced Raman scattering (GERS) is studied using gradual fluorination of chemical vapour deposition grown graphene covering the Rhodamine 6G molecules. While upon a mild fluorination the GERS effect is preserved, the GERS enhancement disappears in case of a strong fluorination. After partial removal of the fluorine from the strongly fluorinated graphene by water vapor treatment, the GERS effect is restored. [ABSTRACT FROM AUTHOR]

Fluorinated graphene (fluorographene) has attracted increasing attention due to the combination of unique properties of graphite fluoride and graphene. Development of fluorographene-based technology relies on the availability of fluorographene nanosheets in large quantities. Here, a melamine assisted solid exfoliation method is developed for the synthesis of fluorographene nanosheets. Under optimized solid ball milling condition, micrometer-sized ultrathin (less than 2 nm in thickness) fluorographene nanosheets can be exfoliated from graphite fluoride in the presence of melamine. The melamine assisted solid ball milling method is facile and highly efficient, and holds great promise for the large-scale preparation of few-layered fluorographene nanosheets. [ABSTRACT FROM AUTHOR]

A gas sensor is fabricated by dropping fluorinated graphene oxide (f-GO) onto SiO 2 /Si wafers patterned with Pt electrodes. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy are used to characterize the graphene oxide (GO) after fluorination. In addition, resistance measurement is used to investigate the ammonia (NH 3 ) gas sensing behavior and resistivity of the f-GO based gas sensor. The f-GO shows that the fluorine content on the GO surface increases with increasing fluorine partial pressure without any significant structural changes. The gas sensor fabricated using f-GO shows an approximately 7% change in the resistive response, whereas the non-treated GO does not exhibit any sensing ability to NH 3 gas. This change in the response is attributed to the lower Fermi level of GO and the increased number of holes in the GO after fluorination, which is helpful for effectively attracting NH 3 gas. The improvement indicates that the fluorination of GO can provide a novel modification method for GO-based NH 3 gas sensor. [ABSTRACT FROM AUTHOR]

In this study, we report a potentially scalable strategy for the cost/time-efficient production of water-soluble functionalized few layered graphene (FcG) through the mild defluorination of graphite fluoride (GF) at room temperature (RT). The strategy includes mechanical milling which is of high simplicity and operability, and subsequently water purification. By using heteroatom-containing alkaline such as NaNH 2 and Na 2 S, N or S dopants can be functionalized into the defluorinated graphene, leading to the formation of N- and S-doped FcG, respectively. Our methodology of defluorination of GF allows the fabrication of water soluble FcG in much safer ways relative to the conventional Hummers' method that involves strong acidic/oxidative ambience and disposal of large amount of salt wastes. Meanwhile, the abundance of GF and the simplicity of processibility may also facilitate the practical uses of FcG obtained via our methodology. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new route for efficient and high-yield production of F-diamane-like nanosheets. • Using expanded graphite allows uniform dispersion of F atoms in the carbon lattice. • The exfoliation of expanded fluorinated graphite can be readily achieved. • Mild sonication produced F-diamane-like nanosheets up to micrometers in size. • Pre-exfoliation/fluorination and sonication is suitable for large-scale preparation. Ultrathin diamond (diamane)-like films or nanosheets have recently been experimentally obtained through chemically induced phase transition (e.g., fluorination) of bilayer graphene films or graphite flakes. To fully exploit the properties of diamane, further advances in the synthesis methods for its large-scale production are required. Herein, we report a new route for the efficient and high-yield production of fluorinated diamane (F-diamane)-like nanosheets. This is achieved by direct fluorination of expandable graphite or thermally expanded graphite with molecular fluorine to form stage-2 graphite fluoride (C 2 F) n made of stacked layers of F-diamane. Subsequently, mild sonication is implemented to exfoliate the layers into F-diamane-like nanosheets of hundreds of nanometers to a few micrometers in lateral size, with a thickness of mostly < 10 nm. [ABSTRACT FROM AUTHOR]

The tribologic properties of graphitized carbon blacks and their fluorinated derivatives are investigated as a function of the fluorination rate. Very low intrinsic friction coefficients are obtained for highly fluorinated compounds. The correlation of the tribologic results and structural investigations of the initial compounds by TEM strongly suggests that the friction mechanisms involve surface effects in the early stage of friction. Long-term tribologic experiments and Raman analyses point out an evolution of the structure and composition of the tribofilms during the friction process leading to similar friction properties of the tribofilms. Wear studies revealed that highly fluorinated derivatives appear less efficient than pristine and weakly fluorinated compounds. [ABSTRACT FROM AUTHOR]

Inclusion compounds (intercalates) of fluorinated graphite matrix with butanone (CFBr· yCHCOCH, x = 0.49, 0.69, 0.87, 0.92, z ≈ 0.01) were prepared by guest substitution from acetonitrile to butanone. The kinetics of the thermal decomposition (the 1st stage of filling → the 2nd stage of filling) was studied under isothermal conditions at 294-313 K. The relationship of the host matrices structure with inclusion compounds' thermal properties and kinetic parameters is discussed. [ABSTRACT FROM AUTHOR]

We have synthesized (CFBr · yG) intercalation compounds with (CFBr) as a host and G (dichloromethane, chloroform, carbon tetrachloride, and dichloroethane) as a guest ( x and y are stoichiometric coefficients). The behavior of the functional groups in the guest and host subsystems has been studied by IR spectroscopy. We have examined the influence of the degree of fluorination of the polymer host (0.5 < x < 1.0) and the nature of the guest on the vibrational frequencies of the C-F and C-Cl bonds. [ABSTRACT FROM AUTHOR]

Silicene is the graphene-like silicon nanosheet, which has been synthesized very recently [B. Lalmi, H. Oughaddou, H. Enriquez, A. Kara, S. Vizzini, B. Ealet, and B. Aufray, Appl. Phys. Lett. 97, 223109 (2010)]. Using first-principles calculations, we systematically investigate the structures and properties of fluorinated and hydrogenated silicene, the silicon analogues of graphane. Different from the carbon-counterpart, the fluorination prefers the conformation with a zigzag-line buckling, while the hydrogenation keeps the chair conformation similar to graphane. A direct band gap is opened in the silicene fluoride, and the gap values can be continuously modulated by the strain. While for the hydride, a strain-induced indirect-to-direct band gap transition is found. [ABSTRACT FROM AUTHOR]

Thermal dissociation processes for acetonitrile inclusion compounds based on the polymer fluorographite host matrix CFBr· yCHCN, where x = 0.49-0.92, y = 0.174-0.285, are investigated. Thermodynamic parameters (Δ H°, Δ S°, Δ G°) for deintercalation of the compounds of the first filling step into the compounds of the second step and gaseous guest within temperature range 294-352 K were determined. The effect of the host matrix fluorination degree on the thermodynamic characteristics of the studied processes is demonstrated. [ABSTRACT FROM AUTHOR]

The properties of intercalated compounds of graphite fluoride with highly volatile polar guest components were studied by DTA, XRPA, and IR spectroscopy. The role of guest host and host host intermolecular interactions in the formation of layered inclusion compounds based on polymer matrices with different degrees of fluorination is shown. [ABSTRACT FROM AUTHOR]

Abstract: Carbothermal treatment was used to improve the discharge rate performance of primary lithium/carbon monofluoride (Li/CF x with x =1) batteries. The treatment was carried out by heating a mixture of CF x and carbon black (CB) just below the decomposition temperature of CF x under nitrogen for 2h. In the treatment, poly(vinylidene fluoride-co-hexafluoropropylene) (Kynar) was used as a fluorinated polymer binder to press the CF x /CB mixture into pellets. It was shown that the content of Kynar significantly affected the discharge performance of the resulting treated-CF x (T-CF x ). This can be attributed to the catalytic effect of HF formed by the pyrolysis of Kynar on the decomposition of CF x and on the reaction of CB with the volatile fluorocarbons formed by the decomposition of CF x . The discharge performance of T-CF x cathode was also affected by the temperature of carbothermal treatment and by the ratio of CF x to CB. In this work the best result was obtained from a treatment conducted at 470°C on a 87CF x /10CB/3Kynar (by weight) mixture. In the discharge condition of C/5 and 20°C, the Li/CF x cell with such-obtained T-CF x cathode showed about 95mV higher voltage than the control cell while retaining nearly the same specific capacity. Impedance analyses indicate that the improved discharge performance is mainly attributed to a reduction in the cell reaction resistance (R cr) that includes an ohmic resistance related to the ionic conductivity of the discharge product shell and a Faradic resistance related to the processes of charge-transfer and Li+ ion diffusion in the CF x reaction zone. [Copyright &y& Elsevier]

The energy level structure of fluorinated graphite intercalation compounds C2FxBr0.01· yCH3CN ( x = 0.49–0.87, y = 0.084–0.136) has been studied by X-ray photoelectron spectroscopy providing the information on the electronic structure of compounds in question. The analysis of variations of the binding energy of core levels C1 s, F1 s, and O1 s opens the possibility to explore the nature of the chemical bond C-F in the fluorographite matrix with a varying degree of fluorination, as well as to model the structure of these compounds. The examination of decomposition results of spectra into components has revealed the occurrence of C-F fragments, carbon atoms not bonded directly to fluorine atoms, and “graphite-like” areas, whose contribution to the overall structure increases with the degree of matrix fluorination decreasing. The presence of oxygen was considered from the viewpoint of surface phenomena characteristic of low-temperature carbon materials. [ABSTRACT FROM AUTHOR]

The reaction mechanisms of a stage-1 fluorine–graphite intercalation compound (GIC), C2.5F, with 0.10 MPa of fluorine gas have been studied at 573–773 K. The original stage-1 structure of C2.5F with semi-ionic C–F bonds and planar sp2 carbon sheets is maintained in most part of the compound after the reaction at 573 K, although a large number of covalent C–F bonds are formed on the surface. This compound is partially or completely converted to poly(carbon monofluoride), (CF)n, with covalent C–F bonds and puckered sp3 carbon sheets at 673 or 773 K, respectively. Single-phase (CF)n obtained at 773 K possesses remarkably small BET specific surface area, 61 m2/g carbon, almost unchanged from the value of the precursor C2.5F (69 m2/g carbon). In this reaction, the accommodation of fluorine atoms supplied from the atmosphere into the galleries of C2.5F is facilitated by the rearrangement of originally intercalated fluorine atoms in the GIC, forming (CF)n with fewer defects compared to those by the conventional direct fluorination of graphite. [Copyright &y& Elsevier]

A facile method for the synthesis of highly fluorinated reduced graphene oxide from graphene oxide using BF3-OEt2 solution and alkylthiol/alkylamine on the Gram scale has been described using a detailed mechanism. The maximum fluorination was as high as 38 wt% and the fluorinated reduced graphene oxide produced has great wettability and high insulating properties. [ABSTRACT FROM AUTHOR]

Materials often contain minor heterogeneous phases that are difficult to characterize yet nonetheless significantly influence important properties. Here we describe a solid-state NMR strategy for quantifying minor heterogenous sample regions containing dilute, essentially uncoupled nuclei in materials where the remaining nuclei experience heteronuclear dipolar couplings. NMR signals from the coupled nuclei are dephased while NMR signals from the uncoupled nuclei can be amplified by one or two orders of magnitude using Carr-Meiboom-Purcell-Gill (CPMG) acquisition. The signal amplification by CPMG can be estimated allowing the concentration of the uncoupled spin regions to be determined even when direct observation of the uncoupled spin NMR signal in a single pulse experiment would require an impractically long duration of signal averaging. We use this method to quantify residual graphitic carbon using 13 C CPMG NMR in poly(carbon monofluoride) samples synthesized by direct fluorination of carbon from various sources. Our detection limit for graphitic carbon in these materials is better than 0.05 mol%. The accuracy of the method is discussed and comparisons to other methods are drawn. [ABSTRACT FROM AUTHOR]

Abstract Fluorinated graphene (FG), the most stable derivative of graphene, is suggested for the role of functional material (weak fluorination degree) and the dielectric layers for graphene and other 2D materials, especially for flexible and printed electronics. The main findings discussed in the present study are (1) an excellent mechanical properties of FG in bending conditions for the first time measured for FG with different fluorination degree; (2) the 97–99% transparency of FG films with thickness up to 25 nm in wide range of wavelengths, (3) a ultralow leakage current and a high breakdown field in the printed cross-bar structures; (4) a smooth increase in interplanar spacing by 1–2% from the center of few-layered fluorinated graphene flakes to their edges; (5) observation of only C C related G line without defect related D line in Raman spectra in the case of giant amplification of Raman scattering for FG films printed at Ag layers. Unchanged characteristics of fluorinated graphene films up to stretching-strain values of 2.5–4% were demonstrated. Generally, it can be stated that fluorinated graphene films have great promise in flexible and printed electronics. Graphical abstract Unlabelled Image Highlights • Excellent mechanical properties for the fluorinated graphene films with different fluorination degree are demonstrated. • FG films possess a unique combination of properties for 2D dielectric films including the transparency. • Fluorinated graphene suspension is suggested for the dielectric films, especially for flexible and printed electronics. [ABSTRACT FROM AUTHOR]