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International audience; In this work, we address the properties of fluorinated carbonaceous nanoparticles (F-CNPs) prepared using a low-temperature process in molten Li-Na-K carbonates at the eutectic composition. The electrochemical performance of these materials is evaluated as the positive electrode of primary lithium ion batteries. Structural analyses show that CNPs are composed of both amorphous and graphitized domains with low crystallinity that induces presence of different types of CO bonds. In contrast with commercial CFx materials, F-CNPs do not give rise to a flat potential plateau but exhibit a continuous decrease of the potential. The difference in the electrochemical performance observed for F-CNPs (CF∼0.43) can be significantly noted for high discharge at 1C rate, for which the discharge potential is about 0.7–0.9 V higher than that obtained with commercial CFx with an increase of the specific capacity to ca. 450 mA h g−1.

Fluorine-containing polymers occupy a peculiar niche among conventional polymers due to the unique combination of physicochemical properties. Direct surface fluorination of the polymeric materials is one of the approaches for the introduction of fluorine into the chemical structure that allows one to implement advantages of fluorinated polymers in a thin layer. Current review considers the influence of the surface interaction of the polymeric materials and membranes with elemental fluorine on gas, vapor and liquid transport as well as swelling and related phenomena. The increase in direct fluorination duration and concentration of fluorine in the fluorination mixture is shown to result mostly in a reduction of all penetrants permeability to a different extent, whereas selectivity of the selected gas pairs (He-H2, H2-CH4, He-CH4, CO2-CH4, O2-N2, etc.) increases. Separation parameters for the treated polymeric films approach Robeson’s upper bounds or overcome them. The most promising results were obtained for highly permeable polymer, polytrimethylsilylpropyne (PTMSP). The surface fluorination of rubbers in printing equipment leads to an improved chemical resistance of the materials towards organic solvents, moisturizing solutions and reduce diffusion of plasticizers, photosensitizers and other components of the polymeric blends. The direct fluorination technique can be also considered one of the approaches of fabrication of fuel cell membranes from non-fluorinated polymeric precursors that improves their methanol permeability, proton conductivity and oxidative stability.

International audience; Nano-CoF3 powders were synthesized by direct fluorination at various temperatures (up to 300 °C) of cobalt nanoparticles and their electrochemical features in lithium battery were investigated. The structure and composition of the raw and fluorinated materials are explored by SEM/TEM, HRTEM, XRD and XPS experiments. The influence of the fluorination temperature on the crystallite size has been evidenced by XRD. It is shown that such fluorination process allows the direct synthesis of nano-CoF3, at TF2 = 100 °C. The XPS investigation of mixtures of CoF3 and acetylene black has shown that, when handled in very dry atmospheres, CoF3-based samples can be used to prepare electrodes for Li-ion batteries in safe conditions. The electrochemical reaction of nano-CoF3 powders vs. lithium metal studied in organic medium involves a conversion process as described in the case of cobalt oxide. Successive impedance measurements were carried out at different discharge states to follow the modifications occurring at the electrode/electrolyte interface during the discharge step. The evolution of the reversible capacity retention of Li+ vs. time capacity of the powdered materials as well as the cycle life of the battery were investigated as a function of the fluorination temperature used for the preparation of the cobalt fluoride nanopowders. The best electrochemical performances were obtained with nano-CoF3 powders prepared at fluorination temperature of 100 °C, for which a reversible capacity of about 390 mAh/g is obtained after subsequent cycles.

International audience; Silicon-mediated fluoride abstraction is demonstrated as a means of generating the first fluorido-cyanido transition metal complexes. This new synthetic approach is exemplified by the synthesis and characterization of the heteroleptic complexes, trans-[M IV F 4 (CN) 2 ] 2À (M = Re, Os), obtained from their homoleptic [M IV F 6 ] 2À parents. As shown by combined high-field electron paramagnetic resonance spectroscopy and magnetization measurements, the partial substitution of fluoride by cyanide ligands leads to a marked increase in the magnetic anisotropy of trans-[ReF 4 (CN) 2 ] 2À as compared to [ReF 6 ] 2À , reflecting the severe departure from an ideal octahedral (O h point group) ligand field. This methodology paves the way toward the realization of new heteroleptic transition metal complexes that may be used as highly anisotropic building-blocks for the design of high-performance molecule-based magnetic materials.

Last few decades, fluorine and fluorinated products have attracted significant attention, because they are greatly involved in our daily life and environment. Although many beneficial breakthroughs have been brought to us thanks to fluorine and fluoride compounds, they are decried today because of some environmental drawbacks. The goal of this book is to provide a better understanding of the many advantages, but also some disadvantages, of these products, focusing on the real place and importance of fluorine and fluorinated products in our current environment and everyday life. Of course, everyone knows that this element is present in toothpastes we use regularly, but who is really aware that it surrounds us in most instances of our life? Fluorine is not a rare element. In fact, it is the 13th most abundant element constituting the Earth's crust, where it is present at about 0.06% to a depth of 16 km. It is the second anion after oxygen. It is most found in minerals such as fluorite, apatite, topaz, and tourmalines, but also in the oceans, groundwater, lakes, and rivers. Much closer to us, it is also an essential constituent of our teeth and our skeleton, as well as those of all mammals. Finally, fluorinated molecules also exist in several plants. Unlike oxygen (O2), which is the essential constituent of our atmosphere, fluorine gas (F2) could not be found in nature until very recently, due to its high chemical reactivity. Indeed, due to its electronic structure (1s2 2s2 2p5), one electron is missing in the 2p electronic layer to complete the valence shell to eight electrons (2s2, 2p6), which corresponds to the electron configuration of the nearest noble gas, neon (octet rule). Thus, because of the reaction ½F2 + e− → F−, the element oxidizes almost all other elements, leading to generally very stable compounds in which it is present under the form of a fluoride ion, F−. However, for simplicity, the word fluorine is often used to identify the species present in a product, whatever the charge. Physical chemical properties of fluorine will illustrate how it is certainly the most paradoxical of the elements, because the majority of its properties derive from a duality: so reactive on one hand that it could not be isolated for centuries, and on the other hand, giving most stable bonds with almost all other elements (particularly with carbon), so stable that the formed products often stay unmodified in the stratosphere. Obviously, we will discuss the contribution of the refrigerant gases containing fluorine, CFC and HCFC, to the depletion of the ozone layer, and perfluorocarbons and other perfluorinated molecules’ contribution to the greenhouse effect. Discoveries and anecdotes about the real history of fluorinated materials throughout centuries will be illustrated using some major examples in the first section. We will present some decisive discoveries and stages of development in fluorinated products that took place during the 20th century following the isolation of fluorine by H. Moissan in 1886, with particular emphasis on the technological advances that have followed. The contributions of fluorinated products these last 50 years will be described in the second section. Issues relative to these products are of primary concern for humans in important areas such as modern technology, medicine, pharmacy, and biotechnology. Examples will be given in various fields: photonics, energy production, new drugs, surfactants, fire emulsions, TV components, fluorinated polymers, alternative materials in cardiovascular surgery, anti-decay products, and medical imaging applications. A third section will deal with the presence of fluorine and fluorinated products around us and their effect on our environment (atmosphere, lithosphere, water, gaseous emissions), focusing on efforts to limit harmful consequences. We will conclude this section on fluorine's impact on man by giving examples of different types of fluoride contaminations (water, food, industrial environmental), together with the physiological effects of fluorides on living organisms; the solutions that have been proposed to solve these problems will be also considered. Because of the importance of this element, international meetings are regularly devoted to all fields involving Fluorine. The last International Symposium on Fluorine Chemistry was held in Oxford, UK on July 2018 and the next European one will take place in Warsaw on August 2019. It can be added that several “Fluorine Networks” have been created in various countries, including France , USA, UK, Germany, Russia and Japan, to promote activities related to fluorine in various sectors of chemistry, new technologies, life sciences, medicine and the environment. It should be noted that several specialized books have appeared in recent years dealing with many fields of fluorine chemistry and fluorinated materials: organic and inorganic compounds, fluoropolymers, pharmaceutical molecules, industrial and biomedical applications, etc. These volumes, which propose highly specialized information, are collected in a table at the end of this book. But so far, no attempt had been made to produce an English-language work with a comprehensive and global approach to this element's impact on humanity, that is, advanced technologies we use every day, the air we breathe, the water we drink, the land we live on, etc. Rather than listing tedious documents on the various classes of fluorinated products (the features and applications of which can be better found in more specialized books), it was decided that the following pages should propose an original global approach to the topic, illustrating (I hope) the importance of this element on our environment and life. The varied fields involving fluorine, such as history, cosmochemistry, global warming, radiative forcing, natural and anthropogenic emissions, the water cycle, etc., will be thus evoked, but without ignoring some negative aspects of these products. The place of fluorine and fluorinated products in key areas for our future will be also evoked, dealing with waste reduction, global warming, energy independence, microelectronics, nanotechnologies, etc. In this book, the author wanted to show a personal version of the image of fluorine and fluorinated products, of their importance in our daily lives, as well as all the promising contributions in many fields of science and technology. However, the disadvantages caused to our health and environment by some of these products have not been underestimated. Unfortunately, the author could not consider all properties and applications of these materials, and begs concerned colleagues to excuse him in case of important omissions. Note: In this book, the word “fluorine” may be taken either for the element or for the F2 gas (difluorine); on the other hand, the word “fluoride” may be taken either for a compound/material or the anion F−.

New exotic phenomena have recently been discovered in oxides of paramagnetic Ir4+ ions, widely known as ‘iridates'. Their remarkable properties originate from concerted effects of the crystal field, magnetic interactions and strong spin-orbit coupling, characteristic of 5d metal ions. Despite numerous experimental reports, the electronic structure of these materials is still challenging to elucidate, and not attainable in the isolated, but chemically inaccessible, [IrO6]8– species (the simplest molecular analogue of the elementary {IrO6}8− fragment present in all iridates). Here, we introduce an alternative approach to circumvent this problem by substituting the oxide ions in [IrO6]8− by isoelectronic fluorides to form the fluorido-iridate: [IrF6]2−. This molecular species has the same electronic ground state as the {IrO6}8− fragment, and thus emerges as an ideal model for iridates. These results may open perspectives for using fluorido-iridates as building-blocks for electronic and magnetic quantum materials synthesized by soft chemistry routes., Iridates are known to exhibit a range of exotic electronic and magnetic behaviours but it is difficult to prepare isolated [IrO6]8− species via soft chemical routes. Here, the authors isolate the isoelectronic [IrF6]2− complex, and assess it as a model and for iridate analogues.

International audience; After a review on the wide variety of inorganic fluorinated components in modern technologies, in particular for energy conversion/storage systems, the use of fluorinated carbons as electrodes for primary lithium batteries will be highlighted; in particular conventional graphite fluorides will be compared to recently investigated fluorinated carbon nanoparticles (F-CNPs) prepared from electrochemical reduction of molten carbonates.

International audience; This book addresses current societal debates around the globe. Written by respected researchers from France, Germany, Belgium, Denmark, Spain, Portugal and Italy, the chapters are based on presentations given at a conference organized by the European Academy of Sciences, in partnership with the Royal Academy of Belgium and French Academy of Sciences, in Brussels (Belgium) in November 2016.

International audience; Fluorine–graphite intercalation compounds were prepared from highly oriented pyrolytic graphite (HOPG) and natural graphite under high pressure of fluorine (16 MPa) at room temperature and were analyzed by means of X-ray diffraction. The rate of intercalation under high pressure of fluorine was higher than that under ordinary pressure. The compositions of the compounds obtained from HOPG and natural graphite were estimated by the weight change before and after fluorination to be C3.41F and C5.62F, respectively. They were blue–black compounds composed of two different phases. One phase is a conventional stage II CxF with the repeat distance of ca. 0.93–0.96 nm which was the same compound as that obtained under ordinary pressure of fluorine, and the other was also a stage II with a different repeat distance of ca. 1.03–1.18 nm. The fluorine species intercalated between the graphene layers can easily move between both phases and the phase transition occurs periodically. The decomposition rate of fluorine-intercalated HOPG was extremely low and it shows a long-term stability in air for 26 years.

Heavy 5d elements, like osmium, feature strong spin-orbit interactions which are at the origin of exotic physical behaviors. Revealing the full potential of, for example, novel osmium oxide materials ("osmates") is however contingent upon a detailed understanding of the local single-ion properties. Herein, two molecular osmate analogues, [OsF

Modern Synthesis Processes and Reactivity of Fluorinated Compounds focuses on the exceptional character of fluorine and fluorinated compounds. This comprehensive work explores examples taken from all classes of fluorine chemistry and illustrates the extreme reactivity of fluorinating media and the peculiar synthesis routes to fluorinated materials. The book provides advanced and updated information on the latest synthesis routes to fluorocompounds and the involved reaction mechanisms. Special attention is given to the unique reactivity of fluorine and fluorinated media, along with the correlation of those properties to valuable applications of fluorinated compounds.

Heat capacity, thermal dilatation, structure, Mossbauer spectra and dielectric permittivity of fluoride KFe 2 F 6 with tetragonal tungsten bronze crystal structure were studied. The as-made sample undergoes two structural phase transitions P 4/ mbm ( T 1 ≈ 340 K) → Pbam ( T 2 ≈ 250 K) → G 2 and magnetic phase transformation at T m ≈ 133 K. Heating up to 600–700 K and subsequent cooling in helium atmosphere leads to a change of phase transition temperatures and diffused anomalies in thermal expansion. The results obtained and influence of thermal prehistory of the sample on its physical properties are discussed in the context of previous studies on related fluorides KFe 2 F 6 , which sometimes suggest conflicting structural details.

International audience; Heat capacity, Mössbauer and Raman spectra as well as magnetic properties of fluoride CsFe2F6 with defect pyrochlore structure were studied. In addition to recently found above room temperature three successive structural transformations Pnma-Imma-I41amd-Fd-3m, phase transition of antiferromagnetic nature with the 13.7 K Neel temperature and a broad heat capacity anomaly with a maximum at about 30 K were observed. The room temperature symmetry Pnma is unchanged at least down to 7 K. Simple model of indirect bond used to estimate the exchange interactions and to propose a magnetic structure model.

International audience; The physicochemical properties of amorphous silica prepared by the fluoride technology are studied; the surface of silica is modified by direct fluorination with F2 gas or cC4F8 radio frequency plasma. The modification of the surface physical chemical properties after fluorination are compared with the initial silica and analyzed by X-ray photoelectron spectroscopy, IR spectroscopy, and transmission electron microscopy.

International audience; Many structural networks of transition metal fluorides and oxide fluorides may be derived from simple units of octahedral MF6 units, connected by common corners, generally in a 3D way: e.g., perovskite, ReO3, elpasolite, HTB, TTB, pyrochlore, etc. The accurate knowledge of these structures, together with the stabilities of these phases vs. temperature, allows deeper interpretation and fitting of many of their physical properties. Among the numerous fluoro-compounds which derive from these structural arrangements, several fluorinated and oxyfluorinated series have been chosen to illustrate the great range of outstanding physical properties, including ferromagnetism, piezoconductivity, ferroelasticity, high TC superconductivity, surface functionalization, that can be better understood with the help of structural considerations. The concept of nanometric particles in materials science has also drastically changed the investigations in solid state fluorine chemistry, not only for finding original synthetic routes, but also new characterization tools. As an example, in nanostructured M(OH,F)3 metal hydroxyfluorides that can be used as acidic heterogeneous catalysts, the morphological nature and specific area of the materials can be tuned by changing the experimental parameters of synthesis. In particular, the number and strength of Brønsted/Lewis acidic sites and the thermal stability can be correlated to the structural arrangements.

International audience; The effect of fluorination on various types of phyllosilicate minerals has been investigated. Two different fluorination techniques have been used: direct F2 gas and cold radio frequency plasma involving c-C4F8 or O2/CF4 mixtures. The modifications of the surface composition and properties have been followed mostly by x-ray photoelectron spectroscopy (XPS). Depending of the fluorination reagents, a reactive etching process involving M-F bonding occurs (direct F2 gas; O2–CF4 rf plasma) or a carbon fluoride deposition takes place (c-C4F8 rf plasma). In the case of F2-gas treated minerals, Si 2p XPS signal accounts for the presence of fluorinated Si environments.

International audience; The electrochemical reduction of molten Li–Na–K carbonates at the eutectic composition was (43.5/31.5/25 mol%) performed in the range 450–700 °C. The analysis of the electrochemical mechanism was done by cyclic voltammetry with an inert vitreous carbon electrode. “Quasi-spherical” carbonaceous particles were obtained with average diameter comprised between 30 and 50 nm. The specific surface area as well as the crystallinity and morphology of the powders were strongly influenced by the operating conditions, i.e. potential deposition, temperature of the molten carbonates, temperature of the drying process after washing. The carbon prepared in our experimental conditions contains micro-, meso- and macroporisty. The proportion of each one is strongly dependent on the operating deposition conditions. The highest specific surface area value (1315 m2 g−1) was obtained with carbon powder deposited at 450 °C for an applied potential of −6 V and dried at 600 °C under vacuum after washing.

International audience; The microwave-assisted route allows the synthesis of a new Ti hydroxyfluoride adopting a derived form of a ReO3-type network. Combined techniques such as (i) powder X-ray and neutron diffraction coupled with electron microscopy; (ii) chemical analysis and density measurements; and (iii) FTIR and TGA analyses support the occurrence of Ti vacancies and the stabilization of hydroxyl groups in the vicinity of Ti4+ cations. A superstructure of the ReO3 network has been proposed with two Ti sites and two anionic (OH/F) positions. This original compound exhibits UV-shielding properties with an optical band gap around 3.2 eV and could be considered for potential applications as protective UV absorbers.The O(2p)−Ti(3d) charge transfer band, responsible for this absorption, implies the OH groups and the nonbonding character of the 2p valence band. By changing the synthesis conditions which become reducing, Ti3+ can be stabilized in this network in an elongated octahedral site as revealed by ESR experiments and UV−visible spectroscopy. This is a second example following the recently prepared Al-based fluoride hydrate with Al vacancies, in which a polarizing cation such as Ti4+ can accommodate cationic vacancies.

International audience; The direct F2 gas fluorination of a mesoporous silica gel has been shown to be a unique method leading to very high levels of fluorination (up to 13 wt % F in the bulk). The final powders are homogeneous with a controlled amount of grafted fluorine. In this study, various conditions of fluorination were tested, such as duration, temperature, F2 gas concentration of the fluorinating gas, or an annealing pretreatment. The content of grafted fluorine on silica was quantified by XPS and by the Seel method. Infrared spectroscopy measurements accounted for the consumption of different types of hydroxyl groups, that is, isolated (3740 cm−1), terminal (3715 cm−1), and bound (3520 cm−1), and also for the presence of unreacted internal hydroxyl groups inaccessible to D2O molecules and so to F2. Results showed that an F/OH substitution occurs during the fluorination process and that the grafted amount depends on the F2 concentration of the fluorinating gas and on the concentration of surface hydroxyl groups and physisorbed water trapped on starting silica. Elemental analyses and FTIR data led to the bulk composition of fluorinated silicas: SiO2−x−y(OH)2xF2y. Finally, on a quantitative basis, the elimination of silanol groups parallels the grafting of fluorine for low fluorine content. At higher fluorine contents, a reaction path takes place involving the Si−O−Si opening. Redox processes involving O2/OH− and F2/F− couples explain the wide range of reached F/OH substitution rates without formation of SiF4 or SiF62− species which are observed in classical routes with aqueous fluorinating agents.

Microwave-assisted synthesis has been applied for the preparation of aluminum hydroxyfluorides derived from β-AlF3. In the course of obtaining high-surface-area and homogeneous nanocrystallites, several key parameters have been adjusted. A relationship between the OH/F molar ratio and the stabilized allotropic forms has been pointed out. The surface area has been monitored depending on the water/isopropanol volume ratio. The microstructural properties of the as-prepared material have been thoroughly investigated highlighting X-ray line broadening arising from strains and size effects. It has been concluded from X-ray diffraction data refinements and TEM results that the prepared crystallites possess a platelet shape with an average particle size of 15 nm associated with a high surface area of 82 m2 g−1. The occurrence of hydroxyl groups inside the network has been detected by FTIR spectroscopy and considered angles and bond distances are probably located in peculiar crystallographic sites, i.e., 8f (F1) a...

Coprecipitations of Ce(III) nitrates and Ca chlorides have been performed in basic medium at pH > 12 using NaOH, H2O2, and HF as fluorinating agent. Powders have been annealed under air at 600 °C d...

Plasma-fluorination of natural graphite samples with average particle sizes of 5 μm, 10 μm and 15 μm (NG5μm, NG10μm and NG15μm) was performed using CF 4 and charge/discharge characteristics of surface-fluorinated samples were investigated in 1 mol dm −3 LiClO 4 –ethylene carbonate (EC)/diethyl carbonate (DEC)/propylene carbonate (PC) (1:1:1, v/v/v). Fluorine contents obtained by elemental analysis were in the range of 0.3–0.6 at.% and surface fluorine concentrations determined by X-ray photoelectron microscopy (XPS) were 14.8–17.3 at.%. Plasma-fluorination increased surface disorder of natural graphite samples though reduced surface areas due to its surface etching effect. Electrochemical decomposition of PC was highly reduced on surface-fluorinated NG10μm and NG15μm with high disorder. First coulombic efficiencies of plasma-fluorinated NG10μm and NG15μm increased by 9.7 and 19.3% at 150 mA g −1 , respectively.

International audience; Plasma-fluorination of petroleum coke and those heat-treated at 1860, 2300 and 2800 °C (abbreviated to PC, PC1860, PC2300 and PC2800) was conducted for 15, 30 and 60 min using CF4 gas at 90 °C. Fluorine contents obtained by elemental analysis were negligible except PC fluorinated for 60 min (0.7 at.%). Fluorine concentration on the surface decreased with increasing heat-treatment temperature of petroleum coke, i.e. from PC to PC2800 when plasma-fluorination was made for 30 and 60 min. Transmission electron microscopic observation revealed that the closed edges of PC2800 were destroyed and opened by plasma-treatment. Plasma-fluorination increased surface disorder of heat-treated petroleum cokes, however, slightly reduced surface areas. These surface structure changes increased first coulombic efficiencies of PC2300 and PC2800 by 6–8 and 8–10% at both 60 and 150 mA g−1, respectively.

The outstanding characteristics of fluorine gas, e.g., extreme reactivity and oxidizing power, and the utmost electronegativity of F− ion, lead to very strong bonds between fluorine and most of the other elements of the periodical table. Treatments involving F2, fluorinated gases and rf plasma-enhanced fluorination (PEF) constitute exceptional tools for modifying the surface properties of materials. Many advantages of these techniques can be indeed outlined, when compared to more conventional methods: low-temperature reactions (even at room temperature), chemical modifications limited to surface only without changing the bulk properties, possible non-equilibrium reactions. Depending on the type of starting materials and employed techniques, the improved properties may concern wettability, adhesion, chemical stability, barrier properties, biocompatibility, grafting, mechanical behavior. Several examples of surface fluorination will be given on various types of carbon-based materials, elastomers and polymers.

International audience; High magnetic field and high spinning frequency one- and two-dimensional one-pulse MAS 19F NMR spectra of -ZrF4 and CeF4 were recorded and reconstructed allowing the accurate determination of the 19F chemical shift tensor parameters for the seven different crystallographic fluorine sites of each compound. The attributions of the NMR resonances are performed using the superposition model for 19F isotropic chemical shift calculation initially proposed by Bureau et al. (Bureau, B.; Silly, G.; Emery, J.; Buzaré, J.-Y. Chem. Phys. 1999, 249, 85-104). A satisfactory reliability is reached with a root-mean-square (rms) deviation between calculated and measured isotropic chemical shift values equal to 1.5 and 3.5 ppm for -ZrF4 and CeF4, respectively.

On December 10, 1906, Henri Moissan (1852-1907) became the first French chemist to be awarded the Nobel Prize...

A neutron diffraction study of temperature induced phase transition in Rb2KFeF6 elpasolite has been performed. At room temperature the structure is cubic with space group Fm3m. At T = 170 K a structural phase transition takes place. Space group and atom coordinates in this phase has been defined. The crystal structure is good refined by orthorhombic space group Pmnn. Possible models are discussed.

International audience; Sequences of phase transitions (PTs) occurring in (AI)2BIMIIIF6 elpasolites have been studied via X-ray diffraction, differential scanning calorimetry (DSC) and adiabatic calorimetry at low temperature (LT). The substitution of NH4+ ions for alkaline ions in sites with either 6 or 12 coordination number considerably affects both transition temperature and entropy change associated with the transition(s). Two main mechanisms are responsible for the PTs: displacive transitions, as for the Rb2KMIIIF6 series, in which the transitions are associated with small octahedral tilts and are followed by a rather small entropy change; order-disorder transitions of rigid octahedra, as for (NH4)2NH4MIIIF6. In this latter case, the fluoride atoms located at the apices of the octahedra are disordered onto several possible positions in the cubic...

The heat capacity and the effect of hydrostatic pressure on structural phase transitions in ammonium hexafluoroaluminate, (NH4)3AlF6, have been studied. Two heat capacity anomalies have been found with maxima at T 1 = 218.5 ± 0.5 K and T 2 = 179 ± 2 K. Respective entropy changes of phase transitions are ΔS1 = 15.3 ± 0.5 J mol−1 K−1 and ΔS2 = 2.5 ± 0.5 J mol−1 K−1. It is shown that the p–T phase diagram of this compound is rather complex and contains a triple point (ptp = 0.12 GPa, Ttp = 221 K) and high-pressure phase. The mechanism of transformations and generalized p–T phase diagram for compounds of the (NH4)3MIIIF6 family are discussed within the framework of the rotational order–disorder model.

International audience; Surface modification of graphite powder has been performed by elemental fluorine and radiofrequency (rf) plasma fluorination. Both methods give rise to an enlargement of the surface areas of graphite samples and a change of the pore volume distribution. The capacities of surface-fluorinated graphite samples are higher than those of original samples and even more than the theoretical capacity of graphite, 372 mAh g−1, without any reduction of the first colombic efficiencies. The increments of the capacities are ∼5, 10, and 15% for graphite samples with average particle diameters of 7, 25 and 40 μm, respectively.

Because of their exceptional reactivity, fluorine and fluorinated gases are of primary importance for the modification of the surface properties of materials. This study is devoted to surface treatment of thin nitrile gloves, made of carboxylated nitrile butadiene rubber latex, using either direct fluorination (10% F2gas diluted in N2) or plasma-enhanced fluorination in radio-frequency cold plasmas using fluorinated gases (CF4, CHF3). Mechanisms of fluorination of these co-elastomers have been proposed on the basis of the assignment of the different components of the XPS spectra. Several mechanisms have been observed depending on the fluorination conditions. Although the modification of nitrile gloves is already effective for fluorination reactions at room temperature, an important activation is observed for experiments carried out at 90°C. When the treatments are carried out at room temperature, a gradual fluorination occurs: in the case of 10% diluted F2 gas, monofluorinated C—F groups are the species most found at the surface and perfluoro groups CFn are present in lower amount. An addition reaction takes place at the \(\rlap{--} (\)CH=CH\(\rlap{--} )\) double bonds of the polybutadiene entities, leading to \(\rlap{--} (\)CHF=CHF\(\rlap{--} )\) units. Whatever the fluorination method, thermal activation yields a more massive fluorination of the surface that finally leads to perfluorinated \(\rlap{--} (\)CF2\(\rlap{--} )\) groups and terminal —CF3 groups.

International audience; Cs2NH4GaF6 prepared by solid-state reaction exhibits at room temperature a cubic FmView the MathML sourcem elpasolite structure with a0=9.167 Å. Calorimetric measurements have shown the presence of a first order phase transition at T0=161 K. Pressure dependence of the phase transition temperature has been studied by DTA under pressure. The data are analyzed in the framework of orientational disordering of [NH4]+ and [GaF6]3− ions.

importance in the development of many new technologies, and are impacting various key points of modern life, that is, energy production and storage, microelectronics and photonics, catalysis, automotive, building, etc. Many research fields and applications are indeed concerned by a better knowledge of the relationships occurring between the structure of such compounds and some pertinent physical properties. This Review deals with the structural chemistry of solid-state inorganic fluorides and oxide-fluorides, mostly transition metal-based, including rare-earth elements. Such a Review has not been published for a long time.1 Articles that recently appeared on inorganic fluorinated compounds were mostly focused on material science characteristics: morphology, surface functionalization, nanostructuration of the materials and applications, rather than on the description of characteristic structural features.2−5 Detailed reviews focused on rare earthbased inorganic fluorides have also appeared some years ago...

M II M IV F 6 ( M II =Ni, Pd, Cu; M IV =Pd, Pt) and PdSnF 6 complex fluorides have been synthesized via different preparative methods using either BrF 3 as oxidizer and solvent, or solid state reactions. For M II =Ni, Pd, the phases crystallize in the rhombohedral space group R 3 (LiSbF 6 type). Cationic ordering has been studied by X-ray diffraction and 119 Sn Mossbauer resonance for PdSnF 6 . A lowering of symmetry has been observed when the involved divalent cation presents a Jahn–Teller configuration (Cu II ). Except for PdSnF 6 , which is paramagnetic down to 4 K, all compounds are Pd 2 F 6 -type ferromagnets at low temperature. This behavior has been related to the ordering between half-filled e g orbitals of the divalent cation and empty e g orbitals of the tetravalent cation. A drastic increase in conductivity has been observed under high pressures. In particular the insulator–semiconductor transition induced under pressure (up to 80 kbar) in Pd 2 F 6 corresponds to a decrease of the electrical resistivity by six orders of magnitude. The assumption of an electronic transition induced under pressure from mixed oxidation states ( M II + M IV ) to an unique trivalent M III oxidation state has been proposed.