X-ray spectroscopic study of graphite fluoride (C2F) n intercalated with benzene

Samples of intercalated graphite fluoride of the C₂F·zR type (R is C₆H₆) before and after heating to 150 °C in a spectrometer vacuum chamber were studied by X-ray fluorescence spectroscopy. The C-Kα differential spectra of the samples mainly characterizes the electron state of carbon atoms in the benzene molecule inside the C₂F matrix. The differential spectrum is distinct from the spectrum of solid benzene by additional maxima, which indicate the interaction between the benzene molecules and the graphite fluoride matrix. Comparative analysis of the spectrum of the heated sample and those of graphite and graphite fluoride (CF) _n suggests that the layers of the C₂F matrix contain considerable regions of both completely fluorinated and graphite-like regions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 705–708, April, 2000.     

X-ray photoelectron spectroscopy study of intercalated compounds of fluorinated graphite C2FxBr0.01·yCH3CN

The energy level structure of fluorinated graphite intercalation compounds C₂F_xBr_0.01·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 C1s, F1s, and O1s 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.     

IR spectra of the reaction products of trioctylamine intercalated into graphite fluoride with a series of solutions

The formation of compounds (TOAH)Cl, (TOAH)₂[PdCl₄], (TOAH)₂[PtCl₆], and (TOAH)[FeCl₄] in the interlayer spaces of graphite fluoride, similar to the process occurring during extraction in solution, was shown by IR spectroscopy. The cation-anion interaction in these compounds was considered.     

Electronic structure and charge transfer in the ternary intercalated graphite beta-KS0.25C3

The electronic structure of the ternary intercalated graphite beta-KS(0.25)C3 is studied by means of a first-principles density functional theory approach. The nature of the partially filled bands is analyzed, and the K sublayers of the intercalate are shown to have an important contribution to the Fermi surface. This K-based contribution confers a sizable three-dimensional character to the conductivity even if considerably less than that for the related binary KC8. The electronic structure of beta-KS(0.25)C3 differs noticeably from that of the related ternary compound, KH(x)C4. The charge transfer is analyzed, and a way to evaluate it, which can be used in general for intercalated graphites, is proposed. The charge transfer per C atom in this ternary material is shown to be smaller than that in the KC8 binary compound despite a more favorable stoichiometry ratio between K and C.     

Fire intumescent compositions based on the intercalated graphite

A possibility of creation of the swelling type fire-retardant compositions of paints and varnishes based on intercalated graphite dispersed in the polymer matrix in the amount of 5.0–15.0 mass percent was investigated and proved. The expediency of use of the rough aqueous dispersions of polymers obtained with the use of protective colloids as a binder was shown.     

Reaction of graphite fluoride with NaOH-KOH eutectic

Graphite fluoride has been generally considered chemically inert against strong alkalis under ambient conditions. In the present study we demonstrate that treatment of graphite fluoride with eutectic NaOH-KOH mixture at 250 °C induces dramatic structural and textural changes in the solid as evidenced by XRD, FT-IR, Raman, UV-vis absorption and fluorescence and microscopy techniques (TEM, AFM). The reaction proceeds in the molten state leading to water-soluble, graphitized carbon particles which unlike graphite fluoride, adopt a variety of morphologies, like platy, tetragonal, triangular, discoid and spherical. The resulting carbon particles are dispersible in water and fluoresce under UV excitation.     

Synthesis,properties, and structure of intercalated graphite fluosulfonate fluorides

Graphite fluosulfonate fluorides of the composition C₂F_x−y(SO₃F)_y (x+y≈1) have been synthesized. The new compounds can be treated as derivatives of graphite fluorides C₂F_x(x≈1) in which approximately 1/50 of the F atoms have been replaced by SO₃F groups. The intercalates based on the new matrices have been studied by X-ray phase analysis, IR spectroscopy, mass spectrometry, and thermography. The ability of the intercalates to absorb various substances is investigated. It is shown that the introduction of a few SO₃F groups into the C₂F_x matrices significantly changes the physicochemical properties and the structure of intercalates; in particular, for intercalates of stage II structure this expands the scope of substances that can penetrate into interlayer spacings. The dependence of the penetration ability of the substances on the van der Waals sizes of their molecules makes intercalates resemble zeolites in properties. Institute of Inorganic Chemistry, Russian Academy of Sciences, Siberian Branch, Novosibirsk. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No, 1, pp. 144–151, January–February, 1995 Translated by I. Izvekova     

Solvent free synthesis of polyaniline-clay nanocomposites from mechanochemically intercalated anilinium fluoride

Nanocomposites consisting of conducting polyaniline and clay minerals were successfully synthesized from mechanochemically intercalated anilinium fluoride; the nanocomposites prepared by the mechanochemical intercalation method contained much more polyaniline in the clay layers than those prepared by a conventional solution method.     

Superconductivity in Li3Ca2C6 intercalated graphite

In this paper, we report the discovery of superconductivity in Li₃Ca₂C₆. Several graphite intercalation compounds (GICs) with electron donors, are well known as superconductors [T. Enoki, S. Masatsugu, E. Morinobu, Graphite Intercalation Compounds and Applications, Oxford University Press, Oxford, 2003]. It is probably not astonishing, since it is generally admitted that low dimensionality promotes high superconducting transition temperatures. Superconductivity is lacking in pristine graphite, but after charging the graphene planes by intercalation, its electronic properties change considerably and superconducting behaviour can appear. Li₃Ca₂C₆ is a ternary GIC [S. Pruvost, C. Hérold, A. Hérold, P. Lagrange, Eur. J. Inorg. Chem. 8 (2004) 1661-1667], for which the intercalated sheets are very thick and poly layered (five lithium layers and two calcium ones). It contains a great amount of metal (five metallic atoms for six carbon ones). Its critical temperature of 11.15 K is very close to that of CaC₆ GIC [T.E. Weller, M. Ellerby, S.S. Saxena, R.P. Smith, N.T. Skipper, Nat. Phys. 1 (2005) 39-41; N. Emery, C. Hérold, M. d’Astuto, V. Garcia, Ch. Bellin, J.F. Marêché, P. Lagrange, G. Loupias, Phys. Rev. Lett. 95 (2005) 087003] (11.5 K). Both CaC₆ and Li₃Ca₂C₆ GICs possess currently the highest transition temperatures among all the GICs.     

Preparation and characterization of intercalated misfit-layer compounds and natural superlattices

This paper presents the preparation and characterization of the new types of misfit-layer compounds and natural superlattices consisting of Ce_xNb_1−x−y□_yS (Q′) and Ni_zNbS₂ (H) layers, where □ is an atomic deficit at a metal site. A Q′ layer is larger by about 1 Å in thickness than a CeS (Q) layer in (CeS)_1.16NbS₂. They are prepared by chemical vapor transport reaction in a closed silica tube under quasi-equilibrium conditions. The 1Q′/3H type of compound are grown as a single crystal while the 1Q′/4H type of compound is grown as composite crystals with the 1Q′/3H and 1Q/2H compounds. Natural superlattices which have a long period in a direction perpendicular to layers are found. Their chemical formulae are given by (Ce_xNb_1−x−y□_yS)_m(Ni_z)_n−m(NbS₂)_n, where m and n are integers. It is found from an X-ray-photoelectron spectroscopy (XPS) study that Nb affects the valence and the bonding of Ce in the Q′ layers. It is in a higher oxidation state than Nb in NbS₂ layers. A scanning tunneling microscope (STM) study shows that some of the superlattices form a hexagonal supercell in the (a,b)-plane and behave as a narrow-gap semiconductor so that no STM images are obtained at bias voltage less than 0.3 eV.     

Facile sonochemical synthesis of graphite intercalation compounds

[reaction: see text] Graphite intercalation compounds (GICs) are useful as powerful reducing agents in organic chemistry and are typically prepared by anaerobic solid-state reactions at high temperatures for 1-8 h. We have been able to prepare KC(8) in situ in toluene using ultrasound in less than 5 min. This allows for a convenient approach to reductive chemical syntheses involving GICs.     

Geometry and orientation of molecules in a graphite fluoride matrix

Polarization dependences of the EXAFS and XANES spectra of graphite fluoride intercalation compounds C₂F_x·yA (x ≈ 1, A=Br₂, Fe(AA)₃, FeCl₃, SnCl₄; AA=acetylacetonate) synthesized by diffusion from solution were measured. The measurements were carried out in the FeK-, BrK-, and SnK-edge of absorption spectral regions using synchrotron radiation of the VEPP-3 storage ring (Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences). The polarization dependences of effective coordination numbers and edge σ-resonance intensity are analyzed, and parameters of the local surroundings of atoms (coordination numbers, interatomic distances, Debye-Waller factors σ²) are determined. For the Br₂ intercalates, the orientation angle with respect to the matrix layers is 64±1.5°, and the interatomic distances are close to those in the gas phase. The FeCl₃ molecule forms dimers in the matrix as it does in the gas phase, and the iron atoms have tetrahedral surroundings. For the Fe(AA)₃ molecules intercalated into the matrix, the iron atoms have significantly distorted octahedral environments. For the SnCl₄ intercalates, the lowering of temperature does not cause additional coordination of Sn atoms, and structural disorder of SnCl₄ makes the major contribution to σ². Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 6, pp. 1081–1088, November–December, 1996 Translated by L. Smolina     

Highly fluorinated graphite prepared from graphite fluoride formed using BF3 catalyst

Fluorinated graphites (CF_0.47) were obtained by reaction at room temperature of fluorine gas with graphite in the presence of boron trifluoride and hydrogen fluoride as catalysts. Their thermal treatments under fluorine at temperatures up to 600 °C lead to a progressive increase of the fluorine level resulting in an highly fluorinated graphite (CF_1.02). Whatever the fluorination level, a stage one fluorine-graphite intercalation compound is obtained. The sp² carbon hybridization is maintained for treatment temperature below 300 °C and two types of structure coexist for T_T in the range 350-550 °C. Finally, above 550 °C, carbon hybridization is sp³.The resulting materials were studied by ¹¹B, ¹H, and ¹⁹F NMR and EPR at different experimental temperatures giving informations about the intercalated fluoride species, the temperature of their removal from the host fluorocarbon matrix, as well as their mobility.