FeCl3-graphite Intercalation Compounds Research Articles

Structural, electrical and optical properties of highly conductive FeCl3-intercalated graphitised poly(p-phenylene vinylene) films prepared by the solution method

A stage-3 FeCl3 graphite intercalation compound has been successfully synthesised by the solution method from graphitised poly(p-phenylene vinylene) film. Graphitised film intercalated by the solution method is a highly conductive material with a metallic conductivity as high as 2*105 S cm-1, and this is higher than the values for FeCl3-intercalated films prepared by vapour-growth technique. Metallic behaviour of the temperature dependence of the electrical conductivity and of the optical reflectance have been observed.

The synthesis of NiCl 2FeCl 3-graphite intercalation compounds

NiCl 2FeCl 3-graphite intercalation compounds have been synthesized by using mixtures of nickel chloride and ferric chloride. With NiCl 2/FeCl 3 molar ratios from 1 9 to 6 4 , the stage one and stage two compounds were obtained at 400 °C in three days. The stage of the compounds obtained can be controlled by changing the starting graphite/chlorides ratio and also the NiCl 2/FeCl 3 ratio. The compounds obtained are very stable in air and even in water.

Stability and Preparation Condition of CuCl2-and FeCl3-Graphite Intercalation Compounds

The stability of CaCl2-and FeCl3-graphite intercalation compounds (GICs) was examined. CuCl2-and FeCl3-GICs were prepared from Grafoil strips by the“two-bulb” or “mixed” methods. The composition and the stage structure of the resultant GICs were determined by the weight-increase and X-ray diffraction measurements.The stability of the GICs was examined by the two methods. Firstly, the GICs prepared were kept in the air at room temperature, and their degradation with time was followed up to 35 days by X-ray diffraction and electrical resistivity measurements. It was found that CuCl2-GICs were rather stable and only a small change was found in both the resistivity and X-ray diffraction pattern, while a considerable degradation was observed on FeC13-GICs in a few days. The tests for the thermal stability of the GICs also showed the similar tendency. Thedegradation temperatures in the air and in the nitrogen atmosphere were determined as 310°C and 330°C for CuCl2-GIC (1st stage), and about 300°C in both cases for FeCl3-GIC (1st stage), respectively.

Magnetic order of FeCl3 and CoCl2 intercalated graphite

We have investigated by neutron diffraction the magnetic properties of first- and second-stage FeCl3 and CoCl2 graphite intercalation compounds. They can be considered as quasi-two-dimensional magnetic systems in which one can vary both the 3D magnetic coupling and the intralayer magnetic interactions. The FeCl3 compounds are Heisenberg systems in which we have found that strong 2D magnetic correlations develop below 40 K; in the first-stage compound, the 3D coupling is strong enough to allow a transition to a 3D order below 3.8 K. The in-plane order is always an incommensurate modulation. In the CoCl2 compounds we have observed on the contrary an antiferromagnetism along c axis with the moments in the layer plane. They are 2D X-Y systems with a Kosterlitz–Thouless transition in which however the 3D coupling plays an important role.

Contactless measurements of the basal plane resistivity of FeCl3and SbF5intercalated graphites under pressure

The basal plane resistivities of stage 1 SbF5 and stage 2 FeCl3 graphite intercalation compounds have been measured for the first time at high pressure, using a recently developed contactless method. The resistivity is found to increase with increasing pressure in both materials. In the SbF5 intercalated material a phase transition was found at 1.2 GPa. This could be the first pressure-induced stage transformation observed in an acceptor intercalation compound.

Inelastic electron scattering spectroscopy of graphite-acceptor compounds

Electron energy loss spectroscopy has been used to measure the valence and core electronic excitations up to 300 eV in low stage AsF 5-graphite residual intercalation compounds. The results are compared with similar measurements on FeCl 3-graphite intercalation compounds and graphite which has been doped substitutionally with a small amount of boron. The AsF 5-graphite samples showed well defined intraband plasmons near 1.2 eV which exhibited dispersion similar to that observed in stage-2 FeCl 3-graphite. The excitation spectra of carbon 1s electrons in a stage-2 compound were used as a direct measurement of the Fermi level position which is shown to be 0.9 eV below that of pristine graphite. Using an empirical model for the density of states the charge transfer per carbon atom is estimated as 0.025 electrons in stage-2 AsF 5-graphite.

Composé d'insertion du fer dans le graphite obtenu par réduction electrochimique

Several authors have studied the chemical reduction of FeCl 3-graphite intercalation compounds. According to the reducers employed (hydrogen or potassium at high temperatures, reducing agents in solution: Na or Li in organic solvent, or Na in liquid NH 3 at low temperatures) several compounds are obtained: FeCl 2-graphite intercalate, α-iron clusters, iron-graphite (iron monolayer intercalated in graphite) and Fe 0-graphite π complex. We have studied the slow electrochemical reduction of first stage FeCl 3-graphite intercalates in a cell of this type: (−) Li/LiClO 4 1 M in organic solvent/G-FeCl 3 (+) The reduced compound contains solvent that can be washed out with H 2O or HCl, or removed by heat treatment at 400 °C. A mixture of free graphite, incompletely reduced FeCl 2-graphite and iron graphite compound is found. X-ray diffraction gives several lines which can be indexed in a tetragonal lattice with a = 2.82 A ̊ and I c = 5.6 A ̊ for the iron-graphite intercalate. Only bromine can react with this new compound at room temperature, with corresponding disappearance of the lattice. Magnetic and Mössbauer studies are in progress on the reduced intercalate.