Tantalum Pillared Montmorillonite - a New Family of Bidimensional Microporous Catalysts

Careful control of (i) the hydrolysis of Ta(C2H5)(5) in ethanolic solution and (ii) of the pillaring process allows the synthesis of a stable tantalum pillared montmorillonite (Ta PILC). This solid presents a basal spacing of 26 Angstrom after calcination at 500 degrees C. The surface area and the microporosity were evaluated by N-2 adsorption isotherms and through the alpha(s)-plot method

Ab-initio Structure of Graphite Monofluoride (cf)(n)

Using the Density Functional Theory formalism, we examined the structure of graphite monofluoride (CF)(n) where two conformations (chair and boat) were found to be experimentally possible. The chair structure is found to be energetically favoured with respect to the boat one by 0.145 eV per CF unit with a transition barrier estimated to be 2.72 eV. We conclude that the synthetized material could depend on the kinetics of the intercalation or could be a mix of both conformations

Transport-properties of a Graphitized Polyimide Film and its Stage-2 Fecl4- Intercalation Compound

The temperature variation of the thermal conductivity, the electrical resistivity and the thermoelectric power of a graphitized polyimide film has been measured in the temperature range 2 < T < 300 K. The effect of electrochemical intercalation with FeCl4- ions has also been studied. The thermal conductivity results confirm the high degree of graphitization that may be obtained with polyimide films. It shows how intercalation increases the structural disorder and how the intercalate substantially contributes to the thermal conductivity at low temperatures. The electrical-resistivity and thermoelectric-power measurements reveal that the density of free carriers is about three times lower in stage-2 FeCl4- solvated intercalation compounds obtained by an electrochemical way than in stage-2 FeCl3 compounds synthetized by a classical method

Anionic Intercalation in La2cuo4 Oxide By Fluorine Or Chlorine Treatment

The influence of a halogen-gas (Cl-2 or F-2) treatment on both structural and physical properties of La2CuO4 has been studied. In ail cases, the resulting product contains an excess of anionic species and shows superconducting properties below 32K and 40K respectively for the chlorine- or fluorine-treated sample. But these treatments have a different influence on the evolution of the: structural properties comparatively to those observed for the starting oxide : after chlorination a decrease of the orthorhombic distortion is detected, whereas an opposite trend is shown after fluorination. The Cl-2-gas treatment leads to an oxygen-excess phase La2CuO4.08, whereas the fluorination yields an oxyfluoride La2Cu(O,F)(4.17)