Volume 221, Issue 8

Density of five (0.124, 0.334, 0.706, 1.055, and 1.123) mol kg -1 and viscosity of seven (0.124, 0.2918, 0.334, 0.706, 0.8472, 1.055, and 1.123) mol kg -1 binary aqueous Na 2 CO 3 solutions have been measured with a constant-volume piezometer and capillary flow techniques, respectively. Measurements were performed at pressures up to 52MPa for the density and 40MPa for the viscosity. The range of temperature was from 299 to 577K for density and from 293 to 478K for the viscosity. The total uncertainty of density, viscosity, pressure, temperature, and composition measurements was estimated to be less than 0.06%, 1.6%, 0.05%, 15mK, and 0.02%, respectively. Apparent molar volumes were derived using measured values of density for the solutions and for pure water calculated with IAPWS formulation. The effect of the thermodynamic variables (temperature, pressure, and concentration) on density, apparent and partial molar volumes, and viscosity of Na 2 CO 3 (aq) solutions was studied. The derived apparent molar volumes have been interpreted in terms of the Pitzer’s ion-interaction model of electrolyte solutions to accurate calculates the values of partial molar volumes at infinite dilution V ¯ 2 ∞ and the second ( B V ) and third ( C V ) virial coefficients for the apparent molar volume as a function of temperature. The viscosity data have been analyzed and interpreted in terms of extended Jones–Dole equation for the relative viscosity ( η / η 0 ) of strong electrolyte solutions to accurate calculate the values of viscosity A - and B -coefficients as a function of temperature. The Arrhenius–Andrade parameters η A and b = E a / R (where E a is the flow activation energy) were calculated using present experimental viscosity data. The effective pressures P e due to the salt (Na 2 CO 3 ) in water in the TTG (Timmann-Tait-Gibson) model were calculated from present viscosity measurements.

Gibbs energies of transfer of H + ion [Δ G 0 t(w→s) (H + )] from water (w) to different aquo + alcoholic mixtures (s) were calculated using no extrathermodynamic assumptions. Δ G 0 t(w→s) (H + ) values with and without interactions are given. Δ G 0 t(w→s) (H + ) values (without interaction terms) compare well with the selected values of Δ G 0 t(w→s) (H + ) in different aquo + alcoholic mixtures recommended by Marcus from compilations of data reported by various workers using different extrathermodynamic assumptions. Suitable conversion was made to bring the data into the range of the TATB scale. Δ G 0 t(w→s) (H + ) values in binary mixtures (without interaction terms) are lower and qualitatively to some extent close to the values reported in the literature at least at low percentages. The results show that Δ G 0 solv (H + ) and Δ G 0 t(w→s) (H + ) values are increasingly positive i.e. less basic as the mass% of organic solvents increases and the sequence of basicities are in the order i.e. the organic solvent and solvent mixtures are less basic than water contrary to the prevalent conceptions. The main factor appears to be the number of O-atoms with lone-pair of electrons responsible for H + acceptance, H-bonding and other structural modifications of the solvent mixtures. Obviously, the lower the molar mass of the organic solvent, the greater will be the basicity of the solvent and solvent mixtures.

The specific surface area is a key factor in heterogeneous catalysis. Lithium-doped MgO is well known as one of the best catalysts for the oxidative coupling of methane (OCM) with respect to activity and selectivity. Doping with Li causes MgO to sinter severely resulting in a dramatic decrease of the specific surface area. Li/MgO catalysts prepared from Li 2 CO 3 and MgO in addition with charcoal have been examined by several surface characterization techniques. The addition of activated charcoal was found to increase the specific surface area and to modify the morphology of the Li/MgO catalysts. As a result, the specific activity on a per gram basis increased.

A novel stick-like polymer based on poly(methyl methacrylate)(PMMA) and poly(vinylidene fluoride) (PVDF) has been prepared. Its physical properties were studied with scanning electronic microscopy (SEM), X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR). Due to the interaction of PVDF with PMMA, the dispersion of PVDF is homogeneous. Its gelled polymer electrolyte (GPE) with 1M LiPF 6 /ethylene carbonate (EC)/ethyl methyl carbonate (EMC)/dimethyl carbonate (DMC) (1:1:1) is very stable with an electrochemical window up to 5V vs. Li + /Li. The ionic conductivity reaches 0.32mS/cm at ambient temperature. The electrochemical performances of a polymer lithium ion battery consisting of graphite anode, the GPE and LiCo 1/3 Ni 1/3 Mn 1/3 O 2 cathode has been studied, initial results show that this gelled polymer electrolyte is very promising.

The crystal structure of anhydrous cadmium hexacyanoferrate (II), Cd 2 [Fe(CN) 6 ], has been solved from powder diffraction data using information extracted from low resolution radial distribution function. Such anhydrous solid is obtained by soft heating of its parent octahydrate. The radial distribution function proves to be useful for observing changes in heavy atoms interatomic distances in the structure during phase transition related to the material dehydration process. These distances were then used for guessing the heavy atom positions from the direct methods results. Cd 2 [Fe(CN) 6 ] crystallizes in the hexagonal system, space group P - 3 (147) and cell parameters: a = 6.32046(5) and c = 6.33786(10)Å. The structure was refined to final agreement factors of R wp = 6.26% and S = 1.99. The proposed structural model is supported by the obtained information from Mössbauer, IR and Raman spectra.

The UV absorption spectra of aqueous solutions of [C 4 mim][Br], [C 4 mim][BF 4 ], and [C 8 mim][Br], along with the differential UV spectra of aqueous [C 8 mim][Br] solutions, were measured at room temperature in this work. It is found that three transformations, denoted respectively as α , β and γ , can occur over the interested concentration range of solutions due to ionic liquid aggregation. Further, the content of ionic liquids and the wavelength of absorption maximum at these transformations are determined, and the implications at each transformation are analyzed. As a result, this paper discusses the effects of imidazolium cation, alkyl chain length and counterion type on the aggregation behavior and the contribution of interactions (such as hydrogen bonds, Coulombic, aliphatic and π – π stacking interactions) to the aggregation of 1-alkyl-3-methylimidazolium salts in water. Moreover, the possible structures of both aggregate and bulk phase in the aqueous solutions of ionic liquids are predicted also.

We consider organic polyatomic molecules, which contain hydrocarbon antennas i.e. substructures of identical periodically located C–H dipoles. In these antennas collective vibrational excitations (excimols) are coherently produced by resonant absorption of photons in the mid-IR energy range. The energy of an excimol is lower than the energy of the first vibrational excited state of an isolated antenna dipole and the excimol lifetime does not exceed 10 -11 s. The excimols are excited successively and independently in the C–H dipoles resulting in energy accumulation in the antenna. The accumulated vibrational energy can be transmitted to a trap bond, which is also forming a dipole inside the molecule, however, not acting as an antenna. The trap bond is cleaved, if the absorbed excimol energy is equal to its dissociation energy. Under certain conditions the accumulated energy can be transformed to electronic excitation of a molecular constituent resulting in molecular luminescence. The emitted luminescence photons have energies much higher than the energy of each of the IR photons, which induce an excimol. Thus the hydrocarbon antennas in organic molecules are able to work as amplifiers of external IR radiation. These intramolecular energy transmission processes complete within a time period less or equal to the excimol lifetime and thus can be referred to as super-fast compared to typical time scales calculated by statistical models. The model presented here predicts that the probabilities of the considered processes resonantly depend on the frequency and intensity of IR radiation. The presented theoretical model is supported by the results of our experimental studies of the considered type of molecular fragmentation.