The good stability and suitable polarity of the 1-alkyl-3-methyl bis(trifluoromethylsulfonyl)imide ionic liquids have prompted their use as solvents for the extraction of mixtures of aromatic and aliphatic hydrocarbons. In this paper, aiming to extend the study of these ionic liquids, the liquid-liquid equilibrium for the systems tolueneThe experiments with [mmim][Tf 2 N] and [emim]Tf 2 N have shown good results in the separation of toluene from heptane compared with the distribution ratio and separation factor of sulfolane in the whole range of composition. The degree of consistency of the experimental LLE data was ascertained by applying the Othmer-Tobias correlation. The phase diagrams for the ternary systems were plotted, and the tie lines correlated with the NRTL model compare satisfactorily with the experimental data.

The use of the N-butylpyridinium tetrafluoroborate ([bpy][BF 4 ]) + N-butylpyridinium bis(trifluoromethylsulfonyl)imide ([bpy][Tf 2 N]) binary ionic liquid mixture as an aromatic extraction solvent has recently been proposed. To establish the potential of this mixture to be applied in an aromatic separation process, its physical properties must be measured. In this work, refractive indices, densities, and viscosities of this binary ionic liquid mixture have been determined over the temperature range from (303.15 to 353.15) K at atmospheric pressure. A comparison between the physical properties of the sulfolane and the properties gathered in this work has also been performed. The Bingham mixing rule has successfully estimated the viscosities of the IL mixtures from viscosity data of pure ILs. The accuracy of the group contribution method proposed by Ye and Shreeve and extended by Gardas and Coutinho in predicting densities of pyridinium-based IL mixtures has been studied. Refractive index deviations, excess molar volumes, and viscosity deviations have been correctly fitted to Redlich−Kister polynomial equations.

The liquidÀliquid equilibrium (LLE) data for the systems heptane + toluene + 1-ethyl-3-methylimidazolium methanesulfonate ([emim]) at T = 313.2 K and atmospheric pressure were determined. To evaluate the suitability of these three ionic liquids for the extraction of aromatics from their mixtures with aliphatic hidrocarbons, the distribution ratios and separation factor curves from the LLE data were plotted and compared to those for the conventional solvent sulfolane. The degree of quality of the experimental LLE data was ascertained by applying the OthmerÀTobias correlation. In addition, the phase diagrams for the ternary systems were plotted, and the experimental tie lines were satisfactorily correlated with the nonrandom two-liquid (NRTL) model.

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Liquid-liquid equilibrium (LLE) data for the ternary systems {heptane + toluene + N-butylpyridinium tetrafluoroborate ([bpy]BF 4 )} and {heptane + toluene + N-hexylpyridinium tetrafluoroborate ([hpy]BF 4 )} at 313.2 K and atmospheric pressure are reported. The degree of consistency of the experimental LLE data was ascertained by applying the Othmer-Tobias correlation. To check the feasibility of using the [bpy]BF 4 and [hpy]BF 4 ionic liquids as solvents in aromatic separation processes, their values of the distribution ratio and separation factor over the whole range of compositions were plotted and compared with those of sulfolane. In addition, the LLE data were successfully correlated with the thermodynamic NRTL model.

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We have analyzed the electrical properties and bonding characteristics of SiNx:H thin films deposited at 200 °C by the electron cyclotron resonance plasma method. The films show the presence of hydrogen bonded to silicon (at the films with the ratio N/Si<1.33) or to nitrogen (for films where the ratio N/Si is higher than 1.33). In the films with the N/Si ratio of 1.38, the hydrogen content is 6 at. %. For compositions which are comprised of between N/Si=1.1 and 1.4, hydrogen concentration remains below 10 at. %. The films with N/Si=1.38 exhibited the better values of the electrical properties (resistivity, 6×1013 Ω cm; and electric breakdown field, 3 MV/cm). We have used these films to make metal-insulator-semiconductor (MIS) devices on n-type silicon wafers. C–V measurements accomplished on the structures indicate that the interface trap density is kept in the range (3–5)×1011 cm−2 eV−1 for films with the N/Si ratio below 1.38. For films where the N/Si ratio is higher than 1.4, the trap density suddenly increases, following the same trend of the concentration of N–H bonds in the SiNx:H films. The results are explained on the basis of the model recently reported by Lucovsky [J. Vac. Sci. Technol. B 14, 2832 (1996)] for the electrical behavior of (oxide–nitride–oxide)/Si structures. The model is additionally supported by deep level transient spectroscopy measurements, that show the presence of silicon dangling bonds at the insulator/semiconductor interface (the so-called PbN0 center). The concentration of these centers follows the same trend with the film composition of the interface trap density and, as a consequence, with the concentration of N–H bonds. This result further supports the N–H bonds located at the insulator/semiconductor interface which act as a precursor site to the defect generation of the type •Si≡Si3, i.e., the PbN0 centers. A close relation between interface trap density, PbN0 centers and N–H bond density is established.

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