Study on the effect of Li doping in spinel Li4+xTi5−xO12 (0 ⩽ x ⩽ 0.2) materials for lithium-ion batteries

The effect of Li doping in spinel Li_4+xTi_5−xO₁₂ (0 ⩽ x ⩽ 0.2) materials on the structural and electrochemical properties were investigated. The ratio of the capacity in the voltage plateau (1.5 V) to the overall discharge capacity for Li_4.1Ti_4.9O₁₂ (x = 0.1) and Li_4.2Ti_4.8O₁₂ (x = 0.2) were higher than that of Li₄Ti₅O₁₂ especially at high current rates due to their enhanced lithium-ion and electronic conductivity by the substitution of Ti atoms by Li atoms. With the increasing of Li doping amount, lithium-ion and electronic conductivity of Li_4+xTi_5−xO₁₂ increased, however its cycling stability was depressed when the Li doping was of x = 0.2. The Li doping of x = 0.1, the appropriate Li doping amount, showed improved rate capability and better high rate performance comparing to undoped Li_4+xTi_5−xO₁₂ (x = 0).     

Synthesis,characterization and thermochemistry of Cs(ASP) · nH2O (n = 0, 1)

New compounds of aspartic acid Cs(ASP) · nH₂O (n = 0, 1) have been synthesized and characterized by XRD, IR and Raman spectroscopy as well as TG. The structural formula of this new compound was Cs(ASP) · nH₂O (n = 0, 1). The enthalpy of solution of Cs(ASP) · nH₂O (n = 0, 1) in water were determined. With the incorporation of the standard molar enthalpies of formation of CsOH(aq) and ASP(s), the standard molar enthalpy of formation of −(1202.9 ± 0.2) kJ · mol⁻¹ of Cs(ASP) and −(1490.7 ± 0.2) kJ · mol⁻¹ of Cs(ASP) · H₂O were obtained.     

Modelling (vapour + liquid) and (vapour + liquid + liquid) equilibria of {water (H2O) + methanol (MeOH) + dimethyl ether (DME) + carbon dioxide (CO2)} quaternary system using the Peng–Robinson EoS with Wong–Sandler mixing rule

The (vapour + liquid) equilibria (VLE) and (vapour + liquid + liquid) equilibria (VLLE) binary data from literature were correlated using the Peng–Robinson (PR) equation of state (EoS) with the Wong–Sandler mixing rule (WS). Two group contribution activity models were used in the PRWS: UNIFAC–PSRK and UNIFAC–Lby. The systems were successfully extrapolated from the binary systems to ternary and quaternary systems. Results indicate that the PRWS–UNIFAC–PSRK generally displays a better performance than the PRWS–UNIFAC–Lby.     

(Vapour + liquid) equilibria for the binary mixtures (cis-pinane + α-pinene) and (cis-pinane + 1-butanol)

The isothermal and isobaric (vapour + liquid) equilibria for (cis-pinane + α-pinene) and (cis-pinane + 1-butanol) measured with an inclined ebulliometer are presented. The experimental results are analysed using the UNIQUAC equation with the temperature-dependence binary parameters with satisfactory results. Experimental vapour pressures of cis-pinane are also included.     

Thermally-driven processes on rutile TiO2(1 1 0)-(1 × 1): A direct view at the atomic scale

The technological importance of TiO₂ has led to a broad effort aimed at understanding the elementary steps that underlie catalytic and photocatalytic reactions. The most stable surface, rutile TiO₂(1 1 0), in particular, has became a prototypical model for fundamental studies of TiO₂. In this critical review we have selected oxygen, water, and alcohols to evaluate recent progress relevant for applications in the areas of water splitting and oxidation of organic contaminants. We first focus on the characterization of defects and the distribution of excess charge that results from their formation. The subsequent section concentrates on the role of individual surface sites and the effect of available charge in the adsorption processes. The discussion of adsorbate dynamics follows, providing models for intrinsic and extrinsic diffusion processes as well as rotational dynamics of anchored alkoxy species. The final section summarizes our current understanding of TiO₂(1 1 0) catalyzed reactions between water, oxygen, and their dissociation products.     

(Liquid + liquid) equilibria for (water + 1-propanol or acetone + β-citronellol) at different temperatures

On this paper, experimental (liquid + liquid) equilibrium (LLE) results are presented for systems composed of β-citronellol and aqueous 1-propanol or acetone. To evaluate the phase separation properties of β-citronellol in aqueous mixtures, LLE values for the ternary systems (water + 1-propanol + β-citronellol) and (water + acetone + β-citronellol) were determined with a tie-line method at T = (283.15, 298.15, and 313.15 ± 0.02) K and atmospheric pressure. The reliability of the experimental tie-lines was verified by the Hand and Bachman equations. Ternary phase diagrams, distribution ratios of 1-propanol and acetone in the mixtures are shown. The effect of the temperature on the ternary (liquid + liquid) equilibria was examined and discussed. The experimental LLE values were satisfactorily correlated by extended UNIQUAC and modified UNIQUAC models.     

Viscosity of {xCO2 + (1 − x)CH4} with x = 0.5174 for temperatures between (229 and 348) K and pressures between (1 and 32) MPa

A vibrating wire instrument, in which the wire was clamped at both ends, was used to measure the viscosity of {xCO₂ + (1 − x)CH₄} with x = 0.5174 with a combined uncertainty of 0.24 μPa · s (a relative uncertainty of about 0.8 %) at temperatures T between (229 and 348) K and pressures p from (1 to 32) MPa. The corresponding mass density ρ, estimated with the GERG-2008 equation of state, varied from (20 to 600) kg · m⁻³. The measured viscosities were consistent within combined uncertainties with data obtained previously for this system using entirely different experimental techniques. The new data were compared with three corresponding states-type models frequently used for predicting mixture viscosities: the Extended Corresponding States (ECS) model implemented in REFPROP 9.1; the SUPERTRAPP model implemented in MultiFlash 4.4; and a corresponding states model derived from molecular dynamics simulations of Lennard Jones fluids. The measured viscosities deviated systematically from the predictions of both the ECS and SUPERTRAPP models with a maximum relative deviations of 11 % at (229 K, 600 kg · m⁻³) and −16 % at (258 K, 470 kg · m⁻³), respectively. In contrast, the molecular dynamics based corresponding states model, which is predictive for mixtures in that it does not contain any binary interaction parameters, reproduced the density and temperature dependence of the measured viscosities well, with relative deviations of less than 4.2 %.     

Thermodynamics of the oxidation–reduction reaction {2 glutathionered(aq) + NADPox(aq)=glutathioneox(aq) + NADPred(aq)}

Microcalorimetry, spectrophotometry, and high-performance liquid chromatography (h.p.l.c.) have been used to conduct a thermodynamic investigation of the glutathione reductase catalyzed reaction {2 glutathione_red(aq) + NADP_ox(aq)=glutathione_ox(aq) + NADP_red(aq)}. The reaction involves the breaking of a disulfide bond and is of particular importance because of the role glutathione_red plays in the repair of enzymes. The measured values of the apparent equilibrium constant K^′ for this reaction ranged from 0.5 to 69 and were measured over a range of temperature (288.15 K to 303.15 K), pH (6.58 to 8.68), and ionic strength I_m (0.091 mol · kg⁻¹ to 0.90 mol · kg⁻¹). The results of the equilibrium and calorimetric measurements were analyzed in terms of a chemical equilibrium model that accounts for the multiplicity of ionic states of the reactants and products. These calculations led to values of thermodynamic quantities at T=298.15 K and I_m=0 for a chemical reference reaction that involves specific ionic forms. Thus, for the reaction {2 glutathione_red⁻(aq) + NADP_ox³⁻(aq)=glutathione_ox²⁻(aq) + NADP_red⁴⁻(aq) + H⁺(aq)}, the equilibrium constant K=(6.5±4.4)·10⁻¹¹, the standard molar enthalpy of reaction Δ_rH^o_m=(6.9±3.0) kJ · mol⁻¹, the standard molar Gibbs free energy change Δ_rG^o_m=(58.1±1.7) kJ · mol⁻¹, and the standard molar entropy change Δ_rS^o_m=−(172±12) J · K⁻¹ · mol⁻¹. Under approximately physiological conditions (T=311.15 K, pH=7.0, and I_m=0.25 mol · kg⁻¹ the apparent equilibrium constant K^′≈0.013. The results of the several studies of this reaction from the literature have also been examined and analyzed using the chemical equilibrium model. It was found that much of the literature is in agreement with the results of this study. Use of our results together with a value from the literature for the standard electromotive force E^o for the NADP redox reaction leads to E^o=0.166 V (T=298.15 K and I=0) for the glutathione redox reaction {glutathione_ox²⁻(aq) + 2 H⁺(aq) + 2 e⁻=2 glutathione_red⁻(aq)}. The thermodynamic results obtained in this study also permit the calculation of the standard apparent electromotive force E^′o for the biochemical redox reaction {glutathione_ox(aq) + 2 e⁻=2 glutathione_red(aq)} over a wide range of temperature, pH, and ionic strength. At T=298.15 K, I=0.25 mol · kg⁻¹, and pH=7.0, the calculated value of E^′o is −0.265 V.     

Reactive epitaxy of beryllium on Si(1 1 1)-(7×7)

Scanning tunneling microscopy (STM) and photoelectron spectroscopy (PES) have been used to investigate the nucleation, growth, and structure of beryllium on Si(1 1 1)-(7×7). STM indicates that a chemical reaction occurs at temperatures as low as 120 K, resulting in a nano-clustered morphology, presumed to be composed of a beryllium silicide compound. Upon annealing to higher temperatures, PES data indicate that beryllium diffuses into the selvage region. High temperature annealing (∼1175 K) results in the formation of a universal ring cluster structure suggesting a Be–Si bond length less than 2.5 Å, in agreement with previous calculations regarding hypothetical Be₂Si.     

The (p, ρ, T) properties and apparent molar volumes Vϕ of (ZnBr2 + C2H5OH)

The (p, ρ, T) properties and apparent molar volumes V_? of ZnBr₂ in ethanol at temperatures (293.15 to 393.15) K and pressures up to p = 40 MPa are reported. The measurements were made with a recently developed vibration-tube densimeter. The system was calibrated using double-distilled water, methanol, ethanol, and aqueous NaCl solutions. The experiments were carried out at molalities of m = (0.05681, 0.16958, 0.30426, 0.43835, 0.93055, 1.49016, and 1.88723) mol · kg^?1 using zinc bromide. An empirical correlation for the density of (ZnBr₂ + C₂H₅OH) with pressure, temperature, and molality has been derived. This equation of state was used to calculate other volumetric properties such as isothermal compressibility, isobaric thermal expansibility, the differences in specific heat capacities at constant pressures and volumes, apparent molar volumes of ZnBr₂ in ethanol, and partial molar volumes of both components.     

New (p, ρ, T) data for carbon dioxide – Nitrogen mixtures from (250 to 400) K at pressures up to 20 MPa

Comprehensive (p, ρ, T) measurements on two binary mixtures (0.10 CO₂ + 0.90 N₂ and 0.15 CO₂ + 0.85 N₂) were carried out in the gas phase at seven isotherms between (250 and 400) K and pressures up to 20 MPa using a single sinker densimeter with magnetic suspension coupling. A total of 69 (p, ρ, T) data for the first mixture and 69 (p, ρ, T) data for the second are presented in this article. The uncertainty in density was estimated to be (0.02 to 0.15)%, while the uncertainty in temperature was 3.9 mK and the uncertainty in pressure was less than 0.015% (coverage factor k = 2). Experimental results were compared with densities calculated from the GERG equation of state and with data reported by other authors for similar mixtures. Results yielded that, while deviations between experimental data and values calculated from the GERG equation were lower than 0.05% in density for low pressures, the relative error at high pressures and low temperatures increased to about (0.2 to 0.3)%. The main aim of this work was to contribute to an accurate density data base for CO₂/N₂ mixtures and to check or improve equations of state existing for these binary mixtures.