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Journal of Solid State Electrochemistry - Gas-tight Nd2 − xCaxZr2O7 − δ (x = 0, 0.05) pyrochlore materials have been prepared via...  相似文献   

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In this article, the experimental data of excess molar enthalpies HmE and excess molar volumes VmE are presented for a set of 20 binary mixtures comprised of the first four butyl alkanoates (methanoate to butanoate) and five α,ω-dichloroalkanes (1,2-dichloroethane to 1,6-dichlorohexane), obtained at atmospheric pressure and at a temperature of 298.15 K. The results indicate the existence of specific interactions between both kinds of compounds resulting in exothermic processes for most mixtures, except for those containing butyl methanoate which give rise to net endo/exothermic effects. The VmE are positive for mixtures of (butyl esters + 1,2-dichloroethane or 1,3-dichloropropane) and negative for the remaining ones. The change in HmE with the dichloroethane chain length for a same ester is regular although the VmE presents an irregular variation. It can, therefore, be deuced from this that the mixing process involves both effects, exothermic/endothermic and expansion/contraction, simultaneously. The behaviour of the mixtures is interpreted on the basis of the results observed and attributed to different effects taking place among the molecules studied.To improve application of the UNIFAC model using the version of Dang and Tassios, average values were recalculated again for parameters of the ester/chloride interaction, distinguishing, during its application, the functional group of the acid part of the ester. In spite of this, the model does not adequately reproduce the systems’ behaviour.  相似文献   

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The important zinc borate of 2ZnO · 3B2O3 · 3H2O has been synthesized and characterized by means of chemical analysis, XRD, FT-IR, and DTA–TG techniques. The molar enthalpies of solution of H3BO3(s) in HCl · 54.561H2O, of ZnO(s) in the mixture of HCl · 54.561H2O and calculated amount of H3BO3, and of 2ZnO · 3B2O3 · 3H2O(s) in HCl · 54.604H2O were measured, respectively. With the use of the standard molar enthalpies of formation for ZnO(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of ?(5561.7 ± 4.9) kJ · mol?1 for 2ZnO · 3B2O3 · 3H2O(s) was obtained. Thermodynamic properties of this compound were also calculated by a group contribution method.  相似文献   

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Measurements of the critical parameters for {xNH3 + (1 ? x)H2O} with x = (0.9098, 0.7757, 0.6808) were carried out by using a metal-bellows variable volumometer with an optical cell. The expanded uncertainties (k = 2) in temperature, pressure, density, and composition measurements have been estimated to be less than 3.2 mK, 3.2 kPa, 0.3 kg · m?3, and 8.8 · 10?4, respectively. In each mole fraction, the critical temperature Tc was first determined on the basis of the intensity of the critical opalescence. The critical pressure pc and critical density ρc were then determined as the point at which the meniscus disappears on the isotherm at T = Tc. The expanded uncertainties (k = 2) in the present critical parameters have also been estimated. Comparisons of the present values with the literature data as well as the calculated values afforded using the equation of state are also presented.  相似文献   

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Relative permittivities of { CH3OH  +  CH3OCH2(CH2OCH2)3CH2OCH3(2,5,8,11,14-pentaoxapentadecane, tegdme)} at temperatures from 283.15 K to 323.15 K and atmospheric pressure, were measured over the whole composition range. Experimental relative permittivities were fitted by a polynomial function in mole fraction. Values of relative permittivity were measured using a HP4284A precision LCR Meter together with the measuring cell HP16452A at 1 MHz. Relative permittivity increments were determined from experimental data and fitted to a variable-degree polynomial function. Different theoretical models were used to predict the permittivity of this mixture. The predictions are better when the volume change on mixing is considered.  相似文献   

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This paper describes a chemical model that calculates (solid + liquid) equilibria in the (m1Rb2SO4 + m2CoSO4)(aq), (m1Rb2SeO4 + m2CoSeO4)(aq), (m1Rb2SO4 + m2NiSO4)(aq), (m1Rb2SO4 + m2ZnSO4)(aq), (m1Rb2SeO4 + m2ZnSeO4)(aq), (m1Cs2SO4 + m2CoSO4)(aq), (m1Cs2SeO4 + m2CoSeO4)(aq), (m1Cs2SO4 + m2NiSO4)(aq), (m1Cs2SeO4 + m2NiSeO4)(aq), (m1Cs2SO4 + m2ZnSO4)(aq), and (m1Cs2SeO4 + m2ZnSeO4)(aq) systems, where m denotes molality at the temperature T=298.15 K. The Pitzer ion-interaction model has been used for thermodynamic analysis of the experimental osmotic and solubility data presented in the literature. The thermodynamic functions needed (binary and ternary parameters of ionic interaction, thermodynamic solubility products) have been calculated and the theoretical solubility isotherm has been plotted. The mixing parameters {θ(MN) and ψ(MNX)} have been chosen on the basis of the compositions of saturated ternary solutions and data on the binary solubility of the sulfate M2SO4. MSO4 · 6H2O double salts in water. To validate the mixing solutions model two different approaches have been used in evaluation of the ternary parameters: (I) preserving the same value of the binary mixing θ(MN) for the corresponding chloride, bromide, sulfate, and selenate systems with the same cations, and (II) with constant θ(MN) value (set equal to −0.05) for the all 11 sulfate and selenate systems. Very good agreement between experimentally determined and model predicted solubilities has been found. Important thermodynamic characteristics (thermodynamic solubility products, standard molar Gibbs free energy of formation) of the solid phases (simple salts, six sulfate – M2SO4 · MSO4 · 6H2O, and five selenate – M2SeO4 · MSeO4 · 6H2O – double salts) crystallizing in the systems under consideration are determined.  相似文献   

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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.  相似文献   

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The Fe2(Sr2 ? xAx)FeO6.5 ? δ/2 systems have been investigated, by doping the iron rich 2201-type parent structure with Ba2+, La3+ and 5d10 post-transition cations. The syntheses have been carried out up to the limit of the 2201-type solid solutions, in order to test the role of the double iron layer Fe2O2.5 ? δ/2. The localisation of the charge carriers in these compounds is consistent with their strong antiferro-magnetism. The investigation was then carried out in the transition part of the diagram up to the formation of stable phases. The study of structural mechanisms was carried using high resolution electron microscopy (transmission and scanning transmission), electron diffraction and energy dispersive spectroscopy. Different non-stoichiometry mechanisms are observed, depending on the electronic structure and chemical properties of the doping elements. The specific behavior of the modulated double iron layer is discussed.  相似文献   

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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.  相似文献   

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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 %.  相似文献   

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