The Soret coefficients of the ternary system water/ethanol/triethylene glycol and its corresponding binary mixtures

Thermodiffusion in ternary mixtures is considered prototypic for the Soret effect of truly multicomponent systems. We discuss ground-based measurements of the Soret coefficient along the binary borders of the Gibbs triangle of the highly polar and hydrogen bonding ternary DCMIX3-system water/ethanol/triethylene glycol. All three Soret coefficients decay with increasing concentration, irrespective of the choice of the independent component, and show a characteristic sign change as a function of temperature and/or composition. With the exception of triethylene glycol/ethanol at high temperatures, the minority component always migrates toward the cold side. All three binaries exhibit temperature-independent fixed points of the Soret coefficient. The decay of the Soret coefficient with concentration can be related to negative excess volumes of mixing. The sign changes of the Soret coefficients of the binaries allow to draw far-reaching conclusions about the signs of the Soret coefficients of the corresponding ternary mixtures. In particular, we show that at least one ternary composition must exist, where all three Soret coefficients vanish simultaneously and no steady-state separation is observable. Graphic abstract

Statistical model used to assessment the sulphate resistance of mortars with fly ashes

The use of low (LCFA) and high (HCFA) calcium fly ashes in the cement industry allows the implementation of European Union proposals on waste management and energy saving. However, the possibility of using HCFA is limited, because the properties of such waste from coal-fired power plants must comply with national regulations. The paper shows the effect of partial replacement of Portland cement (OPC) by these fly ashes on the resistance of the sulphate attack of the mortars immersed in a 5% solution of sodium sulphate. In order to determine the optimal amount of ash additive, a research plan was designed using statistical methods using the Gibbs triangle for mixtures. Samples of control mortars of OPC, binary mixtures of HCFA or LCFA and ternary mixtures of HCFA/LCFA were made. The composition of the blends was designed in accordance with the statistical plan of the experiment for mixtures. The testing program included linear strains, compressive strength and microstructure tests using SEM with EDXA and XRD analysis. The results of laboratory tests and statistical analyzes have shown that fly ash has a positive effect on the sulphate resistance of cementitious composites.

Numerical Prediction of the Thermodynamic Properties of Ternary Al-Ni-Pd Alloys

Thermodynamic properties of ternary Al-Ni-Pd system, such as exGAlNPd, µAl(AlNiPd),µNi(AlNiPd) and µPd(AlNiPd) at 1,373 K, were predicted on the basis of thermodynamic properties of binary systems included in the investigated ternary system. The idea of predicting exGAlNiPd values was regarded as calculation of values of the exG function inside a certain area (a Gibbs triangle) unless all boundary conditions, that is values of exG on all legs of the triangle are known (exGAlNi, exGAlPd, exGNiPd). This approach is contrary to finding a function value outside a certain area, if the function value inside this area is known. exG and LAl,Ni,Pd ternary interaction parameters in the Muggianu extension of the Redlich–Kister formalism were calculated numerically using the Excel program and Solver. The accepted values of the third component xx differed from 0.01 to 0.1 mole fraction. Values of LAlNiPd parameters in the Redlich–Kister formula are different for different xx values, but values of thermodynamic functions: exGAlNiPd, µAl(AlNiPd), µNi(AlNiPd) and µPd(AlNiPd) do not differ significantly for different xx values. The choice of xx value does not influence the accuracy of calculations.

Solidification Paths within the Ceramic Systems

The aim of this work is to assemble the computer models of phase diagrams (PD) for the typical ternary systems and to examine the processes of crystallization on its base. Spatial schemes of mono-and invariant equilibria have been used for it. Analysis of concentration fields, obtained by the projection of the surfaces on the Gibbs triangle, allows establish the boundaries of phase regions (located above the considered fields), the sequence of phase transformations and microstructural elements for the solidification of the initial melt at equilibrium condition. Concentration fields have been analyzed by means of mass balances for their centers of masses. Based on this technology, the research identifies concentration fields with coinciding sets of phase reactions and microconstituents, and the fields with individual characteristics.

Thermochemistry in the system Cu–In–S at 723 K

A thermochemical analysis is performed in the system Cu-In-S at 723 K. Free energies of In6,S7, In417S583, “In2S3”, Cu951In49, and CuIn5S8 have been estimated, the numerical values (kJ/mol) of which are −1285, −97 780, −481.1, −31 680, and −1444. The free energy (kJ/mol) of CuInS2 is calculated from the relation G° = (-306.1 ± 54.4) + 0.5092T −1.397 10−5T2 −0.09468T In T + 268.2T−1, which is obtained from published assessed standard formation enthalpy and specific heat and entropy data. The free energy of the Cu-In melt is taken from very new literature. A consistent set of data is used for the calculation of a tentative Gibbs triangle as well as of the corresponding predominance area diagram. The Gibbs triangle is calculated with the program thermo, the algorithm of which is given. The results are in agreement with the results of published measurements, also for the equilibria which involve the melt. The compound CuInS2, one of the possible base materials for thin film solar cells, is shown to equilibrate with most of the compounds of the system. Predictions are made how to prepare CuInS2 from Cu-In alloys and H2S/H2 gas mixtures. However, more experiments are necessary to establish the data, the experiments, and/or the results of the calculations.

Thermochemistry in the system Cu–In–S at 298 K

A thermochemical analysis is performed in the system Cu–In–S at 298 K. Free energies of the compounds In6S7, In2.8S4, CuInS2, CuIn5S8, and of the recently discovered CuIn2 have been estimated, the numerical values (kJ/mol) of which are −1043 ± 21, −556 ± 8.8, −315 ± 54, −1238 ± 113, and −51 ± 26. A consistent set of data is used for the calculation of the Gibbs triangle as well as of the predominance area diagram. The results are in nearly complete agreement with the measurements published recently, in particular with those using the nuclear method of perturbed angular correlations (PAC). The compound CuInS2, one of the possible base materials for thin film solar cells, is shown to equilibrate with nearly all of the compounds of the system. A nonvariant four-phase equilibrium CuIn2−InS–In–CuInS2 is found at about 298 K. It is noted where more precise data are needed.