Z. Moser

Surface tension of liquid Ag-Sn alloys: Experiment versus modeling

The maximum bubble pressure method has been used to measure the surface tension of pure tin and seven binary alloys with concentrations of 15, 30, 40, 60, 75, 87.8, and 96.2 at.% Sn. Measurements were performed at the temperature range from 500 to about 1400 K depending on the composition of the investigated alloy. Densities of the Ag-Sn alloys were measured dilatometrically. The linear dependencies of densities and surface tensions on temperature were observed, and they are described by a straight-line equation.

Thermodynamic studies and the phase diagram of the Li-Mg system

By means of the electromotive force (emf) method of concentration cells of the following scheme: Li (1) / LiCl-LiF (eut) or LiCi-KCl (eut) / Li-Mg (1) or Li (1) / LiCl-LiF (eut) / Li-Mg (s) Li activities for liquid and solid alloys at the (Mg), (Li), and (Mg) + (Li) two-phase region of the Li-Mg system were determined. Liquid alloys were examined at temperatures from 638 to 889 K at various Li concentrations. The (Mg) solid solutions were investigated in two series: at constant temperatures between 773 and 876 K, with varying Li content, and at fixed Li concentrations, equal to 0.125 and 0.160 molar fractions, at different temperatures between 772 and 849 K. At the two-phase region, (Mg) + (Li), emf measurements were performed in the temperature range 773 to 838 K, with fixed Li concentrations equal to 0.20, 0.25, and 0.275 molar fractions. For (Li) solid alloys, experiments were done at temperatures 773 to 849 K for several constant Li concentrations, between 0.30 to 0.45 molar fractions, respectively. Studies on solid alloys enabled us also to determine the boundaries (Li)/[(Mg) + (Li)] and (Mg)/[(Mg) + (Li)] at temperatures 773 to 831 K. The resulting thermodynamic and phase boundary data of this study were used with other selected references for a critical assessment of the Li-Mg system. The Lukas BINGSS optimization program and BINFKT for the calculation of the thermodynamic functions and of the phase diagram were used. The calculated equilibrium phase diagram at temperatures below 750 K indicates a slightly lower solid solubility of Mg in (Li) in comparison with results from thermal analysis and the recently published Saunders evaluation.

Density and surface tension of the Pb-Sn liquid alloys

The maximum bubble pressure method and the dilatometric method were used, respectively, in measurements of surface tensions and densities of Pb-Sn liquid alloys. The experiments were carried out in the temperature range from 573 to 1200 K for the pure Pb, pure Sn, and 7 alloys of the compositions 0.1, 0.2, 0.26, 0.36, 0.5, 0.7, and 0.9 mole fraction of Pb. A straight-line dependence on temperature was observed and fitted by the method of least squares both for the densities and the surface tensions. The calculated density isotherm at 673 K showed a positive deviation from the linearity over the entire range of composition, and the same tendency was seen at 1173 K for compositions higher than XPb=0.26. At the lower concentration of Pb, a nearly linear character of 1173 K isotherm was noted. In the case of surface tensions, both at the lowest and the highest temperatures (673 and 1173 K), the deviation from linearity with composition was negative, but deviation decreased with increasing temperature. The isotherms of the compositional dependence of surface tension calculated from the Butler model exhibit good agreement with experimental data.

Enthalpies of formation of AlNi: Experiment versus theory

The thermodynamic properties of theB2 AlNi phase have been revisited with calorimetric and a priori theoretical estimates of the enthalpy of formation of the stoichiometric compound. The calorimetric study has surveyed the temperature dependence of the enthalpy of formation and extrapolated it to zero temperature (for which the a priori estimates have been made), while the theoretical estimate explores the consequences of an apparent error in local density-based potentials in yielding the magnetic contribution to the reference energy of Ni metal. The present experimental value, extrapolated to 0 K, is 65.915 kJ/g-atom while the local density-based calculated value is 67.5 kJ/g-atom. These are in accord with each other and with much, but not all, the previous experimental data. An estimate of the error in the local density magnetic energy was made by comparing experimental and calculated heats for nonmagnetic Fe compounds, where the energy and its associated error are much larger, and scaling the result to Ni. This yields a “corrected” theoretical heat of 66 kJ/g-atom.

Enthalpies of formation of Ni3Al: Experiment versus theory

Using Al solution calorimetry, enthalpies of formation of Ni3Al in the L12 structure ranging from-41.3 to -42.3 kJ/mol were determined at temperatures from 300 to 1123 K. These enthalpies are substantial for an intermetallic compound and display a slight temperature dependence, which is contained within the experimental error. This temperature dependence is related to the lack of any transformations of the compound, which remains ordered up to the melting temperature. The measured enthalpies were combined with other thermodynamic data to estimate the excess entropy of formation of Ni3Al. The high degree of ordering in the compound is reflected in the large negative value of the excess entropy,whose absolute value exceeds those for other high melting temperature intermetallic compounds. The full-potential linearized augmented Slater-type orbital method (FLASTO) was used to calculate the enthalpies of formation of paramagnetic and ferromagnetic Ni3Al. These enthalpies of formation indicate the compound to be a weak ferromagnet, and they are in good agreement with the calorimetric data.

Calorimetric and emf studies on liquid Li-Sn alloys

By means of high temperature calorimetry the mixing enthalpies ΔH of liquid Li-Sn alloys have been measured; however, due to experimental problems they were determined only forxLi = 0.01 to 0.5 andxLi = 0.87 to 0.99. The range of temperatures studied was 691 to 938 K. High compound forming tendency in Li-Sn is reflected by a triangular-shaped relation for ΔH vs xLi. The extrapolated maximum of this plot is about −40 kJ mol−1 close to Li4Sn. Using the concentration cell Bi(l)Li3Bi(s)¦ LiF-LiCl¦Li-Sn(l) the emf was measured as function of temperature (775 to 906 K) atxLi = 0.1 to 0.603 enabling calculations of partial thermodynamic data for lithium in liquid Li-Sn solutions. Integral enthalpies calculated from partial enthalpies of lithium correspond well to the calorimetrically obtained integral mixing enthalpies in the concentration range where both emf and calorimetric data were obtained. The extrapolated maximum of ΔH from calorimetric studies and minimum of integral excess entropies from emf measurements correlate well with results of structure measurements and of other structure sensitive properties. All this experimental information indicates a maximum chemical short range order close to the composition Li4Sn.

Thermodynamic studies and the phase diagram of the Li-Sn system

By means of the electromotive force (emf) method of concentration cells of the following scheme: Li (1) / LiCl-LiF (eut) or LiCi-KCl (eut) / Li-Mg (1) or Li (1) / LiCl-LiF (eut) / Li-Mg (s) Li activities for liquid and solid alloys at the (Mg), (Li), and (Mg) + (Li) two-phase region of the Li-Mg system were determined. Liquid alloys were examined at temperatures from 638 to 889 K at various Li concentrations. The (Mg) solid solutions were investigated in two series: at constant temperatures between 773 and 876 K, with varying Li content, and at fixed Li concentrations, equal to 0.125 and 0.160 molar fractions, at different temperatures between 772 and 849 K. At the two-phase region, (Mg) + (Li), emf measurements were performed in the temperature range 773 to 838 K, with fixed Li concentrations equal to 0.20, 0.25, and 0.275 molar fractions. For (Li) solid alloys, experiments were done at temperatures 773 to 849 K for several constant Li concentrations, between 0.30 to 0.45 molar fractions, respectively. Studies on solid alloys enabled us also to determine the boundaries (Li)/[(Mg) + (Li)] and (Mg)/[(Mg) + (Li)] at temperatures 773 to 831 K. The resulting thermodynamic and phase boundary data of this study were used with other selected references for a critical assessment of the Li-Mg system. The Lukas BINGSS optimization program and BINFKT for the calculation of the thermodynamic functions and of the phase diagram were used. The calculated equilibrium phase diagram at temperatures below 750 K indicates a slightly lower solid solubility of Mg in (Li) in comparison with results from thermal analysis and the recently published Saunders evaluation.

Thermodynamic investigations of solid CuNi and FeNi alloys and calculation of the solid state miscibility gap in the CuFeNi system

Abstract Activity values for fcc CuNi and FeNi alloys have been determined from solid electrolyte emf measurements. The results are discussed together with values reported by other investigators and evaluated data are presented for the thermochemical properties of CuNi and Fez.sbnd;Ni alloys. The evaluated data have been combined with a published assessment of the CuFe system to calculate the miscibility gap in the fee phase of the CuFeNi system.

Evaluation of the influence of Bi and Sb additions to Sn-Ag-Cu and Sn-Zn alloys on their surface tension and wetting properties using analysis of variance -ANOVA

Purpose – The purpose of this paper is a comparable evaluation of the influence of a particular element (Bi and Sb) added to Sn‐Ag‐Cu and Sn‐Zn alloys on their surface and interfacial tensions, as well as the wetting properties on the Cu substrate expressed by the wetting angle.Design/methodology/approach – The authors applied the L8 orthogonal Taguchi array to carry out the experiments and discussed the results using analysis of variance (ANOVA).Findings – It was expected, on the base of previous studies, the decrease of the surface and interfacial tensions and thus improving wettability after the Bi and Sb addition to Sn‐Ag‐Cu and Sn‐Zn alloys. Unfortunately, the obtained results on the quinary Sn‐Ag‐Cu‐Bi‐Sb alloys and the quaternary Sn‐Zn‐Bi‐Sb alloys do not confirm these trends. The performed analyses suggest that the compositions of the quinary Sn‐Ag‐Cu‐Bi‐Sb alloys, as well as the quaternary Sn‐Zn‐Bi‐Sb alloys, do not have optimal compositions for practical application. The Cu, Bi and Sb elements i...

Surface Tension, Density, and Molar Volume of Liquid Sb-Sn Alloys: Experiment Versus Modeling

Through the application of the maximum bubble pressure and dilatometric method, density and surface tension were investigated. The experiments were conducted in the temperature range from 583 K≤T≤1257 K. The surface tension was measured for pure antimony and for six liquid Sb-Sn alloys (mole fractions XSn=0.2, 0.4, 0.6, 0.8, 0.9, and 0.935 mm2) and measurements of the density were only for alloys. It has been observed that both surface tension and density show linear dependence on temperature. The temperature-concentration relation of both surface tension and density were determined with minimization procedures. The surface tension isotherms calculated at 873 K and 1273 K show slight negative deviations from linearity changes, but the observed maximal differences did not exceed 30 mN · m−1. The surface tension calculated from Butler’s model was higher than the experimental value for most concentrations and also showed curvilinear temperature dependence. The experimental densities and the molar volumes of the Sb-Sn liquid alloys conform very closely to ideal behavior with differences comparable to the experimental errors.