Thermodynamic and surface properties of Ge–Ga and Ge–Sb liquid alloys

Thermodynamic and surface properties of Ge–Ga and Ge–Sb liquid alloys have been studied using statistical mechanical formulations based on complex formation and that based on the concept of layered structure near the interface. The study showed that low level of complex formation of the form Ge _{2 Sb} exists in Ge–Sb toward the Ge-rich end of the concentration range and the surface properties of Ge–Ga are almost equal to their corresponding bulk equivalent.     

Predicting the formation enthalpies of Cd–Ga–In–Sn–Zn liquid alloys by the limiting partial enthalpies

The formation enthalpies of Cd–Ga–Sn, In–Sn–Zn, Cd–Ga–In–Sn, Ga–In–Sn–Zn and Cd–Ga–In–Sn–Zn liquid alloys are calculated by molecular interaction volume model (MIVM), which only using the limiting partial enthalpies of binary systems and the coordination numbers of the constituent elements in liquid alloys. The predicted values are compared with the experimental data and the values calculated using Hoch–Arpshofen model, which indicate that the model is reliable and convenient.     

Thermodynamics and vacuum distillation studies of liquid Al–Ga and In–Sn alloys

Activities of components in liquid Al–Ga and In–Sn alloys, the separation coefficients and vapour–liquid phase equilibrium in vacuum distillation were predicted using the molecular interaction volume model as a function of the activity coefficients. The results indicated that both Al and In are preferentially volatilised into vapour phase while Ga and Sn remain in residue. Similarly, we found that both the mass fraction and the content of Al and In in vapour phase increase as distillation temperature increases such that when the content of Al is 0.005985 wt% and In is 0.004141 wt% in vapour phase, respectively, in liquid phase, it was 70 wt% at T = 1073 K for both. The calculated values of activity and activity coefficients at various temperatures are presented. Comparison of the predicted values with experimental data indicates good agreement, thus verifying from statistical thermodynamics viewpoint that the model is stable and reliable.     

Viscosity of liquid Cu–Sn alloys

We investigated of the kinematic viscosity of liquid Cu–Sn alloys upon heating and subsequent cooling by the method of the oscillating cylinder. For the liquids alloys Cu75Sn25, Cu50Sn50, Cu48Sn52, Cu32Sn68, and Cu17Sn83, the temperature dependencies of the viscosity upon heating deviate from the Arrhenius relation. The temperature dependencies of viscosity show the Arrhenius-like behaviour upon cooling for all investigated alloys. A discrepancy between the temperature dependencies of viscosity obtained upon heating and cooling arised. We built the concentration dependences of the kinematic viscosity of liquid Cu–Sn alloys upon cooling. The increase of the values of viscosity and activation energy of viscous flow in the concentration range corresponding to the existence of intermetallic compounds Cu₃Sn in the solid state was observed. These results were qualitatively interpreted using the concept of microheterogeneities of liquid alloys.     

Electrical conductivity and thermoelectric power of liquid Co–Sn alloys

The electrical conductivity and thermoelectric power of liquid Co–Sn alloys were investigated in a wide concentration and temperature range. It was shown that the electrical conductivity of the melts decreased with an increase of the Co content. The results are interpreted in the context of the s–d hybridisation model. The corresponding behaviour is caused by sharing electrons from one metal to another one. This is in agreement with the concept of Fermi enthalpy, according to which up to two electrons from Sn transfer to the uppermost bands of Co.     

Système AsGeTe: II. Diagramme de phase du système ternaire AsGeTe

The AsGeTe system is formed by three independent triangles, corresponding to the two quasibinary systems GeAsGeTe and As₂Te₃GeTe. The presence of four phases As₂Ge_nTe_3+n (n = 1 to 4) having peritectic decomposition introduces eight ternary peritectic invariants, whose temperatures and compositions are described. The three ternary eutectics have the following characters: E₁, As₁₉Ge₅₂Te₂₉ (662°C); E₂, As₄₂Ge₅Te₅₃ (368°C); E₃, As₂₂Ge₅Te₇₃ (350°C).     

Viscosity of liquid Co–Sn alloys: thermodynamic evaluation and experiment

Shear viscosity measurements were performed for liquid Co–Sn alloys over a wide temperature range above the respective liquidus temperatures. A high temperature oscillating-cup viscometer was used. It was found experimentally that viscosity as a function of temperature obeys an Arrhenius law. The data were compared with calculated values, obtained from different thermodynamic approaches. A good agreement was found between experimental results and calculated ones by the Budai–Benkö–Kaptay model.     

Determination of the copper activity of liquid CuLa alloys

The thermodynamic activities of liquid CuLa alloys were obtained at 1549 K by Knudsen effusion experiments. The experimentally known concentration and temperature dependences of thermodynamic properties of liquid CuLa alloys are explained on the basis of an association model. These results are discussed in comparison with the enthalpy of crystallization and the crystallization temperature as well as the enthalpy of melting and the melting temperature of lanthanum-rich glassy and crystalline alloys respectively.     

Crystallization study of Sn additive Se–Te chalcogenide alloys

Calorimetric study of Se_85−x Te₁₅Sn _x (x = 0, 2, 4 and 6) glassy alloys have been performed using Differential Scanning Calorimetry (DSC) under non-isothermal conditions at four different heating rates (5, 10, 15 and 20 °C/min). The glass transition temperature and peak crystallization temperature are found to increase with increasing heating rate. It is remarkable to note that a second glass transition region is associated with second crystallization peak for Sn additive Se–Te investigated samples. Three approaches have been employed to study the glass transition region. The kinetic analysis for the first crystallization peak has been taken by three different methods. The glass transition activation energy, the activation energy of crystallization, and Avrami exponent (n) are found to be composition dependent. The crystallization ability is found to increase with increasing Sn content. From the experimental data, the temperature difference (T _p − T _g) is found to be maximum for Se₈₃Te₁₅Sn₂ alloy, which indicates that this alloy is thermally more stable in the composition range under investigation.     

Optical and other physical characteristics of amorphous Ge15Te85−xCux alloys

Composition dependencies of the optical properties of as- deposited amorphous Ge₁₅Te_85−xCu_x (x = 2, 3, 4, 5 and 6 at %) prepared by thermal evaporation have been studied. The optical transmission and reflection spectra are measured in the wavelength range (200–1200 nm). The optical absorption coefficient are studied for as- deposited samples. The optical absorption edge shift to higher energy range, as the copper content, x, increases in the film. Tauc's relation for the allowed direct transition is successfully describing the mechanism of the optical absorption. The refractive index, n has been determined from the transmission spectra measured at normal incidence. The absorption coefficient, α, therefore extinction coefficient, k, have been determined from the transmission spectra at the strong absorption region. The dispersion of refractive index is discussed in terms of the Single-oscillator Wimple–DiDomenico model. The optical dielectric constant is also estimated. The average heat of atomization and related parameters such as the average coordination number were also calculated from the heat of atomization and coordination number of the used elements. These obtained results were discussed in terms of chemically ordered network model and constraints theory.     

Surface properties and wetting characteristics of liquid Ag–Bi–Sn alloys

Abstract  

Surface tension and density measurements of liquid Ag–Bi–Sn alloys were carried out over a wide temperature range using the sessile drop method. The experimental data of surface tension were analyzed by the Butler thermodynamic model in the regular solution approximation. The Sn-rich Ag–Bi–Sn liquid alloys show better wetting behavior on the Cu substrates as compared to the Ni substrates.     

Calorimetric study of Sb-modified Ge–Se–Te glassy alloys

The glassy compositions of Ge ₁₆ Se ₅₂ Te _32?x Sb _x system, obtained using rapid melt quenching technique, have been characterized by calorimetric study at different heating rates in this study. A systematic investigation of the crystallization kinetics is carried out for these compositions. Composition corresponding to atomic % 8 of Sb has good thermal stability. The material exhibits the unique thermal properties, which makes it suitable to use for electrical or memory switching devices. Various thermal parameters, activation energies of glass transition and crystallization are calculated using relevant approaches.     

The density and surface tension of In–Sn and Cu–In–Sn alloys

Abstract  

The density and surface tension of binary In–Sn and ternary Cu–In–Sn alloys have been measured by a sessile-drop method. Decrease of the density and of the surface tension was observed with rising temperature. With increased Sn content in the alloys, the density increased while the surface tension reduced slightly. Addition of Cu could significantly increase the density and surface tension in the Cu–In–Sn system. The surface tension of the Cu–In–Sn alloys was also calculated by means of Butler’s equation, and compared with experimental values, showing good agreement.     

The extraction and determination of free lithium in LiB alloys

Extraction of the lithium phase from lithium-rich LiB alloys was achieved by reaction of the alloy with dry naphthalene dissolved in anhydrous tetrahydrofuran. The resulting radical anion was hydrolyzed and the lithium was determined by potentiometric titration from the moles of hydroxide formed. The composition of the Li_xB_y residue was determined by difference.     

Crystallization kinetics of tellurium-rich Se–Te–Sn glassy alloys

The objective of this study was to explore an innovative type of form-stable phase-change materials (PCMs) with flexible cellulose acetate (CA) nano-fibrous felts (nano-felts) absorbed with capric–myristic–stearic acid ternary eutectic mixture for thermal energy storage/retrieval. Capric–myristic–stearic acid (CMS) ternary eutectic mixture as model PCM was firstly prepared. The developed CA nano-felts as supporting material was mechanically flexible and was made from CA/polyvinylpyrrolidone (PVP) precursor composite nanofibers followed by removal of PVP components. The effects of original mass ratio of CA/PVP on absorption capacities of CA nano-felts were studied. The modified CA nano-felts with groove/porous structure and rough surfaces were capable of absorbing a large amount of PCMs. The morphological structures, as well as the properties of thermal energy storage, thermal stability and reliability, and thermal insulation of composite PCMs were characterized by scanning electron microscopy, differential scanning calorimetry, and thermal performance measurement, respectively. The results showed that CMS eutectic was absorbed in and/or supported by modified CA nano-felts. The heat enthalpy values of composite PCMs have slightly decreased in comparison with the corresponding theoretical values. The composite PCMs demonstrated good thermal stability and reliability after thermal cycles. The composite PCMs had high thermal insulation capability for temperature regulation.