Experimental study and thermodynamic assessment of the Ag–Ti system

A thermodynamic assessment of the binary Ag–Ti system was performed based on the evaluation of the literature and the results of the present experiments. For the experimental study, special deep embedding diffusion couples were prepared and analyzed by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The phase equilibrium relationship and the conjugate phase compositions were determined at 1023 K, 1253 K, 1373 K and 1474 K respectively. For the thermodynamic assessment, the Redlich–Kister polynomial was used to describe the solution phases, liquid (L), bcc, hcp, and fcc. The sublattice-compound energy model was employed to describe the intermediate phase, (AgTi), with a homogeneity range. The other intermediate phase, AgTi₂, without a homogeneity range was treated as the stoichiometric phase. A set of self-consistent thermodynamic parameters of the Ag–Ti system has been obtained. The calculated phase diagram was presented and compared with the experimental data.     

An optimal method to calculate the viscosity of simple liquid ternary alloys from the measured binary data

An optimal method to calculate the viscosity of simple liquid ternary alloys from the measured binary data is investigated in this paper. In order to find a relationship which describes the ternary viscosity data from binary data most adequately, a comparison was made between three different approaches tested on the example of the Au–Ag–Cu system. The optimal method turned out to be the extension of the Redlich–Kister polynomial to excess viscosity without any ternary term. This optimal method was applied further on the Fe–Ni–Co system. The estimation of viscosities for liquid Fe–Ni–Co alloys was done in different sections with molar ratio of two components equal to 1:1, 1:3 and 3:1. A diagram showing iso-viscosity lines was constructed at the investigated temperature of 1873 K.     

The experimental study of the Bi–Sn, Bi–Zn and Bi–Sn–Zn systems

The binary Bi–Sn was studied by means of SEM (Scanning Electron Microscopy)/EDS (Energy-Dispersive solid state Spectrometry), DTA (Differential Thermal Analysis)/DSC (Differential Scanning Calorimetry) and RT-XRD (Room Temperature X-Ray Diffraction) in order to clarify discrepancies concerning the Bi reported solubility in (Sn). It was found that (Sn) dissolves approximately 10 wt% of Bi at the eutectic temperature.

The experimental effort for the Bi–Zn system was limited to the investigation of the discrepancies concerning the solubility limit of Zn in (Bi) and the solubility of Bi in (Zn). Results indicate that the solubility of both elements in the respective solid solution is approximately 0.3 wt% at 200 C.

Three different features were studied within the Bi–Sn–Zn system. Although there are enough data to establish the liquid miscibility gap occurring in the phase diagram of binary Bi–Zn, no data could be found for the ternary. Samples belonging to the isopleths with w(Bi) 10% and w(Sn) 5%, 13% and 19% were measured by DTA/DSC. The aim was to characterize the miscibility gap in the liquid phase. Samples belonging to the isopleths with w(Sn) 40%, 58%, 77/81% and w(Zn) 12% were also measured by DTA/DSC to complement the study of Bi–Sn–Zn. Solubilities in the solid terminal solutions were determined by SEM/EDS. Samples were also analyzed by RT-XRD and HT-XRD (High Temperature X-Ray Diffraction) confirming the DTA/DSC results for solid state phase equilibria.     

Thermodynamic optimization of the Ni–Sn binary system

Through the CALPHAD method and based on experimental data of thermodynamic properties and phase boundaries, the phase diagram of the Ni–Sn binary system has been reassessed. The liquid and fcc_A1 (terminal rich nickel solid solution) phases were described by using a simple substitutional model, the excess Gibbs energy being formulated with a Redlich–Kister expression. The other intermediate phases (Ni₃Sn_HT, Ni₃Sn₂_HT, Ni₃Sn₂_LT, Ni₃Sn₄), were described with a several sublattice model with different formula; the Gibbs energy of the reference compounds was assumed to be linear, and the binary interaction terms on the sub-lattices to be constant. Ni₃Sn_LT was treated as a stoichiometric compound. The solubility of Ni in the terminal phase bct_A5(Sn) was neglected because it is very small. Finally a set of self-consistent thermodynamic parameters for all condensed phases in the Ni–Sn binary system was obtained, which can reproduce most of the experimental data.     

Thermodynamic description of the Cu–Ag–Zr system

Based on the CALPHAD method, the Ag–Zr and Ag–Cu systems have been assessed thermodynamically. The excess Gibbs energy of the solution phases in the Cu–Ag–Zr system was modeled assuming random mixing of components. The ternary phase was defined as a stoichiometric compound due to the lack of efficient thermodynamic data. At first, parameters capable of describing all phases in the Ag–Zr and the Ag–Cu systems were assessed. Combined with the parameters of the Cu–Zr system assessed previously, the isothermal sections of the Cu–Ag–Zr system at 1023 K and 978 K were extrapolated, which can reproduce the measured phase-relations.     

Preparation of Ag–Au nanoparticle and its application to glucose biosensor

In this paper, Ag–Au nanoparticles are produced in sodium-bis(2-ethylhexyl)-sulfosuccinate (AOT)–cyclohexane reverse micelle system. The properties of the obtained nanoparticles are characterized with transmission electron microscope (TEM) and UV–vis absorption spectrophotometer. Glucose biosensors have been formed with glucose oxidase (GOx) immobilized in Ag–Au sol. GOx are simply mixed with Ag–Au nanoparticles and crosslinked with a polyvinyl butyral (PVB) medium by glutaraldehyde. Then a platinum electrode is coated with the mixture. The effects of the various molar ratios of Ag–Au particles with respect to the current response and the stability of the GOx electrodes are studied. The experimental results indicate the current response of the enzyme electrode containing Ag–Au sol increase from 0.32 to 19 μA cm⁻² in the solution of 10 mM β-d-glucose. In our study, the stability of enzyme electrodes is also enhanced.     

Thermodynamic assessment of the Pt–Si binary system

The Pt–Si binary system was thermodynamically assessed using the CALPHAD method based on the available experimental data from the literature. The solution phases, including Liquid, Fcc_A1 (Pt) and Diamond_A4 (Si), were treated as substitutional solution phases, of which the excess Gibbs energies were expressed with Redlich–Kister polynomial functions. Meanwhile, the intermetallic compounds, PtSi, Pt₆Si₅, Pt₂Si, Pt₁₇Si₈, Pt₅Si₂, Pt₃Si and Pt₂₅Si₇, were modeled as stoichiometric compounds. Subsequently, a set of self-consistent thermodynamic parameters formulating the Gibbs energies of various phases were obtained and the calculated values of phase diagram and thermodynamics were found to be in reasonable agreement with experimental data.     

The phase equilibria in the Mg–Ni–Ca system

The three binary systems Mg–Ni, Ca–Ni and Mg–Ca have been re-optimized. A self-consistent thermodynamic database of the Mg–Ni–Ca system is constructed by combining the optimized parameters of these three constituent binaries. Lattice stability values are not added to the pure elements Mg-hcp, Ni-fcc, Ca-fcc and Ca-bcc to construct this database. The Redlich–Kister polynomial model is used to describe the liquid and the terminal solid solution phases, and the sublattice model is used to describe the non-stoichiometric phase, in this system. The constructed database is used to calculate the three binary and the ternary systems. The calculated binary phase diagrams along with their thermodynamic properties such as Gibbs energy, enthalpy, entropy and activities are found to be in good agreement with experimental data from the literature. This is the first attempt to construct the ternary phase diagram of the Mg–Ni–Ca system. The established database for this system predicted three ternary eutectic, five ternary quasi-peritectic, two ternary peritectic and two saddle points.     

A thermodynamic description of the Al–Ca–Zn ternary system

A comprehensive thermodynamic database of the Al–Ca–Zn ternary system is presented for the first time. Critical assessment of the experimental data and re-optimization of the binary Al–Zn and Al–Ca systems have been performed. The optimized model parameters of the third binary system, Ca–Zn, are taken from the previous assessment of the Mg–Ca–Zn system by the same authors. All available as well as reliable experimental data both for the thermodynamic properties and phase boundaries are reproduced within experimental error limits. In the present assessment, the modified quasichemical model in the pair approximation is used for the liquid phase and Al_FCC phase of the Al–Zn system to account for the presence of the short-range ordering properly. Two ternary compounds reported by most of the research works are considered in the present calculation. The liquidus projections and vertical sections of the ternary systems are also calculated, and the invariant reaction points are predicted using the constructed database.     

Thermodynamic and ab initio investigation of the Al–H–Mg system

A coupled ab initio and thermodynamic study of the Al–H–Mg system has been carried out and a self-consistent thermodynamic database has been obtained. Magnesium alanate Mg(AlH₄)₂, a candidate material for hydrogen storage, has been included into the database. According to Density Functional first principles calculations, the alanate is an insulator and its thermodynamic properties have been obtained at room temperature. This compound has been found metastable at 298.15 K and 1 bar. The alanate has been found thermodynamically stable only at high pressure when the formation of the binary β-MgH₂ phase is neglected. A reassessment of thermodynamic parameters of the liquid phase in the binary Mg–H system has also been carried out in order to be consistent with the Al–H system. The present results can reproduce reasonably well the available experimental data.     

Thermodynamic modeling of the Mg–Ge–Pb system

All available thermodynamic and phase diagram data of the Mg–Ge and Mg–Pb binary systems, and the Mg–Ge–Pb ternary system have been critically evaluated and all reliable data have been simultaneously optimized to obtain one set of model parameters for the Gibbs energies of the liquid and all solid phases as functions of composition and temperature. The liquid phase was modeled using the Modified Quasichemical Model in order to describe the strong ordering in Mg–Ge and Mg–Pb liquid. Mg₂Ge–Mg₂Pb solid solution phase was modeled with consideration of a solid miscibility gap. All calculations were performed using the FactSage thermochemical software.