Effect of temperature on mixing behavior and stability of liquid Al-Fe alloys

A theoretical model based on the assumption of compound formation in binary liquid alloy has been used to investigate the thermodynamic properties (free energy of mixing, enthalpy of mixing and entropy of mixing), microscopic properties (concentration fluctuation in long wavelength limit and chemical short range order parameter), surface properties (surface tension and surface composition) and dynamic properties ( viscosity and diffusion coefficient). All the properties of Al2Fe binary melt have been measured using the same energy parameters configured for experimental values of free energy of mixing. The energy parameters are detected as independent of concentration, but depend on temperature. The findings are well consistent with the experimental standards.

Thermodynamic analysis of oligomeric blends by applying the Kirkwood-Buff theory of solutions

The accurate prediction of the thermodynamic properties of oligomeric blends and, in general, binary liquid mixtures from atomistic simulations is a challenging task. In this work we develop a methodology for the full thermodynamic analysis of oligomeric blends and the extraction of the Flory-Huggins interaction parameter from the Gibbs energy of mixing, combining Flory-Huggins thermodynamics with Kirkwood-Buff theory of solutions. We perform a series of Molecular Dynamics (MD) simulations of 2-methylpentane/n-heptane mixtures, at various mole fractions. Firstly we validate the forcefield we apply in our MD simulations, comparing the density and excess volume we obtain against the corresponding experimental estimates found in the literature. Then we calculate the Kirkwood-Buff integrals in the isothermal-isobaric (NpT) ensemble, applying the particle fluctuations method, and we extract the component activity coefficients, the excess Gibbs energy, the excess enthalpy, and the excess entropy of mixing as functions of the mole fraction. Finally we calculate the Flory-Huggins interaction parameter χ by interpreting the Gibbs energy of mixing in the framework of Flory-Huggins theory, and explore its dependence on composition. All results are compared against experimental measurements in order to evaluate our methodology. Agreement is found to be very good.

Theoretical assessment for the mixing properties of AlMg liquid alloys at 1073K

The alloying behavior of AlMg alloy in the liquid form at 1073 K has been theoretically investigated in the framework of four-parameter model which is based on Maclaurin series. The analytical expressions for thermodynamic functions such as excess free mixing energy, free mixing energy, enthalpy of mixing and entropy of mixing and microscopic functions such as concentration fluctuations at the long wavelength limit and Warren-Cowley chemical short range order parameter have been derived. These expressions have been used to compute the excess Gibbs free energy of mixing, Gibbs free energy of mixing, activity, enthalpy(heat) of mixing, excess entropy of mixing, entropy of mixing, concentration fluctuations in long wavelength limit and Warren-Cowley short range order parameters of AlMg liquid alloys at 1073 K. The investigation shows the excellent concurrence between the experimental and theoretical measurements of the mixing properties of AlMg liquid alloys at 1073 K. Interaction parameters of energy depends on temperature.

Design of Composites by Infiltration Process: A Case Study of Liquid Ir-Si Alloy/SiC Systems

The design of processing routes involving the presence of the liquid phase is mainly associated with the knowledge of its surface and transport properties. Despite this need, due to experimental difficulties related to high temperature measurements of metallic melts, for many alloy systems neither thermodynamic nor thermophysical properties data are available. A good example of a system lacking these datasets is the Ir-Si system, although over the last fifty years, the structures and properties of its solid phases have been widely investigated. To compensate the missing data, the Gibbs free energy of mixing of the Ir-Si liquid phase was calculated combining the model predicted values for the enthalpy and entropy of mixing using Miedema’s model and the free volume theory, respectively. Subsequently, in the framework of statistical mechanics and thermodynamics, the surface properties were calculated using the quasi-chemical approximation (QCA) for the regular solution, while to obtain the viscosity, the Moelwyn-Hughes (MH) and Terzieff models were applied. Subsequently, the predicted values of the abovementioned thermophysical properties were used to model the non-reactive infiltration isotherm of Ir-Si (eutectic)/SiC system.

Evaluation of viscosity in binary mixtures of dimethyl sulphoxide at 298.15K

The viscosity of binary mixtures of dimethyl sulphoxide with different alcohols such as methanol, ethanol, 1-propanol, iso-propanol, 1-butanol, iso-butanol, tertiary butanol has been determined at 298.15K. The experimental values are compared with theoretical values evaluated by different theories. It is observed that for some theories, values are in agreement with the experimental values. Further, an attempt has been made to study the intermolecular interactions in studied solutions in terms of excess free energy of mixing, strength of interaction parameters and interaction energy. The viscosity data of pure liquids and their mixtures are needed to design various chemical processes where heat and mass transfer are important.

Design of Composites by Infiltration Process: A Case Study of Liquid Ir-Si Alloy/SiC Systems

The design of processing routes involving the presence of the liquid phase is mainly associated with the knowledge of its surface and transport properties. Despite this need, due to experimental difficulties related to high temperature measurements of metallic melts, for many alloy systems neither thermodynamic nor thermophysical properties data are available. A good example lacking these datasets represents the Ir-Si system, although over the last fifty years, the structures and properties of its solid phases have been widely investigated. To compensate the missing data, the Gibbs free energy of mixing of the Ir-Si liquid phase was calculated combining the model predicted values for the enthalpy and entropy of mixing using Miedema’s model and Free Volume Theory, respectively. Subsequently, in the framework of statistical mechanics and thermodynamics, the surface properties were calculated using the Quasi Chemical Approximation (QCA) for the regular solution, while to obtain the viscosity, the Moelwyn-Hughes (MH) and Terzieff models were applied. Subsequently, the predicted values of the abovementioned thermophysical properties were used to model the non-reactive infiltration isotherm of Ir-Si (eutectic) / SiC system.

Thermodynamic Assessment of the AF–CrF3 (A = Li, Na, K) and CrF2–CrF3 Systems

Understanding the corrosion mechanisms and the effect of corrosion products on the basic properties of the salt (e.g., melting point, heat capacity) is fundamental for the safety assessment and durability of molten salt reactor technology. This work focused on the thermodynamic assessment of the CrF2−CrF3 system and the binary systems of chromium trifluoride CrF3 with alkali fluorides (LiF, NaF, KF) using the CALPHAD (computer coupling of phase diagrams and thermochemistry) method. In this work, the modified quasi-chemical model in the quadruplet approximation was used to develop new thermodynamic modelling assessments of the binary solutions, which are highly relevant in assessing the corrosion process in molten salt reactors. The agreement between these assessments and the phase equilibrium data available in the literature is generally good. The excess properties (mixing enthalpies, entropies and Gibbs energies) calculated in this work are consistent with the expected behaviour of decreasing enthalpy and Gibbs energy of mixing with the increasing ionic radius of the alkali cations.

Study of Structural Behavior of Cadmium Based Alloys at Molten State

The simple statistical model or simple theory of mixing has been used to study the structural behavior of cadmium based alloys at their molten state at a temperature of 800 K by computing thermodynamic functions and structural functions. The thermodynamic functions include free energy of mixing (GM), activity (a), the heat of mixing (HM), and the entropy of mixing (SM). The structural functions include concentration fluctuation in the long-wavelength limit (SGG(0)) and Warren-Cowley short-range order parameter (α1). Interchange energy or interaction energy or ordering energy (ω) was calculated for the respective alloys system and found to be positive and temperature-dependent. Based on interchange energy (ω) and coordination number (Z), theoretical values of all the functions are calculated by applying the grand partition function. All the computed values for the mentioned functions are in good agreement with experimental values. For the cadmium based alloys, viz., Cd-Zn & Cd-In, both show the segregating in nature at temperature 800 K for the concentration of range 0.1 to 0.9, however, Cd-Zn is more segregating than Cd-In.

PEGylated DPPC/Anti-SNAP25 Antibody Targeted Liposomes: From Langmuir Monolayer Study to Formulations

Background: Molecule compatibility is an important factor to be considered before preparing antibody-targeted liposomes, stealth-liposomes, and stealth antibody-targeted liposomes. Objective: To determine the intermolecular interaction of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamide-N-[methoxy(polyethyleneglycol)-2000] (ammonium salt), DOPE PEG2000 and Anti-SNAP25 (AS25) in 1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine (DPPC) monolayer, and their liposomes. Methods: In this study, DPPC was used to create a monolayer mimicking the half membrane of liposomes to investigate its interactions with a polyclonal antibody, AS25, and DOPE PEG2000, respectively based on Langmuir-Blodgett (LB) techniques. The surface morphology of DPPC— AS25 and DPPC— DOPE PEG2000— AS25 bilayers were also imaged and analyzed by using atomic force microscopy (AFM) to support the LB findings. The LB findings were then utilized as a reference to prepare DPPC liposomes in this work. Results: The best mole ratio of DPPCDOPE PEG2000, determined to be 50 to 1, was used to study the interaction with the polyclonal antibody AS25. The free energy of mixing (〖Δ G〗_mix) of DPPC— DOPE PEG2000—AS25 was more negative than DPPC— AS25 in the entire investigated ranges, indicating that the ternary mixture of DPPC— DOPE PEG2000— AS25 was more compatible than the binary mixture of DPPC— AS25. The presence of DOPE PEG2000 in DPPC— AS25 increased the fluidity of the membrane, which resulted in a greater interaction of AS25 with DPPC. Conclusion: The constant values of particle size and zeta potential measurements of DPPC— DOPE PEG2000— AS25 liposomes showed agreement with the LB findings, indicating that LB is a good technique to predict precise liposomal formulations.

Calculation of Darken Stability Functions of Al-In and Bi-Zn Binary Liquid Alloys

The thermodynamic model based on clustering of two atoms is considered with the view to obtain the concentration-concentration fluctuation, Scc(0) and the darken stability function. The thermodynamic properties of these alloys were evaluated based on clustering of two atoms (A & B) or (B & A). Each system has the view of obtaining concentration-concentration fluctuation, Scc(0) enumerating the low-order atomic correlation in the nearest neighbour shell of liquid binary alloys. The highlights of reciprocals of Scc(0) of these alloys were noted . The values of Scc(0) for Al-In alloy throughout the entire concentration were positive and higher for activity ratio and lower than the ideal solution values for free energy of mixing at specific Al composition. The values of darken stability function of Al-In alloy fall below the ideal darken stability function for activity ratio and free energy of mixing . The indication of the reciprocal of Scc(0) for all the alloys is in support of homocoordination / heterocoordination in the nearest neighbour shell. The Scc(0) and darken stability function of Bi-Zn binary alloys were noted with fluctuations. Keywords: Concentration-concentration fluctuation, Darken stability function, Ordering energy.