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.

Theoretical assessment on hetero-coordination of Alloys Silver-Antimony at Molten State

The thermodynamic and structural properties of binary alloy Ag- Sb at temperature 1250K have been reported theoretically using quasi lattice model. The interchange energy has been considered a function of a temperature and thus various thermodynamic quantities are calculated at elevated temperature. The theoretical values of free energy of mixing, heat of mixing, entropy of mixing and chemical activity are reasonable agreement with experimental values in all concentrations of antimony from 0.1 to 0.9. The theoretical analysis tells that the alloy shows both ordering nature in Ag rich end and segregating nature in Sb rich end .The study reveals that the properties of alloy are asymmetric around equi-atomic composition. The Ag_3 Sn complexes are most likely to exist in the liquid state and are moderately interacting.

Theoretical investigation of mixing properties of Sb-Sn binary liquid alloy at 905K

The thermodynamic, microscopic, surface and transport properties of Sb-Sn liquid alloy at 905K have been studied using regular solution model. In thermodynamic properties, free energy of mixing(GM) , activity(a), entropy of mixing(SM), heat of mixing (HM) have been studied. To understand structural behavior of the liquid alloys concentration fluctuations in the long wavelength limit i.e. (Scc(0)) and short range order parameter (α1) have been computed. Surface property is studied with the help of Butler’s model while transport property is computed from Moelwyn-Hughes equation. The theoretical and experimental values of thermodynamic and microscopic properties of Sb-Sn liquid alloy at 905K have been compared. In present work the value of interchange energy (w) is found to be negative suggesting that there is a tendency of unlike atoms pairing (i.e. Sb-Sn) as the nearest neighbor indicating the ordering behavior in Sb-Sn liquid alloy. The symmetric behavior of concentration fluctuations of the liquid alloy has been well explained by the model. The temperature dependence of interchange energy (w) has been found during the computation of entropy of mixing (SM) and heat of mixing (HM) of the liquid alloy.BIBECHANA 15 (2018) 1-10

Thermodynamic and Transport Properties of Molten Bi-In Alloys

We have used simple statistical theory to describe the mixing behavior of liquid Bi-In alloys in terms of energetic and structure through the study of their thermodynamic and transport properties. The structural characteristics of Bi-In melts are described by the two microscopic functions, i.e. the concentration fluctuation in long wavelength limit and the Warren-Cowley short range order parameter. The transport properties are analyzed through the diffusion coefficient ratio and viscosity. The Gibb’s free energy of mixing, enthalpy of mixing and entropy of mixing are the thermodynamic functions which are used to describe the thermodynamic behaviors. In whole analysis thermodynamic input parameter, i.e. interchange energy take important role which is temperature dependent. The computed results are in good agreement with experimental data and support a weak ordering tendency in molten Bi-In system.The Himalayan Physics Vol. 6 & 7, April 2017 (5-9)

Free Energy of Mixing of some Binary Liquid Alloys

<p>Binary liquid alloys often show interesting behaviour as regards their thermodynamic properties. The heat of mixing often bears a large negative value and the entropy of mixing an S-shape. The free energy of mixing becomes asymmetric around the equi-atomic composition especially in case of complex forming alloys. In the present theoretical work we have tried to compute the free energy of mixing of some binary alloys e.g. lithium-lead, potassium amalgam and magnesium-tin―all in liquid state near their respective melting points. All these alloys form strongly interacting systems. So, we have applied Flory’s model which is a statistical mechanical model considering the size factor of the constituent species of a binary liquid alloy. We have ignored the interaction between the complex and each ingredient within an alloy and amended the formula accordingly. In the light of observed activity of a metal within an alloy we have ascertained the interchange energy by the method of successive numerical approximations and then calculated the free energy of mixing according to the said model for different concentrations of the ingredients. Our results explain the observed anomaly in the free energy of mixing of the present liquid alloys.</p><p>Journal of Nepal Physical Society Vol.3(1) 2015: 97-101</p>

Free Energy of Mixing of the Binary Liquid Alloys of Sodium

Sodium is a highly reactive alkali metal. Within a binary liquid alloy it generally forms complexes. Due to formation of such complexes the thermodynamic properties of the binary alloys of sodium often show anomaly-deviating maximally from that of the ideal alloys. In the present work we have confined our investigation into the free energy of mixing (GM) of two binary alloys of sodium in liquid phase-Na-Pb and Na-Hg-near the melting point. For this purpose we have used Flory’s model and started with the activity of sodium in the sodium-lead liquid alloy and that of mercury in the sodium amalgam at molten stage. By the method of successive approximations we have ascertained the value of interchange energy for each alloy in the light of the experimental values of activity and finally computed GM for different concentrations of the constituent species. Our computation explains the observed symmetry and anomaly in the free energy of mixing of the Na-Pb and Na-Hg liquid alloys respectively.The Himalayan PhysicsVol. 3, No. 32012Page : 24-26

The Solubility of Organic Compounds in Supercritical CO2

A simple liquid solution model is proposed to describe the effect of solvent-solute interactions on the solubility of nonpolar and slightly polar substances in supercritical solvents. Treating the system as an ideal solution, the effect of pressure on the solubility is zero or nearly zero, as it is governed by the difference in molar volume of the pure supercooled liquid solute and the pure solid solute, and this may be nearly zero. Deviations from ideal behavior are given by activity coefficients of the Margules type with the interaction parameter w interpreted as interchange energy as in the lattice theory. The hypothesis is put forward that the interchange energy is of the same form as a function proposed by Liptay and others to describe the effect of the solvent on the wavelength of the absorption maximum of the solute dissolved in the solvent. The function consists of a radius of interaction a and a function g(ε ) of the dielectric constant ε of the solvent, treated as a continuum. The function g depends on pressure through the pressure dependence of the dielectric constant ε (P). The attractive feature of this formalism, introduced by Baumann et al. and here justified thermodynamically, is that plots of the logarithm of solubility vs. g are linear, except for polar solutes near the solvent’s critical point. Changes in slope then admit interpretation as changes in the radius of interaction a with possible clues about the mechanism of solvation of these molecules.

Modeling the Evaporation of Multicomponent Diesel Droplets

A multicomponent fuel evaporation model was developed to describe diesel fuels. This model is based on the principles of continuous thermodynamics. In contrast to conventional. models, each component is not described by discrete relations for energy and mass, but the whole mixture is characterized by a distribution function. In most CFD (computational fluid dynamics)-applications the droplet interior is assumed to be well mixed, this means that composition and temperature are spatially constant inside the droplet. But this assumption is only correct in the case of turbulent mixture with high velocity gradients between spray and surrounding gas, e.g. the area near the nozzle. Due to areas with low relative velocities this formulation is inaccurate and demands a more detailed description of the processes inside the droplet. For these areas the use of a model based on a droplet consisting of several shells is advantageous, because composition and temperature are not spatially constant inside the droplet. The model divides the droplet into a finite number of layers that interchange energy and mass. The implementation of these two models into the CFD-code KIVA-3V implifies the effects of the multi-component character of the fuel by describing the different areas of the spray more correctly. Both models are compared in single droplet calculations and show a detailed description of evaporation.