J. P. Hajra

Bio: J. P. Hajra is an academic researcher from Indian Institute of Science. The author has contributed to research in topics: Adsorption & Series (mathematics). The author has an hindex of 9, co-authored 19 publications receiving 185 citations. Previous affiliations of J. P. Hajra include Technical University of Berlin.

Thermodynamics of binary systems using interaction parameters

Abstract: A four-parameter equation for determining the excess integral property of a binary system is deduced based on the Maclaurin infinite series. The series is expressed separately in the neighborhood of each of the pure components of the system. The components are subjected to appropriate boundary conditions at the various stages of the treatment. The present form of the function is found to be capable of interpreting thermodynamic properties of several relatively weakly interacting binary systems based on the present equation. The infinite dilution parameters compare favorably with the values reported in the literature.

The Determination of the Surface Tensions of Liquid-Iron, Nickel and Iron-Nickel Alloys using the electromagnetic Oscillating Droplet Technique

Abstract: An oscillating droplet method combined with electromagnetic levitation technique has been applied to determine the surface tensions of liquid pure iron, nickel and iron-nickel alloys as a function of the temperature. The natural frequency of the oscillating droplet is evaluated using a Fourier analyser. The theoretical background of this method and the experimental set-up were described, and the influence of magnetic field strength was also discussed. The experimental results were compared with those of other investigators and interpreted using theoretical models (Butler's equation, subregular and perfect solution model for the surface phase)

Applicability of Butler's equation in interpreting the thermodynamic behavior of surfaces and adsorption in Fe-S-O melts

Abstract: Expressions for various second-order derivatives of surface tension with respect to composition at infinite dilution in terms of the interaction parameters of the surface and those of the bulk phases of dilute ternary melts have been presented. A method of deducing the parameters, which consists of repeated differentiation of Butler's equations with subsequent application of the appropriate boundary conditions, has been developed. The present investigation calculates the surface tension and adsorption functions of the Fe-S-O melts at 1873 and 1923 K using the modified form of Butler's equations and the derived values for the surface interaction parameters of the system. The calculated values are found to be in good agreement with those of the experimental data of the system. The present analysis indicates that the energetics of the surface phase are considerably different from those of the bulk phase. The present research investigates a critical compositional range beyond which the surface tension increases with temperature. The observed increase in adsorption of sulfur with consequent desorption of oxygen as a function of temperature above the critical compositional range has been ascribed to the increase of activity ratios of oxygen to sulfur in the surface relative to those in the bulk phase of the system.

Thermodynamics and phase equilibria in the system GaIn using multi-parameter functions

Abstract: A four and a five-parameter functions are used to analyse and interpret the high and low temperature thermodynamic data and phase equilibria in the GaIn system.

Thermodynamics of surfaces and adsorption in the Fe-C-S-O system

Abstract: Surface tension experiments have been conducted on Fe-C-S-O alloys using the sessile drop technique at 1823, 1873, and 1923 K in a purified argon atmosphere. The experimental data indicate lowering of surface tension values for alloys with low carbon and oxygen contents relative to the corresponding ternary Fe-S-O system of comparable compositions. The data exhibit an increasing trend of the surface tension values as a function of carbon and oxygen contents and temperature of the melt. Modified Butler's equations have been used in conjunction with the consistent thermodynamic relations for a dilute quaternary system to calculate the surface tensions and adsorption functions of the system. The calculated values are in excellent agreement with those of the experimental data for compositions having lower oxygen at 1823 K, however, the values for the alloys containing higher oxygen contents depart from those of the experimental data. The calculated surface tension values agree within 150 mN/m with those of the experimental data at 1873 K. The agreement, in general, has been favorable despite the constraints involved in the calculations as discussed in the text.

Review of surface tension data for metallic elements and alloys: Part 1 – Pure metals

Abstract: There have been a large number of papers on the surface tensions of metals since Keene published his critical review in 1993. Consequently, current data for both the surface tensions of metals and their temperature dependencies have been critically assessed and recommended values are given. Experimental uncertainties can arise from two sources: systematic errors associated with the experimental methods (typically ±2%) and changes in surface tension arising from oxygen contamination of the specimen. Uncertainties arising from the latter can be variable.

Thermodynamic description for concentrated metallic solutions using interaction parameters

Abstract: The integral molar excess Gibbs energy of a multicomponent system is expressed in terms of interaction parameters, from which the analytical formulae of the activity coefficients of the solutes and solvent, as Eqs. [23] and [24], were deduced. This approach, named the e approach, is able to describe quantitatively the thermodynamic properties of multicomponent systems. It features thermodynamic consistency, high accuracy, and a rather small influence of the higher-interaction parameters on the thermodynamic properties of metallic solutions. A simple modification to the first-order interaction parameters extends the e approach, to be applicable to systems with strong interactions between components at both low and concentrated levels.

Use of Thermodynamic Data to Determine Surface Tension and Viscosity of Metallic Alloys

Abstract: During the last three decades, various thermodynamic databases have been compiled to be applied mainly to the calculation of phase diagrams of alloys, salts, and oxides. The accumulation and assessment of thermodynamic data and phase-equilibrium information to establish those databases is sometimes called the CALPHAD (calculated phase diagram) approach. The CALPHAD approach has been recognized as useful in various aspects of materials science and engineering. In addition to the use of thermodynamic databases for the calculation of phase diagrams, it would be very desirable to apply them to the calculation of other physicochemical quantities, such as surface tension. By doing this, not only can the Utility of databases be enlarged, but also a deeper understanding of the physical properties in question can be reached.On the basis of the concepts just mentioned, we have applied those thermodynamic databases to the calculation of the surface tension of liquid alloys and molten ionic mixtures. In these calculations, we have applied Butler's equation for the surface tension of liquid alloys. In addition, we have modified Butler's equation to be extended to molten ionic mixtures by considering the relaxation structure in the surface. These approaches will lead us to develop a multifunctional data-bank System that will be widely applicable in the evaluation of physicochemical properties of liquid alloys and molten ionic mixtures from thermodynamic data.In this article, we explain some physical modeis for the surface tension and viscosity of liquid alloys and molten ionic mixtures, in which thermodynamic data can be directly applied to evaluate these physical properties. In addition, the concept for the just-mentioned multifunctional thermodynamic data-bank System will be described by demonstrating the simultaneous calculation of phase diagrams, surface tension, and viscosity of some alloys used for new, Pb-free soldering materials.

Application of a thermodynamic database to the calculation of surface tension for iron‐base liquid alloys

Abstract: Thermodynamic models based on Butler's equation for surface tension of liquid alloys has been discussed. In alloys, in which activities of components deviate largely from Raoult's law, the calculated surface tensions are found to be affected by the selection of the ratio of the coordination number in the surface phase to that in the bulk phase. Then, the surface tension of liquid Fe-Al, Fe-Co, Fe-Cr, Fe-Mn, Fe-Mo, Fe-Ni, Fe-Si, Fe-Ti and Fe-W binary alloys and liquid Fe-Cr-Ni ternary alloys have been calculated from thermodynamic data in a database constructed by Kaufman. The calculated results reproduce the concentration dependence of the surface tension in those alloys reported so far, but their absolute values are dependent upon the selection of surface tension values for pure elements