Chandra Bhanu Basak

Classical molecular dynamics simulation of UO2 to predict thermophysical properties

Interatomic potential parameters of UO2, for a partially ionic potential model, were found out by a fitting method using isothermal compressibility data up to 1600 K. The inter-atomic potential used here is essentially a combined potential model comprising of Bushing–Ida and Morse-type potential to simulate UO2 system using classical molecular dynamics. It has been shown that the deviation in the estimated lattice parameter from the experimental data as reported in literature is due to the inadequacy of the potential parameter. The calculated deviations in lattice parameter, due to the generation of point defects, with variation of temperature have been discussed. The calculated lattice parameters, thermal expansivity, isothermal compressibility of UO2, using the current potential parameters are in close agreement with the experimental values. The model also successfully predicts Bredig transition.

Applicability of Scheil–Gulliver solidification model in real alloy: a case study with Cu-9wt%Ni-6wt%Sn alloy

The present work explores the possibilities of the application of Scheil–Gulliver equation in modelling the solidification of a real alloy. For this study, Cu-9 wt%Ni-6 wt%Sn alloy was chosen which exhibits profuse micro-segregation during solidification, and hence easy to quantify experimentally. Also, this alloy is spinodally strengthened high strength copper alloy and has industrial importance. In this study, thermodynamic assessment using Scheil–Gulliver solidification model was carried out. Subsequently, the assessed result was compared with the experimentally obtained results from energy-dispersive X-ray spectroscopy analysis, and a good agreement was observed between these results. Therefore, it could be concluded that the solidification of this particular alloy system can be modelled using Scheil–Gulliver equation.

Compositional partitioning during the spinodal decomposition in Cu–Ni–Sn alloy

Abstract Spinodal decomposition in Cu–9.4at%Ni–3.1at%Sn alloy was elucidated with the new insight from the experimental EXAFS analysis supported by ab initio total energy calculations suggesting the strong influence of the first near-neighbour atoms. Enthalpy of mixing was calculated for all crystallographically unique first near-neighbour configurations and finally an average positive enthalpy of mixing of 1604 J/mol was obtained. Combination of ab initio results, XRD and EXAFS analysis indicate that one of the daughter phase becomes rich in Ni and Sn than the other phase; in contrary to the earlier proposition that Cu/Ni ratio remains constant in both daughter phases. It is also shown that the present thermodynamic description requires further refinement to extend the miscibility gap towards lower Ni content in Cu–Ni–Sn system.

The effect of ZnO addition on thermo-physical and structural properties of 45S5 bioactive glass/glass-microspheres

The aim of this study is to investigate the effects of ZnO addition on structural properties of 45S5 glass. The glasses with nominal composition 45SiO2-(24.5-x) CaO-24.5 Na2O-6 P2O5-x ZnO (x= 0-15 wt.%) are prepared by melt-quench technique and characterized for thermo-physical properties using DTA and micro-hardness measurements. Glass transition and peak crystallization temperature decrease with an increase of ZnO content, which implies the weakening of glass network and increased tendency of glasses towards crystallization.