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Phase diagrams exhibiting extended solid-solution and lens-like melting are often reproduced using ideal solutions, where ideal mixing considers a fully random configurational entropy of mixing. In the field of irreversible thermodynamics, experimental measurements of the composition variation of high-temperature electronic transport and molten-state properties suggest however a strong role for short-range atomic ordering in these systems. Herein, measurements of the thermopower and resistivity are reported for Cu-Ni solid-solutions as a function of temperature and composition. The electronic transport properties were interpreted with an irreversible thermodynamic framework, revealing a large electronic contribution to the entropy of mixing. Through appeal to a cluster model for the configurational entropy that uses the electronic contribution to inform the existence of ordered associates, we rationalize such contribution of the electronic entropy with the ideal entropy of mixing commonly used to model such systems. These results suggest that the short range order (S.R.O.) of the atoms plays a significant role in both the solid and molten states, even when there are no dominant intermetallic compounds in these alloys.

A thermal imaging furnace (TIF) was used to study the physical properties of molten Sc2O3 , La2O3, Y2O3, Al2O3 and MgO via a containerless method. The density and surface tension of molten droplets of Sc2O3 , La2O3, Y2O3, Al2O3, and MgO suspended from their own solid were measured in situ using live video under a range of oxygen partial pressures (1→10−6 atm O2). To the best knowledge of the authors, this is the first time the surface tension and density of molten MgO and Sc2O3 have been reported. A relationship between molten oxide surface tension and the enthalpy of vaporization is proposed, and a comparison is drawn between the oxide properties and similar relationships previously established for liquid metals.

A thermal imaging furnace (TIF) was used to study the physical properties of molten Sc2O3 , La2O3, Y2O3, Al2O3 and MgO via a containerless method. The density and surface tension of molten droplets of Sc2O3 , La2O3, Y2O3, Al2O3, and MgO suspended from their own solid were measured in situ using live video under a range of oxygen partial pressures (1→10−6 atm O2). To the best knowledge of the authors, this is the first time the surface tension and density of molten MgO and Sc2O3 have been reported. A relationship between molten oxide surface tension and the enthalpy of vaporization is proposed, and a comparison is drawn between the oxide properties and similar relationships previously established for liquid metals.

Cu₃Au experiences a phase transition at 662 K from an ordered low-temperature phase to a disordered solid solution. While significant work has been devoted to characterizing the enthalpy of this transition, the apportionment of the entropy has remained out of reach. Current estimates of the vibrational and configurational entropy for the transition are larger than the total entropy of the transition experimentally measured by calorimetry, while calculations of the electronic entropy via ab initio methods have remained difficult. This work calculates an electronic entropy difference of −6.29 J/mol K based on a recent formalism that links experimentally measured electronic transport data and equilibrium thermodynamic properties. The application of this formalism brings some estimates of the vibrational and configurational entropy in line with the calorimetrically measured total entropy.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2018., Cataloged from PDF version of thesis., Includes bibliographical references (pages 34-36)., An atomistic approach to modeling the sintering of nanocrystalline alloys has been developed. It has been shown that there exist alloys that exhibit both nanostructured stability and undergo an accelerated sintering process [1], [2]. However, the widespread adoption of such alloys has been limited by a lack of understanding of the processing kinetics that lead to the accelerated sintering phenomena. To better understand the role of surface diffusion, and the effect that system enthalpies of mixing have on inter-particle neck formation, a 3D kinetic monte carlo (KMC) model was proposed to study these phenomena. The results of these simulations demonstrate that positive enthalpy of mixing highlighted as a necessary criterion for nanocrystalline stability in [1], also leads to the fast diffusing elements ability to form the interparticle neck. The condition of lower temperature neck formation by fast diffusing alloy elements is hypothesized to be the mechanism behind which accelerated sintering occurs. The findings in this paper demonstrate that positive enthalpy of mixing alloys can be designed to sinter at lower temperatures and shorter cycle durations if they have adequate solute present on the surface of the particle., by Jonathan Paras., S.B.