Heat capacity measurements of the Fe2Nb and Fe7Nb6 intermetallic compounds

Autor(es)

Silva, Antonio A. A. P. ; Lamoglia, Marcela S. ; Silva, Gilbert ; Fiorani, Jean-Marc ; David, Nicolas ; Vilasi, Michel ; Coelho, Gilberto C. ; Nunes, Carlos A. ; Eleno, Luiz T. F.

• Tipo de documento: Artigo Científico
• Fonte: Journal of Alloys and Compounds; v. 878, p. 7-pg., 2021-05-21.

Resumo

The molar heat capacities of the Fe2Nb and Fe7Nb6 intermetallic compounds are reported here for the first time. The results were obtained via Differential Scanning Calorimetry (DSC) measurements, performed in a temperature range between 348 and 1038 K. The alloys were prepared by arc-melting high purity metals under argon flux and later heat-treated at 1200 degrees C for 336 h encapsulated in quartz tubes under argon to ensure thermodynamic equilibrium. The resulting samples were then characterized using X-Ray Diffractometry (XRD) and Scanning Electron Microscopy (SEM). The heat-capacity DSC measurements were carried out using an alternating step method with 20 and 50 K steps, with the resulting C-p associated with the midpoint of each temperature interval. A fit to a simplified C-p(T) curve was employed, due to the scatter in the data. Quasi-Harmonic Approximation (QHA) calculations were also performed, showing a good agreement with the measured values. Experimental results of heat capacity, along with other thermodynamic properties and phase equilibria, are key information for binary and ternary systems, specially for CALPHAD-type assessments. The results were therefore compared with the Kopp-Neumann approximation, used in recent assessments, showing that the parameters of both compounds can be improved in current CALPHAD databases, which motivates future work on the Fe-Nb system. (C) 2021 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 19/05005-7 - Laboratório de Computação em Materiais para o estudo ab initio da estabilidade de compostos intermetálicos
• Beneficiário: Luiz Tadeu Fernandes Eleno
• Modalidade de apoio: Auxílio à Pesquisa - Regular