Thermodynamic properties and phase equilibria for Pt-Rh alloys

Jacob, KT and Priya, S and Waseda, Y (1998) Thermodynamic properties and phase equilibria for Pt-Rh alloys. In: Metallurgical and Materials Transactions A, 29 (6). pp. 1545-1550.

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Abstract

The activity of rhodium in solid Pt-Rh alloys is measured in the temperature range from 900 to 1300 K using the solid-state cell $Pt-Rh,Rh+Rh_2O_3/(Y_2O_3)ZrO_2/Pt_{1-x}Rh_x+Rh_2O_3,Pt-Rh.$ The activity of platinum and the free energy, enthalpy, and entropy of mixing are derived. Activities exhibit moderate negative deviation from Raoult's law. The mixing properties can be represented by a pseudosubregular solution model in which excess entropy has the same type of functional dependence on composition as the enthalpy of mixing, $?H=x_{Rh}(1-X_{Rh})[-10,970+45X_{Rh}] J/mol ?S^E=X_{Rh}[-3.80+1.55×10^{-2}X_Rh] J/mol.K.$ The negative enthalpy of mixing obtained in this study is in qualitative agreement with predictions of semiempirical models of Miedema and co-workers and Colinet et al. The results of this study do not support the solid-state miscibility gap suggested in the literature, but are consistent with liquidus data within experimental uncertainty limits.

Item Type:	Journal Article
Publication:	Metallurgical and Materials Transactions A
Publisher:	Minerals, Metals & Materials Society and ASM Intl
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	08 Jan 2007
Last Modified:	03 May 2011 07:07
URI:	http://eprints.iisc.ac.in/id/eprint/9191

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