Thermodynamic properties and phase equilibria for Pt-Rh alloys
- Indian Inst. of Science, Bangalore (India). Dept. of Metallurgy
- Tohoku Univ., Sendai (Japan). Inst. for Advanced Materials Processing
The activity of rhodium in solid Pt-Rh alloys is measured in the temperature range from 900 to 1,300 K using the solid-state cell Pt-Rh, Rh + Rh{sub 2}O{sub 3}/(Y{sub 2}O{sub 3})ZrO{sub 2}/Pt{sub 1{minus}x}Rh{sub x} + Rh{sub 2}O{sub 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, {Delta}H = X{sub Rh} (1 {minus} X{sub Rh})[{minus}10,970 + 45X{sub Rh}] J/mol, {Delta}S{sup E} = X{sub Rh} (1 {minus} X{sub Rh})[{minus}3.80 + 1.55 {times} 10{sup {minus}2} X{sub Rh}] J/mol{center_dot}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.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 634634
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Vol. 29, Issue 6; Other Information: PBD: Jun 1998
- Country of Publication:
- United States
- Language:
- English
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