Oxygen potentials in Ni + NiO and Ni + Cr[sub 2]O[sub 3] + NiCr[sub 2]O[sub 4] systems

Journal Article · Wed Jun 01 04:00:00 EDT 1994 · Metallurgical Transactions, B (Process Metallurgy); (United States)

OSTI ID:7199349

Kale, G M; Fray, D J ^[1]

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1. Univ. of Leeds (United Kingdom). Dept. of Mining and Mineral Engineering

The chemical potential of O for the coexistence of Ni + NiO and Ni + Cr[sub 2]O[sub 3] + NiCr[sub 2]O[sub 4] equilibria has been measured employing solid-state galvanic cells, (+) Pt, Cu + Cu[sub 2]O [vert bar][vert bar] (Y[sub 2]O[sub 3])ZrO[sub 2] [vert bar][vert bar] Ni + NiO, Pt (-) and (+) Pt, Ni + NiO [vert bar][vert bar] (Y[sub 2]O[sub 3])ZrO[sub 2] [vert bar][vert bar] Ni + Cr[sub 2]O[sub 3] + NiCr[sub 2]O[sub 4], Pt (-) in the temperature range of 800 to 1,300 K and 1,100 to 1,460 K, respectively. The electromotive force (emf) of both he cells was reversible, reproducible on thermal cycling, and varied linearly with temperature. for the coexistence of the two-phase mixture of Ni + NiO, [Delta][mu][sub O[sub 2]](Ni + NiO) = [minus]470,768 + 171.77T ([+-]20) J/mol (800 [le] T [le] 1,300 K) and for the coexistence of Ni + Cr[sub 2]O[sub 3] + NiCr[sub 2]O[sub 4], [Delta][mu][sub O[sub 2]](Ni + Cr[sub 2]O[sub 3] + NiCr[sub 2]O[sub 4]) = [minus]523,190 + 191.07T ([+-]100) J/mol (1,100 [le] T [le] 1,460 K). The third law analysis of the present results for Ni + NiO gives the value of [Delta]H[degree][sub 298] = [minus]239.8 ([+-]0.05) kJ/mol, which is independent of temperature, for the formation of one mole of NiO from its elements. This is in excellent agreement with the calorimetric enthalpy of formation of NiO reported in the literature.

• OSTI ID: 7199349
• Journal Information: Metallurgical Transactions, B (Process Metallurgy); (United States), Journal Name: Metallurgical Transactions, B (Process Metallurgy); (United States) Vol. 25:3; ISSN MTTBCR; ISSN 0360-2141
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360100* -- Metals & Alloys
ALLOYS
CHALCOGENIDES
CHROMATES
CHROMIUM COMPOUNDS
CHROMIUM OXIDES
COATINGS
CORROSION RESISTANT ALLOYS
ELEMENTS
ENTHALPY
FORMATION HEAT
MEASURING METHODS
METALS
MINERALS
NICKEL
NICKEL COMPOUNDS
NICKEL OXIDES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PHYSICAL PROPERTIES
PROTECTIVE COATINGS
REACTION HEAT
SPINELS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS