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Alloy/oxide equilibria in Fe—V—O and Fe—Nb—O systems
Author(s) -
Kumar B. Venkatanna,
Jacob K. Thomas
Publication year - 1987
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.198701586
Subject(s) - niobium , vanadium , chemistry , alloy , oxide , analytical chemistry (journal) , phase (matter) , natural bond orbital , thermodynamics , solid solution , chemical stability , crystallography , materials science , metallurgy , inorganic chemistry , physics , computational chemistry , organic chemistry , chromatography , density functional theory
An experimental characterization of three‐phase equilibria in Fe—V—O and Fe—Nb—O systems at 1 823, 1 873, and 1 923 K has been carried out using a solid state cell and by analysis of quenched samples. The oxygen potentials corresponding to these three‐phase equilibria were monitored by a solid state cell incorporating Y 2 O 3 doped ThO 2 with Cr + Cr 2 O 3 as reference electrode. Similar measurements were carried out for Fe—Nb—O alloys in equilibrium with a mixture of FeNb 2 O 6 and NbO 2 . These measurements permit evaluation of interaction parameters ( e v o = ‐6590/ T +2.892 and e Nb o = ‐4066/ T +1.502) and activity coefficients of vanadium and niobium in dilute solution (In y o v = ‐35320/ T +12.68 and In y o Nb = ‐ 12386/ T + 4.34) in liquid iron. The results obtained in this study resolve a number of discrepancies in thermodynamic data reported in the literature, especially regarding the activity coefficients of V and Nb and the stability ranges for V 2 O 3 and VO 1+x .