The Determination of Phase Boundaries and Thermodynamic Functions in the Iron-Oxygen System by EMF Measurements

Abstract

Coulometric titration in a high-temperature cell employing a stabilized zirconia electrolyte was used successfully in the determination of phase boundaries and related thermodynamic data in the iron-oxygen system. The standard free energy of formation of oxygen-deficient wiistite was determined between 540 ~ and 1200~ Values agree to within 500 cal of the most critically reviewed data. The free energy of reaction for the formation of magnetite from wiistite and oxygen was determined between 900 ~ and 1200~ The composition of the iron-rich boundary of wiistite was found to decrease very slightly in oxygen content with increasing temperature. For all practical purposes, however, the composition of the boundary can be considered constant at FeOi.05. The compositions of oxygen-rich wiistite agreed fairly well with existing data. Evidence was presented, however, for the existence of additional phases in the region of the Fe-O diagram between the presently reported oxygen-rich wfistite and magnetite. The temperature for the Fe, FexO, Fe304 three-phase equilibrium was found experimentally to be 610 ~ • 10~ Extrapolation of low temperature (T < 900~FezO-Fe304 equilibrium data resulted in lower transformation temperatures.

Solid State Electrochemical Study of Phase Equilibria and Thermodynamics of the Ternary System Y-Fe-O at Elevated Temperatures

“…In contrast, the oxygen equilibrium pressures of the Y203-Fe-YFe03 region (A) are lower than those obtained by Tretyakov et al [7]. The oxygen equilibrium pressures of the Fei_?/0-Fe304-YFe03 region (G) are consistent with the data given in [19] for the Fei_2/0-Fe304 system. However, the agreement with other published data is poor and it should be emphasized that the differences are greater than our experimental error.…”

“…The cell voltage or equilibrium oxygen partial pressure of the 2-phase mixture of Fe and Fei-^O can be taken from the literature [15][16][17][18][19][20][21][22]. Data taken from Refs.…”

Thermodynamic study of the reduction of titanium magnetite concentrate with solid carbon

“…The results obtained are listed in Table I and shown in Figure 2 represents the temperature dependence of EMF of the obtained experimental data compared to some authors. [2,4] [11] and [13] can be recovered by Reaction [12]. The CO-CO 2 ratio can be regulated by the gasification reaction equi-B.…”

“…Through a definition of the thermodynamic functions on A ⇔ B ϩ O 2 the phase borders in the Fe-O system, Rizzo et al [2] used a If a A ϭ a B ϭ 1, the equilibrium constant K ϭ (P O 2 ) exp. solid electrolyte galvanic cell with an air reference electrode.…”

Thermodynamics of Impurities in Pure Iron Obtained by Hydrogen Reduction

“…1,2) The thermodynamic study and phase diagram work have been performed in the early stage of the 20th century and systematic integration has been done. [3][4][5][6][7] The reduction behaviors were analyzed in details and the mathematical models such as the shrinking core model [8][9][10][11][12][13] were developed and applied to an experimental and actual process data. On the basis of these fundamental studies, the understanding of reduction reaction of iron ore has been significantly promoted.…”