Activities of oxygen in liquid copper and silver from electrochemical measurements

Modified coulometric titrations on the galvanic cell:O in liquid Cu or Ag / ZrO₂( + CaO) / Air, Pt, were performed to determine precisely the oxygen activities in liquid copper and silver in the range of relatively low oxygen concentration. The present experimental results were remarkably reproducible in comparison with the published data. The standard Gibbs energies of solution of oxygen in liquid copper and liquid silver for 1/2 O₂(l atm) → O(l at. pct) were determined respectively to be ΔG° (in Cu) = −18040 −0.03 T(K) (± 120) cal · g-atom−1 = −75500 −0.12 T(K)(± 500) J · g-atom−1, ΔG°(inAg)= -3860+ 1.56 T(K) (±90) cal · g-atom−1 = −16140 + 6.52 T(K)(±380) J · g-atom−1 where the reference state for dissolved oxygen was an infinitely dilute solution. The present value of the partial entropy of oxygen dissolved in liquid copper differs significantly from that suggested by many investigators. Further, the present equation for liquid copper has been found to be consistent with a correlation proposed previously by the present authors. The equation for liquid silver is in good agreement with the published ones.     

The detection of solutal convection during electrochemical measurement of the oxygen diffusivity in liquid tin

Electrochemical titration was used as a means to determine the mass diffusivity of oxygen in liquid tin at various temperatures. Solutal convection was present depending on the conditions, and this was inferred from an enhancement in the effective diffusivity. The experiments were conducted in two different modes of operation, and in each case, we attempted to align the oxygen concentration gradient such that it was parallel to the gravitational field. In the first mode, the concentration gradient was such that the fluid was heavy at the bottom and lighter at the top, and in the second, the reverse was true. The second mode was potentially unstable and sometimes gave rise to substantial convection for large values of the oxygen concentration gradient. The measured effective diffusivities were then higher than the corresponding measurements in the first mode of operation. Activation energies in two different temperature ranges were obtained by using an Arrhenius relationship. Formerly Graduate Student, Chemical Engineering Department, University of Florida     

The diffusivity of oxygen in liquid copper-lead alloys

The oxygen diffusivity in liquid copper-lead alloys at 1403 K (1130‡C) was measured us-ing the electrochemical cell: Ni-NiOJZrO₂(+CaO)/O in liquid Cu-Pb alloy(I)/ZrO₂(+CaO)/O in liquid Cu-Pb alloy(II). Oxygen in liquid Cu-Pb alloy(I) was transferred to the right by applying a preselected voltage between the two liquid Cu-Pb alloys. The oxygen diffusivity in liquid Cu-Pb alloy(I) was calculated from the emf change with time between the Ni-NiO and liquid Cu-Pb alloy (I) electrodes. The results were: D_o (in pure Cu) = 8.14 (^+0.70 _-0.43) × 10⁵ cm²/s, D_o (in Cu-25 at. pct Pb) = 11.4(^+0.4 _-0.6) × 10^-5 cm²/s, D_o (in Cu-50 at. pct Pb) = 12.9(^+1.9 _-1.5) × 10^-5 cm²/s, D_o (in Cu-75 at. pct Pb) = 11.0(^+2.4 _-1.2) x 10^-5 cm²/s, D_o (in pure Pb) = 26.3(^+4.8 _-3.7) × 10^-5 cm²/s. It was found that the oxygen diffusivity in liquid copper-lead alloys did not change dras-tically over the entire composition range, in contrast with that reported by other investi-gators for liquid copper-nickel alloys. The oxygen diffusivity in pure liquid lead agreed with the results of our previous work using an FeO-Fe₃O₄ mixture as a sink for oxygen.     

The diffusivity of oxygen in liquid copper-lead alloys

The oxygen diffusivity in liquid copper-lead alloys at 1403 K (1130° C) was measured using the electrochemical cell: Ni−NiO/ZrO₂(+CaO)/O in liquid Cu−Pb alloy(I)/ZrO₂(+CaO)/O in liquid Cu−Pb alloy (II). Oxygen in liquid Cu−Pb alloy (I) was transferred to the right by applying a preselected voltage between the two liquid Cu−Pb alloys. The oxygen diffusivity in liquid Cu−Pb alloy(I) was calculated from the emf change with time between the Ni−NiO and liquid Cu−Pb alloy (I) electrodes. The results were: It was found that the oxygen diffusivity in liquid copper-lead alloys did not change drastically over the entire composition range, in contrast with that reported by other investigators for liquid copper-nickel alloys. The oxygen diffusivity in pure liquid lead agreed with the results of our previous work using an FeO−Fe₃O₄ mixture as a sink for oxygen.     

Activities of oxygen in liquid thallium and indium from electrochemical measurements

Modified coulometric titrations on the galvanic cell;O in liquid Tl or In/ZrO₂(+CaO)/Air, Pt, were performed at 973, 1073, and 1173 K to determine the oxygen activities in liquid thallium and liquid indium. The standard Gibbs energies of solution of oxygen in liquid thallium and liquid indium for l/2 O₂ →O (1 at. pct) were determined respectively to be δG‡(in Tl) = -22000 + 0.74T (±300) cal/g-atom = -92000 + 3.10T (±1300) J/g-atom, δG‡(in In) = -42450+ 3.30T (±350) cal/g-atom = -177600 + 13.8T (±1500) J/g-atom, where the reference state for dissolved oxygen was an infinitely dilute solution. It was reconfirmed that the apparent initial oxygen concentration observed in the range of very low oxygen concentration in liquid metal was attributed to the oxygen released from the solid electrolyte.     

The diffusivity and solubility of fluorine in solid nickel from electrochemical measurements

The diffusivity and solubility of fluorine in solid nickel were determined using the following solid-state electrochemical cells: Co + CoF₂| BaF₂| Ni | BaF₂| Co + CoF₂ Co + CoF₂| CaF₂| BaF₂| Ni | BaF₂| CaF₂| Co + CoF₂ In the temperature range 1023 to 1223 K, the diffusion coefficient of fluorine in solid nickel is given by: 1 $$D_F (cm^2 /s) = (2.13_{ - 1.54}^{ + 5.54} ) \times 10^{ - 3} \exp (( - 118,600 \pm 12,000J/mol)/RT)$$ The dissolution of atomic fluorine in solid nickel obeys Sieverts’ law; however, the solubility results showed considerable scatter. In the temperature range 1073 to 1223 K, the mean solubility of fluorine in solid nickel, corresponding to the equilibrium Ni + NiF₂, follows the relationship: N _-F ^S (at. pct) = 5.73 x 10^-3 exp((10,850 J/mol)/RT)     

The diffusivity and solubility of oxygen in liquid tin and solid silver and the diffusivity

The diffusivity and solubility of oxygen in liquid tin and solid silver in the temperature range of about 750° to 950°C (1023 to 1223 K) and the diffusivity of oxygen in solid nickel at 1393°C (1666 K) were determined using the electrochemical cell arrangement of cylindrical geometry: Liquid or Solid Metal + O (dissolved) | ZrO₂ + (3 to 4%)CaO | Pt, air The diffusivity and solubility of oxygen in liquid tin are given by:D _O(Sn) = 9.9 × 10⁻⁴ exp(−6300/RT) cm²/s (9.9 × 10⁻⁸ exp − 6300/RT m²/s) andN _O ^S (Sn) = 1.3 × 10⁵ exp(−30,000/RT) at. pct The diffusivity and solubility of oxygen in solid silver follow the relations:D _O(Ag) = 4.9 × 10⁻³ exp (−11,600/RT) cm²/s ( 4.9 × 10⁻⁷ exp − 11,600/RT m²/s) andN _O ^S (Ag) = 7.2 exp (−11,500/RT) at. pct The experimental value for the preexponential in the expression forD _O(Ag) is lower than the value calculated according to Zener’s theory of interstitial diffusion by a factor of 11. The diffusivity of oxygen in solid nickel at 1393°C (1666 K) was found to be 1.3 × 10⁻⁶ cm²/s (1.3 × 10⁻¹⁰ m²/s). Formerly Graduate Student, Department Formerly Graduate Student, Department Formerly Graduate Student, Department This paper is based upon a This paper is based upon a This paper is based upon a This paper is based upon a     

Activity and diffusivity measurements of copper in γ and δ Fe by equilibration between solid Fe and liquid Ag

The activities of Cu in solid Fe for 1323 <=T <= 1773 K have been determined by equilibrating the surface of initially pure Fe plates with liquid Ag-Cu alloys and by using the literature values of the Cu activity in Ag-Cu alloys. The equilibrations have been confirmed by the agreement of surface compositions between an initially pure Fe plate and an Fe-Cu alloy plate having more content of Cu than the surface concentration. The equilibrated Fe plates were essentially binary Fe-Cu alloys, because no Ag was detected by an electron probe analyzer in the Fe plates. Interdiffusivities in solid Fe-Cu alloys for the same temperature range have also been determined from penetration profiles of Cu in the plates. The ternary phase diagram for the Ag-Cu-Fe system at 1480 K has been determined from solubility measurements of Fe in liquid Ag-Cu alloys. M. Tanaka, formerly at Tokyo Institute of Technology, is now with Clinap Industries, Tokyo, Japan.     

Activities of oxygen in liquid Bi,Sn, and Ge from electrochemical measurements

Modified coulometric titrations on the galvanic cell: O in liquid Bi, Sn or Ge/ZrO₂( + CaO)/Air, Pt, were performed to determine the oxygen activities in liquid bismuth and tin at 973, 1073 and 1173 and in liquid germanium at 1233 and 1373 K. The standard Gibbs energy of solution of oxygen in liquid bismuth, tin and germanium for 1/2 O₂ (1 atm) →O (1 at. pct) were determined respectively to be ΔG° (in Bi) = −24450 + 3.42T (±200), cal· g-atom⁻¹ = − 102310 + 14.29T (±900), J·g-atom⁻¹, ΔG° (in Sn) = −42140 + 4.90T (±350), cal· g-aton⁻¹ = −176300 + 20.52T (± 1500), J-g-atom⁻¹, ΔG° (inGe) = −42310 + 5.31 7 (±300), cal·g-atom⁻¹ = −177020 + 22.21T(± 1300), J· g-atom⁻¹, where the reference state for dissolved oxygen was an infinitely dilute solution. It was reconfirmed that the modified coulometric titration method proposed previously by two of the present authors produced far more reliable results than those reported by other investigators. TOYOKAZU SANO, formerly a Graduate Student, Osaka University     

The chemical diffusivity of oxygen in liquid iron oxide and a calcium ferrite

Measurements have been made of the chemical diffusion coefficient of oxygen in liquid iron oxide at temperatures from 1673 to 1888 K and in a calcium ferrite (Fe/Ca = 2.57) at temperatures from 1573 to 1873 K. A gravimetric method was used to measure the oxygen uptake during the oxidation of the melts by oxygen or CO₂-CO mixtures. The rate was shown to be controlled by mass transfer in the liquid melt. The chemical diffusivity of oxygen in liquid iron oxide at oxygen potential between air and oxygen was found to be 4.2±0.3 × 10⁻³ cm²/s at 1888 K. That in iron oxide at oxidation state close to iron saturation was established to be given by the empirical expression log D=−6220/T + 1.12 for temperatures between 1673 and 1773 K. For the calcium ferrite (Fe/Ca=2.57) at oxygen potential between air and oxygen, the diffusivity of oxygen was found to be given by log D=−1760/T−1.31 for temperatures between 1673 and 1873 K. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium,” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS.     

Oxygen solubility in liquid indium and oxygen diffusivity in liquid indium and tin

The solubility of oxygen in liquid indium, C_o, at 973 and 1073 K in equilibrium with its oxide was determined by an isopiestic equilibration technique in order to resolve discrepancies reported in the literature. The present results, C_o = 0.0092 at. pet at 973 K and 0.0377 at. pet at 1073 K, agree with those obtained by Otsuka, Sano, and Kozuka using a modified coulometric titration method. Oxygen diffusivity in liquid indium from 873 to 1073 K and in liquid tin from 973 to 1273 K was measured utilizing a combined potentiostatic and emf method using the following double electrochemical cells: Fe,FeO/ZrO₂(+CaO)/O in Me(I)/ZrO₂(+CaO)/O in Me(II). The present results are D_O(In) = 6.6 ( _-1.6 ^+2.0 ) x 10⁻³ exp[(-3-600 ± 5600)/RT]873 K ≤T ≤ 1073 K and D_O(Sn), = 8.7( _-5.7 ^+13.5 ) x 10⁻⁴ exp[(-18800 ± 6700)/RT]973 K ≤T ≤ 1273 K. The present results are of the same order of magnitude with the self-diffusivity of the liquid metals, and are about two orders of magnitude greater than the oxygen diffusivity reported by Stevenson and co-workers. The ratio of oxygen diffusivity to self-diffusivity of the solvent was found to be correlated to the enthalpy of formation per mole of oxygen of the respective oxide at 298 K.     

根据铜液氧活度判断冰铜吹炼终点

采用ZrO2（MgO）固体电解质浓差电池测定铜液中氧的活度,研究了铜液氧活度与温度和纯度的关系.实验结果表明：铜液中氧探头的电动势随铜液温度的升高呈曲线下降趋势,随铜液纯度的升高呈线性下降趋势,说明采用固体电解质电池测定铜液中的氧活度可以判断铜液纯度.该实验结果为冰铜吹炼终点的判断提供了一种较为科学的依据.     

Permeability,diffusivity, and solubility of oxygen gas in liquid slag

An experimental procedure for measurement of the permeability of dissolved oxygen gas in liquid slag has been developed using an oxygen concentration cell. The small amount of oxygen gas which penetrated through the liquid oxide from a pure oxygen compartment to a pure argon compartment was determined by the galvanic cell. The permeabilities of oxygen through liquid PbO-SiO₂ and FeO-PbO-SiO₂ were found to be in the range 3 x 10^-8 to 3 x 1O^-7 moles/cm s. The permeabilities were little influenced by temperature but more influenced by the composition. In separate experiments, the oxygen pressure change at the bottom of a column of slag was detected by another galvanic cell. By this method, it is not necessary to quench the specimen to determine the concentration profile of dissolved oxygen and to determine its diffusivity. Liquid oxides in the PbO-SiO₂, CaO-SiO₂-Al₂O₃and FeO-PbO-SiO₂ systems were studied. The oxygen diffusion coefficients (5 x 10^-5 to 3 x 10^-3 cm²/s) were found to increase with temperature for a fixed composition of slag, and with an increase of network-modifier oxide content at constant temperature. The solubility of oxygen gas in PbO-SiO₂ melts was estimated to be 2 x 10^-4 to 2 x 10^-5 moles/cm³ from the determined diffusivities and permeabilities. The solubilities decreased with increasing temperature in the composition range studied. Physical solubilities of gases and metals in slags determined by other investigators are compared with the present results.