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     

Diffusivity and solubility of oxygen in solid copper using potentiostatic and potentiometric techniques

The diffusivity and solubility of oxygen in solid copper have been determined in the temperature range 700 to 1030 °C using potentiostatic and potentiometric techniques. The results are summarized by the following equations: _Do ^Cu = _1.16-0.31 ^+0.42 × 10⁻² exp(−67300 ± 3000/RT) cm² per second; _No ^s = 154 exp(−149600/RT)atom fraction of oxygen where R is in joules/degree/mole. The experimentally determined value of the pre-exponential factor in the diffusivity equation is found to be consistent with Zener’s model for an interstitial diffusion mechanism. on leave of absence from the Banaras Hindu University, India     

Hydrogen permeation through coated and uncoated WASPALOY

Hydrogen permeability, diffusivity, and solubility have been measured for a Ni-base superalloy, WASPALOY,* over the temperature range of 200 to 560 °C. Measurements were made with various surface conditions. The hydrogen diffusivity and permeability values for Pd-coated WASPALOY were between those for pure nickel and for austenitic stainless steel. Hydrogen in uncoated WASPALOY had consistently lower effective diffusivity and permeability than in the Pd-coated condition. Gold-plating on WASPALOY or adding H₂O to H₂ gas substantially reduced both transport parameters, presumably due to slower surface or interface kinetics and lower permeability of hydrogen in the gold layer. Independently measured hydrogen solubility determined by equilibration of bulk specimens with H₂ gas was roughly 60 pct of the solubility obtained by dividing the effective diffusivity into the permeation constant. This is discussed on the basis of internal trapping, which reduced the effective diffusivity and resulted in a higher apparent solubility. WASPALOY is a trademark of United Technologies Corporation. T-P. Perng, Formerly Postdoctoral Associate at the University of Illinois M.J. Johnson, Formerly Student Assistant at the University of Illinois     

Carbon Solubility in the CaO-SiO2-3MgO-CaF2 Slag System

The carbon solubility in the CaO-SiO₂-3MgO-CaF₂ slag system at 1773 K (1500 °C) was investigated under CO/Ar and CO/N₂ gases. Higher extended basicity [(CaO + MgO)/SiO₂) increased the carbon solubility in the slag as the activity of free oxygen ions ( $ \varvec{a}_{{{\mathbf{O}}^{2 - } }} $ ] promoted the reaction of the free carbide mechanism. Higher CaF₂ also resulted in higher carbon dissolution into the slag as fluorine ions interact with the bridged oxygen (O⁰) in the melt structure to increase the activity of the free oxygen ions in the melt. Structural information obtained from the Fourier transformed infra-red (FT-IR) and Raman revealed a depolymerization of the network structure as the simpler structural units of NBO/Si = 4 increased and the Si-O-Si bending vibrations decreased with higher basicity and CaF₂ content. This correlated well with higher free oxygen ions (O^2?) in the slag system and subsequently higher carbon dissolution. A correlation of the theoretical optical basicity (Λ_th) with the logarithm of the carbon content in slag showed a relatively similar trend and an increase of carbon was observed with higher optical basicity.     

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.     

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.     

Dissolution Behavior of Indium in CaO-SiO2-Al2O3 Slag

The solubility of indium in a molten CaO-SiO₂-Al₂O₃ system was measured at 1773 K (1500 °C) to establish the dissolution mechanism of indium under a highly reducing atmosphere. The solubility of indium increases with increasing oxygen potential, whereas it decreases with increased activity of basic oxide. Therefore, a dissolution mechanism of indium can be constructed according to the following equation:

The Thermodynamic Behavior of Copper in the CaO-B<Subscript>2</Subscript>O<Subscript>3</Subscript> and BaO-B<Subscript>2</Subscript>O<Subscript>3</Subscript> Slag System

The Cu solubility was measured in the CaO-B₂O₃ and BaO-B₂O₃ slag systems to understand the dissolution mechanism of Cu in the slags. The Cu solubility had a linear relationship with oxygen partial pressure in the CaO-B₂O₃ slag system, which corresponds with previous studies. Also, the Cu solubilities in slag decreased with increasing the slag basicity, which value of slope was close to –0.5 in logarithmic form. From the results of experiment, the Cu dissolution mechanism established as follows:

Solubility and activity of oxygen in liquid germanium and germanium-copper alloys

The solubility of oxygen in liquid germanium in the temperature range 1233 to 1397 K, and in liquid germanium-copper alloys at 1373 K, in equilibrium with GeO₂ has been measured by the phase equilibration technique. The solubility of oxygen in pure germanium is given by the relation log(at. pct 0)=-6470/T + 4.24 (±0.07). The standard free energy of solution of oxygen in liquid germanium is calculated from the saturation solubility, and recently measured values for the free energy of formation of GeO₂, assuming that oxygen obeys Sievert’s law up to the saturation limit. For the reaction, 1/2 O₂(g)→O_Ge ΔG° = -39,000 + 3.21T (±500) cal = -163,200 + 13.43T (±2100) J. where the standard state for dissolved oxygen is that which makes the value of activity equal to the concentration (in at. pct), in the limit, as concentration approaches zero. The effect of copper on the activity of oxygen dissolved in liquid germanium is found to be in good agreement with that predicted by a quasichemical model in which each oxygen was assumed to be bonded to four metal atoms and the nearest neighbor metal atoms to an oxygen atom are assumed to lose approximately half of their metallic bonds. On leave at the Department of Metallurgy and Materials Science, University of Toronto, when this investigation was undertaken.     

Oxygen pressure dependence of tracer diffusivities of Ca and Fe in liquid CaO-SiO2-FexO system

The tracer diffusivities of calcium and iron in a steel-making slag of 33 pct CaO-27 pct SiO₂-40 pct Fe₂O₃ by charge composition have been measured at 1360 to 1460°C as a function of temperature and oxygen pressure in the gas phase. The results expressed in cm²/s (in SI unit of m²/s, the following equation should be divided by 10,000) are given by $$D^{tr} = D_0 \left[ {P_{O_2 } } \right]^{1/\chi } \exp \left[ { - \frac{E}{{RT}}} \right](at 1360 to 1460^\circ C)$$ where for tracer diffusion of iron, D_o is 0.2,x is 8.5, andE is 26 kcal/mol (1.09 x 10⁴ J/ mol) and for tracer diffusion of calcium, D_o is 0.1,x is 12.5, andE is 28 kcal/mol (1.17 × 10⁴ J/mol). Prior to diffusion runs, the slag was equilibrated with the gas mixture of carbon monoxide and dioxide with an oxygen pressure of 10^?11 to 10^?8 atm. The diffusivity was measured by the instantaneous plane source method, using radioactive tracers of calcium and iron. The increase of the tracer diffusivities with the oxygen pressure was interpreted in relation to a probable increase of the divalent cation vacancies in the slag.     

Solubility and thermodynamic properties of oxygen in solid molybdenum

The solubility of oxygen in solid Mo, determined in the range 1400 to 1900°C by equilibrating rods of zone-refined Mo with mixtures of Mo and MoO₂ powders, can be expressed as ln Χ_O ^α(sat) (atom fraction) = 5.86 - 27,900/T Using the known value of the free energy of formation of MoO₂, the chemical potential of oxygen in the dilute solid solution is calculated to be μ^α _O1/2μ^o _O2 = ΔG ^α _O = -10,760 + (6.92 +R ln χ^μ _O)T ± 1000 cal/g-atom oxygen The heat of solution of oxygen in Solid Mo, ΔH_Oα = -10,760 ± 3000 cal/g-atom oxygen, and the excess entropy for the interstitial solid solution ΔS_Oα(xs, i) =- 9.10 ± 1.5 cal/degree, g-atom oxygen, assuming that the oxygen atoms reside in the octahedral interstices of bcc Mo.     

Dissolution Mechanism of Indium in CaO-Al2O3-SiO2 Slag at Low Silica Region

The solubility of indium was measured in the low-silica region (<20?mass pct SiO₂) of the CaO-Al₂O₃-SiO₂ system by a thermochemical equilibration technique. The dissolution mechanism of indium into the CaO-Al₂O₃-SiO₂ slag at 1773?K (1500?°C) under a reducing atmosphere was elucidated. The indium solubility increases in the calcium silicate-based flux and decreases in the calcium aluminate-based flux with increasing oxygen partial pressure. Also, the solubility was found to decrease initially with increasing slag basicity until the basicity reached a critical level after which the solubility increases. This behavior is believed to indicate that the indium dissolution mechanism changes according to the basicity of the slag.     

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.     

Dissolution of alumina in mold fluxes

The solubility and rate of dissolution of alumina in a range of mold fluxes in the CaO-Al₂O₃-SiO₂-Na₂O-CaF₂ system have been measured at 1530 °C using the rotating finger method. The solubilities were approximately 38 pct for all fluxes studied. The kinetics of dissolution were correlated with the Levich-Chochran equation for a rotating disc and used to determine the effective diffusivity of alumina. The effective diffusivity was inversely proportional to the viscosity of the flux and showed excellent agreement with previous work on CaO-Al₂O₃-SiO₂ slags. This is in keeping with either the Eyring relation or the Stokes-Einstein relation. The value obtained for the size of the diffusing unit when the Stokes-Einstein relation was used, 1.81 Å, was more reasonable, which is not normally expected for silicate slags. This result is explained by the low level of polymerization in these fluxes.     

The diffusion of hydrogen in liquid iron alloys

Rates of absorption of hydrogen in stagnant liquid iron and ten (Fe-X) binary iron alloy systems were studied by an unsteady-state gas-liquid metal diffusion cell technique. These rates were found to be controlled by diffusion of hydrogen in the liquid phase. Chemical diffusion coefficients (D _h) were measured in pure iron and Fe-X alloys in the following (at. pct) composition ranges: Mn (0 to 5), Cr (0 to 25), V (0 to 25), Nb (0 to 10), Mo (0 to 25), W (0 to 5), Ni (0 to 75), Co (0 to 75), Sn (0 to 10), and Cu (0 to 25). All measuredD _H values at 1600°C lie between 7 × 10^-4 and 16 × 10^-4 sq cm per sec. The diffusion coefficients found for pure iron can be represented by D_H ^Fe = 4.37 × 10⁻³ exp (−4134 ± 1012)/RT cm²/sec where the uncertainty in the activation energy, Q, in cal per mole, corresponds to the 90 pct confidence level. A linear relationship was found between the logarithm of the hydrogen diffusion coefficient D_H ^Fe-X and the interaction parameter ε_H ^X for low and medium concentrations of alloying elementX, when applied to a fixed concentration ofX(5 or 25 at. pct) and to individual periods in the periodic table. A useful linear correlation also appears to exist between logD_H ^Fe-X and hydrogen solubility for fixed concentration ofX and with respect to the period in whichX is found. Formerly Research Assistant, Department of Mineral Engineering, Stanford University, Stanford, Calif. This paper is based upon a thesis submitted by P. J. DEPUYDT in partial fulfillment of the requirements of the degree of Doctor of Philosophy at Stanford University and part of a presentation made at the 1970 Annual AIME Meeting.     

Activities in liquid Fe−Al−O and Fe−Ti−O alloys

The solubility and activity of oxygen in Fe?Al and Fe?Ti melts at 1600°C were measured. The activity was measured electrochemically using the following galvanic cells: Cr-Cr₂O₃(s) ? ThO₂(Y₂O₃) ? Fe-Al-O(l), Al₂O₃(s) Cr-Cr₂O₃(s) ? ThO₂(Y₂O₃) ? Fe-Ti-O(l, saturated with oxide) Cr-Cr₂O₃(s) ? ZrO₂(CaO) ? Fe-Ti-O(l, saturated with oxide) Aluminum and titanium decrease the solubility of oxygen in liquid iron to a minimum of 6 ppm at 0.09 wt pct Al and 40 ppm at 0.9 wt pct Ti, respectively. The value of the interaction coefficients ε ₀ ^(Al) and ε ₀ ^(Ti) are ?433 and ?222, respectively. the activity coefficient of aluminum at infinite dilution in liquid iron is 0.021, while that of titanium is 0.038. The value of the aluminum equilibrium constant, the solubility product at infinite dilution, is 5.6×10^?14 at 1600°C. The ThO₂(Y₂O₃) electrolyte exhibited insignificant electronic conductivity at 1600°C down to oxygen partial pressures of 10^?15 atm, which corresponds to about 0.3 ppm O in unalloyed iron.     

Oxygen pressure dependence of tracer diffusivities of ca and fe in liquid CaO-SiO2-FexO system

The tracer diffusivities of calcium and iron in a steel-making slag of 33 pct CaO-27 pct SiO₂-40 pct Fe₂O₃ by charge composition have been measured at 1360 to 1460°C as a function of temperature and oxygen pressure in the gas phase. The results expressed in cm₂/s (in SI unit of m₂/s, the following equation should be divided by 10,000) are given by $$D^{tr} = D_0 [P_{O_2 } ]^{1/x} \exp \left[ { - \frac{E}{{RT}}} \right] (at 1360 to 1460^\circ C)$$ where for tracer diffusion of iron,D _o is 0.2,x is 8.5, andE is 26 kcal/mol (1.09 x 10⁴ J/ mol) and for tracer diffusion of calcium,D _o is 0.1,x is 12.5, andE is 28 kcal/mol (1.17 x 10⁴ J/mol). Prior to diffusion runs, the slag was equilibrated with the gas mixture of carbon monoxide and dioxide with an oxygen pressure of 10^-1 to 10^-8 atm. The diffusivity was measured by the instantaneous plane source method, using radioactive tracers of calcium and iron. The increase of the tracer diffusivities with the oxygen pressure was interpreted in relation to a probable increase of the divalent cation vacancies in the slag.     

Mechanism and optimization of oxide fluxes for deep penetration in gas tungsten arc welding

Five single oxide fluxes—Cu₂O, NiO, SiO₂, CaO, and Al₂O₃—were used to investigate the effect of active flux on the depth/width ratio in SUS304 stainless steel. The flux quantity, stability, and particlesize effect on the weld-pool shape and oxygen content in the weld after welding was studied systematically. The results showed that the weld depth/width ratio initially increased, followed by a decrease with the increasing flux quantity of the Cu₂O, NiO, and SiO₂ fluxes. The depth/width ratio is not sensitive to the CaO flux when the quantity is over 80×10⁻⁵ mol on the 5×0.1×50 mm slot. The Al₂O₃ flux has no effect on the penetration. The oxygen content dissolved in the weld plays an important role in altering the liquid-pool surface-tension gradient and the weld penetration. The effective range of oxygen in the weld is between 70 and 300 ppm. A too-high or too-low oxygen content in the weld pool does not increase the depth/width ratio. The decomposition of the flux significantly depends on the flux stability and the particle size. Cu₂O has a narrow effective flux-quantity range for the deep penetration, while the Al₂O₃ flux has no effect. The SiO₂ flux with a small particle size (0.8 or 4 μm) is a highly recommended active flux for deep penetration in actual gas tungsten arc welding (GTAW) applications.     

Solubility and activity of oxygen in liquid germanium and germanium-copper alloys

The solubility of oxygen in liquid germanium in the temperature range 1233 to 1397 K, and in liquid germanium-copper alloys at 1373 K, in equilibrium with GeO2 has been measured by the phase equilibration technique. The solubility of oxygen in pure germanium is given by the relation R470 log(at. pct 0)=-6470/T+4.24 (±0.07). The standard free energy of solution of oxygen in liquid germanium is calculated from the saturation solubility, and recently measured values for the free energy of formation of GeO₂, assuming that oxygen obeys Sievert’s law up to the saturation limit. For the reaction, 1/2 O₂(g)→ OGe ΔG° =-39,000 + 3.21T (±500) cal = -163,200 + 13.43T (±2100) J. where the standard state for dissolved oxygen is that which makes the value of activity equal to the concentration (in at. pct), in the limit, as concentration approaches zero. The effect of copper on the activity of oxygen dissolved in liquid germanium is found to be in good agreement with that predicted by a quasichemical model in which each oxygen was assumed to be bonded to four metal atoms and the nearest neighbor metal atoms to an oxygen atom are assumed to lose approximately half of their metallic bonds. K. FITZNER was on leave at the Department of Metallurgy and Materials Science, University of Toronto, when this investigation was undertaken.     

The surface tension of liquid silver alloys: Part II. Ag−O alloys

The surface tensions of liquid Ag-O alloys have been determined by the sessile drop method. The surface activity of oxygen, as measured by ?(dσ/dX _O)X_O→0_j, where σ is the surface tension of the metal andX _O the mole fraction of oxygen, is quite large and equals 3.80×10⁵ dyne per cm at 980°C and 1.35×10⁵ dyne per cm at 1108°C. The heat of adsorption of oxygen is estimated to be of the order of 30 kcal per mole. Application of the monolayer approximation shows that liquid silver becomes saturated with oxygen when each adsorbed oxygen atom occupies an area of 33±5Ų. Small additions of platinum to silver do not change the characteristics of the adsorption of oxygen appreciably. An analysis of the data is consistent with the conclusion that saturation of the surface of liquid silver with oxygen results from the formation of an ionic two-dimensional compound at the surface. This hypothesis is tested in the case of several other systems and yields satisfactory results. The structure of these compounds is discussed. In the case of the Ag-O system, it appears to correspond to the stoichiometry Ag₃O.