The diffusion and solubility of oxygen in solid nickel

Solid-state electrochemical measurements using various experimental procedures were made with the double cell: $$ Ni + NiO|ZrO_2 + Y_2 O_3 |Ni + \underline O |ZrO_2 + Y_2 O_3 |Ni + NiO $$ to determine the diffusivity and thermodynamic functions of oxygen dissolved in solid nickel. Non-steady state diffusion of oxygen in the specimen was caused by applying a preselected potential between the reference and specimen electrodes and was monitored by measuring time-dependent potentials and/or currents. The following results were obtained for the diffusivity of oxygen and the solubility of oxygen in nickel in equilibrium with NiO: $$D{\text{ = 4}}{\text{.9 }} \times {\text{ 10}}^{{\text{ - 2}}} {\text{ exp}}\left( {{\text{ - }}\frac{{{\text{164 kJ/mole}}}}{{{\text{R}}T}}} \right){\text{cm}}^{\text{2}} /{\text{sec (850 to 1400 }}{}^{\text{o}}{\text{C)}}$$ $$C_{\text{O}}^s {\text{ = 8}}{\text{.3 exp}}\left( { - \frac{{55{\text{kJ/mole}}}}{{{\text{R}}T}}} \right){\text{at}}{\text{. pct (800 to 1000 }}{}^{\text{o}}{\text{C)}}$$ The thermodynamic and transport behaviors of oxygen in solid nickel were fairly well described by a simple quasi-regular model and an interstitial diffusion model, respectively.     

The thermodynamic properties of liquid Fe−Si alloys

The thermodynamic properties of liquid Fe?Si alloys have been determined electrochemically by use of the following galvanic cells: $$\begin{gathered} Cr - Cr_2 O_3 (s)|ZrO_2 (CaO)|Fe - Si(l), SiO_2 (s) \hfill \\ Cr - Cr_2 O_3 (s)|ThO_2 (Y_2 O_3 )|Fe - Si(l), SiO_2 (s) \hfill \\ \end{gathered} $$ The free energy of formation of SiO₂ was measured and is ?139.0 and ?134.3 kcals per mole at 1500° and 1600°C, respectively. The activity coefficients of iron and silicon for the atom fraction of siliconN _Si<0.35 at 1600° and 1500°C can be represented by the quadratic formalism. $$\begin{gathered} \left. {\begin{array}{*{20}c} {log \gamma _{Fe} = - 2.12 N_{Si}^2 } \\ {log \gamma _{Si} = - 2.12 N_{Fe}^2 - 0.22} \\ \end{array} } \right\}1600^ \circ C (2912^ \circ F) \hfill \\ \left. {\begin{array}{*{20}c} {log \gamma _{Fe} = - 2.50 N_{Si}^2 } \\ {log \gamma _{Si} = - 2.50 N_{Fe}^2 - 0.13} \\ \end{array} } \right\}1500^ \circ C (2732^ \circ F) \hfill \\ \end{gathered} $$ The results indicate that an excess stability peak occurs at about the equimolar composition. Combining the heats of solution determined in this study with previous data indicates that the heats also follow the quadratic formalism. The partial molar heats, \(\bar L_{Si} \) and \(\bar L_{Fe} \) , are represented by $$\begin{gathered} \bar L_{Si} = - 31 N_{Fe}^2 - 4 kcals per mole \hfill \\ \bar L_{Fe} = - 31 N_{Si}^2 kcals per mole \hfill \\ \end{gathered} $$ ForN _Si less than 0.35 and by $$\begin{gathered} \bar L_{Si} = - 22 N_{Fe}^2 \hfill \\ \bar L_{Fe} = - 22 N_{Fe}^2 - 7.0 \hfill \\ \end{gathered} $$ forN _Fe less than 0.35. There is an inflection point in the transition region similar to an excess stability peak for the excess free energies. At 1600°C the ThO₂(Y₂O₃) electrolyte exhibited insignificant electronic conductivity at oxygen partial pressures as low as that in equilibrium with Si?SiO₂ (2×10^?16 atm).     

Thermodynamic studies of liquid copper alloys by electromotive force method: Part II. The Cu−Ni−O and Cu−Ni systems

Oxygen activities in liquid Cu?Ni melts have been measured at 1100°, 1200°, and 1300°C by the solid electrolyte electromotive force method. Addition of nickel lowers the activity coefficient of oxygen in liquid copper. The temperature dependence of \( \in _{\rm O}^{(Ni)} \) can be represented as follows: 1 $$ \in _{\rm O}^{(Ni)} = 17.0 - (3.60 \times 10^4 / T)$$ The solubility and activity of oxygen in liquid Cu?Ni alloys in equilibrium with NiO were measured at 1400°C. Oxygen solubility decreases with increasing nickel in the alloys. Nickel activities in the liquid Cu?Ni system were also calculated from the electromotive force data. Copper activities were evaluated by the Gibbs-Duhem integration. Activities of copper and nickel deviate positively from ideality. The activity coefficient of nickel in the liquid Cu?Ni system at 1400°C can be represented by the Darken's formulation: In 2 $$\gamma _{Ni} = 1.323 (1 - N_{Ni} )^2 ; N_{Ni} = 0.55 to 0.77$$ In 3 $$\gamma _{Ni} = 1.000 (1 - N_{Ni} )^2 + 0.005; N_{Ni} = 0.0 to 0.3$$ Excess entropies in the liquid Cu?Ni system are less than 0.1 eu. A complete set of thermodynamic properties of the system can be calculated by combining the free energy data of this study with the estimated enthalpy data from literature sources.     

The glass-liquid and solid-jelly transition temperatures

The supercooled liquid undergoes a “glass transition” in whichC _p (I) decreases rapidly and approaches that ofC _p (s). The theoretical glass transition temperature T_{g,theoretical} is defined as the temperature below the melting point, whereS (l-s) = 0. Similarly, the overheated solid will undergo a transition, where the lattice softens, as the structure cannot support vibrations with larger and larger amplitudes.S (l-s), the entropy difference between liquid and solid, andG (l-s), the Gibbs energy difference between liquid and solid, cross the zero line above the melting point. WhereS (l-s) crosses the zero line, the entropy of the liquid becomes less than that of the superheated solid. We call this pointT _jS_theoretical. At a higher temperature, G (l-s) crosses the zero line, where the superheated solid becomes stable with respect to the liquid. We call this pointT _jG_theoretical. We do not know yet which of the two are technologically important. For example, what influence does 7T_jS_theoretical, orT _jG_theoretical have on the behavior of aluminum, which melts at a low temperature but is used up to very high temperatures in various alloys. We obtained (T _g, T_jS, andT _jG all theoretical) $$T_g /T_{mp} = (0.4018 \pm 0.1601) + (8.53 \pm 2.68) \cdot 10^{--5} \cdot T_{mp} , R = 0.5228;$$ $$T_g /T_{max} = (0.3816 \pm 0.1074) + (7.47 \pm 1.80) \cdot 10^{--5} \cdot T_{mp} , R = 0.6249;$$ $$T_g /T_j S = (0.1749 \pm 0.1023) + (7.55 \pm 1.71) \cdot 10^{--5} \cdot T_{mp} , R = 0.6470;$$ $$6S_{mp} /d = - (2.08 \pm 2.80) \cdot 10^{10} + (3.84 \pm 0.47) \cdot 10^{--7} \cdot T_{mp} , R = 0.8446;$$ $$T_{bp} /T_j S = 1.066 \pm 0.325;$$ $$T_{bp} /T_j G = 0.703 \pm 0.214$$ whereT _mp is the temperature of the standard melting point,T _bp is the standard boiling point, T_max is the temperature whereS (l-s) is maximum and C_p(l-s) = 0, andR is the regression coefficient.     

Determination of diffusion coefficient of oxygen in γ-iron from measurements of internal oxidation in Fe-Al alloys

The internal oxidation of iron alloys containing between 0.069 and 0.274 wt pct aluminum was investigated in the temperature range from 1223 to 1373 K for the purpose of determining the diffusion coefficients in γ-iron as well as in the internal oxidation layer. A parabolic rate law is obeyed in the internal oxidation of the present alloys. The rate constant for penetration of the oxidation front, the oxide formed, and the concentration of aluminum in the oxidation layer were determined. Pronounced enrichment of aluminum in the oxidation layer was observed, resulting from the counterdiffusion of aluminum. The oxygen concentration at the specimen surface was determined by combining the thermodynamic data on the dissociation of FeO and the solution of oxygen in y-iron. The diffusion coefficient of oxygen in the internal oxidation layer,D _o ¹⁰ , was evaluated on the basis of the rate equation for internal oxidation.D _o ¹⁰ increases at a given temperature as the volume fraction of oxide,f ¹⁰, in the oxidation layer increases. The diffusion coefficient of oxygen in γ-iron,D _o, was determined by extrapolation ofD _o ¹⁰ = 0.D _o may be expressed as $$D_o = \left( {1.30\begin{array}{*{20}c} { + 0.80} \\ { - 0.50} \\ \end{array} } \right) \times 10^{ - 4} \exp \left[ { - \frac{{166 \pm 5(kJ \cdot mol^{ - 1} )}}{{RT}}} \right]m^2 \cdot s^{ - 1} .$$ D _o is close to the diffusion coefficients of carbon and nitrogen in γ-iron.     

Mass-spectrometric determination of activities in Fe−Cr and Fe−Cr−Ni alloys

The Knudsen cell-mass spectrometer combination has been used to study the Fe?Cr system and some Fe?Cr?Ni liquid alloys. The Fe?Cr liquid alloys at 1600°C are found to be essentially ideal when referred to pure liquids as standard states. Phase equilibria over a limited composition range for this system are derived from the behavior of the ion-current ratios. The necessary equations are derived to apply the integration technique to the measured ion current ratios in a ternary system and the method is applied to the Fe?Cr?Ni system at 1600°C. The results are represented, within experimental error, by the following equations: forN _Fe≥0.6, $$\begin{gathered} ln \gamma _{Fe} = - 0.08 N_{Ni}^2 \hfill \\ \ln \gamma _{Cr} = 0.09 - 0.08 N_{Ni}^2 \hfill \\ \ln \gamma _{Ni} = - 0.26 - 0.08(1 - N_{Ni} )^2 \hfill \\ \end{gathered} $$ forN _Fe=0.45, $$\begin{gathered} \ln \gamma _{Fe} = - 0.20 N_{Ni}^2 \hfill \\ \ln \gamma _{Cr} = 0.09 - 0.20 N_{Ni}^2 \hfill \\ \ln \gamma _{Ni} = - 0.19 - 0.20(1 - N_{Ni} )^2 \hfill \\ \end{gathered} $$      

The Solubility and Diffusivity of Fluorine in Solid Copper from Electrochemical Measurements

The solubility and diffusivity of fluorine in solid copper were determined electrochemically using the double solid-state cell $$Ni + NiF_2 \left| {CaF_2 } \right|Cu\left| {CaF_2 } \right|Ni + NiF_2 .$$ In the temperature range 757 to 920°C, the diffusivity of fluorine in solid copper was found to be $$D_F \left( {{{cm^2 } \mathord{\left/ {\vphantom {{cm^2 } s}} \right. \kern-\nulldelimiterspace} s}} \right) = 9.32 \times 10^{ - 2} \exp \left( {\frac{{ - 98,910 {J \mathord{\left/ {\vphantom {J {mole}}} \right. \kern-\nulldelimiterspace} {mole}}}} {{RT}}} \right).$$ . The results obtained for the dissolution of fluorine as atoms in solid copper showed large scatter. However, the equilibrium dissolution of fluorine follows Sieverts’ law. Above the melting point (770°C) of CuF₂, the mean solubility of fluorine in solid copper, for the equilibrium Cu(s)+ CuF ₂(l), follows the relationship $$N_F^s (atom fraction) = 0.98 \exp \left( {\frac{{ - 79,500 {J \mathord{\left/ {\vphantom {J {mole}}} \right. \kern-\nulldelimiterspace} {mole}}}} {{RT}}} \right).$$      

Nitrogen diffusion and solubility in tungsten

The diffusion and solubility of nitrogen in tungsten were determed using an ultrahigh vacuum-and mass-spectrometric technique capable of measuring concentrations of 10^?2 ppm and degassing rates of 10^?3 ppm N per hr. The technique is based on measuring the degassing rate of nitrogen as a function of time from a resistivity heated tungsten wire previously engassed with nitrogen between 1 and 25 torr. The diffusion and solubility constants between 1000° and 1800°C may be summarized by $$D = (2.37 \pm 0.43) \times 10^{ - 3} \exp [( - 35,800 \pm 3900)/RT] cm^2 /\sec ,$$ , and $$S = (0.21 \pm 0.06) \exp [( - 17,600 \pm 5900)/RT] torr \cdot liter cm^{ - 3} torr^{ - 1/2} .$$ . The concentration of nitrogen in tungsten at 760 torr according to these results are 0.4 and 9.2 ppm at 1000° and 2000°C, respectively. The expression for the permeation constants calculated fromD andS is $$K = 5 \times 10^{ - 4} \exp ( - 53,400/RT) torr \cdot liter cm^{ - 1} sec^{ - 1} torr^{ - 1/2} .$$ .     

The kinetics of formation of h2o and co2 during iron oxide reduction

The kinetics of the chemical reaction-controlled reduction of iron oxides by H₂/H₂O and CO/CO₂ gas mixtures are discussed. From an analysis of the systems it is concluded that the decomposition of the oxides takes place by the two dimensional nucleation and lateral growth of oxygen vacancy clusters at the gas/oxide interface. The rates of decomposition of the oxides under conditions of chemical reaction control are dependent not only on the partial pressures of the reacting gases at the reaction temperature but also on the oxygen activity of the prevailing atmosphere. Application of this model to the kinetic data leads to the determination of the maximum chemical reaction rate constants for the decomposition of the iron oxide surfaces. Assuming the reactions H₂ (g) + O(ads) → H₂O(g) andCO(g) + O(ads) → CO₂ (g) to be rate controlling the maximum chemical reaction rate constants for the reduction of iron oxides are given by $$\Phi _{{\text{H}}_{\text{2}} } = 10^{.00} exp \left( {\frac{{ - 69,300}}{{RT}}} \right)mol m^{ - 2} s^{ - 1} atm^{ - 1} $$ and $$\Phi _{CO} = 10^{4.40} \exp \left( {\frac{{103,900}}{{RT}}} \right)mol m^{ - 2} s^{ - 1} atm^{ - 1} $$ The maximum chemical reaction rate constants do not necessarily indicate the maximum rates which can be achieved in practice since these will depend on the limitations imposed by mass transport in the systems. The rate constants are important however since they indicate for the first time the upper limit of any reduction rate in these systems. The fractions of reaction sites which appear to be active on wüstite surfaces in equilibrium with iron are calculated. A direct relationship between chemical reaction rates on liquid iron surfaces and rates on atomically rough iron oxide surfaces is postulated.     

Thermodynamic properties of the liquid Sn−Ge and Sn−Au systems by mass spectrometry

The activities and partial molar heats of mixing have been determined for the liquid Sn?Ge system at 1773 K and the liquid Sn?Au system at 1873 K. The experimental technique consisted of analyzing Knudsen cell effusates with a TOF mass spectrometer. The ion current ratios for the monomeric vapor species were measured as a function of temperature and composition and the thermodynamic properties calculated using a modified form of the Gibbs-Duhem equations. In addition to exhibiting very slight positive deviation from ideal behavior, the Sn?Ge system displayed parabolic solution behavior over the entire composition range. The results for the excess partial molar free energies and partial molar heats of mixing for the Sn?Ge system can be represented by $$G_1^E = 3.06X_2^2 kJ/g \cdot mol$$ and $$H_1^M = 5.86X_2^2 kJ/g \cdot mol$$ at 1773 K. The Sn?Au system exhibited negative deviation from ideal behavior and the results can be partially represented by $$\begin{gathered} \log _{10} \gamma Au = - 0.388 - 0.650 X_{Sn}^2 (0.00 \leqslant X_{Au} \leqslant 0.30) \hfill \\ \log _{10} \gamma Sn = 0.658 - 2.63 X_{Au}^2 (0.00 \leqslant X_{Sn} \leqslant 0.25) \hfill \\ \end{gathered} $$ and $$H_1^M = - 61.7 X_2^2 kJ/g \cdot mol$$ at 1873 K. Comparison of the results with other investigations indicates the heat of mixing for the system becomes more exothermic with increasing temperature above 1100 K. An experimental technique is presented for determining the effect of dissociative ionization of molecular species on the activity coefficient. The effect of dissociative ionization of the molecular species present in the Knudsen cell effusate was determined to be negligible.     

A mass-spectrometric study of the thermodynamics of the Fe−Cu and Fe−Cu−C(sat) systems at 1600°C

The Knudsen cell-mass spectrometer combination has been used to study the Fe?Cu and Fe?Cu?C_(sat) alloys at 1600°C. Activity coefficients in the Fe?Cu system are closely represented by the equations $$\begin{gathered} \ln \gamma _{Fe} = 1.86N_{Cu}^2 + 0.03, (0< N_{Fe}< 0.7) \hfill \\ \ln \gamma _{Cu} = 2.25N_{Fe}^2 - 0.19, (0.7< N_{Fe}< 1.0) \hfill \\ \end{gathered} $$ with an uncertainty in the quadratic terms of about 5 pct. For the iron-rich carbon-saturated alloys, the activity coefficient of copper is given by the equation $$\ln \gamma _{Cu} = 2.45(N'_{Fe} )^2 + 0.3N'_{Fe} + 0.03, (0< N'$$ to within an uncertainty of about 10 pct. N _Fe ^′ represents the fraction N_Fe/(N_Fe+N_Cu), etc. The activity coefficient of iron in this region is found to be essentially constant at 0.69±0.05.     

Chemical potentials of oxygen for mixtures of CaO (s) + Ca4P2O9 (s) + {CaO + P2O5 + FexO} melts and Ca4P2O9 (s) + Ca3P2O8 (s) + {CaO + P2O5 + FexO} melts

Electrochemical measurements involving stabilized zirconia as solid electrode and Mo + MoO₂ as reference electrode were conducted in order to determine the chemical potentials of oxygen for threephase assemblages of CaO (s) + Ca₄P₂O₉ (s) + liquid and Ca₄P₂O₉ + Ca₃P₂O₈ + liquid within the system CaO + Fe_xO + P₂O₅. The results for the former are $$\log (P_{O_2 } /atm) = 6.22 - 27,900 (T/K)$$ while for the latter, $$\log (P_{O_2 } /atm) = 6.35 - 27,600 (T/K)$$      

Thermodynamic properties of the Cu−Sn and Cu−Au systems by mass spectrometry

The activities and partial molar heats of mixing have been determined in the liquid Cu?Sn system at 1320°C and the liquid Cu?Au system at 1460°C. The experimental technique consisted of the analysis of Knudsen cell effusates with a T.O.F. mass spectrometer. The ion current ratio for the alloy components was measured for each system over a range of temperature and composition and the thermodynamic values calculated by a modified Gibbs-Duhem equation. Both systems exhibited negative deviations from ideal behavior. The results can be partially represented by the equations $$\begin{gathered} \log \gamma _{Cu} = - 0.0175x^2 _{Sn} - 0.302 (0 \leqslant x_{Cu} \leqslant 0.20) \hfill \\ log \gamma _{Sn} = - 0.342x^2 _{Cu} + 1.084(0 \leqslant x_{Sn} \leqslant 0.20) \hfill \\ \end{gathered} $$ for the Cu?Sn system at 1320°C and by $$\begin{gathered} \log \gamma _{Cu} = - 0.703x^2 _{Au} - 0.083(0 \leqslant x_{Cu} \leqslant 0.52) \hfill \\ \log \gamma _{Au} = - 1.057x^2 _{Cu} + 0.098(0 \leqslant x_{Au} \leqslant 0.47) \hfill \\ \end{gathered} $$ for the Cu?Au system at 1460°C.     

An Insight into Slag Structure from Sulphide Capacities

The molar sulphide capacities $ C_{\text{S}}^{'} $ ?=?(mol?pct?S) ( $ P_{{{\text{O}}_{2} }} /P_{{{\text{S}}_{2} }} $ )^1/2 on four binary systems, MgO-SiO₂, CaO-SiO₂, MnO-SiO₂ and FeO-SiO₂ are elucidated so as to compare the magnitudes of the basicities of four metallic oxides and to estimate the temperature dependencies of the basicities of metallic oxides. The enthalpy changes of the reaction?2O^??=?O?+?O^2?, viz. the silicate polymerization reaction (denoted as $ \Updelta H_{(8)}^{^\circ } $ ) have been calculated from the slopes of the log $ C_{\text{S}}^{'} $ vs 1/T curves for four binary silicates. The $ \Updelta H_{(8)}^{^\circ } $ value is considered in the present work to be an index of the basicity of silicate melts. The basicities obtained on the basis of the $ \Updelta H_{(8)}^{^\circ } $ values are in the order MgO?<?CaO?<?MnO?<?FeO, which are determined by two effects; (i) ionicity of chemical bonds between metallic and oxygen ions and (ii) clustering of metallic oxides in silicates. It is also found that the basicity of the FeO-SiO₂ system is larger at higher temperatures.     

Interdiffusivities matrix of CaO-Al2O3-SiO2 melt at 1723 K to 1823 K

Ternary oxide mixtures of lime, alumina, and silica were premelted and quenched to produce glassy cylinders. A diffusion couple was selected from the mixtures of six different compositions in such a way that the average composition could be 40 wt pct CaO-20 wt pct A1₂O₃ = 40 wt pct SiO₂. Penetration curves of the components were measured with a X-ray microprobe analyzer. The interdiffusivities matrix defined with the Matano interface has been obtained from 52 successful diffusion runs at 1723 K to 1823 K as follows; 1 $$\begin{gathered} \tilde D_{10 - 10}^{30} = 8.9 \times 10^{ - 11} \exp ( - \frac{{253,700}}{{RT}})(m^2 /s) \hfill \\ \tilde D_{10 - 20}^{30} = - 2.5 \times 10^{ - 11} \exp ( - \frac{{194,300}}{{RT}})(m^2 /s) \hfill \\ \end{gathered} $$ 2 $$\begin{gathered} \tilde D_{20 - 10}^{30} = - 4.0 \times 10^{ - 11} \exp ( - \frac{{177,600}}{{RT}})(m^2 /s) \hfill \\ \tilde D_{20 - 20}^{30} = 6.12 \times 10^{ - 11} \exp ( - \frac{{318,400}}{{RT}})(m^2 /s) \hfill \\ \end{gathered} $$ where symbols, 10, 20, and 30 mean CaO, A1₂O₃, and SiO₂, respectively, and the activation energies are in Joules per mole. The diffusion composition paths obtained are discussed in relation to Cooper’s parallelogram. The composition dependency of the above interdiffusivities is estimated from the quasibinary interdiffusivities in all composition ranges of the present oxide system in liquid state.     

Mass spectrometric determination of activities for alloys with complex vapor species: Bi-Pb and Bi-Tl

For solutions from which complex species vaporize (Bi₂, Si₂, Al₂O, Sb₄, and so forth) new methods of determining the thermodynamic properties from mass spectrometric data are demonstrated. In order to test the feasibility of these new techniques, experiments have been carried out on the liquid Bi-Pb and Bi-Tl systems for which adequate thermodynamic data are available. In evaluating the thermodynamic properties, the ion current ratiosI _Pb ⁺/IBi₂/+ andI _Tl ⁺/IBi₂/+ were employed,e.g. $$\log {\text{ }}\gamma _{{\text{Bi}}} {\text{ = - }}\mathop {\int {\frac{{N_{Pb} }}{{1{\text{ + }}N_{Pb} }}d} }\limits_{N_{Bi} = 1}^{N_{{\text{Bi}}} = N_{Bi} } {\text{ }}\left\{ {{\text{log}}\frac{{{\text{1}}_{{\text{Pb}}}^{\text{ + }} {\text{ }}N_{Bi}^2 }}{{I_{Bi2}^ + {\text{ }}N_{Pb} }}} \right\}$$ Measuring these particular ion current ratios eliminates errors resulting from the fragmentation of the complex vapor species in evaluating the thermodynamic properties. A dimer-monomer technique, which corrects for fragmentation, was also demonstrated. The results using these two independent approaches are in good agreement with each other as well as with previous investigations. The activity coefficients in both systems adhere to the quadratic formalism over large composition ranges,e.g. $$\begin{gathered} \log {\text{ }}\gamma _{{\text{Pb}}} {\text{ = - 0}}{\text{.255 }}N_{Bi}^2 {\text{ }}N_{{\text{Bi}}} {\text{< 0}}{\text{.8}} \hfill \\ \log {\text{ }}\gamma _{{\text{Tl}}} {\text{ = - 0}}{\text{.805 }}N_{Bi}^2 {\text{ }}N_{{\text{Bi}}} {\text{< 0}}{\text{.7}} \hfill \\ \end{gathered} $$      

Thermodynamic properties of the liquid Ge-Cu and Ge-Au systems by mass spectrometry

The activities and partial molar heats of mixing have been determined for the liquid Ge-Cu system at 1525°C and the liquid Ge-Au system at 1400°C. The experimental technique consisted of analyzing Knudsen cell effusates with a TOF mass spectrometer. The ion current ratios for the monomeric vapor species were measured as a function of temperature and composition and the thermodynamic properties calculated using a modified form of the Gibbs-Duhem equations. Both systems exhibited negative deviations from ideal behavior. The results for the Raoultian activity coefficients can be partially represented by $$\begin{gathered} \log \gamma _{Ge} = - 2.521X_{Cu}^2 + 0.948 (0 \leqslant X_{Ge} \leqslant 0.2) \hfill \\ \log \gamma _{Cu} = - 0.048X_{Ge}^2 - 0.466 (0 \leqslant X_{Cu} \leqslant 0.2) \hfill \\ \end{gathered} $$ for the Ge-Cu system at 1525°C and by $$\begin{gathered} \log \gamma _{Ge} = - 2.327X_{Au}^2 + 0.465 (0 \leqslant X_{Ge} \leqslant 0.35) \hfill \\ \log \gamma _{Au} = - 0.510X_{Ge}^2 - 0.489 (0 \leqslant X_{Au} \leqslant 0.30) \hfill \\ \end{gathered} $$ for the Ge-Au system at 1400°C. An experimental technique is presented for determining the contribution of dissociative ionization of polymer species to the measured monomeric ion current ratio . The effect of dissociative ionization of the germanium polymer species present in the Knudsen ceil effusate was determined to be negligible.