Iwao Katayama

Measurements of standard molar Gibbs energies of formation of NiO, Cu2O, and CoO from solid and liquid metals and oxygen gas by an e.m.f. method at high temperatures

Abstract E.m.f. measurements of the following galvanic cells with the solid oxide electrolyte (ZrO 2 + CaO) were carried out to determine the standard molar Gibbs energies of formation of NiO, Cu 2 O, and CoO from solid and liquid metals and oxygen gas: (I) Pt|LaCrO 3 |Ni(s,1),NiO(s)|ZrO 2 +CaO|air|Pt, (II) Pt|LaCrO 3 |Cu(s,1),Cu 2 |ZrO 2 +CaO|air|Pt, (III) Pt|LaCrO 3 |Co(s,1),CoO(s)|ZrO 2 +CaO|air|Pt. The differences between the e.m.f.s of cells (I) and (II), and of cells (I) and (III) were compared with the e.m.f.s of the cells: (IV) Pt|Ni(s),NiO(s)|ZrO 2 +CaO|Cu(s,1),Cu 2 O(s,1)|LaCrO 3 Pt, (V) Pt|LaCrO 3 |Ni(s,1),NiO(s)|ZrO 2 +CaO|Co(s,1),CoO(s)|LaCrO 3 |Pt. The results were compared with previously reported values.

Comparative thermodynamic study and phase equilibria of the Bi-Ga-Sn ternary system

Abstract The results of a comparative thermodynamic investigation of the Bi – Ga – Sn system, giving experimentally obtained results and calculated thermodynamic data, are presented in this paper. Oelsen calorimetry was performed for the experimental determination of thermodynamic properties in the section with a molar ratio of Bi: Sn = 1: 3, while the Redlich – Kister – Muggianu method was applied for thermodynamic predicting in the sections with molar ratio Bi: Sn = 1: 3, 1: 1, 3: 1. Thermodynamic parameters – partial and integral molar quantities, as well as gallium activities, were determined at the temperatures of 873 and 973 K. Phase equilibria in the Bi – Ga – Sn ternary system have been studied experimentally – using differential thermal analysis and scanning electron microscopy with energy dispersive X-rays, while the calculation of phase diagram was done according to the CALPHAD method. The phase diagram of the section with molar ratio of Bi: Sn = 1: 3 is given, as well as the phase diagram of the ternary Bi – Ga – Sn system at 373 K.

Solubility limit and thermodynamic properties of oxygen in liquid nickel

The mole-fraction solubility limit xo∗ of O in liquid Ni has been measured in the temperature range 1722 to 1859 K by a phase-equilibration technique. The result is expressed by the relation: x∗O±0.020=-(25080±480)KT+(9.960±0.269) . The activities of O in liquid Ni at 1733, 1783, and 1833 K have been measured by means of zirconia solid-electrolyte cells with {Ni(l) + NiO(s)} reference electrodes. Based on the results, the standard Gibbs energy of solution ΔGo(O) of O in liquid Ni and the first-order self-interaction coefficient e of O are derived as follows: 12O2(g,101.325 kPa)=O(in liquid Ni, xO=0.01);δG°(O)/J mol-1±240=(70940±6100)-(8.90±3.43)(TK);ϵ±1.0=-(158900±46700)/(TK)+(75.8±26.2) .

Measurement of activity of gallium in GaSbIn alloys by emf method using zirconia as solid electrolyte

Abstract EMF of galvanic cells with zirconia solid electrolytes was measured to determine the activity of gallium in liquid GaSbIn alloys in the temperature range 1050–1150 K in the entire composition range. Fe, Fe x O mixtures were used as a reference electrode. Isoactivity curves in the ternary GaSbIn alloy were derived by combining the activity data of GaSb and GaIn alloys, and the shape of the curves exhibits a slight bend from the GaSb side to the GaIn side. The results were compared with literature data.

Activity Measurement of Liquid Sn-Ag-Bi Alloys by Fused Salt EMF Method

Activity of tin in liquid Sn-Ag-Bi alloys was derived by EMF measurement of galvanic cell with fused salts electrolyte in the temperature range of 700 to 900K in the whole composition range. Activity of tin at 900K shows very small positive deviation from Raoult’s low for Sn-Bi alloys. Activity of ternary alloys was measured along three pseudo binary systems of Sn-(Ag,Bi) (where xAg/xBi =1/3,1/1 and 3/1). Its concentration dependence is very complex. From the iso-activity curves in the ternary system excess free energy of mixing is derived using Darken’s method for Gibbs-Duhem equation

Thermodynamic properties and solubility limits of oxygen in liquid (nickel+copper) alloys

Abstract Oxygen activities in liquid (nickel+copper) alloys at 1733 K were measured by means of zirconia solid-electrolyte cells using a {Ni(l)+NiO(s)} reference electrode. Furthermore, oxygen solubility measurements were carried out for liquid (nickel+copper) alloys in equilibrium with NiO(s) by use of a phase-equilibration technique. Applying a new analytical method to the present results, the values of the activity coefficient of oxygen at infinite dilution γOo and of the first order self-interaction coefficient of oxygen eOO for {xNi + (1 − x)Cu} were determined at 1773 K as follows: x 1 0.9 0.8 0.7 0.6 γ O o 0.249 0.229 0.212 0.199 0.196 ±0.003 ±0.003 ±0.005 ±0.003 ±0.003 e O O −18.0 −17.2 −15.1 −11.8 −10.9 ±1.0 ±0.9 ±1.6 ±1.4 ±0.6 x 0.5 0.4 0.3 0.2 0.1 γ O o 0.193 0.206 0.208 0.268 0.324 ±0.006 ±0.004 ±0.007 ±0.006 ±0.013 e O O −9.7 −9.7 −8.9 −6.9 1.9 ±2.1 ±1.2 ±2.3 ±2.2 ±3.5

Experimental study on gallium activity in the liquid Ga-Bi-Sn alloys using the EMF method with zirconia solid electrolyte

Abstract The EMF of galvanic cells with zirconia solid electrolytes was measured to determine the activity of gallium in liquid Ga-Bi-Sn alloys in the temperature range of 1000–1250 K along three pseudo-binary lines of (Biy, Sn1−y)-Ga where y = 0.25, 0.50 and 0.75. A mixture of Ga and Ga203 was used as a reference electrode. The activity curves of Ga show positive deviations from ideality in the whole composition range. The excess free energies of mixing for Ga-Bi-Sn alloys have been calculated using the general solution model in the same temperature range and along same pseudo-binary lines. The gallium activities obtained by the EMF method and calculated using the general solution model at 1100 K were compared with literature data.

Activity measurements of Ga in liquid Ga - Tl alloys by EMF method with zirconia solid electrolyte

Abstract Electromotive force measurements (EMF) of an electrochemical cell with zirconia as solid electrolyte were performed to determine the Ga activity from 973 to 1273 K in the entire composition range of liquid Ga–Tl alloys. In the whole concentration range, the activity of Ga shows large positive deviations from ideality, and the activity of Tl which is derived by the Gibbs–Duhem equation shows also positive deviation from ideality. The parameters of the Redlich–Kister equation for excess Gibbs energies of mixing are determined from the results obtained in this study which were compared with Chous model calculation.

Measurements of standard molar Gibbs energies of formation of CoGa2O4 and NiGa2O4 by the e.m.f. method

E.m.f. measurements of the following galvanic cells with the solid electrolyte (ZrO2 + CaO) were carried out to determine the standard molar Gibbs energies of formation of CoGa2O4 and NiGa2O4. Pt|Re|Co,CoGa2O4, Ga2O3|(ZrO2 + CaO)|CoO,Co|Pt Pt|Re|Co,CoGa2O4, Ga2O3(ZrO2 + CaO)|air|Pt, Pt|Re|Ni,NiGa2O4, Ga2O3|(ZrO2 + CaO)|air|Pt. The values may be represented by CoO(s) + Ga2O3(s) = CoGa2O4(s); ΔGo/kJ mol−1 ± 0.12 = −22.47 − 4.999 × 10−3 (TK), (TK = 1207 to 1379), 2 Co(s) + 2Ga2O3(s) + O2(g) = 2CoGa2O4(s); ΔGo/kJ mol−1 ± 1.1 = −516.0 + 132.8 × 10−3(TK), (TK = 1057 to 1385), 2Ni(s) + 2Ga2O3(s) + O2(g) = 2NiGa2O4(s); ΔGo/kJ mol−1 ± 1.3 = −524.1 + 165.6 × 10−3(TK), (TK = 1075 to 1374).

Newly developed EMF cell with zirconia solid electrolyte for measurement of low oxygen potentials in liquid Cu-Cr and Cu-Zr alloys

In order to measure the very low oxygen potential by use of stabilized zirconia solid electrolyte emf method, a new cell construction was devised. The idea was based on Janke but a zirconia rod was used instead of the zirconia crucible which contacts liquid alloy electrode. The cell was used for determination of the oxygen potentials in liquid dilute Cu-Cr and Cu-Zr alloys. The reference electrode was Cr,Cr2O3. Emf measurements were performed in the temperature range of 1400-1580K and composition range of 0.198-3.10at%Cr-Cu alloys, and 1380-1465K, 0.085-0.761at%Zr-Cu alloys. The composition of liquid alloys were determined by picking up from the liquid alloys and ICP analysis. By use of the newly devised cell construction in this study, stable emf values were obtained at each temperature and alloy composition. Emf values were corrected by using the parameter for electronic contribution of the YSZ. Activity of Cr obeys Henry’s law and activity coefficient at infinitely dilute alloys of Cr in Cu-Cr alloys are: lng0 Cr =(3.80 at 1423K), (3.57 at 1473K), (3.38 at 1523K) and (3.20 at 1573K). At 1423 K activity coefficient of Zr at infinitely diluted alloy is lnγo Zr = -4.0.