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Two studies have been carried out, one to determine the conditions for the equilibrium between nickel, nickel oxide, carbon dioxide, and carbon monoxide, and the second to determine the kinetics of the oxidation of nickel in carbon dioxide and in CO2/CO mixtures. The equilibrium conditions determined over the temperature range 580~176 are given by the equation ( Pco ~ _ 2381 0.025 log10 \~ TThe kinetic study covered the behavior of pure nickel, commercial impure nickel, and nickel dispersion strengthened with alumina or thoria within the temperature range 700~176The reaction rates were significantly reduced by the normal impurities in commercial nickel and by water vapor in the carbon dioxide. It was deduced that the oxidation rate was at least partially governed by a reaction at the oxide/gas interface and that considerable plastic flow occurred in the oxide scales.The present paper covers the oxidation of nickel and oxide dispersion strengthened nickel by carbon dioxide and COJCO mixtures at elevated temperatures. Examination of the relevant thermodynamic data reveals that the concentration of carbon monoxide necessary to prohibit the formation of nickel oxide in CO2/CO mixtures is small, but considerable scatter exists in the values which can be calculated or have been determined directly for this concentration. The first studies in the present work involved therefore an accurate determination of the conditions for equilibrium between nickel, nickel oxide, carbon dioxide, and carbon monoxide Ni+ CO2~NiO § CO These studies were followed by kinetic studies of the oxidation of four grades of nickel, including oxide dispersion strengthened nickel, in primarily carbon dioxide over the temperature range 700~176 although some work was also carried out with CO2/CO mixtures and oxygen. By comparison with previous work the exposure times were long (e.g., 1000 hr). The data obtained in the equilibrium studies were in the midst of most of those published previously, while the kinetic studies extended previous work. Thermodynamic StudyThe conditions for the equilibrium have been studied previously by four major groups of workers (1-4) and may be calculated from a summary of the thermodynamic data (5) for the four components. The various sets of work are not in good agreement as the values for the ratio of the partial pressures of the two gases at equilibrium at a given temperature can vary by up to a factor of 10. In the present work the equilibrium was studied directly over the temperature range 580 ~ 1016~ Experimental A standard technique was used in which a CO2/CO gas mixture was circulated round a closed loop containing a heated mixture of nickel and nickel oxide. When equilibrium was established samples of the gas mixture were taken and analyzed by two methods, one in which the total pressure and the carbon monoxide partial pressure were measured manometrically and with a McLeod gauge, respectively, and the other using the tracer 14C in the gas and a Geiger-Mueller end window counter attached to the gas circuit. ...

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