Solubility and Diffusion Coefficient of Carbon in Nickel: Reaction Rates of Nickel-Carbon Alloys with Barium Oxide

Abstract

Experimental values for the solubility of carbon in nickel in the range 700°C to 1300°C yield the equation lnS=2.480−4,880/T, where S is the solubility in grams of carbon per 100 grams of nickel. Values obtained for the diffusion coefficient in the same range fit the equation lnD=0.909−20,200/T, where D is in cm2 per second. These results are of some interest in the problem of the activation of thermionic oxide coated cathodes, and the experimental method used to measure the diffusion coefficients is related to phenomena occurring in vacuum tubes. To extend the usefulness of the results in this direction, rates of reaction between diffused carbon and barium oxide coatings on nickel have been measured. It was found that the rates are diffusion limited over a wide range of conditions of interest.