Oxidation of metals subjected to a linear temperature increase : cubic and logarithmic laws /

The total amount of oxidation which occurs up to a given time when a metal is subjected to a continuously increasing temperature has been studied by Fassell and coworkers. A constant rate of increase as well as the linear and parabolic oxidation laws were assumed. The present report extends the analysis to include to the cubic and logarithmic growth laws. The notation for the nth order exponential integral functions which is used here simplifies the equations and the calculations. The rate of heterogenous surface reaction has been assumed to be proportional to the surface coverage of adsorbed molecules, and this in turn is related to the effective gas concentration (P/RT) by Langmuir's adsorption isotherm. It is not known, however, whether this assumption is compatible with the mechanisms which lead to the cubic or logarithmic oxidation growth laws. Two limiting cases of this isotherm are considered - namely that (1) the rate is directly proportional to the gas concentration, and (2) the rate is independent of the gas concentration. These limits lead to simpler equations.Work performed at the Los Alamos Scientific Laboratory, Los Alamos, New Mexico."Metallurgy and Ceramics.""Report written: July 1955.""LA-1929."The total amount of oxidation which occurs up to a given time when a metal is subjected to a continuously increasing temperature has been studied by Fassell and coworkers. A constant rate of increase as well as the linear and parabolic oxidation laws were assumed. The present report extends the analysis to include to the cubic and logarithmic growth laws. The notation for the nth order exponential integral functions which is used here simplifies the equations and the calculations. The rate of heterogenous surface reaction has been assumed to be proportional to the surface coverage of adsorbed molecules, and this in turn is related to the effective gas concentration (P/RT) by Langmuir's adsorption isotherm. It is not known, however, whether this assumption is compatible with the mechanisms which lead to the cubic or logarithmic oxidation growth laws. Two limiting cases of this isotherm are considered - namely that (1) the rate is directly proportional to the gas concentration, and (2) the rate is independent of the gas concentration. These limits lead to simpler equations.Operated by the University of California for the U.S. Atomic Energy CommissionMode of access: Internet