did., 46 [I] 54-58 (1963). Some Refractory Oxides and Their Mixtures in the Tempera-4 R. L. Coble, "Sintering Alumina: Effect of Atmospheres," ture Range 600° to 1500°C," J. Am. Ceram. S~C., 36 [3] 76-83 6 Julius Cohen, "Electrical Conductivity of Alumina," Am. l1 G. H. Johnson, "Influence of Impurities on Electrical Con-Cerum. SOC. Bull., 38 [9] 441-46 (1959). ductivity of Rutile," did., 97-101. 6The growth of nickel-aluminum spinel, NA2O4, in diffusion couples of polycrystalline A203 and NiO was investigated between 1200° and 1500°C.The growth kinetics for the spinel layer obeyed a parabolic rate law in this temperature range. Marker experiments showed that the spinel layer formed by counterdiiksion of nickel and aluminum ions. Comparison of experimental and theoretical values of the parabolic rate constants suggests that the diiksion of aluminum ions through the spinel layer is rate controlling.
The oxidation kinetics of iron‐chromium alloys containing 25 and 37.5% chromium and small additions of yttrium and various other rare earth metals have been measured between 700° and 1200°C. Agreement with the parabolic rate law is generally observed for all alloys. Iron‐chromium binary alloys have good oxidation resistance, but lose their protective oxide film due to spalling above 1000°C. Alloys containing yttrium, lanthanum, dysprosium, gadolinium, and erbium exhibit both good oxidation resistance and scale retention. Enhanced scale retention for alloys containing yttrium and the rare earth metals is attributed to the formation of internal as well as external oxide.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.