Oxidation Characteristics of Some Nickel Alloy Films in Air and Water Vapor

Abstract

Ellipsometric techniques were used to study the oxidation of Ni, Ni‐Cr, and Ni‐P deposits. Oxidation was carried out at temperatures ranging from 100° to 500°C in different ambients including air, saturated water vapor, and gas mixtures containing oxygen at 0.05 and 0.5 atm, respectively. The optical constants and of fresh deposits were found to undergo change on heating. Typically, decreased and k increased, both saturating at longer times. The oxidation of Ni, Ni‐Cr, and Ni‐P was found to be a three stage process. At temperatures below 300°C, mainly oxygen is absorbed; while above this temperature a surface oxide layer is formed. The third stage occurs at 400°C, and for long times where the films become anisotropic or inhomogeneous. The optical constants of the oxide layers formed on all three metals were found to be nearly the same, and their values to be close to those of . The oxidation in different oxygen pressures indicated that water vapor plays a role in the oxidation process. The oxidation in water vapor could not be accounted for by the oxygen normally present in water as a dissolved gas.