Untersuchungen an dünnen oxidschichten—I die oxydation von reineisen bei temperaturen um 200 °C

Abstract

During the early stages of thermal oxidation, crystal nucleii consisting of Fe 3O 4 develop and ultimately form a porous layer. Over the initial homogeneous oxide layer, nucleii of α-Fe 2O 3 then develop and cover the Fe 3O 4 at a relatively rapid rate. No γ-Fe 2O 3 was detected in any of the layers. At 200 °C whiskers grow out of the oxides to about 1 μ long after 30 days. They also form at higher temperature but then develop into plates. Both forms consist of α-Fe 2O 3 with the longest axis parallel to the (1 1 0) direction. It is therefore concluded that the mechanism of formation is the same in either case.