A tem study of oxides formed on ultrafine Fe, Cr and FeCr particles
Abstract High resolution electron microscopy (HREM), electron diffraction (ED) and energy dispersie X-ray analysis (EDX) are used to analyze surface oxides on ultrafine Fe, Cr and FeCr particles. The following oxides are observed: Fe 3 O 4 on Fe particles, CrO 2 on Cr particles, FeCr 2 O 4 or γ-Fe 2 O 3 on FeCr particles depending on the oxidation process. FeCr 2 O 4 is only observed when the particles are thoroughly passivated and no further oxidation is possible. Some passivated FeCr alloy particles show the σ-phase. When a very strong oxidation occurs, i.e. the particles burn, holes are observed in the interior of the FeCr particles.