Oxidation Behavior of Fe-based Amorphous Ribbons

The oxidation behavior of Fe-based amorphous ribbons was tested by annealing at 380 °C in air for different time with heat treatment furnace and analyzed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The mechanism of oxides formation of the amorphous ribbons was discussed in detail. The results showed that the oxides were mostly B2O2, SiO2 and Fe2O3 or FeO. With the increase of annealing time and holding temperature, the fraction of the oxides on the ribbon surface increased and the size of the oxides became larger due to the generation of new oxides and the coalescence of small oxides. The oxides have different shapes, such as round, rod and needle-shaped. Experimental results also showed that the oxides nucleated at fish scale, air pocket and impurities in priority, and the growth of the oxides was controlled by the diffusion of atoms. With the increase of the distance to the ribbon surface, the oxygen concentration decreased dramatically. Due to the low binding energy of B2O3 and the large diffusion coefficient of B atom, the B element was oxidized firstly compared with other elements. Moreover, the oxidation depths of the B2O3 and SiO2 were larger than that of Fe2O3.