The influence of the processing parameters on the formation of iron thin films on alumina balls by mechanical coating technique

Mechanical coating technique (MCT) was used to fabricate Fe thin films on alumina balls. The influence of the processing parameters including the milling atmosphere and the rotation speed of planetary ball mill on the formation of the thin films was investigated. The results of SEM and EDS showed that Fe particles reacted with oxygen in the air atmosphere and the formed ferroferric oxide hindered the formation of the thin films. Rotation speed also had great influence. Continuous Fe thin films with an average thickness of about 10 μm were formed during the milling operation at 300 rpm. However, they could not be formed at 200 and 400 rpm. Furthermore, the evolution of the thin films was also studied and analyzed. An evolution model was proposed to describe it. According to the model, the evolution fell into nucleation, growth of nuclei, formation of thin films and exfoliation. It was considered that mechanical interlocking played an important role in the formation of the thin films.

► Evolution of metal thin films during ball milling was revealed for the first time. ► A model was proposed to describe the film evolution. ► The influence of processing parameters on the films’ formation was clarified.