Carbon films containing transition metal particles of nano and submicron sizes

Aromatic polyimide films containing cobalt compounds were prepared by mixing Co(NO3)(2) and CoCl2 with a polyamic acid in solution and following imidization on glass plates. The effect of heat treatment on structure, texture and magnetic property of the films was investigated, and the formation process of ferromagnetic particles of nano and submicron sizes in the films was examined. As the particle sizes increased with increasing heat treatment temperature (HTT), the magnetic property changed from superparamagnetic to ferromagnetic, and the ferromagnetic particles of single magnetic domain transferred to those with multi-magnetic domain by further heat treatment. The distribution of metal particle size became very wide by the heat treatment. Pores were found on the surfaces of the heat-treated films, and pore sizes were very similar to those for the metal particles, suggesting that pores were paths of the particle movements. These results were compared with those obtained previously for the polyimide films containing nickel and iron compounds. Different metal compounds introduced in polyimide films gave different processes of the formation and growth of metal particles and pores as HTT increased. (C) 2001 Elsevier Science B.V. All rights reserved.