Preparation of colored iron particles by multistratification with alternate thin layers of SiO2 and TiO2

Coloring ferromagnetic fine particles was achieved only by coating the part icles with SiO2 and TiO2 alternate layers of appropriate thickness that act as light interference filters. We propose a new model called the "hemisphe re model'' for the calculation of the optimum thickness of layers on spheri cal particles to obtain any specific colored particles. The stratification of alternative thin layers of SiO2 and TiO2 layers was achieved by depositi on of amorphous SiO2 and quasigranular TiO2 layers by the sol-gel method. ( C) 1999 American Institute of Physics. [S0021-8979(99)32408-7].