Growth of Fe3O4 whiskers from solid solution nanoparticles of Fe–Cu and Fe–Ag systems produced by DC plasma jet method

Fe–Cu and Fe–Ag binary systems are virtually immiscible for a whole range of composition in equilibrium. In the present study, the nanoparticles of Fe–Cu and Fe–Ag systems were produced by direct current plasma jet method. These produced nanoparticles had mean particle sizes of about 70 nm, and were a mixture of bcc and fcc phases. It was revealed by analytical high-resolution TEM observations that the nanoparticles of Fe–Cu and Fe–Ag systems were supersaturated solid solution. It has been found that numerous whiskers with a particle on their tip grow from these nanoparticles by heating above the temperature of 860 K under an Ar–O₂ atmosphere. The whiskers grow as the result of the phase separation in these solid solutions. The whiskers are composed of a Fe₃O₄ rod and a Cu₂O particle on the tip.