Fe-Cu and Fe-Ag binary systems are virtually immiscible for a whole range of composition in equilibrium. In the present study, Fe-Cu and Fe-Ag nanoparticles were produced by DC plasma jet method. The produced Fe-Cu and Fe-Ag 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 were supersaturated solid solution. The Fe-Cu and Fe-Ag nanoparticles were heated up to 700 degreesC under flowing Ar(O-2). Numerous Fe oxide whiskers with a particle on their tip grew from the particles sintered during heating.