Preparation of Fe-Si Nanoparticles in Furnace Aerosol Reactor

Crystalline Fe-Si alloy particles ranging from 37 to 150 nm in diameter were produced by thermal decomposition of a mixture of Fe(CO)(5) and SiH4 in a furnace aerosol reactor. The reactor was made of alumina, 2.4 cm in diameter and 100 cm in length. The operating variables were reactor temperature (800-1400degreesC), the Fe(CO)(5) concentration (2.5 x 10(-5) to 1.5 x 10(-4) mol/ l), the molar ratio of Fe(CO)(5) to SiH4 (100:0 to 50:50), and the residence time (2.5-10 s). The primary particle size increased with reactor temperature increase and decreased when the Si content of the precursor was increased. The sintering of the particles within the agglomerates was an important factor in determining the primary particle size, and the sintering was inhibited by the silicon. The spatial variation of particle morphology was observed by in situ deposition of particles on a TEM grid. At 7 cm from the reactor inlet, nonagglomerated spherical particles encapsulating several smaller iron particles were found. The spherical structure were destroyed downstream to form agglomerates.