Abstract
Crystalline Fe-Si alloy particles ranging from 22 to 155 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 to 1400°C), the Fe(CO)5 concentration (2.5×10-5 to 1.5×10-4 mol/L), the molar ratio of Fe(CO)5 to SiH4 (100:0 to 50:50), and the residence time (1.7 to 5 s). The primary particle size increased with reactor temperature increase and decreased with increasing the Si content of the precursor. 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. By high-resolution transmission-electron-microscopy study, a particle 20 nm in diameter was nearly a single crystal with an external oxide layer 2 nm in thickness. The coercive force ranged from 58 to 493 Oe, increasing with decreasing the particle size, and the saturation magnetization was in the range of 50 to 100 emu/g, lower than that of bulk iron, due to the presence of non-magnetic silicon and of the oxide layer.
