PREPARATION OF ULTRAFINE FE-SI-C POWDERS IN A RADIOFREQUENCY THERMAL PLASMA AND THEIR CATALYTIC PROPERTIES

Ultrafine Fe-Si-C powders were prepared from mixed gases of SiH4-CH4-F e(CO)5 using a newly developed thermal-plasma apparatus with a dual-ra dio-frequency-coupled-plasma-torch system. The phases of the powders p repared were classified into two groups; one composed of beta-FeSi2 wh ich was prepared by rapid quenching, while the other was composed of a lpha-Fe, Fe3Si, Fe5Si3, FeSi, beta-SiC and amorphous Si, which were pr epared by slow quenching. The diameters of these powders were in the r ange 5-50 nm. The catalytic activities of these powders for Fischer-Tr opsch synthesis were examined. The ultrafine beta-FeSi2 powder was ver y active for the selective formation of olefin. On the other hand, pow ders of alpha-Fe, Fe3Si and Fe5Si3 were low in their selectivity but g ave high CO conversion. Relations between the plasma conditions for th e preparation of ultrafine Fe-Si-C powders and their catalytic propert ies are discussed.