FORMATION OF SUPERPARAMAGNETIC NANOCOMPOSITES FROM VAPOR-PHASE CONDENSATION IN A FLAME

Recent work on the magnetic characteristics of nanometer scale materia ls has suggested that magnetically isolated nanometer magnetic particl es would show magnetic behavior different than those found in the bulk . Such behavior could be explored if such materials could be synthesiz ed in sufficient quantities where the magnetic particles could be isol ated from each other via encapsulation within a non-magnetic hen. We h ave investigated application of flame technology for the synthesis of this class of materials. A premixed methane/oxygen flame diluted with nitrogen has been used as the reacting environment in which iron penta carbonyl and hexamethyldisiloxane were added as the magnetic and non-m agnetic precursor materials. The results, based on x-ray diffraction, electron microscopy, Mossbauer effect, and magnetization data have sho wn that: (i) nanometer composite particles are formed containing 5-10 nm Fe2O3. encased in a silica particle whose diameter ranged from 30-1 00 nm, depending on loading and flame temperature, and (ii) the iron o xide clusters are magnetically isolated and in some cases show superpa ramagnetic behavior.