Magnetic iron oxide/mullite nanocomposite stable up to 1400 degrees C

Magnetic nanocomposites consisting of spherical iron oxide particles of aro und 13 nm dispersed in a mullite matrix have been obtained by pyrolysis at 600 degreesC of an aerosol generated from a solution of TEOS and iron and a luminum nitrate in methanol and a posterior heat treatment at 1200 degrees -1400 degreesC. Iron contents higher than the solubility limit of Fe in mul lite (12 wt% Fe2O3) have been used to prepare the precursor samples, It sho uld be emphasized that the new magnetic nanocomposite presents a saturation magnetization of 3.3 emu/g and a coercivity of 546 Oe at room temperature, and preserves its magnetic character up to 1400 degreesC, This behavior re veals that mullite is an excellent matrix to keep the magnetic particles ap art, avoiding sintering during the heat treatment and therefore making phas e transformations difficult. (C) 2000 Academic Press.