Magnetic properties and thermal behavior of mullite–iron nanocomposite powders

摘要

Mullite based iron magnetic nanocomposite powders were synthesized by reduction of sol–gel prepared mullite–iron oxide solid solution in hydrogen flow. Structural characterization studied by TEM revealed that two types of α-iron nanoparticles existed in mullite matrix. The α-iron nanoparticles with the size around hundreds of nanometers appeared as inter-type grains, while those around 10 nm were embedded in the grains of mullite. The magnetic properties of nanocomposites suggest that the intergranular and intragranular α-iron nanoparticles had the ferromagnetic and superparamagnetic behavior at room temperature, respectively. The oxidation behavior of nanocomposite powders showed that there existed two different oxidation stages of α-Fe nanoparticles.