Effect of Heat Treatment on Magnetic and Electrical Properties in Fe/Al2O3 Core/Shell Nanocomposites

With the development of the portable electronics devices, all electrical components, such as power chokes, are integrated with miniaturization. Magnetic-energy storaged materials play an important role in power chokes for DC/DC converters applications. Presently, NiZn-based ferrites are often used in power chokes, but the saturation magnetization Ms~60emu/g is lower due to the intrinsic structure limitations. In order to replace the ferrites for high power application, the iron-based magnetic alloy with highly Ms~180emu/g are good candidates. However, the commercial magnetic alloys are micron-sized in 20-50um with the lower electrical insulations and will induce the high eddy-current loss. In this research, we develop a method to fabricate the sub micron-sized (<;1um) core/ shell nanocomposites. The normal Fe
₂
O
₃
oxides are used as a starting powders and chemically precipitate the Al(OH)
₃
hydroxides on the surface. These as-prepared composite are treated at 800°C for few hours in a reduced Ar/H
₂
atmospheres and successfully transform to the Fe/Al
₂
O
₃
nanocomposites. Fig show the dependences of magnetic and electrical properties on the different Al/Fe ratio. The experimental results shows the optimal Ms value ~161 emu/g and electrical resistivity of 2.6×10
³
Ω-cm in a Al/Fe ratio of 24%. In additions, the crystallization, surface morphology and high-frequency properties are also investigated. In summary, the hydrogen reduced treatment acts as an efficient method to prepare the metal core/insuation shell nanocomposites from oxides systems. Fig: The dependences of magnetic and electrical properties on the different Al/Fe ratio.