Fabrication of Al2O3@BaFe12O19 core-shell powder by a modified heterogeneous precipitation method.

Abstract Core-shell structural composites are promising to quench the desire for low-cost, lightweight and multifunctional magnetic materials, but the fabrication of highly pure shell nanoparticles with a desired morphology on a heterogeneous nuclear is still a big challenge. This study gives a successful illustration by in-situ synthesizing BaFe 12 O 19 nanoparticles as a shell on Al 2 O 3 core powders using BaCl 2 and FeCl 3 as precursors, instead of commonly used Ba(NO 3) 2 and Fe(NO 3) 3 , by a modified heterogeneous precipitation process followed by calcination for crystallization. After calcination of the precipitants from the raw precursor mixture of BaCl 2 :FeCl 3 for 1:10 at 800 °C, and for 1:8.5 at 900 °C, respectively, pure BaFe 12 O 19 formed on pristine Al 2 O 3 , mostly with a hexagonal plane, about 100–200 nm in basal diameter and 20–100 nm in thickness. The highest saturation magnetization and coercivity of the coated Al 2 O 3 @ BaFe 12 O 19 powders was 23.3 emu/g and 5149 Oe, quite higher than that of the direct-mixed Al 2 O 3 -BaFe 12 O 19 composite powder, and BaFe 12 O 19 -containing composites reported in literature, which could be attributed to the hexagonal shape of BaFe 12 O 19 and uniform shell dispersion on Al 2 O 3 core. The formation mechanism for the Al 2 O 3 @BaFe 12 O 19 powders was discussed in detail. [ABSTRACT FROM AUTHOR]