Synthesis of Al2O3-Fe2O3-FeAl2O4 Composites by Colloidal and Traditional Powder Routes of Nano-Al2O3-Fe2O3 Mixtures

Morphological and microstructural changes induced by colloidal and traditional powder synthesis routes of nano-Al2O3-Fe2O3 mixtures were analyzed. Al2O3 was progressively replaced by 1, 2.5, 5, 10, and 20 wt % Fe2O3 nanoparticles. The replacement effect on dense ceramic composites formed by 100 MPa uniaxial pressure and sintered at 1500 degrees C was evaluated by transmission electron microscopy, scanning electron microscopy, and X-ray diffraction. After sintering treatment, the solid solution hercynite spinel-FeAl2O4 is obtained through a colloidal and a solid-state route (in all compositions). The utilization of the colloidal processing route allowed a homogeneous distribution of the Fe2O3 nanoparticles into the alumina matrix. Fe2O3 nanoparticles diffused at the Al2O3 grain boundaries, promoting better densification via hercynite formation. Also, the presence of Fe2O3 nanoparticles at grain boundaries acts, to a certain extent, as a pining component, promoting grain refinement. The colloidal synthesis route is a suitable alternative to promote densification in Al2O3-Fe2O3 dense ceramic composites.