Abstract
Morphological and microstructural changes induced by colloidal and traditional powder synthesis routes of nano-Al(2)O(3)-Fe(2)O(3) mixtures were analyzed. Al(2)O(3) was progressively replaced by 1, 2.5, 5, 10, and 20 wt % Fe(2)O(3) nanoparticles. The replacement effect on dense ceramic composites formed by 100 MPa uniaxial pressure and sintered at 1500 °C was evaluated by transmission electron microscopy, scanning electron microscopy, and X-ray diffraction. After sintering treatment, the solid solution hercynite spinel-FeAl(2)O(4) 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 Fe(2)O(3) nanoparticles into the alumina matrix. Fe(2)O(3) nanoparticles diffused at the Al(2)O(3) grain boundaries, promoting better densification via hercynite formation. Also, the presence of Fe(2)O(3) 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 Al(2)O(3)-Fe(2)O(3) dense ceramic composites.