SYNTHESIS AND CHARACTERIZATION OF NANOMETRIC alpha-ALUMINA

Alumina particles were synthesized by colloidal chemical using aluminum hydroxide, formic acid and ethanol as solvent. The effect of the reaction medium, ripening time, surface modifier and the presence of a-Al2O3 seeds were evaluated. A pH of 2.4 +/- 1 and the presence of seeds of a-Al2O3 assisted by surface modifier produced smaller nanoparticles, which were agglomerated in the form of xerogel after sintering heat treatment. Synthesized particle size was in the order of 7,5 nm to 200 nm according to transmission electron microscopy TEM, and generated secondary particle size in the order of 2 mm after sintering at 1200 degrees C, as seen in scanning electron microscopy SEM. Following the structural changes of the material synthesized with temperature, infrared spectroscopy and X-ray diffraction indicated the presence of a-alumina from the 1000 degrees C, verifying that the Boehmite synthesis route is useful for obtaining a-alumina nanoscale particles. The potential use of the sintered material was assessed by its resistance to bending, and it was found that the sintered nanoalumina was 2.6 times higher in flexural strength than provided by micrometric alumina used for dental ceramics