Nanostructured aluminium oxide powders obtained by aspartic acid–nitrate gel-combustion routes

M.C. GARDEY MERINO; G.E. LASCALEA; L.M. SÁNCHEZ; P.G. VÁZQUEZ; E.D. CABANILLAS; D.G. LAMAS

JOURNAL OF ALLOYS AND COMPOUNDS

ELSEVIER SCIENCE SA

Año: 2010 vol. 495 p. 578 - 582

0925-8388

In this work, two new gel-combustion routes for the synthesis of Al2O3 nanopowders with aspartic acid as fuel are presented. The first route is a conventional stoichiometric process, while the second one is a non-stoichiometric, pH-controlled process. These routes were compared with similar synthesis procedures using glycine as fuel, which are well-known in the literature. The samples were calcined in air at different temperatures, in a range of 600-1200°C. They were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and BET specific surface area. Different phases were obtained depending on the calcination temperature: amorphous, gamma (metastable) or alpha (stable). Theamorphous-to-alpha transition was found for calcination temperatures in the range of 700-900°C, while the gamma-to-alpha one was observed for calcination temperatures of 1100-1200°C. The retention of the metastable gamma phase is probably due to a crystallite size effect. It transforms to the alpha phase after the crystallite size increases over a critical size during the calcination process at 1200°C. The highest BET specific surface areas were obtained for both nitrate-aspartic acid routes proposed in this work, reaching values of about 50 m2/g.