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

MARÍA CELESTE GARDEY MERINO; GUSTAVO E LASCALEA; LAURA M SÁNCHEZ; PATRICIA G VÁZQUEZ; EDGARDO D CABANILLAS; DIEGO G LAMAS

JOURNAL OF ALLOYS AND COMPOUNDS

ELSEVIER SCIENCE SA

Año: 2009

0925-8388

Abstract: In this work, two new gel-combustion routes for the synthesis of Al2O3 nanopowders with asparticacid as fuel are presented. The use of this amino acid as fuel in syntheses by gel-combustion has not beenproposed in the literature before. The first route is a "conventional" stoichiometric process, while the secondone is a non-stoichiometric pH-controlled process. These routes were compared with similar synthesisprocedures using glycine as fuel, which are well-known in the literature. The samples were calcined in air atdifferent temperatures, in a range of 600-1200°C. They were characterized by X-ray diffraction, scanningelectron microscopy and transmission electron microscopy. Different phases were obtained depending onthe calcination temperature: amorphous, g (metastable) or a (stable). The amorphous-to-g transition wasfound for calcination temperatures in the range of 700-900°C, while the g-to-a one was observed forcalcination temperatures of 1100-1200°C. The retention of the metastable g phase is probably due to acrystallite size effect. It transforms to the a phase after the crystallite size increases over a critical size duringthe calcination process at 1200ºC.