Síntese e caracterização de óxidos de cério e de cobalto obtidos por decomposição térmica de quelatos coprecipitados

Abstract

In this work the results of the synthesis and characterization of mixed oxides of cerium and cobalt, obtained by thermal decomposition of coprecipitated 8-hydroxyquinolinates are presented. The 8-hydroxyquinolinates were coprecipitated in aqueous acetic acid medium, with elevation of the pH by the addition of aqueous ammonia solution. The co-precipitates were characterized by X-ray diffractometry (XRD) which indicated coprecipitation of the excess ligand, and, by Fourier-transform infrared absorption spectroscopy (FTIR), which indicated the complexation of the metals characterized by absorption bands M-O and M-N. The thermal behavior study realysed by thermogravimetry (TGA) and differential thermal analysis (DTA) indicate that, following the elimination of excess ligand, the coprecipitate decomposes into only one mass loss step indicated by the TG curve at 371.58 °C, as a function of the oxidative decomposition of the chelate, indicated by the intense exothermic peak in the DTA curve. Studies carried out in muffle indicate that the mixture of oxides CeO2 and CoO.Co2O3 (cobalt spinel) was obtained at 500 °C and that crystallinity increases with increased temperature, provided by XRD.