engleski

Thermal evolution of gels prepared by chelation of aluminum sec-butoxide with ethyl acetoacetate in various amounts

This work presents a thermal evolution study of gels obtained by chelation of aluminum sec- butoxide (Asb) with ethyl acetoacetate (Eaa) in various amounts. Samples were characterized by scanning electron microscopy (SEM), low angle laser light scattering (LALLS), differential thermal and thermo-gravimetric analysis (DTA/TGA), Fourier-transformed infra-red spectroscopy (FTIR) and X-ray diffraction (XRD). It was established that samples with a low Eaa/Asb ratio are mainly amorphous, whilst the samples with greater Eaa/Asb ratio are predominantly chelate. The crystallization of γ-Al2O3 takes place between 600 and 1000 °C in two separate processes for all investigated samples. On the other hand, a complete transition to α-Al2O3 at 1200 °C occurs exclusively in samples with high Eaa/Asb ratio, while it is only partial for samples with low Eaa/Asb ratio. The observed mass loss is in concordance with the hypothesis that the overall gel content in the samples could be represented by a simplified formula Al(Eaa)xO(3−x)/2, where x is the Eaa/Asb ratio. In addition to thermal evolution, the gel-chelate duality of the samples is reflected in the morphology and particle size distribution.

alumina; sol–gel; chelation; thermal analysis

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