Sintese de alumina por processo sol-gel

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

In this work we studied the processes involved in the transformation of gels of a-alumina obtained from saturated aqueous solutions of aluminum nitrate and urea. The saturated aqueous solutions of aluminum nitrate and urea were thermally treated at 90° C for 12 hours and transformed by sol-gel processes into transparent gels. The gels composed of hydroxylated aluminum species were transformed in to g-alumina by calcination at 300° C for 25 minutes. The kinetic of transformation of g-alumina to a-alumina was studied according to the Melvin Avrami s model proposed for the formation of homogeneous phases in the temperature range between 750 to 900° C. The apparent activation energy, determined according to Arrhenius law, indicates that the g-alumina, formed from the gel, presented a high degree of homogeneity. The microstructural analysis of a-alumina, formed by calcination of g-alumina, showed the growth of plates preferencially in dimensions, as expected from the predictions of the Melvin Avrami model.

ASSUNTO(S)

ureia alumina espectroscopia de ressonancia nuclear

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