SYNTHESIS OF G- ALUMINA BY SOLUTION COMBUSTION METHOD USING MIXED FUEL APPROACH (UREA+GLYCINE FUEL)

Abstract

Nano crystalline γ-Alumina powders were synthesized by Solution Combu stion reaction between aluminium nitrate as oxidize r and a mixture of urea and glycine fuel as reducer. In thi s fuel mixture, urea was taken as stoichiometric fu el and glycine was added as excess fuel to alter the exothermicity of redox rea ction between aluminium nitrate and urea. The ratio of urea to glycine had been optimized to obtain single phase gamma alumina. A M ulti channel thermocouple setup was used to measure the flame temperatures to study the nature of combustion of various fuel mixt ures. The variation of adiabatic flame temperature was calculated theoretically for different urea/glycine mixture ratios according to thermodynamic concept and correlated with the obser ved flame temperatures. These powders were characterized by XRD, SEM, showing tha t the powders were composed of polycrystalline oxid es with crystallite size of 81 nm for alpha alumina, ~ 5 nm for gamma alumina ahighly porous microstructure. An interpre tation based on maximum combustion temperature and the amount of gases prod uced during reaction for various urea to glycine ra tio composition had been proposed for the nature of combustion and its corre lation with the characteristics of as synthesized p owder.