Influence of fuel in the microwave assisted combustion synthesis of nano -alumina powder

Abstract

Microwave assisted combustion synthesis is used for fast and controlled processing of advanced ceramics. Single phase and sinter active nano crystalline alpha alumina powders were successfully synthesized by different fuel-to-oxidant molar ratios using aluminium nitrate as an oxidiser, glycine as a reducing agents and millipore water as a solvent by microwave assisted combustion synthesis. Thermodynamic modelling of the combustion reaction shows that as the fuel-to-oxidant ratio increases, the amount of gases produced and adiabatic flame temperature also increases. The precursor powders were investigated by thermogravimetry (TG) analyses. The as prepared precursors calcined at 900 to 1200°C in air atmosphere were characterized for their structure and morphology. The thermal analyses (TG/DSC), X-ray diffraction (XRD) and Fourier transform infra red (FT-IR) results demonstrate the effectiveness of the microwave assisted combustion synthesis. The transmission electron microscopy (TEM) observations show the different morphologies of as-prepared powders and shows the particle sizes in the range of <50 nm. The results confirm that the homogeneous, nano scale alumina powders derived by microwave assisted combustion have high crystalline quality and the morphology of the as-prepared precursor powders. Key words: Synthesis, microwave, glycene-gel, decomposition, alumina, nano crystalline.