Combustion in compressed air

Abstract

The fuel to oxidizers (F/O) ratio determines the effectiveness of combustion reaction and the amount of heat evolution (heat of combustion reaction). Hence, optimization of F/O ratio is important for the formation of phase pure ceramic powders by the solution combustion synthesis (SCS) method. The present work demonstrates the effect of F/O ratio on the synthesis of phase pure MgO, ZnO, CaO ceramic powders by SCS method and also the effect of fuels (urea, glycine and alanine) for ZnO synthesis. To understand the mechanism of the combustion reaction at different F/O ratios, we calculated the theoretical flame temperatures by using the thermodynamic concept and analyzed. Using this information, in association with the phase content of the synthesized samples (obtained by the structural characterization using X-ray diffraction), we described the role of fuel to oxidizer ratio in synthesizing ceramic materials by SCS method. We found that, F/O strongly controls the structural nature and characteristics of the synthesized ceramic powder products. Furthermore, comparing the nature of combustion products for divalent and trivalent cation based ceramics, we conclude that solution combustion synthesis favors the synthesis of trivalent cation based oxides over purely divalent cation based oxides. Our work provides the insights into the understanding and the importance of using proper fuel to oxidizer ratio in synthesizing phase pure ceramic powder by SCS method.