Starch – A suitable fuel in new low-temperature combustion-based synthesis of zinc aluminate oxides

Starch has been tested as single-fuel and in a two-fuel mixture, together with N-methylurea, in a new combustion-based synthesis of zinc aluminate oxides, using different fuel compositions and equivalence ratios Φe (Φe = fuel/oxidant). The combustion process has been analyzed by simultaneous thermal analysis. The corresponding oxides were characterized by X-ray diffraction analysis, UV–Vis spectroscopy, scanning electron microscopy and BET investigations. Crystal structures were refined by Rietveld method. The morphology, specific surface area and optical properties of the obtained zinc aluminate have proved to be strongly dependent on the fuel nature and composition. The lowest crystallite size (131 Å) is achieved for the oxide generated from the starch-based precursor, while the highest surface area (20.69 m2/g) has been obtained for a 3:1 N-methylurea/starch fuel composition. The non-zero value for microstrain has indicated spinelic defects in the starch–fuel corresponding oxide. UV–Vis spectroscopic analysis have confirmed the intrinsic properties of the resulted mixed metal oxide, but also shows the presence of a certain disorder degree for all the other samples. The superior values of the band gap (4.2–4.7 eV) for the obtained oxides relative to the bulk case (3.8 eV) are the result of the nanometric dimensions of the particles.

Nanosized zinc aluminate spinelic oxides have been obtained following novel starch-assisted combustion-based methods. Starch has been used as single low-temperature flame fuel (LTF) or in combination with a high-temperature flame fuel (HTF), N-methyl urea (NMU).Figure optionsDownload as PowerPoint slideHighlights
► Pure and homogenous ZnAl2O4 oxides were synthesized through new combustion methods.
► Starch and/or N-methylurea were involved as reducing organic fuels.
► The mean crystallite sizes range between 131 and 176 Å.
► Surface area and optical properties of the oxides depended on the fuel composition.
► Spinel defects were evidenced for starch-originating oxides.