Gel combustion synthesis and magnetic properties of CoFe2O4, ZnFe2O4, and MgFe2O4 using 6-aminohexanoic acid as a new fuel

Abstract

For the first time, 6-aminohexanoic acid is used as an alternative fuel in the synthesis of the spinel ferrites with compositions CoFe2O4, ZnFe2O4 and MgFe2O4 using gel combustion synthesis with different oxidizer-to-fuel (O/F) ratios. The gel precursors were studied by differential thermal analysis and thermogravimetry (DTA/TG), which showed that the ignition temperature depends on the gel precursor, being around 230 °C, 130 °C and 275 °C for CoFe2O4, ZnFe2O4, and MgFe2O4, respectively. These results showed than the 6-aminohexanoic acid has an ignition temperature lower than the urea and the citric acid when were used in the synthesis of the spinel ferrites by gel combustion. Moreover, the adiabatic flame temperature (Tad) of the reactions of combustion were calculated using thermodynamic analysis, which showed that Tad increases when the mass of the 6-aminohexanoic acid increases. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques confirmed the formation of the spinel structures for all the O/F ratios, but there is a minor impurity phase for some experiments. The particle morphology was evaluated using scanning electron microscopy (SEM), showing aggregated particles with a sponge-like structure due to the released gases during the combustion. A vibrating sample magnetometer (VSM) was used for measuring the magnetic properties of the as-prepared powders. The values of saturation magnetization, Ms, and coercitivity, Hc, were Ms = 66.9 emu/g and Hc = 1505 Oe for CoFe2O4, Ms = 44.6 emu/g and Hc = 75.2 Oe for ZnFe2O4 and Ms = 28.66 emu/g and Hc = 111.4 Oe for MgFe2O4. The optical band gap for CoFe2O4, ZnFe2O4, and MgFe2O4 were 1.11 eV, 1.37 eV and 1.64 eV, respectively. These results show that 6-aminohexanoic acid can be used as an alternative fuel in the synthesis of spinel ferrites using gel combustion synthesis.