Brown pigment of the nanopowder spinel ferrite prepared by combustion reaction

The purpose of the present work was to prepare nanometric brown pigments spinel (Zn1−xNix)Fe2O4 (with x = 0, 0.5 and 1 mol of the Ni2+) structures by combustion reaction and characterize the resulting powders. The compositions were prepared by a single-step solution combustion reaction using nitrates and urea as fuel. Stoichiometric compositions of metal nitrate and urea were calculated using the total oxidizing and reducing valences of the components, which serve as the numerical coefficients for the stoichiometric balance, so that the equivalence ratio Φc is equal to unity and the energy released was maximum. The resulting powders were characterized by X-ray diffraction (XRD), nitrogen adsorption by BET, scanning electron microscopy (SEM), helium pycnometry, sedimentation, transmission electron microscopy (TEM), and CIE-L*a*b* color-measurements. The results demonstrated that the synthesis by combustion reaction was very fast and safe resulting in crystalline spinel containing nanoparticles (18–26 nm) for all of the compositions studied. The results demonstrate the viability of using these powders as brown ceramic pigments.