AbstractIn this study, ceramic nanopigment ZnCr2O4was prepared by solution combustion using glycine, urea and citric acid as fuels. The objective is to study the influence of fuel on the morphology and the diffuse reflectance spectrum. The nanoparticles were characterized by field emission scanning electron microscopy (FESEM), the phase was investigated by X-ray diffraction (XRD), the thermal behavior was studied by thermogravimetry analysis (TGA) and differential scanning microscopy (DSC), the color was determined by diffuse reflectance spectroscopy and CIE L*a*b* colorimetric analysis. The average crystallite sizes obtained were 18.40 nm, 42.05 nm, and 18.69 nm when are used glycine, urea, and citric acid, respectively. Finally, the effect of fuel in the diffuse reflectance showed that the scattering of the light by the particles depend of the morphology. Also, the nanopigment was obtained by solution combustion at lower temperature than solid state reaction and it could be used in digital decoration.

abstractCoAl2O4 pigments were synthesized through Liquid-Feed Flame Spray Pyrolysis (LF-FSP) method using metallorganic precursors of cobalt propionate and alumatrane. The precursors were dissolved in ethanol and aerosolized into a methane/oxygen flame where it was combusted to result in nanopowders at a single step. The resulting nanopowders were collected in electrostatic precipitators and analyzed by x-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), colorimetry, Field Emission Scanning Electron Microscopy (FE-SEM) and BET (Brunauer-Emmett-Teller) nitrogen adsorption. Results show formation of single phase blue nanopigments, suggesting that LF-FSP is an excellent method to produce nanoparticles with high quality in a continuous process for new industrial applications. The nanoparticles presented spherical morphology with specific surface area of 50 m2/g, corresponding to average particle size of 27 nm. The pigments were calcined at 500, 600, 800, 1000, 1200 and 1300 °C, aiming to find the color stability whereby the colors were measured using the color space CIE L*a*b* under standardized D65 light. The brightest and bluest was obtained at calcination temperature of 1200°C and its application into a glaze was carried out at 1200 °C to evaluate the color performance and stability after a decoration process. Finally, LF-FSP produced pigments were compared with those produced by solid state reaction. Differences in the color due to the average particle size and process conditions were observed. It is possible to obtain new hues for ceramic applications by LF-FSP method.