CoAl2O4 nano pigment obtained by combustion synthesis

The aim of this research was to study the influence of pH (2.5, 7, 10.5), molar ratio of fuel to nitrates (0.36, 0.56, 0.75), and calcination temperature (600, 800, 1000, 1200°C) on the characteristics of CoAl2O4 nano pigments synthesized using a solution-based combustion method. Gel formation, morphology, specific surface area, and color of the powder were characterized using TG–DTA (thermogravimetric and differential thermal analysis), XRD (X-ray diffraction), TEM (transmission electron microscopy), BET (Brunauer–Emmett–Teller), and UV–Vis. The results indicate that spinel CoAl2O4 was formed independently of the different variables studied and that higher temperature promotes crystallite size. According to the TEM micrographs, most of particles calcined at 800 and 1000°C have average particle sizes <30 and 75 nm, respectively. Consistent with BET results, maximum specific surface area was obtained at pH of 7. Colorability tests demonstrate that the mixtures of glaze and calcined nano pigments are still dark blue after heating up to 1200°C.