The environmentally benign synthesis of nanosized CoxZn1-xAl2O4 blue pigments

Autores: Visinescu, D.|Paraschiv, C.|Ianculescu, A.|Jurca, B.|Vasile, B.|Carp, O.
Fuente: Dyes and pigments
87 (2), 125-131

Nanosized CoxZn1-xAl2O4 (x = 0, 0.1, 0.2, 0.4, 0.6, 0.8 and 1) blue pigments were prepared using a novel, starch-based synthetic route, in which the carbohydrate acts as chelating, template and gelation agent. The (Zn,Al,Co)-starch gel precursors were characterized using FTIR and thermal analysis, while their corresponding oxides were characterized using FTIR, NIR-UV?Vis spectroscopy, XRD and SEM. The FTIR spectra of the pink-reddish metals-starch gel precursors, dried at 80 °C, indicated the formation of a complex (Zn,Al,Co)-starch assembly as well as the first signs of a spinelic phase. Thermal analysis of the precursors showed that mass loss was accomplished at 430 °C; for CoxZn1-xAl2O4 (0 = x = 0.6) metal-oxide samples the spinel crystallization phase transformation occurred in the temperature range 700?830 °C. The presence of a pure spinel lattice after calcination of the metal-starch gel precursors at 800 °C was confirmed; particles were homogeneous in shape and size, with a pronounced tendency to form agglomerates and aggregatess. NIR-UV?Vis spectra of the blue oxides were characteristic of Co(II) metal ions located in tetrahedral sites and also showed disorder dependence on cobalt(II) cation-content.

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