Navegando por Autor "Melo, Danniely Silva"

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The influence of temperature on the color of TiO2:Cr pigments
(Elsevier, 2009-05-06) Vieira, Fagner Ticiano Gomes; Melo, Danniely Silva; Lima, Severino Jackson Guedes de; Silva, Elson Longo da; Paskocimas, Carlos Alberto; Silva Júnior, Wilson; Souza, Antonio Gouveia de; Santos, Iêda Maria Garcia dos
TiO2:Cr brown pigments were prepared via a polymeric precursor derived from the Pechini method. The pigments were analyzed by infrared spectroscopy, X-ray diffraction, ultraviolet–vis spectroscopy, and colorimetry. The increase of the calcination temperature from 700 to 1000 8C led to a decrease in the L* values, corresponding to darkening of the pigments. The pigments obtained in this work are darker than those produced by a solid-state reaction method reported before. The change in the pigment color is due to the anatase–rutile phase transition, which leads to a shift in the charge transfer bond (Ti4+$O2 ) due to a change in the crystal field around the chromophore ions. Moreover, the oxidation state of chromium was observed to change, and this also alters the color of the pigments

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