Desenvolvimento de pigmentos nanométricos encapsulados.

Abstract

In the present study, perovskite-type NiTiO3 ceramic pigments were prepared by the polymeric precursor method, originally proposed by Pechini. The transluscent and viscous polymeric resin was characterized by thermogravimetric analysis. The product of the resin s pyrolysis, also known as "puff", was desagglomerated and calcined at different temperatures, under room atmosphere. The evolution of the crystalline phase with increasing heat treatment temperature was studied by X-ray diffraction (XRD). A comparative study of the characteristics of the ceramic pigments, which resulted from the calcination of the attrition-milled "puff", was made. The calcined powders presented high specific superficial area values, as determined by the BET method. The pigment colors were measured by the CIE - L*a*b* colorimetric system. It was observed, through the colorimetrics coordinates, that the pigments are yellow. The morphology of the prepared NiTiO3 powders was studied by scanning electron microscopy. A mean particle diameter of approximately 30nm was estimated through transmission electron microscopy (TEM) measurements. The isoelectric point of the particles dispersed in ethanol was determined. Afterwards, the attrition-milled, nanometric, single-phase pigments, calcined at 600ºC for 2 hours, were coated with an amorphous SiO2 layer. The encapsulation was done by a sol-gel process. Moreover, the encapsulation was confirmed through TEM characterization, X-ray dispersive energy analysis and a shift on the position of the isoelectric point of the dispersed particles