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| Author(s): |
Vinícius Dantas de Araújo
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT) |
| Defense date: | 2009-03-27 |
| Examining board members: |
Maria Ines Basso Bernardi;
Edson Roberto Leite
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| Advisor: | Maria Ines Basso Bernardi |
| Abstract | |
In this work, the synthesis of particles from the PbO-CrO3 system, in particular the PbCrO4 and Pb2CrO5 compositions were accomplished, by a polymeric precursor method, evaluating its application as pigments. In order to eliminate the negative toxic aspect of these materials, the dispersion of the same in SiO2 was achieved, by the sol-gel method. The samples were characterized structurally by X-Ray diffraction, Raman spectroscopy and scanning and transmission electron microscopy. From X-Ray diffraction and Raman spectra results it was verified that the polymeric precursors method is able to form single phase Pb2CrO5 and PbCrO4 for both studied stoichiometries. Although, scanning electron microscope images revealed that both compositions present strong coalescence and agglomeration of the particles. Optical characterization was carried out by diffuse reflectance technique and colorimetric coordinates. It was verified that the PbCrO4 samples possess green-yellowish coloration and the Pb2CrO5 samples presents coloration that varies from dark orange to red. The dispersion of Pb2CrO5 particles in SiO2 was reached, however, this process causes the formation of different crystalline phases, besides alteration in color, which have a significant contribution from the SiO2 matrix, confirmed by Kubelka-Munk theory. The incorporation of these particles in a polymeric matrix of ethylene vinyl acetate copolymer (EVA) resulted in the coloration of the same, confirming the efficiency of these particles as pigments. (AU) | |