Authors:D. Gouveia, R. Rosenhaim, M. de Maurera, S. Lima, C. Paskocimas, E. Longo, A. Souza, and I. Santos
With the aim of obtaining materials with applications in pigments, CoxZn7-xSb2O12 spinels were synthesized using the Pechini method. This method consists in the formation of a polymeric net, where the metallic
cations are homogeneously distributed. In this work, two types of alcohol (ethyl glycol and ethylene glycol) were used for
the synthesis of a zinc antimoniate spinel, CoxZn7-xSb2O12 (x=0-7). The materials were characterized by termogravimetry (TG) and differential thermal analysis (DTA). TG results indicated
a decrease in total mass loss when cobalt was added to the solution substituting zinc, for samples prepared using the two
different alcohols. Decomposition temperatures, obtained by TG and DTA, presented a decreasing behavior as cobalt was added
to the material. In relation to the alcohols, all results indicated a better polymerization of the resin when ethylene glycol
was used, being the most indicated one for cation immobilization. X-ray diffraction did not show differences between the two
alcohols - both presented the spinel phase (Co, Zn)2.33Sb0.67O4. Samples with higher quantity of cobalt also presented ilmenite phase (Co, Zn)Sb2O6.
Authors:J. Maul, A. S. Brito, A. L. M. de Oliveira, S. J. G. Lima, M. A. M. A. Maurera, D. Keyson, A. G. Souza, and I. M. G. Santos
Copper monoxide (CuO) was successfully obtained by microwave-assisted hydrothermal method, using different conditions—in a solution without base, in a solution alkalinized with NaOH or with NH4OH. The powders were analyzed by thermal analysis (TG/DTA), X-ray diffraction (XRD), infrared spectroscopy, UV–Visible spectroscopy, and scanning electronic microscopy. XRD results showed that CuO was obtained with monoclinic structure and without secondary phases. Thermal analysis and infrared spectra indicated the presence of acetate groups on the powder surface. TG curves also showed a mass gain assigned to the Cu(I) oxidation indicating that a reduction possibly occurred during synthesis. The high and broad absorption band in the UV–Vis spectroscopy from 250 to 750 nm indicated the coexistence of Cu(II) and Cu(I), confirming the Cu(II) reduction, inside the CuO lattice. It was also possible to confirm the Cu(II) reduction by a displacement of the Me–O vibration bands observed in the IR spectra at around 500 cm−1.
Authors:D. Gouveia, A. Souza, M. de Maurera, C. da Costa, I. Santos, S. Prasad, J. de Lima, C. Paskocimas, and E. Longo
Using the Pechini method, pigments with spinel structure (Zn7Sb2O12)were synthesized by substitution of the cation Zn2+ by Co2+, in compounds with different concentrations of Sb2O3. The doping resulted in CoxZn(7–x)Sb2O12 phases(x=1–7) that were isomorphs to spinel, denominated as samples A and B. After thermal treatment at 400C for 1 h, the powders
were characterized by thermogravimetry(TG) and differential thermal analysis (DTA). The results indicate a different behavior
whena higher amount of Sb2O3 is used, due to the presence of a secondary phase (ilmenite).