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Journal of Thermal Analysis and Calorimetry
Authors:
C. Xavier
,
C. Costa
,
S. Crispim
,
M. Bernardi
,
M. Maurera
,
M. Conceiçăo
,
E. Longo
, and
A. Souza

Abstract  

The pigments used in ceramic applications are of nature predominantly inorganic and they should be thermally stable, insoluble in glazing, resistant to the chemical and physical agents' attacks. This work aimed at the synthesis by the polymeric precursor method of ZrO2-based inorganic pigments, doped with Fe, Ni, Co, Cr and Cu cations. The fired pigments were characterized by thermogravimetry (TG), differential thermal analysis (DTA) and X-ray diffraction (XRD). Among the metals used to zirconium-doping, the best result was achieved with the cations Cu, which presented the monophase pigment, even as 20 mol% of dopant. Up to the temperature of 1000C the pigments presented a good thermal stability.

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Journal of Thermal Analysis and Calorimetry
Authors:
Camila Xavier
,
R. Candeia
,
M. Bernardi
,
S. Lima
,
E. Longo
,
C. Paskocimas
,
L. Soledade
,
A. Souza
, and
Iêda Santos

Abstract  

Magnesium and zinc ferrites have been prepared by the polymeric precursor method. The organic material decomposition was studied by thermogravimetry (TG) and differential thermal analysis (DTA). The variation of crystalline phases and particle morphology with calcination temperature were investigated using X-ray diffraction (XRD) and scanning electronic microscopy (SEM), respectively. The colors of the ferrites were evaluated using colorimetry. Magnesium ferrite crystallizes above 800°C, presenting a yellow- orange color with a reflectance peak at the 600–650 nm range, while zinc ferrite crystallizes at 600°C, with a reflectance peak between 650–700 nm, corresponding to the red-brick color.

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Journal of Thermal Analysis and Calorimetry
Authors:
F. Vieira
,
Soraia Souza
,
A. Oliveira
,
S. Lima
,
E. Longo
,
C. Paskocimas
,
L. Soledade
,
A. Souza
, and
Iêda Santos

Abstract  

In this study undoped and Cr, Sb or Mo doped TiO2 were synthesized by polymeric precursor method and characterized by X-ray diffraction, UV–VIS spectroscopy, infrared spectroscopy and thermogravimetry (TG). The TG curves showed a continuous mass loss assigned to the hydroxyl elimination and Cr6+ reduction. Doped TiO2 samples showed a higher mass loss assigned to water and gas elimination at lower temperatures. In these doped materials a decrease in the anatase–rutile phase transition temperature was observed. After calcination at 1,000 °C, rutile was obtained as a single phase material without the presence of Cr6+.

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Journal of Thermal Analysis and Calorimetry
Authors:
D. Gouveia
,
R. Rosenhaim
,
M. de Maurera
,
S. Lima
,
C. Paskocimas
,
E. Longo
,
A. Souza
, and
I. Santos

Abstract  

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.

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Journal of Thermal Analysis and Calorimetry
Authors:
C. Santos
,
B. Capistrano
,
F. Vieira
,
M. Santos
,
S. Lima
,
E. Longo
,
C. Paskocimas
,
A. Souza
,
L. Soledade
, and
I. Santos

Abstract  

In this work, spinels with the general formula Zn2−xCoxTiO4 were synthesized by the polymeric precursor method and thermally treated at 1,000 °C. The powder precursors were characterized by TG/DTA. A decrease in the DTA peak temperature with the amount of zinc was observed. After the thermal treatment, the characterizations were performed by XRD, IR, colorimetry and UV/VIS spectroscopy. The XRD patterns of all the samples showed the presence of the spinel phase. Infrared spectroscopy showed the presence of ester complexes for Zn2TiO4 after thermal treatment at 500 °C, which disappeared after cobalt addition, indicating that organic material elimination was favored.

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Journal of Thermal Analysis and Calorimetry
Authors:
A. de Oliveira
,
J. Ferreira
,
Márcia Silva
,
Soraia de Souza
,
F. Vieira
,
E. Longo
,
A. Souza
, and
Iêda Santos

Abstract  

NiWO4 and ZnWO4 were synthesized by the polymeric precursor method at low temperatures with zinc or nickel carbonate as secondary phase. The materials were characterized by thermal analysis (TG/DTA), infrared spectroscopy, UV–Vis spectroscopy and X-ray diffraction. NiWO4 was crystalline after calcination at 350 °C/12 h while ZnWO4 only crystallized after calcination at 400 °C for 2 h. Thermal decomposition of the powder precursor of NiWO4 heat treated for 12 h had one exothermic transition, while the precursor heat treated for 24 h had one more step between 600 and 800 °C with a small mass gain. Powder precursor of ZnWO4 presented three exothermic transitions, with peak temperatures and mass losses higher than NiWO4 has indicating that nickel made carbon elimination easier.

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Journal of Thermal Analysis and Calorimetry
Authors:
M. R. S. Silva
,
S. C. Souza
,
I. M. G. Santos
,
M. R. Cassia-Santos
,
L. E. B. Soledade
,
A. G. Souza
,
S. J. G. Lima
, and
E. Longo
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Journal of Thermal Analysis and Calorimetry
Authors:
S. L. Porto
,
M. R. Cassia-Santos
,
I. M. G. Santos
,
S. J. G. Lima
,
L. E. B. Soledade
,
A. G. Souza
,
C. A. Paskocimas
, and
E. Longo
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Journal of Thermal Analysis and Calorimetry
Authors:
S. C. Souza
,
I. M. G. Santos
,
M. R. S. Silva
,
M. R. Cassia-Santos
,
L. E. B. Soledade
,
A. G. Souza
,
S. J. G. Lima
, and
E. Longo
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Journal of Thermal Analysis and Calorimetry
Authors:
Márcia Silva
,
Lydianne de O. Miranda
,
Maria Cassia-Santos
,
S. Lima
,
L. Soledade
,
E. Longo
,
C. Paskocimas
,
A. Souza
, and
Iêda Santos

Abstract  

Undoped and/or doped with 1 mol% of Co2+ Mg2TiO4 andMg2SnO4 powders were synthesized by the polymeric precursor method. The influence of the network former (Sn4+ or Ti4+) on the thermal, structural and optical properties was investigated. The recorded mass losses are due to the escape of water and adsorbed gases and to the elimination of the organic matter. Mg2TiO4 crystallizes at lower temperatures and also presents more ordered structure with a smaller unit call and having more intense green color than Mg2SnO4 has.

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