Black and green pigments based on chromium–cobalt spinels

Eliziário, Sayonara A.; Andrade, Jeferson M. de; Lima, Severino Jackson Guedes; Paskocimas, Carlos Alberto; Soledade, Luiz Edmundo Bastos; Hammer, Peter; Silva, Elson Longo da; Souza, Antônio Gouveia de; Santos, Ieda Maria Garcia dos

Black and green pigments based on chromium–cobalt spinels

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dc.contributor.author	Eliziário, Sayonara A.
dc.contributor.author	Andrade, Jeferson M. de
dc.contributor.author	Lima, Severino Jackson Guedes
dc.contributor.author	Paskocimas, Carlos Alberto
dc.contributor.author	Soledade, Luiz Edmundo Bastos
dc.contributor.author	Hammer, Peter
dc.contributor.author	Silva, Elson Longo da
dc.contributor.author	Souza, Antônio Gouveia de
dc.contributor.author	Santos, Ieda Maria Garcia dos
dc.date.accessioned	2021-04-09T20:50:45Z
dc.date.available	2021-04-09T20:50:45Z
dc.date.issued	2011-09-15
dc.description.resumo	Chromium and cobalt oxides are widely used in the manufacture of industrial pigments. In this work, the Co(Co2−xCrx)O4 powders with different chromium concentrations (x = 0, 0.25 and 1) were synthesized by the polymeric precursor method, heat treatment between 600 and 1000 °C. These powders were characterized by X-ray diffraction, infrared spectroscopy, colorimetry, UV–vis absorption and X-ray photoelectron spectroscopies. Even with the addition of chromium, the XRD patterns revealed that all powders crystallize in a single spinel cubic structure. The spinels with higher cobalt amount, Co(CoCr)O4 and Co(Co1.75Cr0.25)O4, displayed a dark color, without the Co3+ reduction observed in Co3O4 between 900 and 950 °C. The spinel with higher chromium amount, CoCr2O4, was green. The colors were directly related to the occupation of tetrahedral and octahedral sites by the chromophores, as well as to the different oxidation states of chromium and cobalt. The different optical band gap values estimated from UV–vis spectra suggested the existence of intermediary energy levels within the band gap. X-ray photoelectron spectroscopy confirmed an increasing presence of Co(III) and a decreasing amount of Cr(VI) with cobalt enrichment	pt_BR
dc.identifier.citation	ELIZIÁRIO, Sayonara A.; ANDRADE, Jeferson M. de; LIMA, Severino J.G.; PASKOCIMAS, Carlos A.; SOLEDADE, Luiz E.B.; HAMMER, P.; LONGO, E.; SOUZA, Antônio G.; SANTOS, Ieda M.G.. Black and green pigments based on chromium–cobalt spinels. Materials Chemistry And Physics, [S.L.], v. 129, n. 1-2, p. 619-624, set. 2011. Disponível em: https://www.sciencedirect.com/science/article/abs/pii/S0254058411003932?via%3Dihub. Acesso em: 24 fev. 2021. http://dx.doi.org/10.1016/j.matchemphys.2011.05.001	pt_BR
dc.identifier.doi	10.1016/j.matchemphys.2011.05.001
dc.identifier.issn	0254-0584
dc.identifier.uri	https://repositorio.ufrn.br/handle/123456789/32147
dc.language	en	pt_BR
dc.publisher	Elsevier	pt_BR
dc.rights	Attribution 3.0 Brazil	*
dc.rights.uri	http://creativecommons.org/licenses/by/3.0/br/	*
dc.subject	Chemical synthesis	pt_BR
dc.subject	Optical materials	pt_BR
dc.subject	Oxides	pt_BR
dc.subject	X-ray photo-emission spectroscopy	pt_BR
dc.title	Black and green pigments based on chromium–cobalt spinels	pt_BR
dc.type	article	pt_BR