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Previous issue date: 2011-08-05 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The calcium ferrite (Ca2Fe2O5) has a perovskite-type structure with oxygen deficiency
and is used as a chemical catalyst. With the advent of nanoscience and nanotechnology,
methods of preparation, physical and chemical characterizations, and the technological
applications of nanoparticles have attracted great scientific interest. Calcium nanostructured
ferrites were produced via high-energy milling, with subsequent heat treatment. The milling
products were characterized by X-ray diffraction, magnetization and M?ssbauer spectroscopy.
Samples of the type Ca2Fe2O5 were obtained from the CaCO3 and Fe2O3 powder precursors,
which were mixed stoichiometrically and milled for 10h and thermally treated at 700?C,
900?C and 1100?C. The M?ssbauer spectra of the treated samples were adjusted three subespectros:
calcium ferrite (octahedral and tetrahedral sites) and a paramagnetic component,
related to very small particles of calcium ferrite, which are in a superparamagnetic state.
For samples beats in an atmosphere of methyl alcohol, there is a significant increase in area
associated with the paramagnetic component. Hysteresis curves obtained are characteristic
of a weak ferromagnetic-like material / A ferrita de c?lcio (Ca2Fe2O5) possui uma estrutura do tipo perovskita com defici?ncia
de oxig?nio e ? utilizada como catalisador qu?mico. Com o advento da nanoci?ncia
e da nanotecnologia, os m?todos de prepara??o, as caracteriza??es f?sicas e qu?micas, e as
aplica??es tecnol?gicas de nanopart?culas t?m despertado grande interesse cient?fico. Ferritas
de c?lcio nanoestruturadas foram produzidas via moagem de alta-energia, com subsequente
tratamento t?rmico. Os produtos da moagem foram caracterizados por difra??o de raios
X, magnetiza??o e espectroscopia M?ssbauer. Amostras do tipo Ca2Fe2O5 foram obtidas a
partir dos p?s-precursores Fe2O3 e CaCO3, os quais foram estequiometricamente misturados
e mo?dos por 10h e tratados termicamente a 700 C, 900 C e 1100 C. Os espectros M?ssbauer
das amostras tratadas foram ajustados com tr?s subespectros que correspondem ? ferrita de
c?lcio (s?tios octaedrais e tetraedrais) e a uma componente paramagn?tica, relacionada com
part?culas muito pequenas da ferrita de c?lcio, as quais est?o em estado superparamagn?tico.
Para as amostras batidas em atmosfera de ?lcool met?lico, observa-se um aumento significativo
da ?rea associada ? componente paramagn?tica. As curvas de histerese obtidas s?o
caracter?sticas de um material antiferromagn?tico com uma fraca componente ferromagn?tica.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/18594 |
| Date | 05 August 2011 |
| Creators | Amorim, Bruno Ferreira |
| Contributors | CPF:78609801420, http://lattes.cnpq.br/2148858591663240, Carri?o, Artur da Silva, CPF:33014419704, http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4787041Z8, Torres, Marco Morales, CPF:05225041752, http://lattes.cnpq.br/0091292234916055, Medeiros, Suzana N?brega de |
| Publisher | Universidade Federal do Rio Grande do Norte, Programa de P?s-Gradua??o em F?sica, UFRN, BR, F?sica da Mat?ria Condensada; Astrof?sica e Cosmologia; F?sica da Ionosfera |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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