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Previous issue date: 2015-12-07 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / As ferritas de cobalto-mangan?s (Co1?xMnxFe2O4 e Co1,2Fe1,8?xMnxO4) possuem uma
estrutura do tipo espin?lio mista, e t?m sido consideradas como um das candidatas competitivas
para grande variedade de aplica??es em dispositivos, desde a gera??o e detec??o de
ultra-som, sensores, transformadores, bem como na ind?stria m?dica. Ferritas de cobaltomangan?s
nanoestruturadas foram produzidas via moagem de alta energia, com subsequente
tratamento t?rmico, e foram caracterizados por difra??o de raios X, fluoresc?ncia de raios
X, microscopia eletr?nica de varredura e magnetiza??o. Amostras do tipo Co1?xMnxFe2O4 e
Co1,2Fe1,8?xMnxO4 foram obtidas a partir dos p?s precursores Fe3O4, Co3O4 e Mn3O4, os quais foram
estequiometricamente misturados e mo?dos por 10h e tratados termicamente ? 900?C por 2h.
A difratometria confirma a forma??o das fases nanocristalinas puras para s?rie Co1,2Fe1,8?xMnxO4
com umdi?metro m?dio de cerca de 94nm. Verificou-se que o par?metro de rede aumenta com
a substitui??o do Fe3? pelo Mn3?. A fluoresc?ncia de raios X revelou que as por??es de metais nas
amostras estavam pr?xima das composi??es estequiom?tricas nominais. As caracter?sticas microestruturais
observadas nas micrografias demonstraram que as part?culas formadas apresentam
morfologia e granulometria bastante distintas. As medidas de histerese magn?ticas
realizadas em baixa temperatura, mostraram que a magnetiza??o de satura??o e reman?ncia
aumentaram com a concentra??o de mangan?s, enquanto que o campo coercivo diminuiu.
A constante de anisotropia (Ke f ), foi calculada a partir dos ajustes dos dados pela lei de
aproxima??o de satura??o. Verificou-se que a anisotropia diminui substancialmente com a
substitui??o do ferro pelomangan?s. / The cobalt-manganese ferrites (Co1?xMnxFe2O4 and Co1,2Fe1,8?xMnxO4) has a mixed
structure of spinel type and it has been regarded as one of candidates for petitive wide variety of
applications in devices from ultrasonic generation and detection, sensors, transformers, as well
as in medical industry. Ferrites cobalt-manganese nanostructured were produced via mechanical
alloying with subsequent heat treatment and were characterized by X-ray diffraction, X-ray
fluorescence, scanning electron microscopy and magnetization. Samples of Co1?xMnxFe2O4 and
Co1,2Fe1,8?xMnxO4 were obtained from the precursor powders Fe3O4, Co3O4 and Mn3O4 which were
stoichiometrically mixed and ground by 10h and heat treated at 900?C for 2h. The diffraction
confirmed the formation of the pure nanocrystalline phases to series Co1,2Fe1,8?xMnxO4 with an
average diameter of about 94nm. It was found that the lattice parameter increases with the
substitution of Fe3? by Mn3?. The x-ray fluorescence revealed that the portions of metals in
samples were close to the nominal stoichiometric compositions. The microstructural features
observed in micrographs showed that the particles formed show very different morphology and
particle size. The magnetic hysteresis measurements performed at low temperature showed
that the saturation magnetization and remanence increased as the concentration of manganese,
while the coercive field decreased. The anisotropy constant (Ke f ), was estimated from the data
adjustments the law of approaching saturation. It was found that the anisotropy decreases
substantially with the substitution of Fe by Mn.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/20690 |
| Date | 07 December 2015 |
| Creators | Amorim, Bruno Ferreira |
| Contributors | 78609801420, http://lattes.cnpq.br/2148858591663240, Dantas, Ana L?cia, 78604303472, http://lattes.cnpq.br/7211312864602492, Bezerra, Claudionor Gomes, 60992565472, http://lattes.cnpq.br/5085046065890176, Ara?jo, Jos? Humberto de, 24150720444, http://lattes.cnpq.br/2455132422249405, Mello, Vamberto Dias de, 67140475415, http://lattes.cnpq.br/4851197994170100, Torres, Marco Antonio Morales, Medeiros, Suzana N?brega de |
| Publisher | Universidade Federal do Rio Grande do Norte, PROGRAMA DE P?S-GRADUA??O EM F?SICA, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| 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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