Estudo das propriedades magnéticas de nanocompósitos de CoFe2o4/CoFe2

• Ano de defesa: 2016
• Autor(a) principal: Ferreira, Edson Silva
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Mato Grosso; Brasil; Instituto de Física (IF); UFMT CUC - Cuiabá; Programa de Pós-Graduação em Física
• Palavras-chave em Português: Nanocompósitos; Ferrita de cobalto; Produto energético máximo; CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA; Nanocomposites; Cobalt ferrite; Maximum energy product
• Link de acesso: http://ri.ufmt.br/handle/1/2391

The objective of the work is to obtain nanocomposites of CoFe2 / CoFe2O4in their form that best maximizes their magnetic characteristics being they the saturation magnetization and the coercivity and in this way their maximum energetic product. The first step of the work was to prepare the samples (precursor) of CoFe2O4 using the stoichiometric type gelling-combustion synthesis method. After this, the nanocomposites were prepared in which two techniques were used to reduce the cobalt ferrite in cobalt iron. The first is a mixture of cobalt ferrite and activated carbon, which in this case will be the source of carbon in different proportions in order to verify which would be the best combination favoring its transformation into cobalt iron. The samples produced by this method were transformed into pellets with the intention of leaving their components closer to each other and facilitating the chemical reaction. In this method, two thermal treatments were applied, one in the ambient atmosphere and the other in an inert atmosphere of argon, to evaluate in which transformation would be greater. In the first case the samples were subjected to a temperature of 800 °C for 5 hours. And in the second case they were in an inert atmosphere of argon at a temperature of 900 °C for 5 hours. In the second method the cobalt ferrite underwent a thermal treatment at a temperature of 300 °C and 400 °C in time intervals ranging from 6 to 15 hours in an atmosphere of argon (95%) and hydrogen (5%), in which hydrogen Would be the reducing agent. Of the two methods, the most promising was the second with a transformation of 17% in cobalt iron and a 40% increase in the maximum energy product. It was also verified that the exchange spring interaction did not occur for one of the samples at a temperature below 250 k. In this way the study opens new possibilities of improvement of the magnetic properties of the material in view of its technological applications. The characterization techniques used were magnetometry of vibrating samples and X-ray diffraction.