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Previous issue date: 2015-09-14 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Nanopart?culas (Nps) s?o importantes no estudo de novos fen?menos na
f?sica e no desenvolvimento de novas aplica??es tecnol?gicas. Nanopart?culas
magn?ticas met?licas tais como N?quel e Cobalto surgem como objetos
promissores devido as suas aplicabilidades em v?rias ?reas da ci?ncia e tecnologia.
No presente trabalho apresentamos um estudo sobre o m?todo de
s?ntese, caracteriza??o estrutural e magn?tica em nanopart?culas de Ni e Co.
As amostras foram preparadas pelo m?todo sol-gel modi cado e formadas
nos poros do pol?mero quitosana, a redu??o ocorreu em aus?ncia de uxo de
Hidrog?nio. A fase cristalina do Ni e Co ? c?bica de face centrada e seus di?-
metros variaram de 59-77nm e 19-50nm, respectivamente. As superf?cies das
nanopart?culas foram naturalmente passivadas com seus mon?xidos apresentando
estabilidade qu?mica por longos intervalos de tempo. A estrutura formada
? do tipo n?cleo/casca, o que favoreceu as intera??es de exchange bias
entre o n?cleo ferromagn?tico (FM) e a casca antiferromagn?tica (AFM). As
condi??es de s?ntese foram otimizadas para obter principalmente a fase FM.
Ambas NPs foram submetidas ? a??o de um campo magn?tico AC e houve
aquecimento r?pido at? atingir temperatura de aproximadamente 140?C em
intervalos de tempo de at? 5 min. As amostras dispersadas em ?gua, atingiram
temperaturas de 40- 59?C de aquecimento em at? 10 minutos, mostrando
potencial para aplica??es em hipertermia magn?tica. / Nanoparticles are importante for the study of new phenomena and for
the development of new applications. Metallic magnetic nanoparticles like
Cobalt and Nickel are important for their applications in nanoscience and nanotechnology.
In this work, we report on the synthesis and characterization
of Ni and Co nanoparticles. The nanoparticles were prepared by the modi-
ed sol-gel method and were formed in the pore-network of the biopolymer
quitosan. The reduction occurred in absence of H2 ux. The metallic particles
and their monoxides have a face-centered- cubic structure. The metallic
particles sizes ranged from 59 to 77 nm and from 19 to 50 nm for Ni and Co,
respectively. Their monoxides chemically passivated the metallic cores, and
after several weeks we have not observed further increase in oxidation. The
synthesis method was tuned to obtain mainly the ferromagnetic phase. The
system behaves like a core/shell structure with a ferromagnetic core and an
antiferromagnetic shell. Exchange bias e ect was observed at temperatures
below the N?el temperature. Both systems were submitted to an alternated
magnetic eld and the heat released by the particles increased the temperature
to 140?C in an interval of 5 min. Similar studies in samples dispersed in
water increased the temperatures to 40-59?C, these results suggest that these
materials are candidates for magnetic hyperthermia.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/20615 |
| Date | 14 September 2015 |
| Creators | Sousa, Nagilson Mendes de |
| Contributors | 05225041752, http://lattes.cnpq.br/0091292234916055, Soares, Jo?o Maria, 67136958415, http://lattes.cnpq.br/2108722656012583, Medeiros, Suzana N?brega de, 78609801420, http://lattes.cnpq.br/2148858591663240, Torres, Marco Antonio Morales |
| 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/masterThesis |
| 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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