Banca de DEFESA: SUZANA ARAÚJO BARBOSA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : SUZANA ARAÚJO BARBOSA
DATA : 28/08/2017
HORA: 09:00
LOCAL: Anfiteatro B CCET
TÍTULO:

Synthesis and Characterization of Nanocomposites of Ni-Cu and Halide CuCl Systems

PALAVRAS-CHAVES:

Nanoparticles, Nickel Hydride, CuCl, NiCu Alloys, Chitosan, Sol-gel.

PÁGINAS: 90
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Física
SUBÁREA: Física da Matéria Condensada
RESUMO:

The aim of this work is to synthesize and study crystalline, non-aggregated and monodispersed nanoparticles of three systems containing Ni and/or Cu. The samples were prepared through the sol-gel method assisted by chitosan polymer. The first system is a nanocomposite with average particle size of 9-27 nm. The phases are mainly Ni, α-NiH and β-NiH. The α-NiH phase showed a significant magnetic contribution at temperatures below 50 and the hydrides were chemically stable when stored in air along several months. The second system is an ionic semiconductor of Cu(I)Cl with spherical particles and with average diameter of 9 nm. The third system consists of the solid solution of Ni and Cu atoms, and these samples are a mixing of NixCu(1-x) (0,50<x<0,92) alloys with average particle sizes in the range of 11-90 nm. The transmission electron microscopy images seems to reveal Cu rich alloy phases near to the particles surface, and Ni rich alloys located at the center. Magnetic measurements as a function of temperature in the range of 300-800 K showed evidences of magnetic transitions related to alloys with 75<x<92. For temperatures below Tc of the Ni92Cu8 alloy, it was observed a magnetic signal due to the Hopkinson phase. For T>Tc we noticed a feature related to the Griffiths phase which is due to Ni clusters dispersed in the Cu rich alloy phase. The critical parameters for this phase are in close agreement with the literature. The analysis of the hysteresis curves revealed an enhancement of the magnetocrystalline anisotropy constant (Keff) and this result was ascribed to the development of a surface magnetic anisotropy. The Griffiths phase and the Keff effect seem to be related the Cu rich alloy phase, which may be located at the nanoparticles surface. Experiments in samples subjected to AC magnetic field showed absorption specific rates with increasing values in agreement with the whole Ni content of the samples. The maximum variation of temperatures occurred for intervals of 200 s, indicating that these samples have potential for use in magneto hyperthermia in the treatment of tumors.

MEMBROS DA BANCA:
Presidente - 1674707 - MARCO ANTONIO MORALES TORRES
Interno - 350830 - JOSE HUMBERTO DE ARAUJO
Interno - 1675199 - SUZANA NOBREGA DE MEDEIROS
Externo à Instituição - JOSE ALZAMIR PEREIRA DA COSTA - UERN
Externo à Instituição - JOSÉ ANTONIO HUAMANÍ COAQUIRA - UnB