Banca de DEFESA: JOÃO CARLOS ROCHA DE ARAÚJO
Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.DISCENTE : JOÃO CARLOS ROCHA DE ARAÚJO
DATA : 27/07/2018
HORA: 09:00
LOCAL: AUDITÓRIO DO DFTE
TÍTULO:
: Losses mechanisms in blocked and unlocked magnetic nanoparticles submitted to an alternating magnetic field
PALAVRAS-CHAVES:
Magnetic nanoparticle, magnetic hyperthermia, losses mechanisms.
PÁGINAS: 83
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Física
RESUMO:
The heating of magnetic nanoparticles submitted to an alternating magnetic field has attracted increasing interest of the scientific community in recent years. It is a consequence of the wide employment of nanoparticles and magnetic hyperthermia in, for instance, biomedical applications, such as drug delivery thermally activated and as a therapy for cancer treatment. When nanoparticles are under the influence of the alternating magnetic field, the heating is a result of physical mechanisms as magnetic relaxation and hysteresis loss, both directly associated with the magnetization reversion in this systems. In this work we aim to investigate the loss mechanisms in magnetic nanoparticles, as well as the thermal behavior of suspensions of nanoparticles dispersed in water, when submitted to an alternating magnetic field. To this end, we produce two sets of samples with distinct characteristics and investigate the structural, morphologic, magnetic and calorimetric properties in order to understand the effect of the particle size, composition and magnetic behavior on the loss mechanisms in magnetic hyperthermia. The first set of samples consists of magnesium ferrite MgFe2O4 annealed at 400 °C, 500 °C, 600 °C e 1000 °C, presenting particles with different diameters. The second set is composed by cobalt doped magnesium ferrites Mg1-xCox Fe2O4 with x = 0:0, 0:2, 0:5, 0:8 and 1:0, annealed at 1000 °C, allowing the evaluation of the influence of both, particle diameter and composition on the loss mechanisms. From these sets, particles in blocked and superparamagnetic states are obtained and we investigate the contributions of hysteresis loss, Brownian relaxation and Néel relaxation to the magnetic hyperthermia. Specifically, the experimental results reveal that the blocked particles present losses primarily associated with the hysteresis loss and Brownian relaxation, while the superparamagnetic ones have losses due to Néel relaxation. The results also disclose the dependence of such mechanism with the anisotropy field, this latter an important parameter in the process
MEMBROS DA BANCA:
Presidente - 1508681 - FELIPE BOHN
Externo à Instituição - JOHN CARLOS MANTILLA OCHOA - UFRN
Externo à Instituição - RODOLFO BEZERRA DA SILVA - UERN
Interno - 1675199 - SUZANA NOBREGA DE MEDEIROS