Otimização da síntese de nanoferritas de nizn dopada com cobre e cobalto
Different compositions of Ni0,5-xCuxZn0,5Fe2O4 and Ni0,5-xCoxZn0,5Fe2O4 0 ≤ x ≤ 0.3 were synthesized ferrite y the citrate precursor method. The stoichiometric compositions were calcined in air at 350°C and then pressed into pellets and toroids. The pressed samples were sintered at temperatures o...
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Formato: | doctoralThesis |
Idioma: | por |
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Universidade Federal do Rio Grande do Norte
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Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/17731 |
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Resumo: | Different compositions of Ni0,5-xCuxZn0,5Fe2O4 and Ni0,5-xCoxZn0,5Fe2O4 0 ≤ x ≤ 0.3
were synthesized ferrite y the citrate precursor method. The stoichiometric compositions were
calcined in air at 350°C and then pressed into pellets and toroids. The pressed samples were
sintered at temperatures of 1000, 1050 and 1100°C/3h in air control at the speed of heating
and cooling. The calcined powders were characterized by XRD, TGA / DTG, FTIR, SEM and
vibrating sample magnetometry (VSM) and the sintered samples by XRD, SEM, MAV,
density and measurements of permeability and magnetic losses. There was pure phase
formation ferrimagnetism applied at all temperatures except for A-I composition at all
sintering temperatures and A-II only at a temperature of 1100°C. Crystallite sizes were
obtained by Rietveld analysis, nanometer size from 11 to 20 nm for the calcined powders. For
SEM, the sintered samples showed grain size between 1 and 10 micrometers. Bulk density (ρ)
of sintered material presented to the Families almost linear behavior with increasing
temperature and a tendency to decrease with increasing concentration of copper, different
behavior of the B Family, where the increase in temperature decreased the density. The
magnetic measurements revealed the powder characteristics of a soft ferrimagnetic material.
Two processes of magnetization were considered, the superparamagnetism at low
temperatures (350°C) and the formation of magnetic domains at higher temperatures.
Obtaining the best parameters for P and B-II magnetic ferrites at high temperatures. The
sintered material at 1000°C showed a relative permeability (μ) from 50 to 800 for the A
Family and from 10 to 600 for the B Family. The samples sintered at 1100°C, B Family
showed a variation from 10 to 1000 and the magnetic loss (tan δ) of A and B Families, around
of 1. The frequency response of the toroidal core is in the range of 0.3 kHz. Several factors
contribute to the behavior of microstructure considering the quantities μ and tan δ, such as the
grain size, inter-and intragranular porosity, amount of grain boundary and the aspects of the
dynamics of domain walls at high frequencies. |
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