Navegando por Autor "Araujo, José Humberto de"
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Artigo Ni Zn nanoferrite for radar-absorbing material. Journal of Magnetism and Magnetic Materials(Elsevier, 2008-05) Araujo, José Humberto de; Lima, U. R.; Nasar, Marivalva Cerqueira; Nasar, Ricardo Silveira; Rezende, M. C.Nanoparticles of nickel–zinc ferrite have been prepared by using the citrate precursor method. According to scanning electron microscopy (SEM), the particle size is nanometric for the powder calcined at 350 °C/3.5 h. The phase formation has been studied by applying different calcining atmospheres, such as air and argon. Pure Ni–Zn ferrite has been observed when calcined in argon at the temperature of 350 °C. Hysteresis analyses have been done with magnetization of 53.01 emu/g at 350 °C and obtaining 84.62 emu/g at 1100 °C due to an optimization of domains formation at high temperature. Measures of reflectivity of Ni–Zn ferrite/epoxy composite have been obtained below 21% at 350 °C and above 96% at 1100 °C with a coercive field of 26.61 Oe. Low value of coercive field increased the mobilization of domains wall and increased the radiation absorption