Influência do combustível na síntese por reação de combustão de ferritas NI-ZN.

Abstract

In this work the Ni-Zn ferrites were synthesized by combustion reaction using as fuels the urea, glycine and a mixture 1:1 from both, aiming evaluates the influence of the fuels in the structural, morphologic and magnetic characteristics of the powders. The stoichiometric composition was established according to the concepts of the chemistry of propellants. The powders were characterized by: XRD, EDX, nitrogen adsorption (BET), grain sized distribution, SEM and AGM. The results of characterization of the powders showed that all the compositions presented the formation of the phase Ni-Zn ferrite with traces of secondary phases ZnO and Fe2O3. The crystallite size, the surface area and the agglomerates medium diameter were 15, 36 and 31 nm; 67.23, 2.97 and 3.72 m2/g, and 1.3, 6.4 and 11.3 m for the compositions with urea, mixture 1:1 and glycine, respectively. The saturation magnetization and the coercive field for prepared composition using glycine as fuel was 63% and 27%; 10% and 5% larger than the for the compositions with urea and mixture 1:1 of urea:glycine as fuel, respectively. The composition with urea presented the formation of agglomerates approximately in form spherical, smaller than 0,1 m and with maximum size around 2 m, while for the glycine and mixture 1:1, it was observed agglomerates of aspect of porous sponge and irregular form minor than 50 m. It was observed too smaller agglomerates of 3 and 1 m, respectively. The synthesized composition with mixture 1:1 of urea:glycine showed structural, morphologic and magnetic characteristics similar the glycine, indicating that the physiochemical characteristics of the glycine were predominant in the final characteristic of the powders. The produced powders with urea presented better nanocharacteristics, such as crystallite size, particle size and surface area, however they presented lower saturation magnetization. The best result of saturation magnetization was 74.29 emu/g observed for composition with glycine.