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[en] The aim of this work is to synthesize Mn-Zn ferrite powders by the combustion method using glycine as fuel. The influence of the substitution of the Mn²⁺ by the Fe²⁺ on the structural parameters of the powders also was investigated by X rays diffraction. According to the results it can be observed that the decrease in concentration of the metallic ions favored the formation of single crystalline Mn-Zn ferrite phase and the substitution of the Mn²⁺ by Fe²⁺ conferred a decrease in the crystallite size and in the lattice parameters of aleatory mixed spinel. All the powders presented high crystallinity and crystallite size between 37 and 39 nm. (author)

[en] Preparation and characterization of nanosized magnetic particles using alkaline oxidation of ferrous ion retained in acrylonitrile-methyl methacrylate-divinylbenzene (AN-MMA-DVB) spherical micron-sized polymer template is described. Atomic absorption, transmission electron microscopy and magnetic resonance were used to investigate chemically cycled nanoparticle-based composites. The resonance field shifts towards higher values as the nanoparticle concentration reduces in the polymeric template, following two very distinct regimes

[en] The mullite is an extremely important mineral for the field of ceramic applications because of its excellent physical, chemical, thermal and mechanical properties. As this material is rare in nature, many studies focus on the synthesis of the same through processes that are economically viable. One of the methods used for obtaining mullite consists in heating at high temperatures mixing sources of silica with alumina, such as aluminosilicates that are often used for this purpose. The aims of this study is to obtain mullite from compositions containing kaolin and alumina with different particle sizes. Initially the precursors were subjected to chemical, particle size and mineralogical characterization. The alumina has undergone a process of grinding for 15, 45 and 60 minutes. After formulation of the masses, the specimens were pressed and sintered at temperatures of 1200, 1300 and 1400 ° C, with a heating rate of 5 ° C / min and 60 minutes of residence time. Subsequently, the samples were subjected to physical and mechanical characterizations: linear shrinkage, apparent porosity, water absorption, apparent density flexural strength at three points. The results show the influence of granulometric distribution on the kinetics of reactions and the best results were observed for the mass containing kaolin and alumina subjected to milling for 45 minutes. (author)

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[en] The reuse of alumina residue in addition to reducing environmental impacts can be used as raw material in ceramic masses to mullite produce. This study aims to obtain mullite from compositions containing clays and alumina residue used heating in a conventional oven. The raw materials were processed and characterized. Subsequently, these compositions were formulated containing precursors in appropriate proportions based on the stoichiometry of the mullite 3:2. Then, heat treatment was performed at temperatures of 1300 to 1400°C and 5°C rate/min. The products obtained were characterized by XRD, analyzing qualitatively and quantitatively the phases formed. The results showed that is possible, from compositions containing clays and alumina residue to obtain mullite as major phase (>70%) and high crystallinity (> 80%) The percentage of mullite approached the values obtained with the compositions containing alumina and clays. (author)