The purpose of this work is to evaluate the performance of Ni0.5Zn0.5Fe2O4 ferrite doped with 0.1 and 0.4 mol of Cu as a catalyst for the transesterification of soybean oil to biodiesel, using methanol. The samples were characterized by X-ray diffraction, nitrogen adsorption and scanning electron microscopy. The reaction was performed for 2 hours at a temperature of 160 °C, using 10 g of soybean oil, a molar ratio of oil: alcohol of 1:20, and 4% (w/w) of catalyst. The product of the reaction was characterized by gas chromatography, which confirmed conversion to methyl esters. The diffraction patterns showed the presence only of Ni0.5Zn0.5Fe2O4 ferrite phase with a crystallite size of 29 nm. The samples doped with 0.1 and 0.4 mol of Cu showed a surface area and particle size of 22.17 m²g- 1 and 50.47 nm; and 23.49 m²g- 1 and 47.64 nm, respectively. The morphology of both samples consisted of brittle block-shaped agglomerates with a wide particle size distribution. A comparative analysis of the two catalysts indicated that the catalyst doped with 0.4 mol of Cu showed the better performance, with a conversion rate of 50.25%, while the catalyst doped with 0.1 mol of Cu showed 42.71% conversion.

As ferritas geralmente são absorvedoras de radiação eletromagnética e apresentam a versatilidade de poderem ser manufaturadas com geometrias diferentes, e usadas na forma de ferritas policristalinas (corpo sinterizado) ou de compósitos de ferrita (adição de pó em matriz apropriada). A poliamida 6, por sua vez, pertence a uma classe de polímeros atraentes para aplicações em engenharia devido à combinação de propriedades como: estabilidade dimensional, boa resistência ao impacto sem entalhe e excelente resistência química. O objetivo deste trabalho foi sintetizar pós de ferrita NiFe2O4, e avaliar a adição destes em concentrações de 10, 30, 50 e 60% em massa a uma matriz polimérica de poliamida 6 usando um misturador da Haake Blücher, para obter compósitos de poliamida 6/NiFe2O4. Os pós e os compósitos foram caracterizados por difração de raios X (DRX) e microscopia eletrônica de varredura (MEV). Os difratogramas de raios X mostraram picos característicos da poliamida 6 e da ferrita. Por MEV foi observada a formação de aglomerados grandes para a concentração de 60% e, uma grande quantidade de poros. Para a concentração de 10%, as partículas ficaram mais dispersas, com menos aglomerados e menos poros no compósito.

Ferrites normally absorb electromagnetic radiation, being versatile in that they can be manufactured in different geometries and used as polycrystalline ferrites (sintered body) or composites of ferrite (with addition of the powder to an appropriate matrix). On the other hand, nylon 6 is an attractive polymer for engineering applications due to the combination of properties such as dimensional stability, good impact strength without notch indentation and excellent chemical resistance. The aim of this paper was to synthesize ferrite (NiFe2O4) powders and to evaluate their addition in concentrations of 10, 30, 50 and 60 wt% into a nylon 6 polymer matrix using a Haake Blücher mixer. The powders and the composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The X-ray diffractograms showed characteristic peaks of nylon 6 and ferrite. With SEM, large clusters were observed for the concentration of 60%, with a large amount of pores. For the 10% concentration, the particles became more dispersed with less clusters and less pores in the composite.

Este trabalho tem como objetivo analisar o efeito do óxido de níquel sobre as propriedades elétricas do sistema varistor ZnO.Bi2O3.Co2O3.MnO2 . Os sistemas foram sinterizados a 1100ºC, 1150 ºC, 1200 ºC e 1250 ºC, por 1 hora. A caracterização elétrica foi feita por meio de medidas de densidade de corrente em função do campo elétrico aplicado. A caracterização microestrutural foi obtida por meio de difração de raios X e microscopia eletrônica de varredura. As melhores propriedades elétricas foram obtidas para o sistema contendo 1,0% em mol de óxido de níquel, sinterizado a 1100 oC. A elevação da temperatura de sinterização causou uma redução nas propriedades elétricas, provavelmente devido a formação de uma microestrutura mais heterogênea.

The effect of nickel oxide addition on the electrical properties of the ZnO. Bi2O3. Co2O3. MnO2 varistor system was investigated. This system was sintered at 1100 ºC, 1150 ºC, 1200 ºC and 1250 ºC for one hour and electrical measurements (current density as a function of the applied electrical field) were carried out. The microstructural analyses were performed by scanning electron microscopy and X-ray diffraction. The best electrical properties were obtained for the system containing 1.0 mol% of nickel oxide, and sintered at 1100 ºC. A degradation in the electrical properties with increasing sintering temperature has been observed, probably due to an increase in the microstructural heterogeneity.