The response to ballistic impact of alumina-ultra high molecular weight polyethylene (UHMWPE) composites with different relative concentrations of alumina was investigated. The impact tests were carried out at subsonic speed using a compressed air system. The results showed that the depth of penetration (DOP) in a Medium Density Fiberboard (MDF) bulkhead protected by a disk of the composite decreased with increasing concentration of alumina in the composite. Scanning electron microscopy (SEM) images of composites with 80 %, 85 % and 95 % alumina showed transgranular, intergranular and ductile fracture mechanisms.
Ferrites nanoparticles of Ni 1-x Zn x Fe 2 O 4 ferrites with x varying between 0 and 1, in steps of 0.2, were obtained by solution combustion synthesis (SCS) and dispersed in oil paint at the concentrations of 10, 20, 30 and 40% by ferrite weight of ferrite, with the aim of producing electromagnetic wave absorbing composites, in the X band (8-12 GHz). The ferrite powders obtained were characterized by X-ray diffraction (XRD), and to determine to mean crystallite size, crystallographic phases, as well as lattice parameters, was used the Rietveld method. The XRD results revealed the majority presence of the spinel cubic ferrite phase for all stoichiometries with crystallite size between 44 and 81 nm. The composites were characterized by the rectangular waveguide transmission line method to measure the absorption of the electromagnetic wave in the X band. The nanocomposites with 40% of NiFe 2 O 4 and Ni 0.8 Zn 0.2 Fe 2 O 4 presented the highest electromagnetic wave absorption performance.
ResumoManchas de óleo em um meio aquoso foram removidas utilizando compósitos de parafina com nanopartículas de ferritas de cobalto (CoFe2O4), níquel (NiFe2O4) e níquel-zinco (Ni0,7Zn0,3Fe2O4), nas proporções de 13,0% e 28,5% em peso. Para avaliar a eficiência da remoção, foi determinada a velocidade dos compósitos ao serem acoplados a uma mancha de óleo na superfície da água e submetidos ao campo magnético de um imã permanente. O melhor desempenho foi obtido com o compósito de parafina contendo 13,0% em peso de ferrita de níquel-zinco. Palavras-chave: Nanopartículas magnéticas; Remoção de manchas de óleo.
OIL SLICK REMOVAL IN AN AQUEOUS MEDIUM USING MAGNETIC NANOPARTICLES DISPERSED IN A WAX MATRIX AbstractOil slicks in an aqueous medium were removed using composites of paraffin with cobalt ferrite (CoFe2O4), nickel ferrite (NiFe2O4) and nickel-zinc ferrite (Ni0,7Zn0,3Fe2O4) at 13.0 wt% and 28.5 wt%. The removal efficiency was determined by measuring the speed of the composites when they were coupled to an oil slick on the water surface and subjected to the magnetic field of a permanent magnet. The best performance was achieved with the paraffin composite containing 13.0 wt% of nickel-zinc ferrite.
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