Efeito de diferentes rotas de processamento nas propriedades de armazenagem de hidrogênio da liga Mg – 8% p. Fe
Abstract
Interested in developing new, and less dependent on non-renewable
energy sources, researchers have been looking for different alternatives for
energy systems in the recent years. The “Hydrogen Economy” is an alternative
proposed which includes using hydrogen as an energy carrier. However, finding
and developing suitable materials still a technological challenge. One method of
storing hydrogen is through the use of metal hydrides, for which the Mg/MgH2
system is the most studied to this date. In order to improve its properties as a
hydrogen carrier, many additives and processing routes were proposed and
studied. The present work aims to investigate the effect of Fe addition and the
influence of mechanical processing of melt-spun ribbons. As comparison, high
pressure torsion discs were also produced with the same composition. HEBM
was performed using pure powders from Mg and Fe (8% wt.) to obtain the
mixture that underwent melt-spinning and was subsequently submitted to cold
rolling. The hydrogenation kinetic behaviour of the ribbons and HPT samples
was measured in a Sieverts-type apparatus. The (micro)structural aspects of
the samples were investigated with XRD, SEM and TEM and the thermal
properties of the absorbed samples were assessed by using DSC with TG and
QMS coupled analysis. TEM imaging shows that a bi-modal distribution of Fe
particles, ranging around 10-20 nm and 100-200 nm, was achieved in the
ribbons. The results suggest that, in metallic ribbons and with the used
composition, Fe does not have by itself a big effect in absorption kinetics, but
does influence desorption. Furthermore, different processing routes give rise to
different properties, but, within the studied scope, sample dimensions and
cracks were the most important features after the first cycle for kinetic
behaviour