Abstract
Abstract Ball-milled nanocrystalline Mg powders catalyzed by TiO2 powder, titanate nanotubes and carbon nanotubes were subjected to intense plastic deformation by equal-channel angular pressing. Microstructural characteristics of these nanocomposites have been investigated by X-ray diffraction. Microstructural parameters, such as the average crystallite size, the average dislocation density and the average dislocation distance have been determined by the modified Williamson–Hall analysis. Complementary hydrogen desorption and absorption experiments were carried out in a Sieverts’ type apparatus. It was found that the Mg-based composite catalyzed by titanate nanotubes exhibits the best overall H-storage performance, reaching 7.1 wt% capacity. The hydrogenation kinetic curves can be fitted by the contracting volume function for all the investigated materials. From the fitted parameters, it is confirmed that the titanate nanotube additive results in far the best kinetic behavior, including the highest hydride front velocity.
Highlights
Ball-milled nanocrystalline Mg powders catalyzed by TiO2 powder, titanate nanotubes and carbon nanotubes were subjected to intense plastic deformation by equal-channel angular pressing
Despite the advantages of high-energy ball milling (HEBM), there exist some drawbacks, including high-energy consumption, expensiveness of industrial level production and surface oxidation with consequent potential fire risk. These disadvantages can comprehensively be eliminated by other severe plastic deformation (SPD) techniques, resulting in massive bulk samples, including high-pressure torsion (HPT) and equal-channel angular pressing (ECAP)
It was found that the multipass ECAP process of an Mg–Ni alloy at elevated temperature results in the evolution of a two phase (Mg + Mg2Ni) microstructure, which significantly accelerates the kinetics of hydrogenation and increase the equilibrium hydrogen pressure, in correlation with the chemical inhomogeneity formed during deformation [45]
Summary
Abstract: Ball-milled nanocrystalline Mg powders catalyzed by TiO2 powder, titanate nanotubes and carbon nanotubes were subjected to intense plastic deformation by equal-channel angular pressing. Despite the advantages of HEBM, there exist some drawbacks, including high-energy consumption, expensiveness of industrial level production and surface oxidation with consequent potential fire risk These disadvantages can comprehensively be eliminated by other SPD techniques, resulting in massive bulk samples, including high-pressure torsion (HPT) and equal-channel angular pressing (ECAP). It was found that the multipass ECAP process of an Mg–Ni alloy at elevated temperature results in the evolution of a two phase (Mg + Mg2Ni) microstructure, which significantly accelerates the kinetics of hydrogenation and increase the equilibrium hydrogen pressure, in correlation with the chemical inhomogeneity formed during deformation [45]. The hint of the present research is to replace these two types of catalyst additives by applying only metal-oxide-based nanotubes prepared from TiO2 and investigate its effect on the sorption properties of Mg prepared by the combined method of HEBM and ECAP. Magnesium samples catalyzed with TiO2 powder and with TiO2 and MWCNTs were synthesized
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