Electrochemical hydriding of nanocrystalline TiFe alloys

Abstract

Nanocrystalline TiFe alloys with different morphology and microstructure were synthesized by mechanical alloying from the elemental powders with varied milling time. The particle morphology distinctly changes from globular to slaty between the 10th and 15th h of milling and then becomes spherical again after 30 h. The average particle size decreases continuously with milling time from about 50 lm (10 h milling) to 1-2 lm for the 30 h milled sample. X-ray diffraction analysis showed that after 15 h of milling alloying has already started. The initial mixture of metal powders transformed into amorphous or fine nanocrystalline material after 20 h. Further milling did not change the microstructure noticeably, i.e. it remaied nanocrystalline with some amount of amorphous fraction. Nanocrystalline Fe was also present in the end product. DTA analysis displayed exothermic effects due to crystallization reactions, revealing that the end product also contains the amorphous phase. Electrochemical hydrogen charge/discharge measurements of the as-milled alloys were carried out under galvanostatic conditions. It was found that with increased milling time the discharge capacity increased and reached a value of 230 mAh g -1 for the 30 h milled sample, which is a substantially higher value than those published for this alloy composition. The cycle life of the alloy with the finest nanostructure is, however, shorter compared to the coarser nanostructures.

Mechanical Composition Control for Ti-Based Hydrogen Storage Alloys

“…Hydrogen has attracted a great deal of consideration in recent years as a feasibly ideal energy carrier. Its application for mobility and portable electronics is to a large extent limited by the difficulty of finding an available storage method [1]. Developing of hydrogen storage compounds with high structural stability and hydrogen storage capacity makes the practical usage of hydrogen realizable [2].…”

“…Subsequently, the electrodes of AB 5 (LaNi 5 )-and AB 2 (ZrV 2 )-type alloys have already been implemented in rechargeable nickel-metal hydride (Ni/MH) batteries. The representative alloys among the most promising materials for hydrogen storage are titanium-based alloys, because of their storage property and cost-effectiveness [1].…”

“…Mechanical alloying (MA) is able to synthesize various non-equilibrium alloys so that it has been widely applied to modify properties of a hydrogen storage alloy [5]. It is well known that the TiFe alloy also synthesized by MA has been extensively studied [1,[6][7][8][9]. The aim of the present research is to study mechanical composition control for a Ti based hydrogen storage alloy and discuss about mass production of TiCrMn as a hydrogen storage alloy as a model hydrogen carrier.…”

Synthesis and Characterization of TiFe0.7−xMn0.3Vx (x = 0.05, and 0.1) and Ti1−yTayFe0.7Mn0.3 (y = 0.2, and 0.4) Nanostructured Metal Hydrides for Low Temperature Applications

“…These substitutions are used to improve activation properties of TiFe alloys by changing compositions stoichiometry [1,11,12,13]. For example, excess of titanium (Ti) in TiFe, i.e., Ti 1+x Fe, enables the alloy to be hydride without the activation treatment [1,11]. Hydrogenation and dehydrogenation kinetics are quite sensitive to material preparations, gas purity, system design etc.…”

“…In the last decades, many research works devoted to solid hydrogen storage using binary intermetallic compounds. Especially, hydrides based on intermetallic compounds of transition metals like AB type of alloys, are promising materials for light, safe and economical storage of hydrogen [1,2]. The A element is usually a transition metal or a rare earth metal and tends to form a stable hydride.…”