Abstract
In this work, we investigated the effects of heat treatment on the microstructure, hydrogen storage characteristics and corrosion rate of a Ti34V40Cr24Fe2 alloy. The arc melted alloy was divided into three samples, two of which were separately quartz-sealed under vacuum and heated to 1000 °C for 1 h; one of these samples was quenched and the other furnace-cooled to ambient temperature. The crystal structures of the samples were studied via X-ray diffractometry and scanning electron microscopy. Hydrogenation/dehydrogenation characteristics were investigated using a Sievert apparatus. Potentiostat corrosion tests on the alloys were performed using an AutoLab® corrosion test apparatus and electrochemical cell. All samples exhibited a major body-center-cubic (BCC) and some secondary phases. An abundance of Laves phases that were found in the as-cast sample reduced with annealing and disappeared in the quenched sample. Beside suppressing Laves phase, annealing also introduced a Ti-rich phase. The corrosion rate, maximum absorption, and useful capacities increased after both heat treatments. The annealed sample had the highest absorption and reversible capacity. The plateau pressure of the as-cast alloy increased after quenching. The corrosion rate increased from 0.0004 mm/y in the as-cast sample to 0.0009 mm/y after annealing and 0.0017 mm/y after quenching.
Highlights
Ti-V-Cr body-centered-cubic (BCC) solid solution alloys are very promising for the storage of a large quantity of hydrogen at room temperature [1,2,3]
The overall corrosion reaction is written as follows: Mm +2Oxaq → M2+ aq +2Red(e− redox )aq. These reactions are charge-transfer processes that occur across the interface between the metal and the aqueous solution, they are dependent on the interfacial potential that essentially corresponds to what is called the electrode potential of metals in electrochemistry terms
The quenched sample was exposed to oxygen in the quenching medium; suggests homogenized in addition, the sample was annealed a vacuum-sealed the arise in plateau microstructure; pressure suggests the presence of a higher oxygenincontent
Summary
Ti-V-Cr body-centered-cubic (BCC) solid solution alloys are very promising for the storage of a large quantity of hydrogen at room temperature [1,2,3]. 1523 K for 5 min and at 1373 K for 8 h, and found that the sample annealed at 1523 K for 5 min had the best overall hydrogen storage properties, with a desorption capacity of 1.82 wt % and a dehydriding plateau pressure of 0.75 MPa. BCC solid solution alloys have very high gaseous phase hydrogen storage capacities, they suffer from severe capacity degradation during electrochemical applications due to the leaching of Vanadium (V) into the KOH electrolyte [21,22]. The overall corrosion reaction is written as follows: Mm +2Oxaq → M2+ aq +2Red(e− redox )aq These reactions are charge-transfer processes that occur across the interface between the metal and the aqueous solution, they are dependent on the interfacial potential that essentially corresponds to what is called the electrode potential of metals in electrochemistry terms.
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