A2B-type high entropy alloys for hydrogen storage

• Grant number: 18/08956-0
• Support Opportunities: Scholarships in Brazil - Master
• Start date: October 01, 2018
• End date: February 29, 2020
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Agreement: Coordination of Improvement of Higher Education Personnel (CAPES)
• Principal Investigator: Guilherme Zepon
• Grantee: Felipe Marques
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 13/05987-8 - Processing and characterization of amorphous, metastable and nano-structured metallic alloys, AP.TEM
• Associated scholarship(s): 19/01857-9 - In-situ characterization of the Mg22Ti22Nb22Cr11Mn11Ni11 and Mg22Ti22Nb22Fe11Co11Ni11 high entropy alloys for hydrogen storage, BE.EP.MS

Abstract

Hydrogen is a promising energetic vector that allows the use of renewable and sustainable energy, however, the storage of hydrogen in a safe and efficient way is a scientific and technological challenge that still has to be overcome. Recently, it has been reported that some high entropy alloys, multicomponent alloys that have the ability to crystallize as extended solid solutions with simple crystalline structures (BCC or FCC), have promising hydrogen storage properties. For example, the TiVZrNbHf alloy, which crystallizes with BCC structure, has the hydrogen storage capacity much higher than that of conventional metal hydrides. During hydrogenation, this alloy undergoes a hydrogen-induced phase transformation leading to the formation of a tetragonal body-centered structure. A similar behavior was observed in the high entropy alloy MgZrTiFe0.5Ni0.5Co0.5, proposed by the research group of the Hydrogen Laboratory in Metals (LH2M) of the Materials Engineering Department of the Federal University of São Carlos (DEMa / UFSCar) . This alloy was classified as a high entropy alloy of type A2B, where A are hydride-forming metal elements and B are transition metals with lower affinity for hydrogen. This master's project aims to study the hydrogen storage properties of new high entropy alloys of this type. The chemical compositions of five alloys will be selected based on a thermodynamic model that allows to predict which compositions have the greatest tendency to form monophasic microstructures based on extended solid solutions. The five selected alloys will be produced by high energy milling under inert atmosphere and characterized by different characterization techniques, such as X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The storage properties of hydrogen will be evaluated through volumetric techniques using Sieverts type apparatuses, and will be correlated with structural and thermodynamic parameters of the alloys.