Synthesis and Characterization of High Entropy Alloys based on TiFe System

Abstract

Recently high entropy alloys (HEAs) have been tested as hydrogen storage systems and very promising results have been reported, such as, high hydrogen absorption capacities (in addition to high H / M ratios) at room temperature with fast absorption / desorption kinetics; and in some cases without the need of any kind of activation process in the material. In this research project, we will deal essentially with the synthesis and microstructural characterization of the HEAs of TiFe system (not yet explored in the literature) with a focus on the study of H2 storage properties. The alloys will initially be obtained by conventional arc-melting and by reactive milling under hydrogen atmosphere. Three original compositions will be evaluated in this study: TiFe-ZrNbNi, TiFe-ZrNbCr, TiFe-ZrNbCrNi. In order to obtain better activation results, the alloys will be further processed by High-Pressure Torsion (HPT). In this context, this research project aims to explore two main issues: i) to find the better optimization of compositions and the processing conditions in order to improve the activation, absorption and desorption kinetics at room temperature; ii) to evaluate and understand the differences and possible similarities between the crystallographic structures obtained and the mechanisms of activation, absorption and desorption of hydrogen of these alloys; and in this case an essential aspect is try to better understand the stability of deformed nanostructures and to design new nanostructures appropriate for this purpose. The results of this project will certainly contribute to a better understanding of the mechanisms and correlations between the processing, structure and hydrogen storage properties of HEAs envising competitive applications involving the hydrogen storage field. Finally, this research proposal is the result of the ongoing international collaboration between FCA / UNICAMP (Brazil) and Kyushu University (Japan), which has been resulting in joint work and publications. (AU)