Study of hydrogen storage properties of Ti-Nb-Cr alloys

• Grant number: 22/06719-6
• Support Opportunities: Scholarships in Brazil - Master
• Start date: September 01, 2022
• End date: July 31, 2024
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal Investigator: Guilherme Zepon
• Grantee: Gabriela Chimello Mayer Dias
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated scholarship(s): 23/02732-0 - Study of phase transformations under hydrogen absorption and desorption in alloys of the Ti-Nb-Cr system., BE.EP.MS

Abstract

There is a global effort to meet the growing energy demand and, at the same time, reduce the consumption of fossil fuels. Using hydrogen as an energy carrier is one of the most promising solutions, but its efficient and safe storage is still an obstacle to its use on a large scale. In this scenario, the solid-state hydrogen storage, especially through metal hydrides, is very advantageous, allowing a high volumetric energy density at low pressures. Among the metal hydrides currently under study, alloys with a body-centered cubic (BCC) structure, such as the Ti-V-Cr system alloys and the Ti-V-Nb-Cr system alloys, have interesting properties for applications in solid state tanks close to the room temperature. However, the removal of vanadium would bring benefits concerning the cost of the material and the increase of the niobium content in the alloy would be of strategic interest for Brazil, where 98.53% of the reserves of the element are located. Although the literature on Ti-V-Cr ternary system alloys and Ti-V-Nb-Cr quaternary system alloys is quite extensive, studies on Ti-Nb-Cr ternary system alloys for hydrogen storage are scarce. Therefore, this master's project aims to investigate the structure and hydrogen storage properties of alloys of the Ti-Nb-Cr system produced by arc melting. Preliminary results showed that the TiNbCr equiatomic alloy solidifies mainly as a body-centered cubic (BCC) solid solution with small fractions of C15-type Laves phase and presents rapid hydrogen absorption kinetics at room temperature, absorbing 1.82 H/M (2.80 wt%) in 1 minute. Calculations of Pressure-Composition-Isotherm (PCI) diagrams, using a model reported in the literature, showed that an increase in the Nb/Ti ratio, considering the Cr content fixed at 33.3%at., increases the plateau pressures of the PCI diagrams. Thus, the effect of chemical composition on the structure and properties of the Ti-Nb-Cr system will be analyzed experimentally, through the production and characterization of alloys with the composition Ti33.3-xNb33.3+xCr33.3, where x = 0, 10, and 15.