Advanced Characterization of FeTi Alloys for Solid-State Hydrogen Storage
Hydrogen storage remains a major challenge for enabling a large-scale hydrogen economy, and FeTi alloys are strong candidates for hydrogen absorption. When these alloys are produced from recycled materials, additional elements may influence their performance. To ensure reliable and efficient hydrogen storage, it is essential to understand how microstructure and impurities affect the behavior of FeTi during hydrogen cycling.
Hydrogen (H₂) stands out as a promising energy carrier for achieving a CO₂-neutral economy. However, one of the key challenges in establishing a large-scale hydrogen economy is the efficient storage of H₂. Among the various storage methods, solid-state hydrogen storage using metal hydrides offers several advantages over liquid and gas storage, including higher energy density, reduced explosion risk, minimal H₂ loss rates, and the potential for hydrogen purification.
Iron-titanium (FeTi) alloys are particularly attractive for stationary hydrogen storage applications due to their ability to reversibly transform between FeTi and FeTiHx hydride phases under near-room temperature and pressure conditions. Utilizing recycled source materials can help lower production costs and support large-scale FeTi manufacturing. However, the incorporation of recycled materials may introduce additional elements that influence storage capacity and long-term cyclability. Gaining a deeper understanding of the effects of micro-/nanostructure and impurities in FeTi is crucial for optimizing material performance and facilitating the widespread adoption of solid-state hydrogen storage technologies.
Advanced characterization techniques such as transmission electron microscopy (TEM) and atom probe tomography (APT) provide valuable insights into the structural evolution, phase transformations, and microstructural modifications of FeTi during hydrogenation and dehydrogenation cycles. High-resolution scanning transmission electron microscopy (HRSTEM) enables precise identification of phase transitions, while energy-dispersive X-ray spectroscopy (EDS), electron energy loss spectroscopy (EELS), and APT allows for detailed elemental mapping of hydrogen and other elements, as well as the investigation of the influence of impurities on microstructural evolution, lattice defects, and grain boundary properties. In this project, these techniques are employed to assess the impact of the microstructure on both high-purity FeTi alloys and FeTi alloys derived from recycled Fe sources. By investigating the evolution of microstructure following hydrogenation cycles, we study the role of impurities originating from recycled materials. These findings contribute to the advancement of FeTi-based materials for efficient, reversible, and scalable hydrogen storage applications.