• IMDEA Materials Institute researchers are diving deep into High-Entropy Alloys as a solution for hydrogen storage and transportation in the project NATURE.
• NATURE is a subproject of the Coordinated Project “High Entropy Alloys Resistant to Hydrogen Embrittlement” (EARTH) (ref. TED2021-130255B-C31) and it forms one part of the European Union’s strategy to become the first climate-neutral continent by 2050.

In the quest for greener energy solutions, hydrogen-based technologies have emerged as strong contenders. However, one of the challenges lies in efficient hydrogen storage as traditional austenitic steels, commonly used for hydrogen vessels, suffer from embrittlement during storage.

With the aim of tackling that challenge, NATURE centres on the study of high-entropy alloys (HEAs), with their superior properties and potential to revolutionise hydrogen-related applications.

HEAs are a family of metallic materials composed of multiple principal elements in roughly equal proportions, exhibiting unique mechanical, thermal, and chemical properties compared to traditional alloys.

HEAs offer several benefits over traditional materials, such as enhanced mechanical strength, improved ductility, and high temperature stability, among others.

The objectives of the ambitious NATURE project, funded by the State Research Agency (AEI, in spanish) through the program of Strategic Projects Oriented towards Ecological Transition and Digital Transition, and coordinated by the Carlos III University of Madrid (UC3M), involve exploring the composition design, manufacturing, and modelling of these alloys for hydrogen storage.

To achieve the objective of obtaining a HEA with superior resistance to hydrogen embrittlement the study is approached both by the selection of the suitable phase formation through composition design using thermodynamic simulation techniques, and by microstructural modification through advanced powder metallurgy and additive manufacturing.

As well as IMDEA Materials Institute and the UC3M, the Technical University of Madrid (UPM) is also a collaborating partner in the project.

“UC3M and IMDEA Materials are working together on the composition design and manufacturing of HEAs through different routes,” explained Prof. Paula Alvaredo, from the UC3M. “Meanwhile, researchers at the UPM will carry out the simulation and modelling required to understand how the complex lattice influences the diffusion of hydrogen atoms as well as modifications in the morphology of the microconstituents can modulate hydrogen embrittlement,” she added.

The motivation behind the accelerated development of HEAs in recent years stems from the fact that these alloys “have a complex composition, consisting of more than five alloying elements which distorts the lattice, and which can change diffusion mechanisms and resistance characteristics,” revealed Prof. Alvaredo.

As such, extensive research is required in order to fully exploit their potential benefits over traditional metals.

Hydrogen embrittlement occurs when a metal’s ductility is reduced due to hydrogen absorption. Hydrogen atoms, being small, can permeate solid metals. Once absorbed, they lower the stress required for cracks to form and propagate.

IMDEA Materials’ research group composed of Dr. Damien Tourret, Dr. Juan Alberto Meza and Dr. María de Nicolás, is advancing on the study of these alloys. are among the world-class research team behind the project.

“When there is an atmosphere of molecular hydrogen, it often worsens the mechanical properties, causing metallic alloys to become more fragile”, said Dr. Meza.

Dr. de Nicolás added that, “this project involves all processing stages, observing the material’s effects, and also optimising the manufacturing process to prevent embrittlement at all costs”.

This publication is part of the TED2021-130255B-C31 project, funded by MCIN/AEI/10.13039/501100011033 and by the European Union “NextGenerationEU”/PRTR.