This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: University of Sydney researchers have made a breakthrough by directly observing hydrogen in the tiny spaces between the atoms in metal alloys. The world-first observation of hydrogen dissolving in these 'metal crystal lattices' offers fresh insights into why hydrogen can weaken metals and how more hydrogen-resistant materials might be developed.
Hydrogen's role in a cleaner energy future is well known, but storing and transporting it safely remains a challenge. Hydrogen can enter metal pipelines and storage equipment, sometimes making otherwise strong metals prone to unexpected cracking. This is known as hydrogen embrittlement.
To understand and reduce this risk, scientists need to know how much hydrogen enters a metal, where it goes and how it interacts with the metal from within. But hydrogen atoms are tiny and very mobile, and so observing where they lie within alloys is a holy grail for metallurgy researchers. Led by professor Julie Cairney, the research team has made new observations of hydrogen between metal atoms, instead of observing it accumulating at imperfections in metal.
The researchers also found that the arrangement and chemical makeup of metal atoms influence where hydrogen prefers to reside. Published in Nature, these insights will help scientists understand how hydrogen moves through metals, where it collects and how it may contribute to damage. This knowledge could guide the development of stronger, more hydrogen-resistant alloys.
Hydrogen can exist in metals in three main forms: as compounds known as hydrides; trapped within defects; or dissolved in the tiny spaces between metal atoms. The first two have been experimentally observed before but the third, while understood theoretically, has been extremely difficult to observe directly. The research team used cryogenic atom probe tomography (cryo-APT) to investigate the three-dimensional distribution of hydrogen by swapping it out for deuterium, a heavier form of hydrogen, in several metallic alloys.
This allowed them to track hydrogen introduced during experiments while minimizing its loss during sample preparation, making its distribution inside metals easier to study. They found that the deuterium accumulated preferentially in certain regions, revealing how the arrangement and chemical composition of metal atoms influence where hydrogen resides within metal. With the addition of electron microscopy and theoretical calculations, the team verified that hydrogen is present between metal atoms, known as an interstitial state, rather than only being trapped at defects.
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