In the image of the week we see actual deuterium atoms (in red) embedded in steel. The image was produced by Chen et al. as reported in Science (DOI). The presence of hydrogen in steel in general is a serious matter as it causes brittleness and ultimately nasty things like bridges collapsingHydrogen embrittlement can be combated by thermal treatment and by adding vanadium carbide nanoparticles. These particles trap hydrogen and slow their diffusion. As for the visualisation the researchers relied on atom probe tomography (APT). In this technique atoms are stripped one by one from the metal surface and analysed by mass spectroscopy. This generates a 3D microscope image. Now, hydrogen is way too abundant and will photo-bomb any image but replacing hydrogen with deuterium solves that. Regular ferritic steel was used and an electrolytic method was applied to charge it with deuterium. With cryo transfer @100K gas diffusion was suppressed. In the image the blue areas indicate vanadium, clearly indicating H and V have a certain fondness for each other.