Defect breakthrough opens possibilities in structural and electronic engineering Friday, 20 January 2017

Manufacturing stronger steel or more reliable semiconductors may be possible with the development of a new approach to detail the formation of changes in materials at the atomic scale and in near-real time.

A team from the US Department of Energy’s Argonne National Laboratory in Illinois captured images – for the first time ever – of the creation of structural defects in palladium when the metal is exposed to hydrogen.

They took a nanostructured sample of palladium and infused it with hydrogen at high-pressure. At the same time, they exposed the sample to powerful X-rays at their Advanced Photon Source.

Upon hitting the palladium crystal, the X-rays scattered, and their dispersion pattern was captured by a detector and used to calculate the changes in the position of atoms within the palladium structure. Essentially, this process enabled researchers to 'see' deformations within the material.

The changes shown in the scans exemplify the numerous ways in which defects can alter the properties of materials and how they respond to external stimuli. For instance, the defects that formed altered the pressures at which palladium could store and release hydrogen, knowledge that could be useful for hydrogen storage, sensing and purification applications, the researchers said.

“Defect engineering is based on the idea that you can take something you already know the properties of and, by putting in defects or imperfections, engineer things with improved properties,” said Argonne's Andrew Ulvestad.

“The practice applies not only to metals but any material that has a crystal structure, like those found in solar cells and battery cathodes.”

He said defect engineering is used to optimise material design across a variety of fields, but it is most commonly associated with the development of semiconductors. In a process known as doping, manufacturers create defects in these materials by adding impurities in order to manipulate their electrical properties for various technological uses.

“What we’ve done is create a roadmap for other researchers. We’ve shown them a way to model this system and systems that have similar dynamics,” he said.

[To map out changes in the metal palladium on the nanoscale, researchers used the diffraction patterns of X-rays. Image: Mark Lopez/Argonne National Laboratory]