At the Swiss Light Source SLS, researchers have developed a pioneering X-ray technique to probe the 3D orientation of a material’s building blocks at the nanoscale. Applied to a polycrystalline catalyst, the technique allows the visualisation of crystal grains, grain boundaries and defects – key factors dictating catalyst performance. Beyond catalysis, the innovation unlocks previously inaccessible details about the structure of diverse functional materials, including those used in information technology, energy storage and biomedical applications. The findings are reported in Nature.
Zoom in to the micro or nanostructure of functional materials, both natural and manmade, and you’ll find they consist of thousands upon thousands of coherent domains or grains – distinct regions where molecules and atoms are arranged in a repeating pattern.
Such local ordering is inextricably linked to the material properties. The size, orientation, and distribution of grains can make the difference between a sturdy brick or a crumbling stone; it determines the ductility of metal, the efficiency of electron transfer in a semiconductor, or the thermal conductivity of ceramics. It is also an important feature of biological materials: collagen fibres, for example, are formed from a network of fibrils and their organisation determines the biomechanical performance of connective tissue.
These domains are often tiny: tens of nanometres in size. And it is their arrangement in three-dimensions over extended volumes that is property-determining. Yet until now, techniques to probe the organisation of materials at the nanoscale have largely been confined to two-dimensions or are destructive in nature.
Now, using X-rays generated by the Swiss Light Source SLS, a collaborative team of researchers from Paul Scherrer Institute PSI, ETH Zurich, the University of Oxford and the Max Plank Institute for Chemical Physics of Solids have succeeded in creating an imaging technique to access this information in three-dimensions.
Read more on PSI website
Image: Many functional materials are composed of coherent domains or grains, where molecules and atoms are arranged in a repeating pattern that determines performance. X-ray Linear Dichroic Orientation Tomography (XL-DOT) allows 3D mapping of material microstructure at the nanoscale. Here, the technique is applied to a pillar of vanadium pentoxide catalyst, used in the production of sulfuric acid. The colours in the tomogram represent the different orientation of grains.
Credit: Paul Scherrer Institute PSI/Andreas Apseros
