Distinguished iNANO lecture by group leader Jonathan Almer, X-ray Science Division, Argonne National Laboratory, USA

Group leader Jonathan Almer, X-ray Science Division, Argonne National Laboratory, USA

Exploring Materials with High-Energy X-rays
High-energy x-rays from 3rd generation synchrotron sources, including the Advanced Photon Source (APS), possess a unique combination of high penetration power and spatial, reciprocal space, and temporal resolution.  These characteristics, coupled with extensive worldwide efforts over the past decades, have produced a variety of 3D imaging techniques using both density and diffraction/scattering contrast.  I will describe our instrument which combines several of these techniques to study material microstructure through (i) absorption-based tomography, (ii) high-energy diffraction microscopy (HEDM or 3DXRD) and (iii) scattering tomography.   The latter two approaches are complementary, as HEDM provides diffraction information (strain, orientation, shape and size) of individual grains in polycrystalline aggregates while scattering tomography yields spatially resolved but grain-averaged information, particularly relevant for fine-grained materials below HEDM limits as well as non-crystalline and amorphous materials.

These techniques operate in air with large working distances between optics, samples and detectors.  This has enabled development and use of a variety of in situ environments to emulate the service conditions of a given material.  I will describe several of these environments, as well as highlight some illustrative science cases.  These include studies of plastic deformation and fracture in engineering materials for aerospace and nuclear applications, and inhomogeneities driving failure in emerging solid state battery materials.  Finally, planned developments of high-energy x-ray capabilities after the imminent APS upgrade to a diffraction-limited source will be discussed.