Dr. Jonathan Almer
Argonne National Laboratory
Watching Microstructures Evolve 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 efforts to combine 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/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, with an overarching goal to best emulate the (often extreme) service conditions of a given material. I will describe several of these environments, including the RAMS and IRadMat (thermo-) mechanical loading systems and additive manufacturing platforms, while highlighting some of the resulting scientific output – particularly in the area of structural materials. Limitations as well as planned developments of these techniques will be discussed, both prior to and after the planned APS upgrade to a diffraction-limited source.
BIO: Jonathan Almer conducts research in the fields of materials science, chemistry and biology using high-energy X-ray scattering and imaging. As a beamline scientist at the Advanced Photon Source, he develops novel techniques and acts as a scientific liaison to a host of academic and industrial partners.
Ongoing collaborations include micromechanics of bone and teeth with Northwestern University, battery and fuel-cell investigations with Argonne chemistry staff, thermo-mechanical studies of turbine blades and advanced steels with various Argonne and external groups, and archaeo-metallurgy studies with the Art Institute of Chicago.
Prior to coming to Argonne, Almer was a post-doc in Linkoping, Sweden where he designed and evaluated metal-nitride films for improved tribological applications.