In Situ Materials Characterization across Atomic and Microstructure Lengthscales

Advanced materials exhibit complex, hierarchical, and multiscale microstructures that control their performance. Today, optimization of these microstructures requires iterative, ex situ studies using multiple independent instruments with different samples. To address many of the grand challenges facing the material research community, it is desirable to correlate material performance under realistic processing and operating conditions with in situ characterization of material structures across atomic and microstructural length scales. To meet this need, we have made progress in recent years in developing a suite of materials-measurement techniques that combines ultra-small angle X-ray scattering, small-angle X-ray scattering, X-ray diffraction, X-ray photon correlation spectroscopy, and X-ray imaging. When making use of high energy x rays from a third generation synchrotron source, this combined suite of techniques not only enables investigation of thick, complex materials under real operating/ processing conditions, but also allows robust structural characterization over 7 decades of structural and microstructural feature sizes, from sub-angstrom to millimeters. Depending on the scattering characteristics of the material, it can cover an unprecedented 11 decades in scattering intensity. This arrangement also allows the combination of measurement techniques be determined solely by the user's needs, allowing an unparalleled flexibility in addressing any set of microstructure, structure and dynamics material-measurement requirements. In this presentation, we will focus on various considerations required to make this combined technique possible, and use data from a series of in situ studies of aluminum alloys as examples to demonstrate the unique capability of this instrument. We will also discuss the potential impact that multi-bend achromat lattice, a concept being embraced by the worldwide synchrotron community, has on this technique.

Towards in operando material process characterization over many length scales

The properties and performance of complex material systems are frequently controlled by phenomena that operate over many length-scales from sub-nanometers to millimeters. Understanding the behavior of such materials requires statistically-representative measurement of these effects on the structure and microstructure evolution across this entire length-scale range, over timescales that match those of the phenomena of interest. Small-angle X-ray and neutron scattering (SAXS and SANS) can address much of this need and reveal cause-and-effect phenomena acting across many length scales. This is especially true if SAXS or SANS are combined with wide-angle X-ray and neutron scattering (WAXS and WANS) diffraction measurements to follow the corresponding phase evolution. These concepts are demonstrated in several high-impact studies pursued with our collaborators, including in operando studies to measure: the effects of gas sorption on the structures and microstructures of new carbon sorbent materials [1]; precipitate formation and growth, together with associated phase transformations in advanced light-weight alloys during annealing or plastic deformation; real-time dissolution, clustering and agglomeration of silver nanoparticles in an acidic environment (relevant to environmental health and safety concerns) [2]; and even cement hydration phenomena related to concrete shrinkage. Many of these measurements were made at the ultra-small-angle X-ray scattering (USAXS) facility at the Advanced Photon Source where rapid combined USAXS/SAXS/WAXS studies are now possible under in operando conditions. Planned further development of the instrument capabilities will significantly enhance such in operando measurements, as can be demonstrated by the impact on these same studies [3].

From atoms to electrodes: Mesoscale effects in electrochemical conversion

Batteries are complex multicomponent devices wherein mesoscale phenomena-the nanoscale structure and chemistry of different components, and interactions thereof-drive functionality and performance. For example, electron/ion transport within the composite electrodes relies on bi-continuous nanostructuring to form electrically and ionicly conductive paths. Electrochemical conversion of different salts of a given metal yields a common and ostensibly identical product: the zero valent metal. For example, maximal lithiation of iron-based electrodes produces metallic iron nanoparticles for oxide, fluoride, and oxyfluoride electrodes alike. Accordingly, these provide an opportunity to explore the coupling of nanostructure development and anion chemistry, and correlate these with electrochemical performance. We combine synchrotron-based small angle X-ray scattering (SAXS) and pair distribution function (PDF) measurements to probe metallic iron formed by electrochemical conversion of different iron compounds across multiple length-scales and decouple the influence of anion chemistry and reaction temperature on the atomic structure and nanoscale morphology.