Characterization of Materials through High Resolution Coherent Imaging: Coherent Imaging I
Sponsored by: TMS Structural Materials Division, TMS: Advanced Characterization, Testing, and Simulation Committee
Program Organizers: Ross Harder, Argonne National Lab; Xianghui Xiao, Argonne National Laboratory; Richard Sandberg, Los Alamos National Laboratory; Saryu Fensin, Los Alamos National Laboratory; Brian Abbey, LaTrobe University; Ana Diaz, Paul Scherrer Institut

Monday 8:30 AM
February 27, 2017
Room: 25B
Location: San Diego Convention Ctr

Session Chair: Brian Abbey, ARC Centre of Excellence for Advanced Molecular Imaging

8:30 AM  
High Resolution Coherent Imaging for Materials: Anthony Rollett1; 1Carnegie Mellon University
    What if we could image dislocation networks under load? Of course this is possible with electron microscopy but high resolution coherent imaging with light (x-rays) offers the possibility of characterizing behavior in the bulk. This is just one example of how coherent imaging has the potential to transform materials science. In this case, one can imagine a combination of orientation mapping, strain mapping and defect imaging, all in 3D, all in the bulk, which allows the heterogeneity of plastic deformation to be quantified. In addition, the way in which dislocations interact with grain boundaries and particles in general could be better understood. Such capability will impact the validation of, e.g., dislocation dynamics models, and our understanding of practical problems such as the role of second phase particles in creep strength and crack propagation. Other examples of impact beyond structural materials will also be discussed.

9:10 AM  
Applications of High Resolution Coherent X-Ray Imaging Techniques for Investigating Additively Manufactured Materials: Ross Cunningham1; Anthony Rollett1; 1Carnegie Mellon University
    Additive Manufacturing (AM) or “3D-Printing” is rapidly progressing from a prototyping aid to a qualified low-volume fabrication method for highly complex metallic parts. However, before critical or load bearing applications will see industry implementation, a better understanding of the effects of process variables and post-processing history on microstructure, particularly in regards to defect properties, is required. The authors’ work utilizing high energy synchrotron-based µXCT to investigate porosity in AM Ti-6Al-4V will be addressed, as well as developing work using in-situ high speed X-ray imaging to observe defect formation mechanisms in real time. Possible future coherent imaging needs of the AM community will also be addressed.

9:30 AM  
3D Imaging of High-pressure Induced Deformation Twinning in a Nanocrystal: Xiaojing Huang1; Wenge Yang2; Ross Harder3; Yugang Sun4; Ming Lu1; Yong Chu1; Ian Robinson5; Ho-kwang Mao2; 1Brookhaven National Laboratory; 2HPSTAR; 3Advanced Photon Source; 4Center for Nanoscale Materials; 5University College London
    Quantitative in-situ visualization of nanocrystals’ response to external stress provides a unique opportunity to understand the complex process that determines crystal deformation. We will represent a novel method that utilizes Bragg coherent diffraction imaging technique to image three-dimensional morphology and strain evolution of a silver nanocrystal under high-pressure environment sealed inside a diamond anvil cell [1]. The pressure-introduced shearing stress triggered a plastic deformation, and a deformation twin along {111} direction was observed with precisely defined twin width. This method is expected to facilitate the understanding and interoperation of the deformation mechanism of nanocrystals and provide a characterization tool to boost the rational design and tuning properties of nanomaterials. [1] X. Huang, W. Yang, R. Harder, Y. Sun, M. Lu, Y. Chu, I. Robinson and H. Mao, "Deformation Twinning of a Silver Nanocrystal under High Pressure", Nano Letters, 15, 7644–7649, (2015).

9:50 AM  
Nanoscale Chemical Imaging of an Individual Catalyst Particle with Soft X-ray Ptychography: Johanna Weker1; Anna Wise1; Sam Kalirai2; Maryam Farmand3; David Shapiro3; Florian Meirer2; Bert Weckhuysen2; 1SLAC National Accelerator Laboratory; 2Utrecht University; 3Lawrence Berkeley National Laboratory
    Understanding Fe deposition in fluid catalytic cracking (FCC) catalysis is critical for the mitigation of catalyst degradation. We will present recent results employing soft X-ray ptychography with elemental and chemical sensitivity to determine at the nanoscale the distribution and chemical state of Fe in an aged FCC catalyst particle. [1] We will show that both particle swelling due to colloidal Fe deposition and Fe penetration into the matrix as a result of pre-cracking of large organic molecules occur. The application of ptychography with its superior resolution allowed us to provide direct visual evidence for these two distinct Fe-based deactivation mechanisms, which have so far been proposed only on the basis of indirect evidence. We will conclude with a discussion of ongoing work investigating the differences in the distribution and chemical state of Al in a fresh vs. aged FCC catalyst particle. 1. Wise, et al., ACS Catalysis, 2178-2181 (2016).

10:10 AM Break

10:30 AM  
3D X-ray Imaging of Defect Dynamics in Nanostructured Materials: Andrew Ulvestad1; 1Argonne National Laboratory
    Nanostructured materials are essential to solving grand challenges in energy storage, environmental sustainability, and global climate stability given their novel properties relative to their bulk counterparts, including size-tunable thermodynamics. “Defect engineering”, or the rational design and optimization of desired functionalities through deliberate defect manipulation, can be used to further optimize nanomaterial properties, but is limited in scope due to an inability of current probes to characterize defect dynamics under operando conditions in three-dimensional (3D) detail. Here I will discuss how Bragg coherent diffractive imaging (BCDI) can reveal the 3D dislocation distribution in single operating battery cathode nanoparticles, in palladium nanoparticles during the hydriding phase transformation, and in silver nanoparticles during dissolution. Our results point to interesting physics in single nanoparticles.

11:00 AM  
Characterizing Evolving Processes through Coupled CDI and Molecular Dynamics Studies: Mathew Cherukara1; Kiran Sasikumar1; Subramanian Sankaranarayanan1; Ross Harder1; 1Argonne National Lab
    Coherent X-ray diffraction imaging (CDI) is a powerful technique for operando characterization with the ability to provide time-evolving snapshots of defect structure, lattice dynamics and structural changes. It is however, limited to ~10 nm in spatial resolution, and can only image crystalline structures. Molecular dynamics (MD) simulations provide a complete atomic picture of dynamically evolving processes for system sizes that perfectly complement CDI experiments. Integrating the two approaches can provide insights into the underlying physics of materials processes that go beyond what each technique individually is capable of. Case studies from recent joint experimental and modelling studies of slowly evolving, catalytic processes as well as ultra-fast lattice dynamics following laser excitation will be presented. Finally we look at the potential to extend the effective resolution provided by CDI by coupling molecular statics (MS) simulations to experimental data through machine learning approaches.

11:30 AM  
Coherent Diffractive Imaging with Wavelength Spatial Resolution using 13.5nm High Harmonics: Full Field, High-contrast Imaging on a Tabletop: Dennis Gardner1; Michael Tanksalvala1; Elisabeth Shanblatt1; Xiaoshi Zhang2; Benjamin Galloway1; Christina Porter1; Robert Karl1; Charles Bevis1; Margaret Murnane1; Henry Kaptyen1; Daniel Adams1; Giulia Mancini1; 1University of Colorado; 2KM Labs
    Ptychography is a powerful coherent diffractive imaging (CDI) technique that relies on many diffraction measurements from overlapping areas of the sample. This approach introduces redundant information, and allows the ptychography algorithms to solve for both the object and illumination. In this talk, we introduce a novel constraint to the ptychography algorithm, termed Modulus Enforced Probe (MEP), which is based on the measurement of the un-diffracted illumination on the detector. We describe how the MEP constraint is employed within the ptychographic algorithm and show the improved convergence of the algorithm. We demonstrate the power of this additional probe constraint by demonstrating record 14nm spatial resolution imaging at a wavelength of 13.5nm for any light source. This experimental demonstration is the best wavelength-to-resolution ratio for any full-field, non-isolated sample, CDI-based microscope and in our case we achieve this using a tabletop-scale setup.

11:50 AM  
Revolutions in Coherent X-ray Sources Will Enable Dynamic Nanometer Scale Strain Imaging in Structural Materials: Richard Sandberg1; Saryu Fensin1; Ross Harder2; John Barber1; Richard Sheffield1; Reeju Pokharel1; Ricardo Lebensohn1; Cris Barnes1; 1Los Alamos National Laboratory; 2Argonne National Laboratory
    Two revolutionary technologies will continue to change the way we understand how materials are strained, damaged, and eventually fail – brilliant, coherent X-ray sources and coherent diffraction-based imaging techniques. Next generation synchrotrons known as diffraction limited storage rings and hard X-ray free electron lasers will change the available hard X-ray flux by orders of magnitudes and thus enable nanometer scale strain imaging in situ via Bragg coherent diffraction imaging (BCDI). In this talk, we will present our preliminary work on studying nanometer scale strain inside polycrystalline metal films via BCDI and a vision how future facilities will enable massively parallel BCDI on multiple grains simultaneously. This will essentially extend current high energy diffraction microscopy techniques to the nanometer regime and eventually enable imaging of multiple grains under dynamically loaded conditions.