Anisotropic strain variations during the confined growth of Au nanowires

The electrochemical growth of Au nanowires in a template of nano-porous anodic aluminum oxide was investigated in situ by means of grazing-incidence transmission small- and wide-angle x-ray scattering (GTSAXS and GTWAXS), x-ray fluorescence (XRF) and 2-dimensional surface optical reflectance (2D-SOR). The XRF and the overall intensity of the GTWAXS patterns as a function of time were used to monitor the progress of the electrodeposition. Furthermore, we extracted powder diffraction patterns in the direction of growth and in the direction of confinement to follow the evolution of the direction-dependent strain. Quite rapidly after the beginning of the electrodeposition, the strain became tensile in the vertical direction and compressive in the horizontal direction, which showed that the lattice deformation of the nanostructures can be artificially varied by an appropriate choice of the deposition time. By alternating sequences of electrodeposition to sequences of rest, we observed fluctuations of the lattice parameter in the direction of growth, attributed to stress caused by electromigration.. Furthermore, the porous domain size calculated from the GTSAXS patterns was used to monitor how homogeneously the pores were filled.Comment: Short communication manuscript. Four figure

Characterization of Irradiation Damage Using X-Ray Diffraction Line-Profile Analysis

During operation, structural components made of zirconium alloys are subject toneutron irradiation, which leads to the displacement of zirconium atoms fromtheir lattice sites, the production of self-interstitials and vacancies, and eventually dislocation loops. This process can lead to deleterious effects such as irradiation growth, creep, and embrittlement as well as accelerated aqueous corrosion. Quantitative analysis of dislocation line densities is seen as an importantpathway for distinguishing between the irradiation response of different alloys.The analysis of irradiation damage using X-ray diffraction (XRD) line-profile analysis has proven to be a powerful complementary technique to transmissionelectron microscopy, which samples a comparatively large volume and is lessaffected by the subjectivity of image analysis. In this paper we present andanalyze three different types of XRD experiments, describing their purpose andthe new insight achieved using each technique. First, we present work carriedout on neutron-irradiated samples, comparing dislocation line densities measured by XRD with macroscopic growth measurements. A second experimentusing a synchrotron-based X-ray microbeam enabled the mapping of dislocationline densities as a function of depth from the surface of proton-irradiated zirconium alloys. These data are compared with calculated damage profiles, providingnew insight into the early saturation of damage. Finally, the last example presented here focuses on synchrotron-based 3D XRD measurements, for whichdislocation-loop line densities were analyzed in hundreds of individual grains,providing excellent statistics about the grain-to-grain variability of line densities

High Resolution Reciprocal Space Mapping Reveals Dislocation Structure Evolution During 3d Printing

Dislocation structures are ubiquitous in any 3D printed alloy and they play a primary role in determining the mechanical response of an alloy. While it is understood that these structures form due to rapid solidification during 3D printing, there is no consensus on whether they evolve due to the subsequent solid-state thermal cycling that occurs with further addition of layers. In order to design alloy microstructures with desired mechanical responses, it is crucial to first answer this outstanding question. To that end, a novel experiment has been conducted by employing high resolution reciprocal space mapping, a synchrotron-based X-ray diffraction technique, in situ during 3D printing of a single-phase material. It reveals that dislocation structures formed during rapid solidification undergo significant evolution during subsequent solid-state thermal cycling, in particular during addition of the first few (up to 5) layers above the layer of interest

Revisiting Optical Reflectance from Au(111) Electrode Surfaces with Combined High-Energy Surface X-ray Diffraction

We have combined high-energy surface X-ray diffraction (HESXRD) with 2D surface optical reflectance (2D-SOR) to perform in situ electrochemical measurements of a Au(111) electrode in 0.1 M HClO4 electrolyte. We show that electrochemically induced changes to Au(111) surface during cyclic voltammetry can be simultaneously observed with 2D-SOR and HESXRD. We discuss how small one atom high 1x1 islands, accommodating excess atoms after the lifting of the surface reconstruction, can lead to discrepancies between the two techniques. The use of HESXRD allows us to simultaneously detect parts of the truncation rods from the (1 x 1) surface termination and the p x root 3 electrochemically induced surface reconstruction, during cyclic voltammetry. The presence of reconstruction phenomena is shown to not depend on having an ideally prepared surface and can in fact be observed after going to very oxidizing potentials. 2D-SOR can also detect the oxidation of the Au surface, however no oxide peaks are detected in the HESXRD signal, which is evidence that any Au oxide is X-ray amorphous