Nanoscale x-ray and electron tomography
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Introduction A material’s chemical and physical properties are closely related to its structural and compositional variations at the atomic or nanometer scale. An imaging tool that can reveal this information would be very useful and essential for research across many scientific fields. Tomography is such an imaging technique that allows complex structural or chemical features to be visualized in three dimensions, or through timeresolved in situ measurements, in four dimensions. This threedimensional (3D) information yields deep insights into the connection between the chemical composition and structure of a material and its functionality. Though the technique has a long history, the scientific challenges we are facing today have driven the development of many new capabilities such as time-resolved in situ studies, strain mapping, multimodal imaging, and nanoscale spatial resolution. An example of the strength of the approach is provided by the drive to understand the (de)lithiation process in lithium-ion batteries. The microstructural evolution, phase-change, and chemical composition variations accompanying the complicated electrochemical reaction play critical roles in determining the reliability, capacity, and lifetime of the battery. As a result, a 3D imaging tool that can monitor the charge-discharge process at the nanoscale and in real time is essential. Lin et al.,
using electron tomography, visualized, in three-dimensions, how lithiation fronts propagate in a NiO nanoplate and how it deforms (Figure 1a).1 Nanotomography has also been used to elucidate the temporal evolution and mechanical deformation processes in precipitation-strengthened Al-Cu alloys that are the basis of a large class of commercial Al alloys. Karia et al. were able to provide important insights into the deformation mechanisms in bulk samples that involve the nanoscale precipitates in these alloys (Figure 1b) using hard x-ray nanotomography.2 There are many developments in recent years to meet these demands. We discuss a few of these emerging techniques in this article.
Nanoscale x-ray and electron tomography The word tomography is derived from the ancient Greek word “tomos,” which means slice and section. The 3D view in tomography is obtained from a reconstruction of a series of projected two-dimensional (2D) images acquired at different angles. In medical radiology, this is often referred to as computed tomography (CT) for clinical applications because significant computation is involved. A brief history of the technique can be found in the 2016 MRS Bulletin issue3 dedicated to advanced tomography techniques for inorganic, organic, and biological materials. In this issue, we focus on nanoscale
Hanfei Yan, National Synchrotron Lightsource II, Brookhaven National Laboratory, USA; [email protected] Peter W. Voorhees, Northwestern University, USA; [email protected] Huolin L. Xin, Department of Physics and Astronomy, University of California, Irvine, USA; [email protected] doi:10.1557/mrs.2020.90
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• VOLUME 45 • APRIL 2020Univer
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