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Aimo Winkelmann - One of the best experts on this subject based on the ideXlab platform.
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Approximant-based orientation determination of quasicrystals using Electron Backscatter Diffraction.
Ultramicroscopy, 2020Co-Authors: Grzegorz Cios, Gert Nolze, Aimo Winkelmann, Tomasz Tokarski, Ralf Hielscher, Radoslaw Strzalka, Ireneusz Buganski, Janusz Wolny, Piotr BałaAbstract:Orientation mapping of quasicrystalline materials is demonstrated using crystalline approximant structures in the technique of Electron Backscatter Diffraction (EBSD). The approximant-based orientations are symmetrised according to the rotational point group of the quasicrystal, including the visualization of orientation maps using proper colour keys for quasicrystal symmetries. Alternatively, approximant-based orientation data can also be treated using pseudosymmetry post-processing options in the EBSD system software, which enables basic grain size estimations. Approximant-based orientation analyses are demonstrated for icosahedral and decagonal quasicrystals.
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Electron Backscatter Diffraction beyond the mainstream
Crystal Research and Technology, 2017Co-Authors: Gert Nolze, Ralf Hielscher, Aimo WinkelmannAbstract:We present special applications of Electron Backscatter Diffraction (EBSD) which aim to overcome some of the limitations of this technique as it is currently applied in the scanning Electron microscope. We stress that the raw EBSD signal carries additional information which is useful beyond the conventional orientation determination. The background signal underlying the Backscattered Kikuchi Diffraction (BKD) patterns reflects the chemical composition and surface topography but also contains channeling-in information which is used for qualitative real-time orientation imaging using various Backscattered Electron signals. A significantly improved orientation precision can be achieved when dynamically simulated pattern are matched to the experimental BKD patterns. The breaking of Friedel's rule makes it possible to obtain orientation mappings with respect to the point-group symmetries. Finally, we discuss the determination of lattice parameters from individual BKD patterns. Subgrain structure in a single quartz grain. The increased noise level in the left map reflects the lower precision of a standard orientation determination using band detection by the Hough transform. The right map results from the same experimental raw data after orientation refinement using a pattern matching approach. The colors correspond an adapted inverse pole figure color key with a maximum angular deviation of about 2° from the mean orientation.
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pattern matching approach to pseudosymmetry problems in Electron Backscatter Diffraction
Ultramicroscopy, 2016Co-Authors: Gert Nolze, Aimo Winkelmann, Alan P. BoyleAbstract:We demonstrate an approach to overcome Kikuchi pattern misindexing problems caused by crystallographic pseudosymmetry in Electron Backscatter Diffraction (EBSD) measurements. Based on the quantitative comparison of experimentally measured Kikuchi patterns with dynamical Electron Diffraction simulations, the algorithm identifies the best-fit orientation from a set of pseudosymmetric candidates. Using measurements on framboidal pyrite (FeS2) as an example, we also show the improvement of the orientation precision using this approach.
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digital direct Electron imaging of energy filtered Electron Backscatter Diffraction patterns
Physical Review B, 2015Co-Authors: S Vespucci, G Nareshkumar, V Oshea, Aimo Winkelmann, K P Mingard, P. R. Edwards, Dzmitry Maneuski, C TragercowanAbstract:Electron Backscatter Diffraction is a scanning Electron microscopy technique used to obtain crystallographic information on materials. It allows the nondestructive mapping of crystal structure, texture, and strain with a lateral and depth resolution on the order of tens of nanometers. Electron Backscatter Diffraction patterns (EBSPs) are presently acquired using a detector comprising a scintillator coupled to a digital camera, and the crystallographic information obtainable is limited by the conversion of Electrons to photons and then back to Electrons again. In this article we will report the direct acquisition of energy-filtered EBSPs using a digital complementary metal-oxide-semiconductor hybrid pixel detector, Timepix. We show results from a range of samples with different mass and density, namely diamond, silicon, and GaN. Direct Electron detection allows the acquisition of EBSPs at lower (≤5 keV) Electron beam energies. This results in a reduction in the depth and lateral extension of the volume of the specimen contributing to the pattern and will lead to a significant improvement in lateral and depth resolution. Direct Electron detection together with energy filtering (Electrons having energy below a specific value are excluded) also leads to an improvement in spatial resolution but in addition provides an unprecedented increase in the detail in the acquired EBSPs. An increase in contrast and higher-order Diffraction features are observed. In addition, excess-deficiency effects appear to be suppressed on energy filtering. This allows the fundamental physics of pattern formation to be interrogated and will enable a change in the use of Electron Backscatter Diffraction (EBSD) for crystal phase identification and the mapping of strain. The enhancement in the contrast in high-pass energy-filtered EBSD patterns is found to be stronger for lighter, less dense materials. The improved contrast for such materials will enable the application of the EBSD technique to be expanded to materials for which conventional EBSD analysis is not presently practicable.
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Chirality determination of quartz crystals using Electron Backscatter Diffraction.
Ultramicroscopy, 2014Co-Authors: Aimo Winkelmann, Gert NolzeAbstract:We demonstrate the determination of crystal chirality using Electron Backscatter Diffraction (EBSD) in the scanning Electron microscope. The chirality of α-quartz as a space-group-dependent property is verified via direct comparison of experimental Diffraction features to simulations using the dynamical theory of Electron Diffraction.
D. F. Teter - One of the best experts on this subject based on the ideXlab platform.
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Analysis of recrystallized volume fractions in uranium using Electron Backscatter Diffraction
Journal of Microscopy, 2006Co-Authors: Rodney J Mccabe, D. F. TeterAbstract:Summary Electron Backscatter Diffraction was used to examine the recrystallization behaviour of warm, clock-rolled uranium. A new uranium preparation method was developed, resulting in acceptable specimen surface finishes nearly every time, even for as-rolled specimens. Recrystallized fractions were differentiated from unrecrystallized fractions using differences in the grain average misorientation, a measure of the internal level of misorientation within a grain. This new approach better estimates the recrystallized fraction than hardness measurements, and has the advantage over standard metallographic techniques of providing texture information.
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Analysis of recrystallized volume fractions in uranium using Electron Backscatter Diffraction
Journal of Microscopy, 2006Co-Authors: Rodney J Mccabe, D. F. TeterAbstract:Summary Electron Backscatter Diffraction was used to examine the recrystallization behaviour of warm, clock-rolled uranium. A new uranium preparation method was developed, resulting in acceptable specimen surface finishes nearly every time, even for as-rolled specimens. Recrystallized fractions were differentiated from unrecrystallized fractions using differences in the grain average misorientation, a measure of the internal level of misorientation within a grain. This new approach better estimates the recrystallized fraction than hardness measurements, and has the advantage over standard metallographic techniques of providing texture information.
Robert R Keller - One of the best experts on this subject based on the ideXlab platform.
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Restoration of firearm serial numbers with Electron Backscatter Diffraction (EBSD)
Forensic Science International, 2015Co-Authors: Ryan White, Robert R KellerAbstract:Abstract Firearm serial numbers are a critical identifying mark, and restoration of destroyed serial numbers is often crucial for prosecution of a criminal case. A method is presented utilizing Electron Backscatter Diffraction (EBSD) in the scanning Electron microscope (SEM) which allows for clear visualization of die-stamped imprints which have been completely polished away. Evidence of the stamp can be observed to a depth of approximately 760μm below the surface. With further development, the described method is capable of reconstructing an 8 character serial number in approximately 1h.
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Restoration of firearm serial numbers with Electron Backscatter Diffraction (EBSD)
Forensic Science International, 2015Co-Authors: Ryan White, Robert R KellerAbstract:Abstract Firearm serial numbers are a critical identifying mark, and restoration of destroyed serial numbers is often crucial for prosecution of a criminal case. A method is presented utilizing Electron Backscatter Diffraction (EBSD) in the scanning Electron microscope (SEM) which allows for clear visualization of die-stamped imprints which have been completely polished away. Evidence of the stamp can be observed to a depth of approximately 760μm below the surface. With further development, the described method is capable of reconstructing an 8 character serial number in approximately 1h.
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TRANSMISSION Electron Backscatter Diffraction IN THE SEM: SPECIMEN THICKNESS EFFECTS
2012Co-Authors: Katherine P Rice, Roy H. Geiss, Robert R KellerAbstract:Acknowledgements/References Transmission Electron Backscatter Diffraction (t-EBSD) is a new SEM-based Electron Diffraction technique that provides a significant improvement in spatial resolution over conventional EBSD for crystallographic analysis of materials1. The Electron-specimen interaction volume associated with t-EBSD is significantly smaller than that of conventional EBSD because the signal is formed by collecting Kikuchi-scattered transmitted Electrons in the SEM rather than Backscattered Electrons. The smaller volume results from the experimental conditions needed to detect transmitted Electrons:
Rodney J Mccabe - One of the best experts on this subject based on the ideXlab platform.
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a wedge mounting technique for nanoscale Electron Backscatter Diffraction
Journal of Applied Physics, 2013Co-Authors: John S Carpenter, Rodney J Mccabe, Irene J. Beyerlein, Thomas A Wynn, Nathan A. MaraAbstract:The practical spatial resolution of Electron Backscatter Diffraction (EBSD) is around 100 nm, which limits the length scales from which phase and orientation relationship characterization can be accomplished. This precludes collection of statistically relevant data on the crystallography of interfaces within nanomaterials where such information is essential for understanding the unique properties of these materials. In this work, we present a wedge-mounting technique that enables EBSD data to be collected for sub-100 nm thick layers of Cu-Nb bimetallic multilayers fabricated via accumulative roll bonding. We present statistics on layer thickness distributions, grain morphology, orientation distributions, twin volume fraction, and interface character for material with an averaged layer thickness of 86 and 56 nm.
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Analysis of recrystallized volume fractions in uranium using Electron Backscatter Diffraction
Journal of Microscopy, 2006Co-Authors: Rodney J Mccabe, D. F. TeterAbstract:Summary Electron Backscatter Diffraction was used to examine the recrystallization behaviour of warm, clock-rolled uranium. A new uranium preparation method was developed, resulting in acceptable specimen surface finishes nearly every time, even for as-rolled specimens. Recrystallized fractions were differentiated from unrecrystallized fractions using differences in the grain average misorientation, a measure of the internal level of misorientation within a grain. This new approach better estimates the recrystallized fraction than hardness measurements, and has the advantage over standard metallographic techniques of providing texture information.
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Analysis of recrystallized volume fractions in uranium using Electron Backscatter Diffraction
Journal of Microscopy, 2006Co-Authors: Rodney J Mccabe, D. F. TeterAbstract:Summary Electron Backscatter Diffraction was used to examine the recrystallization behaviour of warm, clock-rolled uranium. A new uranium preparation method was developed, resulting in acceptable specimen surface finishes nearly every time, even for as-rolled specimens. Recrystallized fractions were differentiated from unrecrystallized fractions using differences in the grain average misorientation, a measure of the internal level of misorientation within a grain. This new approach better estimates the recrystallized fraction than hardness measurements, and has the advantage over standard metallographic techniques of providing texture information.
Turab Lookman - One of the best experts on this subject based on the ideXlab platform.
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Convolutional neural network-based method for real-time orientation indexing of measured Electron Backscatter Diffraction patterns
Acta Materialia, 2019Co-Authors: Yu-feng Shen, Reeju Pokharel, Thomas Nizolek, Anil Kumar, Turab LookmanAbstract:Abstract Electron Backscatter Diffraction (EBSD) is the most commonly used technique for obtaining spatially resolved microstructural information from polycrystalline materials. We have developed two convolutional neural network approaches based on domain transform and transfer learning to reconstruct crystal orientations from Electron Backscatter Diffraction patterns. Our models are robust to experimentally measured image noise and index orientations as fast as the highest EBSD scanning rates. We demonstrate that the quaternion norm metric is a strong indicator for assessing the reliability of the reconstructions in the absence of the ground truth. We demonstrate the applicability of the current methods on a tantalum sample.
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Convolutional neural network-based method for real-time orientation indexing of measured Electron Backscatter Diffraction patterns
Acta Materialia, 2019Co-Authors: Yu-feng Shen, Reeju Pokharel, Thomas Nizolek, Anil Kumar, Turab LookmanAbstract:Abstract Electron Backscatter Diffraction (EBSD) is the most commonly used technique for obtaining spatially resolved microstructural information from polycrystalline materials. We have developed two convolutional neural network approaches based on domain transform and transfer learning to reconstruct crystal orientations from Electron Backscatter Diffraction patterns. Our models are robust to experimentally measured image noise and index orientations as fast as the highest EBSD scanning rates. We demonstrate that the quaternion norm metric is a strong indicator for assessing the reliability of the reconstructions in the absence of the ground truth. We demonstrate the applicability of the current methods on a tantalum sample.