scholarly journals Characteristic boundaries associated with three-dimensional twins in hexagonal metals

2020 ◽  
Vol 6 (28) ◽  
pp. eaaz2600 ◽  
Author(s):  
Shujuan Wang ◽  
Mingyu Gong ◽  
Rodney J. McCabe ◽  
Laurent Capolungo ◽  
Jian Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Three Dimensional ◽  
Deformation Mode ◽  
Solute Segregation ◽  
Atomic Scale ◽  
Twin Boundaries ◽  
Hexagonal Close Packed ◽  
Transmission Electron ◽  
Dynamics Simulations

Twinning is a critically important deformation mode in hexagonal close-packed metals. Twins are three-dimensional (3D) domains, whose growth is mediated by the motion of facets bounding the 3D twin domains and influences work hardening in metals. An understanding of twin transformations therefore necessitates that the atomic-scale structure and intrinsic mobilities of facets be known and characterized. The present work addresses the former point by systematically characterizing the boundary structures of 3D {1¯012} twins in magnesium using high-resolution transmission electron microscopy (HRTEM). Eight characteristic facets associated with twin boundaries are reported, five of which have never been experimentally observed before. Further, molecular dynamics simulations suggest that the formation and motion of these facets is associated with the accumulation of twinning dislocations. This work provides insights into understanding the structural character of 3D twins and serves to develop strategies for modulating twin kinetics by modifying twin boundaries, such as solute segregation.

Transmission electron microscopy of C70 single crystals at room temperature

1992 ◽  
Vol 7 (9) ◽  
pp. 2440-2446 ◽  
Author(s):  
Vinayak P. Dravid ◽  
Xiwei Lin ◽  
Hong Zhang ◽  
Shengzhong Liu ◽  
Manfred M. Kappes
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Room Temperature ◽  
Three Dimensional ◽  
Real Space ◽  
Acceptable Error ◽  
Hexagonal Close Packed ◽  
Transmission Electron ◽  
High Resolution Tem ◽  
Hcp Structure

Transmission electron microscopy (TEM) techniques have been employed to study the room temperature solid state form of chromatographically purified C70. Tilting and electron diffraction experiments in three-dimensional reciprocal space, on samples prepared by crystallization from several different solvents, show that C70 crystallites adopt hexagonal close packed (hcp) structure with a = 1.01 ± 0.05 nm and c = 1.70 ± 0.08 nm. The extinctions and observed reflections conform to the P63/mmc space group. High resolution TEM images reveal the molecular order and periodicity associated with C70 crystallites in real space. The experimental results are in agreement with the preliminary computations of crystal structure within acceptable error limits.

In situ atomic scale visualization of surface kinetics driven dynamics of oxide growth on a Ni–Cr surface

2016 ◽  
Vol 52 (16) ◽  
pp. 3300-3303 ◽  
Author(s):  
Langli Luo ◽  
Lianfeng Zou ◽  
Daniel K. Schreiber ◽  
Matthew J. Olszta ◽  
Donald R. Baer ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Three Dimensional ◽  
Atomic Scale ◽  
Oxide Growth ◽  
Surface Kinetics ◽  
Initial Oxidation ◽  
Transmission Electron ◽  
Dimensional Growth

We report the in situ atomic-scale visualization of the dynamic three-dimensional growth of NiO during the initial oxidation of Ni–10at%Cr using environmental transmission electron microscopy.

Tomographic Imaging of Nanocrystals by Aberration-Corrected Scanning Transmission Electron Microscopy

2004 ◽  
Vol 839 ◽  
Author(s):  
Klaus van Benthem ◽  
Yiping Peng ◽  
Stephen J. Pennycook
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Scanning Transmission Electron Microscopy ◽  
Three Dimensional ◽  
Atomic Scale ◽  
Scanning Transmission Electron ◽  
Depth Direction ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Aberration Corrected

ABSTRACTIn aberration corrected scanning transmission electron microscopy, the depth of focus is of the order of a few nanometers, so that the three-dimensional shape of nanocrystals could so far not be determined with atomic resolution. Here we show that with the assistance of image simulations it is possible to achieve atomic-scale information in the depth direction by analyzing a through-focal series where the number of atoms in most columns can be determined by Z-contrast simulations. The error in this analysis is about two atoms in the thickest regions, and less in thinner regions.

Atomic Scale Analysis of Planar Defects in Polycrystalline Diamond

2006 ◽  
Vol 12 (6) ◽  
pp. 492-497 ◽  
Author(s):  
Rolf Erni ◽  
Bert Freitag ◽  
Peter Hartel ◽  
Heiko Müller ◽  
Peter Tiemeijer ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Polycrystalline Diamond ◽  
Atomic Scale ◽  
Twin Boundaries ◽  
Axis Orientation ◽  
Planar Defects ◽  
Transmission Electron ◽  
Local Distortions

Planar defects in a polycrystalline diamond film were studied by high-resolution transmission electron microscopy (HRTEM) and high-resolution scanning transmission electron microscopy (STEM). In both modes, sub-Ångström resolution was achieved by making use of two aberration-corrected systems; a TEM and a STEM CS-corrected microscope, each operated at 300 kV. For the first time, diamond in 〈110〉 zone-axis orientation was imaged in STEM mode at a resolution that allows for resolving the atomic dumbbells of carbon at a projected interatomic distance of 89 pm. Twin boundaries that show approximately the Σ3 CSL structure reveal at sub-Ångström resolution imperfections; that is, local distortions, which break the symmetry of the ideal Σ3 type twin boundary, are likely present. In addition to these imperfect twin boundaries, voids on the atomic level were observed. It is proposed that both local distortions and small voids enhance the mechanical toughness of the film by locally increasing the critical stress intensity factor.

Simulation of three Dimensional Defect Images in Transmission Electron Microscopy

1976 ◽  
Vol 34 ◽  
pp. 470-471
Author(s):  
W. D. Cooper ◽  
C. S. Hartley ◽  
J. J. Hren
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Three Dimensional ◽  
Crystalline Lattice ◽  
Continuum Models ◽  
Thin Foils ◽  
Transmission Electron ◽  
Microscope Images ◽  
General Computer Program ◽  
General Computer

Interpretation of electron microscope images of crystalline lattice defects can be greatly aided by computer simulation of theoretical contrast from continuum models of such defects in thin foils. Several computer programs exist at the present time, but none are sufficiently general to permit their use as an aid in the identification of the range of defect types encountered in electron microscopy. This paper presents progress in the development of a more general computer program for this purpose which eliminates a number of restrictions contained in other programs. In particular, the program permits a variety of foil geometries and defect types to be simulated.The conventional approximation of non-interacting columns is employed for evaluation of the two-beam dynamical scattering equations by a piecewise solution of the Howie-Whelan equations.

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