Investigations of Defective β-NiAl by Transmission Electron Microscopy

1981 ◽  
Vol 39 ◽  
pp. 58-59 ◽  
Author(s):  
H. C. Liu ◽  
E. Chang ◽  
T. E. Mitchell
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Defect Structures ◽  
Transmission Electron ◽  
Nial Phase ◽  
Wide Range ◽  
Diffraction Patterns ◽  
B2 Structure

The β-NiAl phase, which is an ordered B2 structure, covers a wide range of compositions extending from ∼46 at.% Ni to ∼60 at.% Ni. For non-stoichiometric β-NiAl, studies (1,2) have shown that, for compositions below 50 at.% Ni, structural vacancies are introduced on the Ni sublattice (denoted as VNi), but for compositions above 50 at.% Ni,excess Ni atoms replace A1 atoms on the A1 sublattice (denoted as NiAl). In this work, defect structures in compositions of 45, 45.5, 46, 47, 50, 55, 58 and 60 at.% Ni were studied by electron diffraction techniques in a Siemens 102 TEM.Figs. 1 and 2 show selected area diffraction patterns at the exact [011] and [001] zone axes respectively.

Compositional variation within some sedimentary chlorites and some comments on their origin

1985 ◽  
Vol 49 (352) ◽  
pp. 375-386 ◽  
Author(s):  
C. D. Curtis ◽  
C. R. Hughes ◽  
J. A. Whiteman ◽  
C. K. Whittle
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Single Crystal ◽  
Compositional Variation ◽  
Analytical Transmission Electron Microscopy ◽  
Decomposition Reactions ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
Crystal Electron

AbstractA range of authigenic sedimentary chlorites from sandstones has been studied by analytical transmission electron microscopy. Selected area (single crystal) electron diffraction patterns are of the Ib (β = 90°) polytype confirming the earlier observations of Hayes (1970).TEM analyses show all samples to be relatively rich in both Al and Fe. In the general formula (Mg,Fe,Al)n [Si8−xAlxO20](OH)16, x varies between 1.5 and 2.6; Fe/(Fe + Mg) between 0.47 and 0.83 and n between 10.80 and 11.54. Octahedral Al is close to 3 in this formulation and Fe2+ predominates over Fe3+. Swelling chlorites have significantly different compositions which are consistent with smectite/chlorite interstratifications.The Ib (β = 90°) polytype appears to be stable under conditions of moderate to deep burial. It replaces berthierine and swelling chlorites formed at lower temperatures. As commonly seen in grain coatings, however, it precipitates from porewater; solutes probably being contributed from several mineral decomposition reactions.

scholarly journals Odd electron diffraction patterns in silicon nanowires and silicon thin films explained by microtwins and nanotwins

2009 ◽  
Vol 42 (2) ◽  
pp. 242-252 ◽  
Author(s):  
Cyril Cayron ◽  
Martien Den Hertog ◽  
Laurence Latu-Romain ◽  
Céline Mouchet ◽  
Christopher Secouard ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Silicon Nanowires ◽  
Si Nanowires ◽  
Silicon Thin Films ◽  
Transmission Electron ◽  
Diffraction Patterns

Odd electron diffraction patterns (EDPs) have been obtained by transmission electron microscopy (TEM) on silicon nanowires grownviathe vapour–liquid–solid method and on silicon thin films deposited by electron beam evaporation. Many explanations have been given in the past, without consensus among the scientific community: size artifacts, twinning artifacts or, more widely accepted, the existence of new hexagonal Si phases. In order to resolve this issue, the microstructures of Si nanowires and Si thin films have been characterized by TEM, high-resolution transmission electron microscopy (HRTEM) and high-resolution scanning transmission electron microscopy. Despite the differences in the geometries and elaboration processes, the EDPs of the materials show great similarities. The different hypotheses reported in the literature have been investigated. It was found that the positions of the diffraction spots in the EDPs could be reproduced by simulating a hexagonal structure withc/a= 12(2/3)1/2, but the intensities in many EDPs remained unexplained. Finally, it was established that all the experimental data,i.e.EDPs and HRTEM images, agree with a classical cubic silicon structure containing two microstructural defects: (i) overlapping Σ3 microtwins which induce extra spots by double diffraction, and (ii) nanotwins which induce extra spots as a result of streaking effects. It is concluded that there is no hexagonal phase in the Si nanowires and the Si thin films presented in this work.

scholarly journals Automated Crystal Orientation Mapping by Precession Electron Diffraction-Assisted Four-Dimensional Scanning Transmission Electron Microscopy Using a Scintillator-Based CMOS Detector

2021 ◽  
Vol 27 (5) ◽  
pp. 1102-1112
Author(s):  
Jiwon Jeong ◽  
Niels Cautaerts ◽  
Gerhard Dehm ◽  
Christian H. Liebscher
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Scanning Transmission Electron Microscopy ◽  
Angular Resolution ◽  
Transmission Electron ◽  
Orientation Mapping ◽  
Scanning Transmission ◽  
Precession Electron Diffraction ◽  
Diffraction Patterns

The recent development of electron-sensitive and pixelated detectors has attracted the use of four-dimensional scanning transmission electron microscopy (4D-STEM). Here, we present a precession electron diffraction-assisted 4D-STEM technique for automated orientation mapping using diffraction spot patterns directly captured by an in-column scintillator-based complementary metal-oxide-semiconductor (CMOS) detector. We compare the results to a conventional approach, which utilizes a fluorescent screen filmed by an external charge charge-coupled device camera. The high-dynamic range and signal-to-noise characteristics of the detector greatly improve the image quality of the diffraction patterns, especially the visibility of diffraction spots at high scattering angles. In the orientation maps reconstructed via the template matching process, the CMOS data yield a significant reduction of false indexing and higher reliability compared to the conventional approach. The angular resolution of misorientation measurement could also be improved by masking reflections close to the direct beam. This is because the orientation sensitive, weak, and small diffraction spots at high scattering angles are more significant. The results show that fine details, such as nanograins, nanotwins, and sub-grain boundaries, can be resolved with a sub-degree angular resolution which is comparable to orientation mapping using Kikuchi diffraction patterns.

Hydrothermal Synthesis of PbS Hollow Spheres with Single Crystal-Like Electron Diffraction Patterns

2008 ◽  
Vol 8 (1) ◽  
pp. 379-385
Author(s):  
Pingtang Zhao ◽  
Jinmin Wang ◽  
Guoe Chen ◽  
Zhou Xiao ◽  
Jing Zhou ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Single Crystal ◽  
Sodium Citrate ◽  
Near Infrared ◽  
Hydrothermal Process ◽  
Hollow Spheres ◽  
Transmission Electron ◽  
Diffraction Patterns

PbS hollow spheres were successfully prepared by a sodium citrate-assisted hydrothermal process at 120 °C for 12 h, employing lead acetate trihydrate, thiourea and sodium citrate as precursors. The diameter of PbS hollow spheres is 200–400 nm, which is composed of about 50–80 nm nanoparticles. The synthesized product was characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), Fourier transform-infrared (FT-IR) spectroscopy, ultraviolet-visible spectrometer (UV-vis) and near-infrared absorption spectrometer (NIR). The effects of the reaction conditions on morphologies of PbS structures were investigated. Star-shaped and flat PbS crystals were obtained by changing some experiment conditions. The results show that temperature, sodium citrate concentration, sulfur sources and solvent play key roles on the final morphologies formation of PbS crystals. Especially, ED result indicates that PbS hollow spheres hold single crystal-like electron diffraction patterns. And the possible formation mechanism of hollow spheres was proposed.

TEMTUTOR - a Teaching Multimedia Program for TEM

1997 ◽  
Vol 3 (S2) ◽  
pp. 1161-1162
Author(s):  
V.-T. Kuokkala ◽  
T.K. Lepistö
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Stacking Faults ◽  
Teaching Tool ◽  
Formation Processes ◽  
Multimedia Program ◽  
Transmission Electron ◽  
Hands On ◽  
Diffraction Patterns

Teaching of transmission electron microscopy usually includes both lectures on the contrast theories, electron diffraction, etc., and practical hands-on operation of the microscope. The number of students attending the lectures is normally unlimited, but at the microscope, only a few persons can work at the same time. Since the microscopes are expensive, it would be of a great help if cheaper 'training' microscopes with basic imaging and diffraction capabilities were available. These functions, in fact, can quite easily be realized with fast personal computers and work stations, where the simulation of transmission electron micrographs and related diffraction patterns can help the student better understand the image formation processes. Adding text, audio and video help capabilities to the program, it can be made an efficient supplemental teaching tool.TemTutor for Windows is based on microScope for Windows, which is a BF/DF TEM micrograph simulation program for dislocations and stacking faults.

D-STEM: A Parallel Electron Diffraction Technique Applied to Nanomaterials

2010 ◽  
Vol 16 (5) ◽  
pp. 614-621 ◽  
Author(s):  
K.J. Ganesh ◽  
M. Kawasaki ◽  
J.P. Zhou ◽  
P.J. Ferreira
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Dark Field ◽  
Transmission Electron ◽  
Electron Diffraction Technique ◽  
Scanning Transmission ◽  
Stem Image ◽  
Diffraction Imaging ◽  
Diffraction Patterns

AbstractAn electron diffraction technique called D-STEM has been developed in a transmission electron microscopy/scanning transmission electron microscopy (TEM/STEM) instrument to obtain spot electron diffraction patterns from nanostructures, as small as ∼3 nm. The electron ray path achieved by configuring the pre- and postspecimen illumination lenses enables the formation of a 1–2 nm near-parallel probe, which is used to obtain bright-field/dark-field STEM images. Under these conditions, the beam can be controlled and accurately positioned on the STEM image, at the nanostructure of interest, while sharp spot diffraction patterns can be simultaneously recorded on the charge-coupled device camera. When integrated with softwares such as GatanTMSTEM diffraction imaging and Automated Crystallography for TEM or DigistarTM, NanoMEGAS, the D-STEM technique is very powerful for obtaining automated orientation and phase maps based on diffraction information acquired on a pixel by pixel basis. The versatility of the D-STEM technique is demonstrated by applying this technique to nanoparticles, nanowires, and nano interconnect structures.

Fast microstructure and phase analyses of nanopowders using combined analysis of transmission electron microscopy scattering patterns

2014 ◽  
Vol 70 (5) ◽  
pp. 448-456 ◽  
Author(s):  
P. Boullay ◽  
L. Lutterotti ◽  
D. Chateigner ◽  
L. Sicard
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Structure Refinement ◽  
Pattern Search ◽  
Phase Identification ◽  
Combined Analysis ◽  
Transmission Electron ◽  
Diffraction Patterns

The full quantitative characterization of nanopowders using transmission electron microscopy scattering patterns is shown. This study demonstrates the feasibility of the application of so-called combined analysis, a global approach for phase identification, structure refinement, characterization of anisotropic crystallite sizes and shapes, texture analysis and texture variations with the probed scale, using electron diffraction patterns of TiO2and Mn3O4nanocrystal aggregates and platinum films. Electron diffraction pattern misalignments, positioning, and slight changes from pattern to pattern are directly integrated and refined within this approach. The use of a newly developed full-pattern search–match methodology for phase identification of nanopowders and the incorporation of the two-wave dynamical correction for diffraction patterns are also reported and proved to be efficient.

The defects and intergrowth of lead oxides revealed by HRTEM

1992 ◽  
Vol 25 (2) ◽  
pp. 199-204 ◽  
Author(s):  
Y. G. Wang ◽  
H. Q. Ye ◽  
K. H. Kuo ◽  
J. G. Guo
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Structural Models ◽  
Planar Defects ◽  
Transmission Electron ◽  
Lead Oxides ◽  
Diffraction Patterns ◽  
Relationship Of

High-resolution transmission electron microscopy (HRTEM) and electron diffraction were used to investigate the microstructure of natural lead oxides found in Panzhihua Mountain, China. The electron diffraction patterns showed crossing of diffraction spots along 〈110〉 directions in litharge and along 〈100〉 directions in massicot and the structural images showed the domain-like texture, probably constructed by arrays of planar defects in the fundamental structures. Based upon the structure of these oxides the possible structural models of planar defects are discussed and the orientation relationship of litharge and massicot is determined.

Sign in / Sign up

Export Citation Format

Share Document