Lattice imaging and pore structure of β ferric oxyhydroxide

1978 ◽  
Vol 36 (1) ◽  
pp. 264-265
Author(s):  
T. Baird ◽  
J.R. Fryer ◽  
S.T. Galbraith
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Bulk Material ◽  
Model Structure ◽  
Bulk Crystals ◽  
Lattice Imaging ◽  
Thin Sections ◽  
Ferric Oxyhydroxide ◽  
Resolution Electron ◽  
Hydrolysis Of

Introduction Previously we had suggested (l) that the striations observed in the pod shaped crystals of β FeOOH were an artefact of imaging in the electron microscope. Contrary to this adsorption measurements on bulk material had indicated the presence of some porosity and Gallagher (2) had proposed a model structure - based on the hollandite structure - showing the hollandite rods forming the sides of 30Å pores running the length of the crystal. Low resolution electron microscopy by Watson (3) on sectioned crystals embedded in methylmethacrylate had tended to support the existence of such pores.We have applied modern high resolution techniques to the bulk crystals and thin sections of them without confirming these earlier postulatesExperimental β FeOOH was prepared by room temperature hydrolysis of 0.01M solutions of FeCl3.6H2O, The precipitate was washed, dried in air, and embedded in Scandiplast resin. The sections were out on an LKB III Ultramicrotome to a thickness of about 500Å.

Structure, Composition and Stability of Heterophase Boundaries

1997 ◽  
Vol 3 (S2) ◽  
pp. 673-674
Author(s):  
M. Rühle ◽  
T. Wagner ◽  
S. Bernath ◽  
J. Plitzko ◽  
C. Scheu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Elevated Temperatures ◽  
Analytical Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Advanced Materials ◽  
Bulk Crystals ◽  
Transmission Electron ◽  
Resolution Electron ◽  
The Stability

Heterophase boundaries play an important role in advanced materials since those materials often comprise different components. The properties of the materials depend strongly on the properties of the interface between the components. Thus, it is important to investigate the stability of the microstructure with respect to annealing at elevated temperatures. In this paper results will be presented on the structure and composition of the interfaces between Cu and (α -Al2O3. The interfaces were processed either by growing a thin Cu overlayer on α- Al2O3 in a molecular beam epitaxy (MBE) system or by diffusion bonding bulk crystals of the two constituents in an UHV chamber. To improve the adhesion of Cu to α -Al2O3 ultrathin Ti interlayers were deposited between Cu and α - Al2O3.Interfaces were characterized by different transmission electron microscopy (TEM) techniques. Quantitative high-resolution electron microscopy (QHRTEM) allows the determination of the structure (coordinates of atoms) while analytical electron microscopy (AEM) allows the determination of the composition with high spatial resolution.

High-Resolution Electron Microscopy on Thin Sections of Monodisperse CdS Particles

1996 ◽  
Vol 183 (1) ◽  
pp. 295-298 ◽  
Author(s):  
Jun-Mo Yang ◽  
Daisuke Shindo ◽  
Grace E. Dirige ◽  
Atsushi Muramatsu ◽  
Tadao Sugimoto
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Thin Sections ◽  
Resolution Electron

Microstructure of epitaxial VO2 thin films deposited on (1120) sapphire by MOCVD

1994 ◽  
Vol 9 (9) ◽  
pp. 2264-2271 ◽  
Author(s):  
H. Zhang ◽  
H.L.M. Chang ◽  
J. Guo ◽  
T.J. Zhang
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Deposition Temperature ◽  
Room Temperature ◽  
High Resolution Electron Microscopy ◽  
Sapphire Substrates ◽  
Resolution Electron ◽  
Initial Nucleation ◽  
Vo2 Thin Films ◽  
Conventional Electron Microscopy

Epitaxial VO2 thin films grown on (1120) sapphire (α-Al2O3) substrates by MOCVD at 600 °C have been characterized by conventional electron microscopy and high resolution electron microscopy (HREM). Three different epitaxial relationships between the monoclinic VO2 films and sapphire substrates have been found at room temperature: I. (200) [010] monoclinic VO2 ‖ (1120) [0001] sapphire, II. (002) [010] monoclinic VO2 ‖ (1120) [0003] sapphire, and III. (020) [102] monoclinic VO2 ‖ (1120) [0001] sapphire. Expitaxial relationships II and III are equivalent to each other when the film possesses tetragonal structure at the deposition temperature; i.e., they can be described as (010) [100] tetragonal VO2 ‖ (1120) [0001] sapphire and (100) [010] tetragonal VO2 ‖ (1120) [0001] sapphire. HREM image shows that the initial nucleation of the film was dominated by the first orientation relationship, but the film then grew into the grains of the second and the third (equivalent to each other at the deposition temperature) epitaxial relationships. Successive 90°transformation rotational twins around the a-axis are commonly observed in the monoclinic films.

Lattice Imaging of a High-Angle Grain Boundary in Germanium at 500kv

1977 ◽  
Vol 35 ◽  
pp. 108-109
Author(s):  
O.L. Krivanek ◽  
S. Isoda ◽  
K. Kobayashi
Keyword(s):  
Phase Contrast ◽  
Room Temperature ◽  
Materials Science ◽  
High Angle ◽  
Lattice Imaging ◽  
Imaging Parameters ◽  
Resolution Electron ◽  
Electron Microscopes ◽  
New Generation ◽  
Transfer Interval

The promise of the new generation of high-voltage, high-resolution electron microscopes (HREMs) for atomic resolution studies in materials science has excited considerable interest (1). This paper describes an application to elemental Ge of the first member of this generation, the Kyoto 500kV HREM (2).Fig. 1 shows a (Oil) Ge crystal almost certainly less than 100Å thick, supported by a thin amorphous Ge film and surrounded by several Au crystallites. The specimen was prepared by vapor co-deposition of Au and Ge from separate sources onto a rock salt substrate held at room temperature. The imaging parameters were: accelerating voltage 500kV, axial illumination, no objective aperture, el. opt. mag. 200 000x, exposureotime 10 secs and, as the optical diffractogram (Fig. lb) shows, defocus =-600Å (≃ Scherzer defocus). The dashed circles in the diffractogram show the theoretical extent of the first phase-contrast transfer interval. The interval easily includes all the 111 diffraction spots, indicating that all the end-on (ill) planes and the defects they contain have been imaged faithfully and without distortion.

“Resolution” in atomic-resolution Electron microscopy

1991 ◽  
Vol 49 ◽  
pp. 498-499
Author(s):  
Michael A. O'Keefe ◽  
John C.H. Spence
Keyword(s):  
Electron Microscopy ◽  
Signal To Noise Ratio ◽  
Dark Field ◽  
Lattice Imaging ◽  
Rayleigh Criterion ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Incoherent Imaging ◽  
General Relations ◽  
Imaging Conditions

The Rayleigh resolution criterion was developed for incoherent imaging conditions and cannot, in general, be applied to coherent high-resolution transmission electron microscopy (HRTEM). In fact, the Rayleigh criterion may lead to paradoxical results since it considers only two scatterers and does not account for the signal-to-noise ratio. It may, however, be used for dark-field HAAD STEM imaging. For the case of strong multiple scattering in HRTEM lattice imaging, the only general relations that can be assumed between the image of a specimen and its projected crystal potential are those imposed by symmetry, and the “local” HRTEM column approximation. The effects of limited resolution may produce an image of lower symmetry than that of the object. Also, misalignment along symmetry axes may preserve some symmetry elements. Under coherent conditions the ability to distinguish atoms in an image depends on their scattering phases, which are a property of the sample.

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