scholarly journals High Resolution Electron Microscopy of Grain Boundaries in Nanophase Palladium

1989 ◽  
Vol 153 ◽  
Author(s):  
G. J. Thomas ◽  
R. W. Siegel ◽  
J. A. Eastman
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Lattice Structure ◽  
High Resolution Electron Microscopy ◽  
Coarse Grained ◽  
Resolution Electron ◽  
The Individual ◽  
Individual Grains

AbstractUsing high resolution electron microscopy, consolidated nanophase palladium samples were examined following electrolytic thinning after a hydriding - dehydriding cycle at 310 K. Due to the small size and random orientations of the individual grains, a large number of grain boundaries were available for examination. Some of these yielded adequate imaging conditions to allow observation of the lattice structure in the grain boundary regions. Image simulations were performed to determine the sensitivity of the technique to lattice disorder. The results of these studies suggest that grain boundary structures in nanophase palladium are similar to those in conventional coarse-grained polycrystals.

Grain Boundary Transformations in Bi-Doped Copper

1991 ◽  
Vol 238 ◽  
Author(s):  
Elsie C. Urdaneta ◽  
David E. Luzzi ◽  
Charles J. McMahon
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Treatment Time ◽  
High Resolution Electron Microscopy ◽  
Transmission Electron ◽  
Resolution Electron

ABSTRACTBismuth-induced grain boundary faceting in Cu-12 at ppm Bi polycrystals was studied using transmission electron microscopy (TEM). The population of faceted grain boundaries in samples aged at 600°C was observed to increase with heat treatment time from 15min to 24h; aging for 72h resulted in de-faceting, presumably due to loss of Bi from the specimen. The majority of completely faceted boundaries were found between grains with misorientation Σ=3. About 65% of the facets of these boundaries were found to lie parallel to crystal plane pairs of the type {111}1/{111]2- The significance of these findings in light of recent high resolution electron microscopy experiments is discussed.

Structure of the ∑=3 (111) Grain Boundary in Cu-1.5%Sb

1992 ◽  
Vol 295 ◽  
Author(s):  
Richard W. Fonda ◽  
David E. Luzzi
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Auger Electron ◽  
Preliminary Investigation ◽  
High Resolution Electron Microscopy ◽  
Transmission Electron ◽  
Resolution Electron

AbstractGrain boundaries in quenched and aged Cu-i.5%Sb were examined with Auger electron microscopy, transmission electron microscopy, and high resolution electron microscopy. The ∑=3 grain boundaries are strongly faceted, with the facets lying primarily along the coincident (111) planes of the two grains. The grain boundaries are enriched in antimony, as demonstrated by both AES and HREM. HREM images of the ∑=3 (111) ║ (111) grain boundary differ from those of the Cu-Bi ∑ =3 (111) ║ (111) grain boundary in the lack of a significant grain boundary expansion to accommodate the excess solute at the boundary. A preliminary investigation of the atomic structure of the ∑=3 (111) ║ (111) facet by HREM and multislice calculations is presented.

Anti-Site Bonds and the Structure of Interfaces in SiC

1990 ◽  
Vol 183 ◽  
Author(s):  
P. Pirouz ◽  
J. Yang
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Compound Semiconductors ◽  
High Resolution Electron Microscopy ◽  
High Energy ◽  
Dangling Bonds ◽  
Resolution Electron ◽  
Elemental Semiconductors

AbstractHigh resolution electron microscopy has been used to study the structure of the 3C/6H interface, Σ,=3 {111}and Σ.=3 {112}grain boundaries in 3C-SiC. In SiC, as in other compound semiconductors, anti-site bonds occur in a variety of defects. These are high energy bonds comparable to that of dangling bonds. But, while dangling bonds at the grain boundaries may be eliminated by reconstruction just as in elemental semiconductors, it may not be possible to avoid anti-site bonds.These problems are discussed for the Σ=3 {112} grain boundary, where the structures proposed for Ge and Si are used as starting models for SiC.

Time-resolved high-resolution electron microscopy of grain migration process in MgO films

1996 ◽  
Vol 54 ◽  
pp. 674-675
Author(s):  
T. Kizuka ◽  
M. Iijima ◽  
N. Tanaka
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Migration ◽  
High Resolution Electron Microscopy ◽  
Video Tape ◽  
Grain Boundary Migration ◽  
Time Resolved ◽  
Resolution Electron

High-resolution electron microscopy (HREM) has been employed intensively to analyze the atomic structures of grain boundaries and interfaces having two dimensional structures inside polycrystalline and composite materials. Furthermore time-resolved HREM (TRHREM) is required to analyze the behavior of grain boundaries and interfaces at atomic scale. The grain boundary migration, which is a typical grain boundary behavior, is a fundamental process relating to structural stability of polycrystalline materials. The mechanism of the migration has been still unknown.In the present study, the variation of atomic arrangement at the grain boundary migration of a MgO [001]Σ5 boundary was analyzed by TRHREM.Magnesium oxide polycrystalline films were prepared by vacuum-deposition on air-cleaved (001) surfaces of sodium chloride at 300°C. TRHREM was carried out at room temperature using a 200-kV electron microscope (JEOL, JEM2010) equipped with a high sensitive TV camera and a video tape recorder. The spatial resolution of the system was 0.2 nm at 200 kV and the time resolution was 1/60 s. Electron beam density was 30 A/cm2.

High-resolution electron microscopy of nanostructured materials

1995 ◽  
Vol 53 ◽  
pp. 172-173
Author(s):  
M. José-Yacamán
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundaries ◽  
Nanostructured Materials ◽  
High Resolution Electron Microscopy ◽  
Hrem Image ◽  
Small Particles ◽  
Resolution Electron ◽  
Nanophase Materials

Electron microscopy is a fundamental tool in materials characterization. In the case of nanostructured materials we are looking for features with a size in the nanometer range. Therefore often the conventional TEM techniques are not enough for characterization of nanophases. High Resolution Electron Microscopy (HREM), is a key technique in order to characterize those materials with a resolution of ~ 1.7A. High resolution studies of metallic nanostructured materials has been also reported in the literature. It is concluded that boundaries in nanophase materials are similar in structure to the regular grain boundaries. That work therefore did not confirm the early hipothesis on the field that grain boundaries in nanostructured materials have a special behavior. We will show in this paper that by a combination of HREM image processing, and image calculations, it is possible to prove that small particles and coalesced grains have a significant surface roughness, as well as large internal strain.

Structural Transformation of a Germanium Σ=13 (510) [001] Tilt Grain Boundary under the Electron Beam

1990 ◽  
Vol 48 (1) ◽  
pp. 52-53 ◽  
Author(s):  
Jean-Luc Rouvière ◽  
Alain Bourret
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Structural Transformation ◽  
Mirror Symmetry ◽  
High Resolution Electron Microscopy ◽  
Structural Transformations ◽  
Covalent Bonds ◽  
Resolution Electron ◽  
Tilt Grain Boundary

The possible structural transformations during the sample preparations and the sample observations are important issues in electron microscopy. Several publications of High Resolution Electron Microscopy (HREM) have reported that structural transformations and evaporation of the thin parts of a specimen could happen in the microscope. Diffusion and preferential etchings could also occur during the sample preparation.Here we report a structural transformation of a germanium Σ=13 (510) [001] tilt grain boundary that occurred in a medium-voltage electron microscopy (JEOL 400KV).Among the different (001) tilt grain boundaries whose atomic structures were entirely determined by High Resolution Electron Microscopy (Σ = 5(310), Σ = 13 (320), Σ = 13 (510), Σ = 65 (1130), Σ = 25 (710) and Σ = 41 (910), the Σ = 13 (510) interface is the most interesting. It exhibits two kinds of structures. One of them, the M-structure, has tetracoordinated covalent bonds and is periodic (fig. 1). The other, the U-structure, is also tetracoordinated but is not strictly periodic (fig. 2). It is composed of a periodically repeated constant part that separates variable cores where some atoms can have several stable positions. The M-structure has a mirror glide symmetry. At Scherzer defocus, its HREM images have characteristic groups of three big white dots that are distributed on alternatively facing right and left arcs (fig. 1). The (001) projection of the U-structure has an apparent mirror symmetry, the portions of good coincidence zones (“perfect crystal structure”) regularly separate the variable cores regions (fig. 2).

scholarly journals Analysis of Stresses and Strains around Dislocations at Grain Boundaries by Quantitative High-Resolution Electron Microscopy

2006 ◽  
Vol 12 (S02) ◽  
pp. 894-895
Author(s):  
M Hytch ◽  
J-L Putaux ◽  
J Thibault
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Resolution Electron

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2006

High-resolution Electron Microscopy Observation of Grain-boundary Films in Superplastically Deformed Silicon Nitride

2000 ◽  
Vol 15 (7) ◽  
pp. 1551-1555 ◽  
Author(s):  
Guo-Dong Zhan ◽  
Mamoru Mitomo ◽  
Yuichi Ikuhara ◽  
Taketo Sakuma
Keyword(s):  
Electron Microscopy ◽  
Silicon Nitride ◽  
High Resolution ◽  
Grain Boundary ◽  
Applied Stress ◽  
Thickness Distribution ◽  
High Resolution Electron Microscopy ◽  
Stress Axis ◽  
Resolution Electron ◽  
Boundary Films

The thickness distribution of grain-boundary films during the superplastic deformation of fine-grained β–silicon nitride was investigated by high-resolution electron microscopy. In particular, grain-boundary thickness was considered with respect to the stress axis in two orientations; namely, parallel and perpendicular to the direction of applied stress. The results showed that the thickness distribution in boundaries perpendicular to the direction of applied stress was unimodal, whereas in parallel boundaries it was bimodal. Moreover, it was found that the majority of film-free boundaries were parallel to the direction of applied stress in the extremely deformed sample. The variation in spacing reflects distribution of stresses within the material due to irregular shape of the grains and the existence of percolating load-bearing paths through the microstructure.

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