Characterization of thick cryogenic fuel layers using convergent-beam interferometry: A numerical investigation

2000 ◽  
Vol 88 (5) ◽  
pp. 2928-2935 ◽  
Author(s):  
P. W. McKenty ◽  
M. D. Wittman ◽  
V. N. Goncharov
Keyword(s):  
Numerical Investigation ◽  
Convergent Beam

convergent-beam diffraction from surfaces

1987 ◽  
Vol 45 ◽  
pp. 30-33
Author(s):  
J. A. Eades ◽  
A. E. Smith ◽  
D. F. Lynch
Keyword(s):  
Reciprocal Lattice ◽  
Three Dimensional ◽  
Grazing Incidence ◽  
Three Dimensions ◽  
Plane Figure ◽  
Transmission Electron ◽  
Convergent Beam ◽  
Beam Patterns ◽  
Beam Diffraction

It is quite simple (in the transmission electron microscope) to obtain convergent-beam patterns from the surface of a bulk crystal. The beam is focussed onto the surface at near grazing incidence (figure 1) and if the surface is flat the appropriate pattern is obtained in the diffraction plane (figure 2). Such patterns are potentially valuable for the characterization of surfaces just as normal convergent-beam patterns are valuable for the characterization of crystals.There are, however, several important ways in which reflection diffraction from surfaces differs from the more familiar electron diffraction in transmission.GeometryIn reflection diffraction, because of the surface, it is not possible to describe the specimen as periodic in three dimensions, nor is it possible to associate diffraction with a conventional three-dimensional reciprocal lattice.

CBED analysis of impurity distributions in AlN

1990 ◽  
Vol 48 (4) ◽  
pp. 214-215
Author(s):  
Daniel Callahan ◽  
G. Thomas
Keyword(s):  
Aluminum Nitride ◽  
Bulk Material ◽  
Strong Dependence ◽  
Lattice Parameter ◽  
Promising Technique ◽  
Nitride Ceramics ◽  
Surface Phases ◽  
Convergent Beam ◽  
Oxygen Impurities

Oxygen impurities may significantly influence the properties of nitride ceramics with a strong dependence on the microstructural distribution of the impurity. For example, amorphous oxygen-rich grain boundary phases are well-known to cause high-temperature mechanical strength degradation in silicon nitride whereas solutionized oxygen is known to decrease the thermal conductivity of aluminum nitride. Microanalytical characterization of these impurities by spectral methods in the AEM is complicated by reactions which form oxygen-rich surface phases not representative of the bulk material. Furthermore, the impurity concentrations found in higher quality ceramics may be too low to measure by EDS or PEELS. Consequently an alternate method for the characterization of impurities in these ceramics has been investigated.Convergent beam electron diffraction (CBED) is a promising technique for the study of impurity distributions in aluminum nitride ceramics. Oxygen is known to enter into stoichiometric solutions with AIN with a consequent decrease in lattice parameter.

Characterization of Contacting Boundaries between Nanoparticles with LACBED

2003 ◽  
Vol 9 (3) ◽  
pp. 237-244 ◽  
Author(s):  
Yiming Yao ◽  
Anders R. Thölén
Keyword(s):  
Nanocrystalline Materials ◽  
Large Angle ◽  
Convergent Beam Electron Diffraction ◽  
Average Accuracy ◽  
Accuracy Of Measurements ◽  
Wide Range ◽  
Grain Orientations ◽  
Rotation Parameters ◽  
Convergent Beam

The boundary parameters between contacting spherical bcc-Fe particles have been characterized with the Large Angle Convergent Beam Electron Diffraction (LACBED) technique. The average accuracy of measurements can reach 0.07°. The rotation parameters are interpreted using matrix algebra and evaluated according to the CSL model. The deviation between the experimental results and the reference misorientations given in the CSL model is determined. It is possible to reveal preferential misorientations between irregularly shaped particles with a size less than 100 nm. The method can be applied to nanoparticles and nanocrystalline materials with a wide range of grain orientations, and it is possible to modify it into an automatic method for TEM measurements.

The characterization of an SCS6/Ti–6Al–4V MMC interphase

1989 ◽  
Vol 4 (2) ◽  
pp. 327-335 ◽  
Author(s):  
C. Jones ◽  
C. J. Kiely ◽  
S. S. Wang
Keyword(s):  
Metal Matrix ◽  
Chemical Interaction ◽  
Auger Spectroscopy ◽  
Carbon Layer ◽  
Convergent Beam Electron Diffraction ◽  
Interphase Region ◽  
The Matrix ◽  
Convergent Beam

Using TEM, Auger spectroscopy, EDX, and convergent beam electron diffraction, a thorough characterization of the interphase region between SCS6 fibers and Ti–6Al–4V matrix in a metal matrix composite has been performed. The interphase region is shown to be very complex, consisting of numerous layers of varying compositions and thicknesses. The chemical interaction of the fiber and matrix results in a 0.5–1.5 μm thick TiC layer. Evidence for the existence of a Tix Siy (C) layer is also presented. The SCS6 overlayer on the fibers has inhibited any chemical interaction between the matrix and the SiC filament itself, 60% of the interphase region originating from the SCS6 protective coating. In situ fracture experiments (in an Auger spectrometer) reveal that fracture takes place between the TiC and an amorphous carbon layer.

Preparation and Characterization of Single-crystal Aluminum Nitride Substrates

1999 ◽  
Vol 595 ◽  
Author(s):  
Leo J. Schowalter ◽  
J. Carlos Rojo ◽  
Nikolai Yakolev ◽  
Yuriy Shusterman ◽  
Katherine Dovidenko ◽  
...  
Keyword(s):  
Aluminum Nitride ◽  
Single Crystal ◽  
Convergent Beam Electron Diffraction ◽  
Large Single Crystal ◽  
High Quality ◽  
Afm Imaging ◽  
Convergent Beam ◽  
Edge Dislocations ◽  
Etching Effect

AbstractLarge (up to 10mm diameter) aluminum nitride (AlN) boules have been grown by the sublimation-recondensation method to study the preparation of high-quality single crystal substrates. The growth mechanism of the boules has been studied using AFM. It has been determined that large single crystal grains in those boules grow with a density of screw dislocations below 5×104 cm−3 while edge dislocations are at lower density (none were observed). High-quality AlN single crystal substrates for epitaxial growth have been prepared and characterized using Chemical Mechanical Polishing (CMP) and AFM imaging, respectively. Also, the differential etching effect of KOH solutions on the N and Al-terminated faces of AlN on vicinal c-faces has been investigated. In order to identify the N or Al-terminated face, convergent beam electron diffraction has been used.

Characterization Of APB's In GaP

1996 ◽  
Vol 442 ◽  
Author(s):  
Dov Cohen ◽  
C. Barry Carter
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Convergent Beam Electron Diffraction ◽  
Antiphase Boundaries ◽  
Beam Electron ◽  
Transmission Electron ◽  
Convergent Beam ◽  
Crystallographic Orientations

AbstractAntiphase boundaries in GaP crystals epitactically grown on Si (001) have been characterized using transmission electron microscopy. Convergent-beam electron diffraction was used to identify the antiphase-related grains. The antiphase boundaries were observed to adopt facets parallel to specific crystallographic orientations. Furthermore, stacking-fault-like contrast was observed along the interface suggesting that the domains may be offset from one another by a rigid-body lattice translation.

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