Phase electron diffraction pattern

Gas-phase electron diffraction patterns of l,2-dicarba-c/oso-hexaborane(6) (Figure 14) and carbahexaborane(7), (Figure 15), yielded a comprehensive set of structural parameters. ... 

Furthermore, the X-ray diffraction pattern of the as-cast Zn55Mg4o Y5 alloy confirms the existence of a stable icosahedral phase. Electron diffraction patterns taken with incident beams parallel to the fivefold, threefold and twofold directions of the icosahedral phase from the as-cast Zn5oMg45Y5 alloy are shown in figs. 104a, b and c, respectively. When the diffraction patterns of the icosahedral Zn5oMg4sY5 alloy are compared with those (Niikura 1995) of the icosahedral AIsLijCu alloy, it is seen that the patterns of the former... 

Figure C2.17.7. Selected area electron diffraction pattern from TiC nanocrystals. Electron diffraction from fields of nanocrystals is used to detennine tire crystal stmcture of an ensemble of nanocrystals [119]. In tliis case, tliis infonnation was used to evaluate the phase of titanium carbide nanocrystals [217].

Fig. 29. Icosahedral phase in electrodeposited Mn-Al alloys (a) bright field image (b) electron diffraction pattern showing 5-fold symmetry. Reproduced from Grushko et al. [126] by permission of Elsevier.

Bismuth Molybdates. Bismuth molybdates are used as selective oxidation catalysts. Several phases containing Bi and/or Mo may be mixed together to obtain desired catalytic properties. While selected area electron diffraction patterns can identify individual crystalline particles, diffraction techniques usually require considerable time for developing film and analyzing patterns. X-ray emission spectroscopy in the AEM can identify individual phases containing two detectable elements within a few minutes while the operator is at the microscope. 

In a famous paper by Shechtman et al. (1984) electron diffraction patterns were shown of rapidly quenched and solidified aluminium-manganese alloys. Sharp diffraction peaks, suggesting long-range translational order, were observed with the presence however of five-fold symmetry (that is of a non-crystallographic symmetry see 3.6.1.1). By different orientation of the specimen five-fold axes (in 6 directions), three-fold axes (in 10 directions) and two-fold axes (in 15 directions) were identified with the subsequent observation of the existence also of an inver-sion centre the assignment of this phase to the icosahedral point group, m36, was defined. 

The transmission electron microscopy (TEM) and correlated electron diffraction patterns of quenched QAB2-4 alloy is shown in Figure 2. When annealed at 773K, by selected-area electron diffraction (SAED) patterns at transmission electron microscopy appears as a bright continuous ring, indicating an amorphous phase. 

We have reconstructed the 3D structure of a complex quasicrystal approximant v-AlCrFe (P6 m, a = 40.687 and c = 12.546 A) (Zou et al, 2004). Due to the huge unit cell, it was necessary to combine crystallographic data from 13 projections to resolve the atoms. Electron microscopy images containing both amplitude and phase information were combined with amplitudes from electron diffraction patterns. 124 of the 129 unique atoms (1176 in the unit cell) were found in the remarkably clean calculated potential maps. This investigation demonstrates that inorganic crystals of any complexity can be solved by electron crystallography. 

A possible economically attractive alternative would be the production of acrylic acid in a single step process starting from the cheaper base material propane. In the nineteen nineties the Mitsubishi Chemical cooperation published a MoVTeNb-oxide, which could directly oxidise propane to acrylic acid in one step [6], Own preparations of this material yielded a highly crystalline substance. Careful analysis of single crystal electron diffraction patterns revealed that the MoVTeNb-oxide consists of two crystalline phases- a hexagonal so called K-Phase and an orthorhombic I-phase, which is the actual active catalyst phase, as could be shown by preparing the pure phases and testing them separately. 

The method of complex study of magnetic effects and the changes of electron diffraction patterns during the heating of amorphous alloys is developed. The study was carried out on the alloys Fe-Si-B, that were the bands in amorphous state. The phase composition that correspond to registrated diffraction patterns and to magnetic effects is established. 

Note that both the x-ray diffraction and Mossbauer characterization do not reveal the presence of phases other than Fe304 with the present statistics of the respective data sets. The presence of a very small amount of FeO(OH) is suggested in the electron diffraction pattern. It is not known whether FeO(OH) exists on the surface of the particles and/or as an independent particle to date. 

Molecules in the gas phase provide an electron diffraction pattern which can be analyzed in order to obtain relative interatomic distances in molecules. Some of the distances depend on molecular conformation and, in principle, it is possible to extract conformational data (conformer structure and population). Rough estimates of energy barriers may also be obtained from the peak widths by comparing calculated and experimental distribution functions. Uncertainties on populations are rather high ( 10-15%). 

Remarkable electron diffraction patterns of the low temperature form (Phase II) of polytetrafluoroethylene have been obtained which exhibit layer lines sharply resolved to the 26th order. These patterns permit accurate measurements of the layer line heights. Equations are developed to relate the layer line... 

Radial electron diffraction patterns (65), XRD and Laser Raman spectroscopy (69) have confirmed the formation of REV04 type phases. 

---