摘要:

Probabilistic arguments concerning the statistical distributions of cell shape and area in the random Voronoi network are presented. By assuming only Euler's topological rule for such networks, which is exact for very large systems, a form of Lewis's law is derived together with analytical expressions for the statistical distribution functions. These results are compared with computer simulations of the network and reasonable agreement is found.

ISSN:0950-0839    

DOI:10.1080/09500839208219037

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Many-beam dynamical simulations and observations have been made for large-angle convergent-beam electron diffraction (LACBED) imaging of crystal defects, such as stacking faults and dislocations. The simulations are based on a general matrix formulation of dynamical electron diffraction theory by Peng and Whelan, and the results are compared with experimental LACBED images of stacking faults and dislocations of Si angle crystals. Excellent agreement is achieved.

ISSN:0950-0839    

DOI:10.1080/09500839208219038

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The Burgers vector of dislocations in the quasicrystalline Al–Cu–Fe icosahedral phase has been studied by means of diffraction contrast analyses and defocused convergent-beam electron diffraction. The size of the Burgers vector in real space is found to be 0·307 nm. This is the first observation of strain field amplitudes induced by dislocations in the quasicrystalline icosahedral phase.

ISSN:0950-0839    

DOI:10.1080/09500839208219039

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Diffuse scattering along the (10000) direction in the quasiperiodic plane in a single-phase decagonal Al–Cu–Co quasicrystal has been studied by the synchrotron X-ray diffraction technique at room temperature. The line shapes along both longitudinal (L) and transverse (T) directions were measured. A peculiar anisotropic line shape along the L direction was found. Two-dimensional contour maps reveal that some peaks have strong diffuse scattering components and that they are elongated along the T direction. The observed diffuse scattering profile varies from peak to peak, although all the peak positions are aligned in the same direction in reciprocal space. The diffuse scattering component, which is elongated along the T direction, can be fitted by a single Lorenzian with a linewidth about 20 times broader than that of the Bragg peak. No simple G‖or G⊥dependences for the diffuse scattering intensity were observed, in disagreement with the current status of the theories. The origin of discrepancies between experiment and theory is suggested.

ISSN:0950-0839    

DOI:10.1080/09500839208219040

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

According to the characteristics of the dislocations of which the small-angle grain boundaries consist, three kinds of small-angle grain boundary have been observed in annealed Al70Co15Ni15decagonal phase for the first time by transmission electron microscopy: A tilt boundary consisting of an edge-dislocation wall; a twist boundary consisting of parallel screw-dislocation pairs; a small-angle grain boundary consisting of a dislocation network.

ISSN:0950-0839    

DOI:10.1080/09500839208219041

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A decagonal phase with a periodicity of 3·78 nm (= 3 × 1·26nm) along the periodic axis has been found for the first time in Al–Cu–Cr alloys in the as-cast state as well as in the annealed state. The temperature range of stability has been found to be very narrow around 1000°C by investigation of differently annealed specimens in a transmission electron microscope. The broken bulk specimens exhibited a few particles with a tenfold-facetted decagonal prismatic shape. The chemical composition of these particles was determined to correspond to Al72Cu12Cr16by energy-dispersive X-ray spectrometry. High-resolution electron microscopy image of the decagonal phase taken along the periodic axis (tenfold axis) has shown a ring contrast with ten bright spots situated symmetrically and located at the vertices of a random tiling with four tiles with the same edge length of about 2·0 nm. The decagonal phase has been examined by comparing with the pseudo-decagonal phase obtained at a lower annealing temperature.

ISSN:0950-0839    

DOI:10.1080/09500839208219042

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The contrast anomaly of a set of planar defects in Fe-doped KTa1−xNbxO3with a Curie point near room temperature has been studied by synchrotron white-beam X-ray topography. A striking wavelength-dependent characteristic of the defect contrast is shown by tuning the synchrotron radiation, and the contrast reversal of the planar defects is displayed in antiparallel reflections. The intense anomaly in contrast is interpreted in terms of anomalous dispersion associated with antiparallel domains.

ISSN:0950-0839    

DOI:10.1080/09500839208219043

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Water-quenched samples of Cu–Pd and Ni–Mo alloys have been studied by electron diffraction and electron-energy-loss spectroscopy. Diffraction patterns from these alloys exhibit pronounced diffuse scattering due to short-range order. Determination of the white-line intensity in the energy-loss spectra from these samples indicated a concentration dependence and the results are discussed in terms of charge transfer associated with short-range order.

ISSN:0950-0839    

DOI:10.1080/09500839208219044

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Qualitative molecular orbital considerations rationalize computed differences in geometry between C60and C6-60and suggest that recent local-density-functional calculations give an incorrect picture of charge vibration coupling in Cg3-60.

ISSN:0950-0839    

DOI:10.1080/09500839208219045

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor