摘要:

C60–15% C70fullerite powder specimens have been studied by high-resolution transmission electron microscopy. Electron diffraction shows the coexistence of f.c.c. and h.c.p. crystallites in the thermally pre-treated fullerite powder. In the high-resolution micrographs the spherical confour of the fullerene molecules is identified and compared with image simulations. In addition to nearly-defect-free crystallites, defected areas with stacking faults and twins were observed.

ISSN:0950-0839    

DOI:10.1080/09500839208205999

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A local-density-functional cluster method is used to calculate the structure and vibrational modes of C60. We find C–C lengths in good agreement with observed values. The effect of doping the molecule with three extra electrons is investigated and shown to result in a surprisingshorteningof the longer bonds. The second derivatives of the energy are evaluated and have enabled, for the first time,allthe normal modes of the molecule to be found. We find these to be in fair agreement with the available experimental results.

ISSN:0950-0839    

DOI:10.1080/09500839208206000

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A microstructural study of the direct bonding between (1120)-oriented Al2O3single crystals and Fe has been conducted by transmission electron microscopy and high-resolution electron microscopy. Two orientation relationships have been found between the ceramic and single grains of α-Fe: (1120)Al2O3//(110)Feand [0001]Al2O3//[112]Fe; (1120)Al2O3/(110)FEand [0001]Al2O3//[]110]Fe. Although the atomic structure of the interfaces has not been resolved yet, no evidence was found for any interfacial product between the two basic components; also, the presence of a minor quantity of Fe3O4(magnetite) in the form of fine precipitates homogeneously distributed within the Fe layer has no apparent influence on the crystallography of the interfaces.

ISSN:0950-0839    

DOI:10.1080/09500839208206001

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The study of crystalline approximant structures is an important way to understand the local order in quasicrystalline phases. We compare here high-resolution electron microscopy (HREM) image simulations of the cubic approximant phase R-Al5CuLi3with experimental HREM images of the icosahedral Al5CuLi3phase. Local two-dimensional (2D) arrangements such as Penrose tiles of different scales and projections of icosahedral clusters (triacontahedra) are found to be common to both phases, confirming the close similarity of their short and medium-range order. The shape and decoration of three-dimensional (3D) tiles is suggested from their 2D projection. A 2D and 3D inflation rule, comparable with that expected in the icosahedral phase is demonstrated in the approximant phase.

ISSN:0950-0839    

DOI:10.1080/09500839208206002

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The sequence of events during the operation of a ‘Bardeen-Herring’ climb source is predicted by using a numerical method in which the dislocation is modelled as a set of finite straight elements. The configuration is determined as a function of the applied stress and an approximate analytical treatment is presented which describes the time dependence of the source operation.

ISSN:0950-0839    

DOI:10.1080/09500839208206003

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The rigid-body displacement at {112} incoherent Σ = 3 grain boundaries in a boron-doped Ni–24at.%Al alloy with the L12structure is determined by transmission electron microscopy using the image matching of fringe contrast in the same g images. From the results, the atomic structure at an incoherent boundary is constructed using a hard-sphere model and interpreted in terms of Ni–Al and Ni–Ni bonding across the boundary.

ISSN:0950-0839    

DOI:10.1080/09500839208206004

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We consider the stress field induced by a planar assembly of edge dislocations. If these dislocations are periodically arranged, the stress field which they produce decreases exponentially with increasing distance from the wall. We show that in this case, disorder is a singular perturbation which leads to fluctuations of the stress field with a power-law dependence. Other physical examples where this mechanism operates are briefly mentioned.

ISSN:0950-0839    

DOI:10.1080/09500839208206005

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor