摘要:

Electron optical structure imaging of haematite (α-Fe2O3) in two projections has allowed the microscopic twinning elements of rhombohedral twins to be determined. The twin is a pure 180° rotation about [0111], the twinning direction, combined with a parallel translation of ⅙[0111]. The twinning plane (0112) forms a perfectly coherent interface, consisting of face and edge-shared octahedra with no change in nearest-neighbour coordination. A search for alternative structural models yielded none which could reproduce the experimental images.

ISSN:0950-0839    

DOI:10.1080/09500838908206427

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Single crystals of Bi2Sr2CaCu2O8were slowly heated in a transmission electron microscope up to about 800 K. Different stages in the heating process were monitored in diffraction and images. Linear bands along theaandbdirections, small crystallites giving rise to satellite spots decorating the basic spots and the incommensurately modulated reflections are observed at 573 K. The Bi2Sr2CaCu2O8crystal gradually transforms into a new phase with a different modulation at 735 K. Heating the specimen repeatedly by a focused intense electron beam gives regions with different degrees of damage which correspond to the different stages in the heating process.

ISSN:0950-0839    

DOI:10.1080/09500838908206428

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Through a simple model of second-phase growth near dislocations, a new mode of self-diffusion in pivalic acid near the melting point is identified to be molecular transport along a network of narrow molten domains.

ISSN:0950-0839    

DOI:10.1080/09500838908206429

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Extended X-ray absorption fine structure experiments are reported above the Cu and V K absorption edges in an icosahedral Al82Cu7V11alloy. The radial distributions of neighbours around Cu and V atoms are compared with previous results obtained in other icosahedral alloys.

ISSN:0950-0839    

DOI:10.1080/09500838908206430

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Khan and Armstrong have found that the shear stress-strain relation of hexagonal soap froth is isotropic (although the elastic limit depends on orientation). This remarkable result is recovered in a compact derivation which explicitly attributes the isotropy to the threefold symmetry of the structure.

ISSN:0950-0839    

DOI:10.1080/09500838908206431

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

We report experimental results on the kinetics of the electron-beam-induced reduction of WO3byin situhigh-resolution electron microscopy. Electron-beam irradiation of WO3results in complete reduction to W. The process is surface-initiated through desorption of oxygen from the crystal surface, and the subsequent growth of tungsten was found to be a diffusion-controlled process. The damage rate follows a para-linear curve, that is, an initially parabolic damage rate degenerating into a linear rate. The epitaxial relationship between WO3and W was found to be (001)wo3//(110)w. The WO3lattice has a critical nucleus size of about 2·6 nm.

ISSN:0950-0839    

DOI:10.1080/09500838908206432

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor