摘要:

Magnetic domains in fine particles of Nd2Fe14B ball-milled to less than several micrometres in size have been studied by the colloid-scanning electron microscope (SEM) method, which is a method for observation of small domains. The single-domain state has been clearly found on thecplane in several particles. Their domain patterns are shown for two single-domain particles of 1·0 and 1·2 μm size. These particle sizes are compared with a simple theoretical estimate.

ISSN:0950-0839    

DOI:10.1080/09500838808214743

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Nitrogen in the forming gas used in deformation experiments as a protecting atmosphere affects the yield point of silicon single crystals at high temperatures. This may explain some unusual results recently published in the literature.

ISSN:0950-0839    

DOI:10.1080/09500838808214744

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A model is proposed for diffusion-induced grain boundary migration. The driving forces are identified as the interface energy and the free energy of mixing. The model explains all the known experimental facts. An expression for the velocity of migration of the grain boundary is derived by assuming thermally activated motion of solute atoms under the influence of the driving forces. The velocity calculated from this expression agrees well with the experimental value.

ISSN:0950-0839    

DOI:10.1080/09500838808214745

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Observations by X-ray photoelectron spectroscopy on LnBa2Cu3O7−x(Ln = Y and Ho) show that there are no significant surface electronic differences as a result of substitution of Y by Ho. The O 1s and Ba 3d envelopes exhibit fine structure which appears to be related to significant electronic and structural properties of the 1–2–3 compounds. Namely, the low-binding-energy component of the O 1s envelope is due to Ba─o bonding as well as being specific to the electronic linkage of the Cu layers in the orthorhombic structure. The anomalous low-binding-energy contribution to the Ba 3d envelope suggests that Ba may play an importantelectronicrole as well as a structural role. There is further evidence that Sr and Ca play similar roles in the related Bi─Sr─Ca─Cu─O high-Tccompounds.

ISSN:0950-0839    

DOI:10.1080/09500838808214746

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Two-dimensional {110} superlattices have been observed in Bi2(Sr, Ca)3Cu2O8+yby transmission electron microscopy from (001) and (110) planes but not from the (100) plane. Lattice images in the (110) plane show stacking faults intersecting the superlattice. It is possible that the existence of superlattices and stacking faults is important in the formation of Cooper pairs for superconductivity, and that ordered multiphase layered assemblages can be used to produce material of higherTc. Comparisons of ionic radii in a similar material, Tl2Ba2CaCu2O8+y, suggest that the superlattice results from periodic lattice strain modulation.

ISSN:0950-0839    

DOI:10.1080/09500838808214747

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Powder X-ray diffraction, electron diffraction and electron microscopic experiments, including high-resolution electron microscopy, have revealed that the Al─Cu─Fe icosahedral phase has a higher degree of structural perfection than other known icosahedral phases. This icosahedral phase exhibits clear equal thickness fringes in bright and dark-field images and also sharp diffraction spots with small Bragg angles, both of which have not been observed in other icosahedral phases. A scaling rule by the golden mean τ along the fivefold, threefold and twofold axes was found in reciprocal space of this icosahedral phase. In the high-resolution electron micrographs observed along the twofold axis, this scaling rule was also recognized to be present in real space. This fact suggests that the Al─Cu─Fe icosahedral phase belongs to a different class of icosahedral phase from the one to which belong other icosahedral phases having a scaling rule of τ3.

ISSN:0950-0839    

DOI:10.1080/09500838808214748

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A decagonal quasicrystal with a periodicity of 1·6 nm along the tenfold axis, similar to that in Al─Pd and Al─Co, has been found in a rapidly solidified Al6Ni alloy containing a few per cent of silicon. In addition, a new decagonal phase has been found in Al4Ni which has a periodicity of 0·4 nm along the tenfold axis. This decagonal phase is different from those reported before in the aluminium–transition metal alloys. A new metastable crystalline phase Al9Ni2having the structure of Al9Co2has been found.

ISSN:0950-0839    

DOI:10.1080/09500838808214749

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor