摘要:

Ultramicrotoming has been employed to prepare thin cross-sections of Ni-P alloys electrodeposited on to a copper substrate. The sections, as thin as 10nm or even less, can be prepared readily with negligible damage to the alloys. Subsequent examination of the ultramicrotomed sections in an analytical transmission electron microscope has revealed that Ni-P alloys of low P content consist of fine layers of different composition and crystallinity. High-resolution transmission electron microscopy of ultramicrotomed sections has also revealed the presence of ordered regions, a few nanometres in size, in the Ni77P23alloy which has been thought previously to be amorphous.

ISSN:0950-0839    

DOI:10.1080/09500839008206478

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The crystalline-to-amorphous (C-A) transition in boron carbide induced by 2 MeV electron irradiation was studied by high-resolution electron microscopy. It is revealed that the C-A transition takes place not homogeneously but heterogeneously over the irradiated volume and the volume fraction of the amorphous phase continuously increases with increasing dose of electrons.

ISSN:0950-0839    

DOI:10.1080/09500839008206479

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Thin fragments of dodecahedral particles, extracted from an as-cast Al65Fe15Cu20alloy ingot, have been studied by transmission electron microscopy. The as-cast state is not icosahedral but trigonal and exhibits a microstructure such that the overall symmetry is pesudo-icosahedral; annealed within the microscope, this microcrystalline state transforms homogeneously into the icosahedral phase, stable until its melting point. During this second transformation (surface melting or sublimation), faceted holes of a dodecahedra] shape were observed to develop within the quasicrystalline phase.

ISSN:0950-0839    

DOI:10.1080/09500839008206480

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A series of electron diffraction patterns displaying continuous transformation of the octagonal quasicrystal into the β-Mn type structure were obtained in a rapidly quenched Cr-Ni-Si alloy. This transformation is interpreted in terms of a gradual introduction of short-range periodical translational order to the octagonal quasicrystal. The presence of nuclei of the β-Mn type structure in the octagonal quasicrystal and the short-range periodical translational order in it have been observed by means of high-resolution electron microscopy.

ISSN:0950-0839    

DOI:10.1080/09500839008206481

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A tenfold diffraction pattern has been observed in a rapidly solidified Nb18Fe52alloy by transmission electron microscopy. This tenfold diffraction pattern has many fewer diffraction spots than that of an Al-TM (transition metal) decagonal phase, but tilting experiments through 90° apparently show that it exhibits decagonal symmetry. High-resolution electron microscopy images corresponding to the tenfold diffraction pattern shows that it comes from an a periodic arrangement of icosahedral chains in real space. The structure factors which are calculated according to the ideal model and real model are nearly consistent with the experimental results. It is suggested that this is a new type of decagonal phase closely related to the Zr4Al3, and MgCu2, units of pentagonal Frank-Kasper phases.

ISSN:0950-0839    

DOI:10.1080/09500839008206482

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The magnitude of the spatial and energy scales in homogeneous intrinsic amorphous semiconductors resulting from the long-ranged Coulomb potential due to a random distribution of charged defects is calculated. It is shown that, for a reasonable concentration of charges, around 1018cm−3, in the absence of strong inhomogeneities, the magnitude of the long-range potential is small and does not affect significantly the electronic structure of the localized states. With strong inhomogeneities, the theoretical situation is not clear and more research is needed.

ISSN:0950-0839    

DOI:10.1080/09500839008206483

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor