摘要:

The structure of {1101} twin dislocations in Ti films evaporated on NaCl substrates at 250°C has been examined and characterized by high-resolution transmission electron microscopy. The results have revealed that a twin dislocation structure with a step height 4d(K1), whered(K1) is the spacing of the {1101} twin planes, actually dissociates into two {11101} twin dislocations with step heights ofd(K1) and 3d(K1). The twin dislocation with a step height of 3d(K1) contains an edge dislocation in the core, while that with a step height ofd(K1) is a simple classical twin-dislocation structure. Twin dislocations with a step height of 2d(K1), including an edge dislocation in the core, also occur. The atomic-scale core structures of {1101} twin dislocations may be derived by analysis of the high-resolution images. The relative mobilities of the three types of twin dislocations are then discussed.

ISSN:0950-0839    

DOI:10.1080/09500839308240944

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The phonon dispersion curves for both ordered and configurationally disordered cubic phases of Cu3Au are calculated using force constants derived from a many-body tight-binding potential. The derived phonon frequency spectra are used to estimate the vibrational contribution to the entropy difference between the two phases. A brief discussion concerning the relative values of interatomic force constants is included.

ISSN:0950-0839    

DOI:10.1080/09500839308240945

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An equation has been derived for the lattice strain that corresponds to the strain measured by X-ray diffraction in a specimen compressed non-hydrostatically in a diamond anvil cell. This equation has been used to discuss the observed difference between the volume compressions of C60fullerite measured under non-hydrostatic and hydrostatic pressure conditions.

ISSN:0950-0839    

DOI:10.1080/09500839308240946

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The continued-fraction expansion algorithm is utilized to clarify the hierarchy among the coincident-site lattice structures. Boundary energies are calculated against twist misorientation based on a two-dimensional version of the model suggested by du Plessis and van der Merwe in 1965, which reveal a fractal energy surface with cusps at very σ value. The origin of the cusps and the effects of local structural relaxation on the boundary energies are discussed.

ISSN:0950-0839    

DOI:10.1080/09500839308240947

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Quasicrystals involving decagonal and icosahedral phases were formed, through two peritectoid reactions on low-temperature annealing, from a non-equilibrium cubic phase prepared by the ball milling of a mixture of equilibrium cubic phase and Al powders in Al—Cu—Co and Al—Cu—Fe systems. In both systems, the peritectoid reaction between residual Al and preliminary milled non-equilibrium cubic phase occurred first to form tetragonal Al7Cu2(Fe, Co) at 623 K. Subsequently, the same reaction between these tetragonal and the non-equilibrium phases occurred to form the quasicrystals at 773 K.

ISSN:0950-0839    

DOI:10.1080/09500839308240948

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A vanishing coercive fieldHchas been obtained with an a.c. flowing along an amorphous Co70·3Fe4·7Si15B10ribbon. Hc= 0 can be obtained over a certain range of the drive-field frequencyfand for core-current (J) frequencies which are odd multiplesf. The phenomenon is explained in terms of the field Hcgenerated byJ, and the condition for the occurrence of Hc=0 is derived. Two possible applications are mentioned.

ISSN:0950-0839    

DOI:10.1080/09500839308240949

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

It is shown that the infrared absorption spectra of pure type IaB diamonds, namely those that on cursory examination show only a B one-phonon component and neither A nor D, and the complete absence of a B' localized-mode platelet absorption peak, may be divided into two subgroups. The defect content of specimens of one of these subgroups has been studied before and comprises slip dislocations and voidites in random homogeneous distributions unconnected with the transformation of platelets to dislocation loops. Electron microscopy of a specimen of the other subgroup, which may be recognized by the presence of weak additional one-phonon absorption near 1100cm−1, shows a population of dislocation loops resulting from the complete transformation of a former platelet population, plus accompanying voidites. It is suggested that the extra absorption is caused by the dislocation loops.

ISSN:0950-0839    

DOI:10.1080/09500839308240950

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor