摘要:

It has been shown that crack propagation in solids can be described by the diffusion equation. The proposed approach enables one to obtain kinetic relations as well as the fracture criterion.

ISSN:0950-0839    

DOI:10.1080/09500839008206471

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A mechanism is proposed to explain the change in the ductility of Ni-rich Ni3Al on addition of small amounts of boron. It is argued that grain boundary segregation of B is not the cause of the increase in ductility. Instead, Ni–B bonds and antisite Ni defects reduce the directionality of the bonding in ordered Ni3Al and enhance the ductility in the interior of grains so that deformation can be easily transmitted from one grain to another. Experimental evidence for this model is presented. An estimate of the concentration of B to achieve maximum ductility is made and the estimate agrees well with the experimental value.

ISSN:0950-0839    

DOI:10.1080/09500839008206472

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

An icosahedral quasicrystalline phase was found to be formed in rapidly solidified Al–Pd–Mn alloys. The quasicrystalline structure was confirmed to have a superlattice structure of the simple icosahedral quasicrystal, similar to the face-centred icosahedral structure for Al–Cu–Fe quasicrystals. The intensity of the superlattice reflections increases successively with increasing Pd content, and hence Pd atoms seem to occupy predominantly the superlattice site rather than the fundamental lattice in the icosahedral structure.

ISSN:0950-0839    

DOI:10.1080/09500839008206473

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A decaprismatic growth morphology has been found for the first time for the decagonal quasicrystal in the Al65Cu20Co15alloy slowly cooled from the melt. Substituting a little si for Al in this alloy, for example, Al62Si3Cu20Co15, results in quasicrystal decaprisms of 0·5 mm in diameter and several millimetres in length. These decaprisms showed possibly a 10/mmmmorphology which was proved later by electron and X-ray single crystal diffraction analyses. Moreover, the sharp selected-area electron diffraction (SAED) and convergent-beam electron diffraction (CBED) patterns show clearly a high degree of perfection and the X-ray precession photographs prove the single crystalline nature across a few millimetres of this decagonal quasicrystal.

ISSN:0950-0839    

DOI:10.1080/09500839008206474

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The solid-state reaction between Al and Pd is studied in a lateral Al–Pd diffusion couple in the temperature range between 250°C and 430°C. The first reaction phase is the crystalline Al3Pd2phase. After this phase reaches a critical length of around 6 μm, the quasicrystalline decagonal Al3Pd phase starts to grow in between the Al and the Al3Pd2phases. After the appearance of the decagonal phase, both the crystalline Al3Pd2and the quasicrystalline Al3Pd phase continue to grow.

ISSN:0950-0839    

DOI:10.1080/09500839008206475

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

It is shown that the calculation of wavefunctions using periodic extension of the sampling boundary points leads to an artificial error in the high-resolution electron microscopy image simulation for a non-periodic object. In a thorough study of this problem, a new method has been proposed for the dynamical image simulation of a non-periodic object.

ISSN:0950-0839    

DOI:10.1080/09500839008206476

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Transient photoconductivity measurements were carried out in thin-film transistors of silicon-on-insulator structures which were formed by oxygen implantation and subsequent lamp annealing. They show that traps arising primarily due to surface states at the top silicon–oxide interface are responsible for the observed dispersive transport in these films. As the gate voltage is increased and more holes are pulled to the surface, the form of transients changes from dispersive to non-dispersive due to saturation of the surface traps. Upon further increase of the gate voltage the form and the magnitude of the photocurrent prior to recombination remains unchanged, but the observed decay time gets longer for higher gate voltages. This occurs due to a reduction in the recombination centre density for the majority carriers corresponding to the movement of the demarcation level.

ISSN:0950-0839    

DOI:10.1080/09500839008206477

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor