摘要:

The type and frequency of grain boundaries, the so-called grain boundary character distribution (GBCD), has been determined in rapidly solidified and subsequently annealed Fe-6·5 mass% Si alloy ribbon by the scanning electron microscopy-electron channelling pattern (SEM-ECP) technique. High frequencies of low-angle boundaries and coincidence boundaries with Σ3, Σ9, Σ11, Σ17 and Σ19 were observed in a fully annealed ribbon with well defined {110} texture. The total frequency of low-angle boundaries and coincidence boundaries is almost one-half of all grain boundaries. The coincidence boundaries which occurred more frequently are exactly those predicted theoretically from the coincidence orientations for ⟨110⟩ rotation in cubic crystals, similar to those observed previously in {100} textured ribbons of the same alloy produced by the same processing method. The presence of a close relationship between the type of texture and GBCD has been confirmed by experiment on differently textured ribbons of the same material.

ISSN:0950-0839    

DOI:10.1080/09500838908214776

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A critique of the structural unit model is presented. It is shown that the predictive capacity of the model is severely limited when it is applied to boundaries with relatively-high-index rotation axes. Recent computer simulations suggest that ‘high index’ means ⟨221⟩ and above. A new approach to grain boundary structure is needed for mixed tilt and twist boundaries.

ISSN:0950-0839    

DOI:10.1080/09500838908214777

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Temperature dependence of the apparent antiphase boundary (APB) energy on cube planes is studied using weak-beam determination of dissociation distances of superdislocations originating from deformation at 20,650 and 850°C. It is difficult to assess how closely the observed dependence applies to the true cube ABP energy because of the uncertainty associated with lattice resistance to the motion of superpartials. It is estimated that the true energy of conservative APB on {001} is liable to decrease with temperature as much as 30% between room temperature and 850°C.

ISSN:0950-0839    

DOI:10.1080/09500838908214778

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Several distinctive image features in principle enable the polarity of ⟨110⟩-oriented compound semiconductors to be determined from high-resolution electron micrographs. In practice, knowledge of objective lens defocus and crystal thickness, and precise control of crystal and beam tilt, are generally required before unambiguous discrimination of crystal polarity is possible. Confirmation of surface polarity for a (1 × 1) reconstruction of a (110) CdTe surface observed profile imaging is reported.

ISSN:0950-0839    

DOI:10.1080/09500838908214779

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A modified Poisson/Weibull probabilistic scheme is shown to yield accurate predictions for the mechanical strength of several types of ultra-high-strength polyethylene fibres. Strong diameter effects observed in such fibres are also conveniently modelled the proposed scheme. This new approach is shown to be at least as satisfactory as previously proposed models for diameter effects based on linear elastic fracture mechanics (LEFM). Moreover, it provides a simple solution to a current problematic issue inherent to the Weibull/weakest-link model, namely the conflicting values generally obtained for the Weibull shape parameter as calculated from Weibull plots and weakest link predictions respectively.

ISSN:0950-0839    

DOI:10.1080/09500838908214780

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The formation, via pulsed laser excitation, from amorphous material of a new crystalline silicon phase with a hexagonal structure is described. The lattice image obtained by high-resolution electron microscopy and the selected-area diffraction patterns provide direct information on this amorphous-to-crystalline transition. It is proposed that laser-induced electronic excitation of amorphous material plays a dominant role in this metastable phase formation.

ISSN:0950-0839    

DOI:10.1080/09500838908214781

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Time-dependent transport of triplet excitons in amorphous benzophenone has been investigated in the low-temperature range down to 6 K. The data exhibit some remarkable features associated with the freezing-in of excitations in energy-disordered glasses. The relaxation process is investigated and explained using Monte Carlo simulations and analytical random-walk techniques. The inadequacy of mean-field type methods is demonstrated for the low-temperature domain, where exact averaging techniques can be applied.

ISSN:0950-0839    

DOI:10.1080/09500838908214782

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This Letter investigates the role of dispersive hydrogen motion in light-induced defect creation from both monomolecular and bimolecular carrier recombination. The dispersive monomolecular model gives better agreement with the experimental time and intensity dependence of the light-induced defect creation process as well as the temperature dependence of the equilibrium defect density than does the dispersive bimolecular process. However, the activation energy of the creation rate and consistency with current degradation experiments remain unresolved issues.

ISSN:0950-0839    

DOI:10.1080/09500838908214783

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Midgap-state densities and profiles in undoped hydrogenated amorphous silicon (a-Si: H), silicon-germanium alloy (a-Si1−xGex: H) and silicon-carbon alloy (a-Si1−xCx:H) films were obtained from a heterojunction-monitored capacitance method. These midgap states were found to correspond to singly-occupied dangling bonds. The density of midgap states increases slowly with the Ge content in the film, while it increases rapidly with the C content. The peak of the midgap-state profile appears clearly in a-Si:H and a-Si1−xGex:H, bit it does not appear clearly in a-Si1−xCx:H.

ISSN:0950-0839    

DOI:10.1080/09500838908214784

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

It is argued that the thermoelectric transport coefficients in a coupled electron-phonon system depend on the interaction of phonons with a heat bath. When the phonon mean free path is short, temperature-dependent energy levels may be introduced in the Boltzmann equation which yields the usual formulae for the thermopower with temperature-dependent energies inserted. For weak phonon-heat-bath interaction and strong electron-phonon interaction, a transport equation for new quasi-particles is obtained and the energy current includes transport of the electron-phonon interaction and phonon energies carried along by a quasi-particle.

ISSN:0950-0839    

DOI:10.1080/09500838908214785

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor