摘要:

Interface structure and epitaxial growth of NiAl on III-V or 11-VI zinc-blende substrate have been studied by using the embedded atom method. Simulation showed that the {001} NiAl on {001} zinc-blende substrate forms a stable epitaxy only if a Ni monolayer is predeposited. A new model for the NiAl-zinc-blende substrate interface is proposed. The investigation of d-spacing changes in the intermetallic overlayer showed anomalies near the interface and free surface, and this behaviour is expected to affect the properties of the epilayer.

ISSN:0950-0839    

DOI:10.1080/09500839108214652

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

As-cast samples of Al65Co20Cu15made without Si were annealed for different times at 1200K. The decagonal phase was never observed. Instead, a decagonal approximant with diffraction features that are virtually indistinguishable from the true decagonal phase was discovered. The pseudo-ten-fold diffraction pattern from this phase contains low intensity, periodic diffraction spots corresponding to ad-spacing of ≈ 10 nm. High resolution electron microscope images taken along the pseudo-ten-fold zone-axis show crystalline domains decorated with ten-fold symmetric clusters. Several variants of this approximant with different periodicities are observed following isothermal annealing. These presumably arise from different packings of the ten-fold symmetric clusters. A new, crystal approximant phase also forms with annealing. Unlike previous reports, we find that silicon not only enhances decagonal formation but is necessary. For Si concentrations < ≈ 3·0 at.%, the weak diffraction spots are triangularly shaped; for concentrations above 4·5 at.%, a one-dimensional quasicrystal is observed.

ISSN:0950-0839    

DOI:10.1080/09500839108214653

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We use the local density approximation to density functional theory to re-examine the well-known ‘theoretical strength’ of metals. This is done by calculating ideal twin stress in five b.c.c. transition metals, and in Ir, Cu and Al. This leads us to a first-principles, quantum-mechanical confirmation of the Frenkel model in the theory of plasticity which has previously been thought to have been too oversimplified to be realistic. We discuss this result in the light of the Peierls—Nabarro model and relate it to the deformation behaviour of group-5 and group-6 transition metals. We also include a general analysis of the geometry of the problem that can be readily extended into a number of new areas in the theory of phase transformations.

ISSN:0950-0839    

DOI:10.1080/09500839108214654

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This Letter presents a solution of the problem of the real temperature of nanoparticles under conditions of electron microscope beam irradiation. It is shown that the average temperature of the nanoparticles (NPs) may increase to several hundred degrees depending on contact conditions with the substrate, the intensity of the beam and the size of the NPs. The temperature increases with NP size a according to the dependence: T α a2for sufficiently small particles.

ISSN:0950-0839    

DOI:10.1080/09500839108214655

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The structure of a faceted ∑ = 3 grain boundary in bismuth-doped copper is analysed using HREM. Experimental image series are compared with calculated image series of model structures of pure copper boundaries and boundaries containing segregated bismuth. A best match is found with a model structure containing an ordered bismuth segregation layer. The results demonstrate the importance of this experimental method for the characterization of complex grain boundary structures using HREM.

ISSN:0950-0839    

DOI:10.1080/09500839108214656

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The mechanism of laser-induced polymer ablation is considered, which takes into account the temperature dependence of the quantum yield of photodissociation of macromolecules. On the basis of the suggested model, new formulae are derived for threshold fluence and for the fluence dependence of the etch depth. It is shown that these quantities depend on the thermo- and photophysical properties of the polymeric material.

ISSN:0950-0839    

DOI:10.1080/09500839108214657

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The nature of the ground state of carriers in high-Tcmetallic oxides is discussed in the light of current theories and new experiments. The latest experiments with isotope substitution, infrared, tunnelling, photoemission, NMR and high-resolution electron-energy-loss spectroscopies favour the bipolaronic nature of high-Tcmetallic oxides.

ISSN:0950-0839    

DOI:10.1080/09500839108214658

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor