摘要:

Based upon our previously developed microscopic model of intergranular embrittlement in A3B L12intermetallic compounds, it is shown that a plot of A versus B s-orbital electronegativity leads to a clear discrimination between ductile and brittle materials. A structure-property relationship is uncovered by constructing the associated structure map using phenomenological Mendeleev numbers, which exhibits a topology identical to the ductile-brittle property map.

ISSN:0950-0839    

DOI:10.1080/09500838708207549

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The process of melting and freezing of In particles in an Al-In alloy have been observed directly in a high-voltage electron microscope. The liquid phase nucleated preferentially at the surfaces of the In particles, surrounding them at the onset of melting. The liquid phase then propagated into the interior of the In particles at the expense of the solid. This observation is thought to provide direct evidence for the surface-nucleation model of melting.

ISSN:0950-0839    

DOI:10.1080/09500838708207550

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A power-law exponent of −3 is found to govern the excess heat capacity during the growth of second-phase domains near dislocations. Good fits are obtained to published data on the melting and polymorphic transitions of diamantane.

ISSN:0950-0839    

DOI:10.1080/09500838708207551

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The microstructure of long-range-ordered vanadium carbides based on V6C5has been analysed by means of high-resolution electron microscopy (HREM). Lattice images have been produced by including in the objective-aperture superlattice spots associated with the ordered distribution of vacancies in the interstitial carbon sublattice of these substoichiometric compounds: ‘perfectly’ ordered structures have been imaged, and a direct discussion of the experimental micrographs is made in terms of positions of the vacancy-containing columns. This HREM study will soon be extended to theinvestigation of various kinds of planar defects within differently annealed specimens.

ISSN:0950-0839    

DOI:10.1080/09500838708207552

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The temperature dependence of the electron magnetic resonance line broadening (ΔHpp) of superparamagnetic particles immersed in an inert matrix is discussed on the basis of the method of moments.

ISSN:0950-0839    

DOI:10.1080/09500838708207553

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The optical and electrical properties of amorphous PbS films prepared by reactive evaporation have been studied. Optical measurements indicate a band gap of 1·66 eV at room temperature. Optical studies and dielectric measurements suggest that amorphous PbS comprises a covalent network, in contrast to the rock-salt structure of crystalline PbS.

ISSN:0950-0839    

DOI:10.1080/09500838708207554

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The long-time transient photocurrent decay in annealed and light-exposed P-doped a-Si: H is examined experimentally and by numerical modelling. The decay is a dispersive power law with sublinear index, extending to times longer than 1s, and the decay rate increases with temperature. Light exposure dramatically decreases the decay amplitude but does not affect the rate of decay. The phenomenon is discussed in terms of a comprehensive multiple-trapping model in which transport of thermalized electrons is essentially non-dispersive, and recombination of free carriers via defects is dispersive, owing to continued thermalization of excess holes. The slower recombination step is free-hole capture by D−states, while the decay of the total excess ensemble is controlled by hole release from valence-band tail traps. The index of the excess photoelectron decay provides information on thevalence-bandtail states, which are exponentially distributed, with a characteristic energy estimated as 0·06 eV.

ISSN:0950-0839    

DOI:10.1080/09500838708207555

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The effect of mechanical stress on light-induced changes in photoconductivity has been studied in films of plasma-deposited hydrogenated amorphous silicon on different substrates. The experimental results reveal no correlation between the degradation of the photoconductivity and the mechanical stress in these films. These findings contradict the observations of Stutzmann but agree with those of Guha, den Boer, Agarwal and Hack.

ISSN:0950-0839    

DOI:10.1080/09500838708207556

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor