摘要:

Anisotropy in the wetting behaviour of a silicate liquid in contact with the faceted sapphire {1010} surface has been demonstrated using a simple specimen geometry. The shape of the glass pockets is influenced by the asymmetric faceting of the α-Al2O3{1010} surface. The glass remains preferentially in contact with the {1010} facets in α-Al2O3. Using this approach, which allows control over temperature and composition of the glass, a sequential study of the mechanisms of solution-precipitation and facet growth is possible.

ISSN:0950-0839    

DOI:10.1080/09500839508242463

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The role of elastic interactions in equilibrium correlations of oxygen distribution in YBa2Cu3O7crystals is investigated. In a broad temperature interval of about 200 K above the tetragonal-orthorhombic transition temperature, a strong tendency for the formation of highly correlated sheet-like regions perpendicular to the ⟨110⟩ directions was found. The correlated oxygen distribution produces an anomalously high amplitude of shear displacement waves ⟨110⟩/⟨110⟩ characteristic of a ‘tweed’ microstructure. The elastic diffuse scattering from the predicted equilibrium tweed microstructure is analysed.

ISSN:0950-0839    

DOI:10.1080/09500839508242464

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Deposition of one monolayer of rhenium on the W(112) surface and subsequent annealing to 820 K results in the formation of an ordered (1 × 2) superstructure of rhenium. The superstructure is stable in ultra-high vacuum even at 1000 K. An atom-probe analysis indicates no formation of a surface alloy layer up to 1000K. Thus the interface remains atomically sharp.

ISSN:0950-0839    

DOI:10.1080/09500839508242465

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The α → γ phase transformation, which occurs during quenching and produces extremely fine α2-γ lamellae, is discussed in relation to the analysis of the α2-γ interface structure. In a high-resolution image obtained from the growth edge of a γ plate in the α2matrix, steps that were always found to be (0002)α2or (111)γ planes high were observed at the α2-γ interface. This indicates that the α → γ phase transformation is performed by the migration of (a/3) ⟨1100⟩hcpShockley partial dislocations on alternate ⟨1100⟩hcpplanes to change the stacking sequence AB… to ABC….Chemical analysis by analytical transmission electron microscopy with energy-dispersive X-rays showed that the α2and γ plates have the same composition, so that the α2→γ phase transformation which occurred during quenching can be interpreted as being composition invariant when these results are taken into consideration, it is suggested that the transformation is marterisitic.

ISSN:0950-0839    

DOI:10.1080/09500839508242466

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The interaction between a fatigue crack and the mechanical twins which are generated in front of the crack tip has been investigated in a compact tension specimen of a Fe-30 wt.% Cr alloy crystal. Significant slip localization and resultant persistent-slip-band-like damage were found along the twin boundaries. It was frequently observed that the fatigue crack captured by the damaged twin boundaries was propagated along these.

ISSN:0950-0839    

DOI:10.1080/09500839508242467

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The results of a transmission electron microscopy observation of the effect of temperature on dislocation microstructures of FeTi with the B2 structure are presented. It is determined that deformation is accomplished by activation of slip systems of type ⟨001⟩{011} in a wide range of temperatures, accompanied by a small density of slip systems of type ⟨111⟩{011} at room temperature. Also, morphological features of the activated dislocations are presented as a function of temperature.

ISSN:0950-0839    

DOI:10.1080/09500839508242468

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Large millimetre-sized grains of Al‒Cu‒Fe grown by the annealing technique developed at the Centre d'Etudes de Chimie Métallurgique in Vitry, France, and subgrains cut in centimetre-sized Al‒Pd‒Mn quasicrystals grown by solidification (Bridgman-Czochralsk) at the Laboratoire de Thermodynamique et Physicochimie Métallurgiques in Grenoble, France, were investigated by X-ray topography. Two types of defect were identified: loops and bands. Both the nature of the strain field around these defects and their origin are discussed.

ISSN:0950-0839    

DOI:10.1080/09500839508242469

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In general, current transport through thin-film metal-semiconductor-metal diodes containing hydrogenated silicon-rich amorphous silicon nitride (a-SiNx: H) is determined by electron tunnelling through the potential barriers at the metal-semiconductor contacts. After prolonged current stressing, however, there is a change in the transport mechanism and a large increase in the current. It is shown that the excess current flow is well described by field-enhanced emission of carriers via charged defect states throughout the bulk of the silicon nitride. The effect of the electric field and dependence on defect concentration is consistent with the transport of holes in the vicinity of the valence band tail. As stressing proceeds, more defect states are introduced and the conductivity of the a-SiNx:H increases.

ISSN:0950-0839    

DOI:10.1080/09500839508242470

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Pressure-induced irreversible amorphization and crystallization were definitively observed at the atomic scale, using high-resolution electron microscopy, in the uniaxially compressed icosahedral phase of Al68Pd23Mn9, at pressures from 10 to 20 GPa at ambient temperature. The pressure-amorphized state was found to comprise a random packing of atomic clusters. The pressure-induced crystalline phase was identified to have a fcc structure with a lattice parametera= 0·38 nm which is not an approximant of the icosahedral phase of Al‒Pd‒Mn.

ISSN:0950-0839    

DOI:10.1080/09500839508242471

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The χ-phase is an isostructure of the α-manganese which frequently precipitates in steels during annealing. We discuss the structural defects identified by transmission electron microscopy in χ-phase particles. These defects are translational boundaries characterized by very simple fault vectors: ⅓⟨110⟩ and ¼⟨111⟩. Interpretation of the latter fault vector leads to a new description of the α-manganese crystal. It is worth recalling that α-manganese is considered as a complex phase because it does not follow the rules established by Frank and Kasper for the topologically close-packed phases. Hence using the information given by the defects, as proposed here, constitutes a new approach to these phases.

ISSN:0950-0839    

DOI:10.1080/09500839508242472

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor