ISSN:0950-0839    

DOI:10.1080/09500838708210431

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Some results of transmission electron microscopyin-situstraining of single-phase boron-doped Ni3Al are presented which suggest that superdislocation partials can become rather widely separated (50 nm) and bowed (scalloped) along their length. The significance of these observations toin-situstraining experiments on superalloys of γ/γ′ is discussed.

ISSN:0950-0839    

DOI:10.1080/09500838708210432

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Some recent experimental results on boundary dislocations are discussed with reference to the concepts of extrinsic and intrinsic boundary dislocations and the associated stress and displacement fields. It is shown that the presence of a long-range stress field is not only dependent on the origin of the boundary dislocations, but also results from the external displacement conditions allowed at the outer limits of the crystals. The conditions for this long-range stress field to vanish are specified. The difficulties in experimental studies of the mechanical aspects of boundary dislocations arrays are commented on, and some suggestions are made to help in their analysis.

ISSN:0950-0839    

DOI:10.1080/09500838708210433

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The formation of point-defect clusters in irradiated magnesium aluminate spinel is sensitive to composition. No dislocation loops develop in stoichiometric materials bombarded with 1 MeV electrons, but pre-existing screw dislocations climb into helices. This is attributed to difficulties in loop nucleation rather than in the generation and diffusion of point defects or their differential absorption at dislocation sinks. The bias for interstitials is calculated to be 1·6% at 1073 K.

ISSN:0950-0839    

DOI:10.1080/09500838708210434

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Convergent-beam electron diffraction from a fivefold axis of icosahedral Al6Mn has revealed interference patterns not previously observed in this material. The microcrystals have a habit plane with the matrix.

ISSN:0950-0839    

DOI:10.1080/09500838708210435

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Al13Fe4tenfold twins, found in rapidly cooled Al–Fe alloys, have been studied by transmission electron microscopy. The development of the tenfold diffraction pattern from the twins is clearly shown, and compared to the tenfold pattern of the decagonal phase found in the same specimen. The coexistence of the tenfold twins and decagonal quasicrystal is confirmed by high-resolution electron microscopy.

ISSN:0950-0839    

DOI:10.1080/09500838708210436

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

In a rapidly solidified V41Ni36Si23alloy, the microdomain structure of a pentagonal Frank-Kasper phase (I phase) and the icosahedral as well as the decagonal quasicrystals, giving different tenfold electron diffraction patterns, have been found. Formation of quasicrystals in alloys which would crystallize into Frank–Kasper phases, having a large proportion of icosahedra in their equilibrium structures, is discussed.

ISSN:0950-0839    

DOI:10.1080/09500838708210437

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The efficiency of B and As in gas-phase doping of hydrogenated amorphous silicon (a-Si: H) prepared by r.f. sputtering has been experimentally evaluated. The dopant incorporation, i.e. the solid-phase concentration, was found to be linear with gas-phase concentration for both dopants, and independent of the substrate temperature. The creation of defects with doping has been investigated by electron spin resonance and photothermal deflection spectroscopy. The results suggest that a dangling bond is created for each fourfold-coordinated dopant atom, in agreement with the general concept of the modified 8 −Nrule. However, the variations of the doping efficiency with the solid-phase concentrations of B and As (Csol) are ν ∼C0soland ν ∼C−2/3solrespectively, instead of the predictedC−1/2soldependence. We conclude that the laws of mass action cannot be applied under conditions of sputtering and propose that the incorporation of dopant atoms occurs in a non-equilibrium process at the growing surface, in contrast to previous findings on glow-discharge a-Si:H.

ISSN:0950-0839    

DOI:10.1080/09500838708210438

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The molecular structures of disiloxane, silanol and water have been determined by a local density functional method employing Gaussian bases. Bond lengths and angles are found to be within a few per cent of the observed values. A 4% expansion of the Si–O bonds in disiloxane is sufficient on energy grounds to allow hydrolysis to occur. These results are used to support the Griggs-Blacic-Frank models of hydrolytic weakening in quartz and to justify the use of an interatomic potential used in a previous investigation.

ISSN:0950-0839    

DOI:10.1080/09500838708210439

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Previously reported experimental results on the electron-stimulated oxidation of Si are quantitatively described. The framework of the analysis is a macroscopic continuum model which includes transport processes through the oxide layer, and surface effects mainly connected to the O2sticking coefficient. The existence of the chemisorbed precursor states is pointed out and a simple picture of the potential energy experienced by the O2molecule approaching the surface of the oxide layer is proposed.

ISSN:0950-0839    

DOI:10.1080/09500838708210440

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor