摘要:

The growing processes of the lattice defects with atomic resolution in Si crystals under the 400 kV electron beam irradiation with the dose rate of 5 × 1019electrons/cm2s and the rapid fluctuations of atom images of Si crystal lattice under the 800 kV electron irradiation with the dose rate of 1.56 × 1019electrons/cm2s were recorded using JEOL 400kV analytical atom resolution electron microscope (AARM) at Osaka University and JEOL 1 MeV atom resolution electron microscope (ARM) at UC-Berkeley respectively equipped with a TV image viewings and video recording systems.

ISSN:1042-0150    

DOI:10.1080/10420159908229091

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

57Fe Mössbauer study of the point defects induced by electron beam irradiation in aluminum containing 100 ppm of57Fe impurities has been presented.57Fe Mössbauer spectra obtained at 10 K just after the electron irradiation at 77 K show satellite lines rising from the defects associated with the57Fe probe atoms in aluminum matrix. The intensity of the satellite line (defect line) abruptly diminished around 20 K. Apparent reduction in the intensity of the defect line is interpreted as a result of the local jump of the probe57Fe atoms in the cage, which consists of six geometrically equivalent mixed-dumbbell positions. The local jump collapses the coherence of the Mössbauer gamma-rays and the time dependent relaxation of the quadrupole interaction occurs.

ISSN:1042-0150    

DOI:10.1080/10420159908229092

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:1042-0150    

DOI:10.1080/10420159908229093

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The behaviour of Kr atoms in aluminium has been investigated by an ion channelling method with a He+beam on Al specimens implanted at room temperature at 50 keV to various doses from 1 × 1014to 1 × 1016Kr/cm2. The Kr atoms are distributed over random (R), substitutional (S), tetrahedral (T) and octahedral (O) sites. From the implantation-dose dependence of the site occupancies, it is considered that, at the initial stage of implantation, Kr-vacancy (V) complexes such as KrV4and KrV6are formed and they act as nucleation centres for the subsequent growth to bubbles. KrV4and KrV6complexes are dissociated around 433 and 593 K, respectively. It is observed that post-implantation irradiation enhances the formation of solid krypton. On the basis of this result the mechanism for solidification of bubbles is discussed.

ISSN:1042-0150    

DOI:10.1080/10420159908229094

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Polycrystalline TiN/ZrN, TiN/CrN and TiN/TaN multilayers were grown by reactive magnetron sputtering on WC/Co sintered hard alloy substrates. Hardness and elastic modulus were measured by nanoindentation testing. Hardness of TiN/ZrN multilayers decreased rapidly with increasing bilayer thickness (Λ), peaking at hardness values ≈ 30% lower than the rule-of-mixtures value at Λ = 30 Å, and increased with further increases in Λ. A comparison with other lattice mismatched systems showed a similar hardness variation, but the sign was negative. The results suggest that coherency strains are responsible for the larger hardness change. Nanoindenter elastic modulus results showed the same behavior with hardness dependence on Λ, i.e., elastic softening at Λ = 30 Å. TiN/CrN system showed no hardness and elastic anomalies. In TiN/TaN systems, hardness was lower than the rule-of-mixtures value of individual single layers for Λ > 80 Å, and increased rapidly with decreasing Λ, peaking at Λ = 43 Å. As a result of analysis on the inclination of applied load for indenter displacement (δP/δh), this paper exhibits that the enhancement of the resistance to dislocation motion and elastic anomaly due to the change of lattice spacing are responsible for the hardness change.

ISSN:1042-0150    

DOI:10.1080/10420159908229095

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Experiments designed by the author for the research of production and reaction of point defects during his stay in eight universities and research institutes for about forty years are reviewed. Two-step aging method elucidated the stability of vacancy cluster nucleus in quenched metals, and the deformation induced vacancies were detected by the aid of quenched-in vacancies. High-voltage electron microscopes were efficiently used as micro-laboratories, especially to do the quantitative electron microscopy to extract fundamental properties of point defects and defect interactions. Fusion neutron irradiation with a neutron source RTNS-II was a unique systematic experiment on defects produced by large collision cascades. Advantage of the use of thin foil samples for neutron irradiation was emphasized. The temperature control in fission reactor irradiation was improved to eliminate the influence of the reactor power. Temperature cycle reactor irradiation became possible, and a multi-section removable rig was constructed for systematic irradiation. The role of freely migrating point defects in microstructure evolution was detected by changing the depth of damage zone with the incidence of self-ions with glancing angles. Finally, the ultra-high-speed plastic deformation gave rise to the anomalous production of vacancies and vacancy clusters, and then to the proposal of plastic deformation of metals without dislocations.

ISSN:1042-0150    

DOI:10.1080/10420159908229096

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Clustering of atomic defects leads to changes in the microstructure of materials, and hence induces drastic variations in their properties. In many technical fields, the role of defect clustering is very significant, and is sometimes limiting to further progress. We present here a comprehensive review of the theory of atomic defect clustering under non-equilibrium conditions, particularly encountered during irradiation of materials with energetic particles, as well as during material processing by energetic sources. These conditions are met in a wide range of technical applications, ranging from nuclear and fusion energy to microelectronics and surface engineering. We first present a general stochastic framework for the evolution of atomic clusters, and show how this can be described within the context of death-and-birth processes. This leads to the well-known master equation for microscopic atomic clusters. In the limiting case of a Poissonian process for the transition probabilities between cluster sizes, the master equation tends, in the macroscopic limit, to the mean-field approximation embodied by the theory of rate processes. When atomic clusters grow or shrink by the absorption of single atomic defects, a continuum Fokker-Planck approximation can be derived. Within this approximation, the evolution of interstitial loops, voids, bubbles, and general clusters of complex phases is presented, and in some cases, good agreement with experiments is obtained. It is shown that because of coalescence reactions, the evolution of surface atomic clusters during atom deposition processes is best described by kinetic moment equations, directly derived from rate equations. It is shown that breaking the symmetry of space or time leads to drastic variations in the size and space distributions of defect clusters. Examples are given for pulsed irradiation conditions, where it is shown that non-linear rate processes enhance cluster formation during on-time, and could lead to their dissolution during the off-time at high temperature. On the other hand, fluctuations are shown to result in instabilities and spatial self-organization of defect clusters. Description of pattern formation during irradiation, such as void and interstitial loop lattices, is very well described by a Ginzburg-Landau type equation, reminiscent of phase transitions under thermodynamic equilibrium conditions.

ISSN:1042-0150    

DOI:10.1080/10420159908229097

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A focused ion beam (FIB) system was applied in preparing thin foil specimens of Si and alumina which contained cracks in the plane of foil. It was possible to observe a much larger area at and near a crack tip than has been hitherto possible.

ISSN:1042-0150    

DOI:10.1080/10420159908229098

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The structure and/or the state of dislocation core often play a significant role in the glide process of the dislocation and hence control the plasticity of the crystal. We show various examples in this paper. (1) The yield stress of single crystals controlled by the Peierls mechanism for screw dislocation does not obey the Schmid law. (2) A narrow dissociation of the core can produce a plateau in the τy-Trelation. (3) Duality of the core structure can produce «yield stress anomaly». (4) Multiphonon emission at the core of dislocation in semiconducting crystals by non-radiative recombination of electron-hole pairs enhances drastically the dislocation mobility.

ISSN:1042-0150    

DOI:10.1080/10420159908229099

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In crystalline solids, ductility and strength are known to be governed by generation of dislocations and their motion either by glide or climb. Meanwhile, a transmission electron microscope (TEM) has been developed as an indispensable tool for studying the micro-structures of crystalline solids used for various purposes. Topics related to the dislocation structures may be examined most critically by TEM observations, especially by stereo microscopy using a high voltage electron microscope.

ISSN:1042-0150    

DOI:10.1080/10420159908229100

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor