摘要:

It is believed that creep in materials containing a dispersed second phase may be controlled by the climb of edge dislocations around the second phase. The above model is proposed to be applicable to neutron irradiated materials containing Seeger zones. It is assumed that edge dislocations are pinned by the zones and can escape by (1) climbing out of the zones by absorption of neutron produced point defects, (2) the dissolution of the zones by absorption of neutron produced interstitials, (3) the dissolution of the zones by vacancy emission from the zones and (4) thermally activated cutting of the zones by the dislocations. The above four mechanisms are incorporated into a set of equations similar to those originally proposed by Seeger for hardening in neutron irradiated copper. The effects of temperature, neutron flux, fluence, and applied stress are considered.

ISSN:0033-7579    

DOI:10.1080/00337577108231097

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Recent experimental and theoretical studies of the reflection of keV heavy-ion beams have been extended to higher energies and to non-perpendicular incidence. The reflection coefficient for Na+and K+ions backscattered from polycrystalline gold and silver targets has been obtained for perpendicular incidence at energies of 100–500 keV. The dependence on angle of incidence has been investigated at 30 keV for the same combinations of targets and projectiles. Effects of electronic stopping have been included in the theoretical calculations. Good agreement between the experimental results and the theoretical calculations is found.

ISSN:0033-7579    

DOI:10.1080/00337577108231098

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Bombardment of thin (1–10 μ) single crystal targets with energetic ion beams has been found to result in macroscopic distortion of the thin film in the bombarded region. This effect, which has been euphemistically termed a ‘dimple’, is readily observed with the naked eye even at relatively low particle fluence. A useful first-order model has been developed which interprets the dimpling as an expansion of the bombarded region. For very thin samples, this expansion can be accommodated by bowing of the crystal out of the original crystal plane. For this simple model, the fractional expansion is proportional to (δ/d)2where δ is the maximum displacement from the original crystal plane anddis the diameter of the bombarded area. This measurement allows expansioh to be determined with a sensitivity comparable to or better than the most sensitive existing methods.

ISSN:0033-7579    

DOI:10.1080/00337577108231099

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

The theory of diffusion-limited bimolecular reaction kinetics is investigated for the case in which the reactants are initially produced in spatially correlated pairs. The intent of the study is to discover to what extent information concerning the initial distribution of pair member separations (generally unknown for such systems) can be deduced from empirically observable quantities. The analysis predicts the form of the dependence of the fractional concentration of recombined pairs on various moments of the distribution function as well as the approximate concentration dependence of very late time correlated reactions. It is expected that the model may be applicable to many systems of radiation-and photo-physics, chemistry, and biology; the specific examples of radical reactions in solution and the annealing of damage produced by electron irradiation of metals and semiconductors are discussed.

ISSN:0033-7579    

DOI:10.1080/00337577108231100

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Samples of pyrolytic graphite and nuclear graphite have been irradiated at 27 or 77 K with neutrons and electrons. The dynamic Young's modulus has been studied by an isochronal annealing method and the internal friction has been measured as a function of temperature. The modulus changes with irradiation dose and annealings have been interpreted using a model based on the pinning of basal dislocations by interstitial atoms. The anneals have revealed an additional effect which was attributed to bonds between interstitial defects and atoms in the adjacent graphite layers. The observed modulus annealing stages are consistent with results of several authors.

ISSN:0033-7579    

DOI:10.1080/00337577108231101

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

The nature of damage present in ion implanted silicon crystals has been observed by transmission electron microscopy for a wide range of ion species (A, Xe, Pd, Au, Si, Ge, at 40–100 keV) over the dose range 1013to 1017ions/cm2so that the marked dose dependence of defects after annealing (up to 900°C)and special impurity effects could be investigated. Electrical measurements (sheet resistivity and Hall effect) have been made on antimony dopedp-njunction structures irradiated with non-doping ions to support these observations and determine some electrical effects of the damage. It was found that dislocation loop structures were evolved in the case of annealed low dose irradiations where there was only a small degree of overlap of adjacent disordered zones in the as irradiated state. For irradiations which created a complete surface amorphous film, the damage remaining after 650°C anneals consisted of a compIex dislocation array with microtwins, planar defects, and often some polycrystallinity following epitaxial regrowth of the surface.

ISSN:0033-7579    

DOI:10.1080/00337577108231102

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Proton channeling effect measurements were used to study the implantation lattice disorder in silicon as a function of ion flux (dose-rate), fluence, implant temperature, ion mass, and the presence of ionizing radiation. For both O+and Sb+implantation at 87°K the lattice disorder production is the same for equal total energy into atomic processes/cm3at a fixed rate of energy into atomic processes/cm3-sec. The disorder production for both light (O+)and heavy (Sb+) ions exhibits a flux dependence at low temperatures and at room temperature. At low temperatures an increase in disorder is observed for increasing flux at constant fluences; however, for low fluence Sb implantation at 300°K, lower disorder is observed with increasing flux. The lattice disorder increases for all ions with decreasing implant temperature from 300°K down to temperatures as low as 38°K, but the variation with temperature is greater for lighter ions. The stimulation of lattice disorder annealing (typically ≈ 10 per cent) by ion beams was observed between 87 and 360°K. The results of disorder production and lattice reordering are interpreted in terms of the energy deposited into atomic and electronic processes, and previously observed lattice defect properties in Si. Ionization due to the energy deposited into electronic processes by the ions is believed to stimulate the anneal of defects from a disorder cluster in a manner similar to the charge state and injection-stimulated vacancy annealing previously observed for neutron and electron damage in Si. We suggest that ionization-stimulation of the lattice disorder annealing during implantation is responsible for the large differences observed in Si between the implant temperature and anneal temperature curves.

ISSN:0033-7579    

DOI:10.1080/00337577108231103

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Fission-track and K-Ar dating of basaltic glass from the Mid-Atlantic Ridge gives results which are consistent with the proposal of ocean-floor spreading. Correlation exists between the magnetic anomaly patterns over the Crest Mountains at 45°N and the age of the outcropping basalts. The observed sequences of ages progressing outward from the Median Valley 11,000, 230,000, 310,000, 750.000, 8,000,000, and 16,000,000 years constitute strong, direct support for the idea of ocean-bottom spreading.

ISSN:0033-7579    

DOI:10.1080/00337577108231104

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Micrographs of energetic particles in nuclear emulsion are simulated by computing the spatial distribution of developed grains with the δ-ray theory of track structure, and representing the developed grains by points of light on an IBM 2250 visual display unit. The simulated tracks display many of the features of actual track structure and serve as a visual comparison between experiment and theory.

ISSN:0033-7579    

DOI:10.1080/00337577108231105

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

The defect production rate in platinum irradiated with energetic charged particles is measured as a function of irradiation temperature from below stage I to above the ‘so-called’ stage III. On the basis of these measurements, supplemented by recovery studies, and by other types of irradiations a consistent model of defect production and recovery is platinum on the basis that two distinct interstitial species are present is put forward.

ISSN:0033-7579    

DOI:10.1080/00337577108231106

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor