摘要:

The voids forming a three-dimensional lattice in a molybdenum specimen irradiated at 550°C to a fast neutron fluence of approximately 1 × 1022n cm−2have been investigated for the fist time by the field ion microscope (FIM) technique. The numerical values obtained for the mean void diameter, the number density, and mean spacing are in approximate agreement with transmission electron microscope observations. Controlled field evaporation sequences through sixteen voids revealed complex atomic displacements around each void much of which is a result of the void intersecting the surface. The advantages of the FIM technique for the study of high number densities (< 5 × 1017cm−3) of voids are discussed and the potentialities of the FIM atom probe for the solution of problems concerning the nucleation and stabilization of voids is also considered.

ISSN:0033-7579    

DOI:10.1080/00337577508240789

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

5 μm foils of supersaturated ferromagnetic nickel-14.3 at –% beryllium have been irradiated at various temperatures between 120 and 200°C with 50 to 200 μA/cm2electrons of 2.5 MeV. The precipitation of beryllium induced by the irradiation is determined from the variation of the magnetization vs. temperature curves with dose. The magnetic analysis yields the differential variation of the dissolved beryllium per beryllium concentration interval.

ISSN:0033-7579    

DOI:10.1080/00337577508240790

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

In contrast to existing high dose electron irradiation data approximately 50% recovery occurs below 70 K in pure lead (R273K/R4.2K< 10,000) irradiated at 7.3 K with either 11 MeV protons or 22 MeV deuterons with doses up to 33 × 10−9ωcm. Recovery decreased with increasing dose for doses between 5.8 and 33 × 10−9ωcm and was increased by pre-irradiation and partial annealing. Previous identification of stageIDas that occurring at 170 K appears in error in view of the results presented here. Furthermore annealing data after neutron irradiation and plastic deformation data are substantially in agreement with the present interpretation.

ISSN:0033-7579    

DOI:10.1080/00337577508240791

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Effects of neutron irradiation and subsequent thermal annealings on positron annihilation rates inp-type germanium have been studied. Two annihilation rates (4.17 ± 0.08 ± 109sec−1with an intensity of 98% and 7.1 ± 1.0 × 109sec−1with an intensity of 2%) are observed in unirradiated samples. Only the annihilation rate of the dominent component becomes smaller upon irradiation, showing that some neutron-induced defects in Ge can act as traps for positrons. The effect saturates at high neutron fluence around 7 × 105n/cm2. The annihilation rate in saturated samples decreases further upon annealing around 200°C. The mean electron densities of the positron-sensitive defect after irradiation and after the 200°C annealing are 35% and 49% less than that in the perfect part of the crystal respectively. It is concluded that the non-planar vacancy clusters may be formed during the 200°C annealing. All positron sensitive defects disappear upon annealing below and around 350°C.

ISSN:0033-7579    

DOI:10.1080/00337577508240792

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Nous décrivons une expérience qui permet de distinguer les rôbs respectifs des collisions atomiques et de l'excitation électronique dans l'amorphisation d'un alliage Pd-Si par irradiation avec les fragments de fission. On montre que dans un tel alliage, où il existe des liaisons covalentes, l'excitation électronique provoque une “pointe thermique” qui en surface donne naissance à de la pulvérisation, et en volume conduit ou bien à l'amorphisation au coeur de cette pointe ou bien à une modification de l'orde local. Les collisions atomiques provoquent également l'amorphisation de l'alliage et on montre que le volume ainsi amorphisé comprend les atomes déplacés mais aussi leurs proches voisins comme si la rupture de certaines liaisons conduisait à un réarrangement local des atomes.

ISSN:0033-7579    

DOI:10.1080/00337577508240793

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Theoretical analysis of the effects of radiation on creep of metals, made on assumption of predominance of radiation-enhanced interstitial diffusion, has shown that irradiation should accelerate the motion of vacancy-emitting dislocation jogs, while, on the other hand, slowing down the motion of jogs emitting interstitials. Under such conditions, irradiation should slow down the creep controlled by jogged screw dislocation glide, and increase the creep-rate, when it's controlled by edge dislocation climb. The conclusion to this effect has been substantiated by experimental study of the effects of electron irradiation on creep of aluminium within the temperature range of 10 to 50°C. It has been found that electron irradiation causes the creep-rate to decrease; simultaneously, one observes a substitution of a mechanism controlled by the glide of jogged screw dislocations by one controlled by edge dislocation climb.

ISSN:0033-7579    

DOI:10.1080/00337577508240794

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Mössbauer parameters, measured with a resonance counter, have been compared with channeling results on the same samples, for ′119mSn implanted into silicon single crystals. The implantation dose was varied between ∼1014and ∼1017atoms/cm2, for target temperatures of 2O°C and 400°C. The channeling results in hot implants show that Sn is embedded substitutionally, and the Mössbauer parameters are nearly dose independent in the range indicated above. Except for a very low-dose implant (∼1013atoms/cm2) the room-temperature implants lead to complete damage (no channeling dip) and significantly different Mössbauer parameters. Subsequent annealing at 700°C, however, leads to values close to those characteristic of hot implants. The small dose dependence for hot implants, even for doses leading to ∼80% damage, as measured by channeling, indicates that the microscopic ordering is preserved.

ISSN:0033-7579    

DOI:10.1080/00337577508240795

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The temperature dependence of tracer self-diffusion measurements in cadmium is analyzed in conjunction with investigations of the equilibrium concentration of vacancies by thermal expansion and positron annihilation. The following values for the monovacancy migration enthalpies are obtained: HMIV,A= 0.48 eV forA-jumps (nearest-neighbour jumps in the basal plane), HMIV,B= 0.40 eV forB-jumps (nearest-neighbour jumps out of the basal plane).

ISSN:0033-7579    

DOI:10.1080/00337577508240796

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

A measure of the rate of self-decomposition of human luteinizing hormone (HLH) labelled with iodine-125 has been determined as a function of time at -10°C, 22°C, and 37°C. Particular attention was given to the data at -10°C, as this has been the recommended storage temperature of the tagged hormone used as a tracer in the radioimmunoassay of HLH. A standard procedure was used to iodinate the hormone, and the corresponding data from it indicated 3.7 to 4.7 iodine-125 atoms per molecule of luteinizing hormone. Chromatography of HLH-125on columns of Sephadex G-100 dextran gel as a function of storage time indicated lower molecular weight degradation products as well as polymerized species. It was surmised that these reactions were essentially the result of primary and secondary radiation effects leading to a variety of radiolysis products along with the normal chemical breakdown.

ISSN:0033-7579    

DOI:10.1080/00337577508240797

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

ISSN:0033-7579    

DOI:10.1080/00337577508240798

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor