摘要:

The annealing behaviour of Ta, Nb, W and AISI 316L stainless steel samples implanted with 20 keV helium ions and either with 15 keV hydrogen or 12 keV deuterium ions was studied. By observing the release of trapped hydrogen and deuterium, it was concluded that the helium associated hydrogen trapping defects recover at a temperature of 488 K in steel, 583 K in W, 648 K in Ta, and 553 K in Nb. The observed recovery temperatures of hydrogen irradiation induced traps are lower than the recovery temperatures of traps trapping solid soluble hydrogen migrating from the metal bulk after the helium implantation, deduced in an earlier study [P. Haussalo, J. Keinonen, U.-M. Jäske, and J. Sievinen,J. Appl. Phys.75, 7770 (1994)]. This indicates that the hydrogen implantation changes the characteristics of the helium associated defects. The proposed trapping mechanism is binding at the surface of helium bubbles, as suggested in the above mentioned study, affected by the properties of the ion-implantation induced damage.

ISSN:1042-0150    

DOI:10.1080/10420159708216848

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The change in interaction potential of iron and nickel atoms under a magnetic phase transition has been studied. It has been shown that the energy of interaction between atoms increases when spins of the atoms become parallel. For the interaction of two Fe or two Ni atoms with parallel spins, the potential well is deeper, and is shifted towards shorter distances than for the case of random spin orientation. This effect has to be taken into account when explaining a step-like change in sputtering yield of magnetic materials during a magnetic phase transition.

ISSN:1042-0150    

DOI:10.1080/10420159708216849

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A 1080 grade aluminium reactor component, irradiated to various neutron fluences, has been examined using X-ray energy dispersive spectrometry (XEDS) on scanning and transmission electron microscopes (SEM and TEM) to determine the levels of radiogenic Si. Thermal neutron irradiation resulted in radiogenic Si levels up to 0.64 wt%. Quantitative SEM analysis of XEDS spectra, yielded a precision of 200 ppm, a lower limit of quantification of 300 ppm and a lower limit of detection of around 200 ppm Si. TEM analysis yielded software processed results in good agreement with SEM data at Si levels > 0.4 wt%, while manual processing of spectra improved the agreement between the techniques at lower Si levels. These techniques enable radiogenic Si levels in 1080 grade aluminium to be determined independently of the original impurity Si. From these silicon levels, thermal neutron fluences can be derived independently of fluences determined from a core flux model and exposure histories, even in the absence of an unirradiated control specimen.

ISSN:1042-0150    

DOI:10.1080/10420159708216850

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

It is known that ion-irradiated polymers are capable to adsorb dopants from solid, liquid or gaseous phases. For simple ambient atmosphere exposures, oxygen and water vapor are the most prominent dopants. Though the quantity of the latter one is not sufficient to be probed by conventional spectroscopic techniques, it can be detected indirectly via its ionic conductivity on applying a strong electric field along the track direction, as long as it is not yet masked by the intrinsic ion track conductivity, which is the case for low-fluence polymer irradiation. The conductivity is of similar order for most low-fluence irradiated polymers examined – namely 10−15−10−13Ω−1cm−1.

ISSN:1042-0150    

DOI:10.1080/10420159708216851

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The phenomenological treatment of ion dechanneling in crystals is done. A simple analytical model has been developed in order to take into account the simultaneous effect of energy losses, dechanneling, rechanneling and volume trapping into the channeling regime on the ions' dechanneling function (channeling probabilityvs.crystal depth).

ISSN:1042-0150    

DOI:10.1080/10420159708216852

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We have stuided the sodium migration in β″-alumina systems irradiated by heavy energetic ions. The phenomenon has been discussed in terms of transport equations which include three main processes: radiation enhanced diffusion, electric field assisted migration and preferential sputtering of the alkali element. We have developed a theoretical model which describes the process relating the diffusion constant, the sodium mobility and the electric field function to the characteristic effects of the radiation. The numerical solutions of this model indicate a Na+compositional profile strongly dependent on the form of the electric field function. A comparison with experimental results suggested an additional step in the procedure, which includes a subsequent bombardment of the sample with protons. This step simulates the acquisition of the profile by nuclear reaction techniques and adequately describes the experimental results.

ISSN:1042-0150    

DOI:10.1080/10420159708216853

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

New technique for examination of latent track etching based on the transmission of charged particles is suggested and some of preliminary experimental results are presented proving the feasibility of the method.

ISSN:1042-0150    

DOI:10.1080/10420159708216854

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In this paper we continue with our previous study on Cu precipitation in Fe–Cu binary alloys [1] under irradiation. In the latter it was shown that a simple model, including growth and coarsening and assuming that the only effect of irradiation is to enhance Cu diffusion, provides a good description of the kinetics of copper matrix depletion during precipitation in Fe–Cu model alloys. In the present work, using this model, we perform a detailed study on: (a) the incidence of Cu solubility limit on precipitation kinetics; (b) the evolution of the elasticity limit and material hardness with Cu precipitation, with the help of the model of Russell and Brown, [2] and (c) the variation of the ductile–brittle transition temperature (ΔDBTT) component due to Cu precipitation, using an empiric relation between this temperature transition and hardness. Theoretical results are compared with experimental ones.

ISSN:1042-0150    

DOI:10.1080/10420159708216855

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The zero-field splittingD, the anisotropicg-factorsg∥, Δg(=g∥−g⊥) and the first excited state splitting Δ(2E) for the trigonal Cr3+–VKcenter in KMgF3: Cr3+crystals have been studied from Macfarlane's high-order perturbation formulas. From the studies, the local structure of the trigonal center is obtained. The local lattice distortions (i.e., the displacement directions of the ions in the center) are consistent with the expectation based on the electrostatic interaction.

ISSN:1042-0150    

DOI:10.1080/10420159708216856

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The trigonal distortions of Ni2+, V2+, Mn2+and Co2+ions in ZnSiF6· 6H2O crystal have been studied by analysing their zero-field splittings and the anisotropy ofgfactor (characterized by Δg=g⊥−g∥). From the studies, it is found that the sign of trigonal distortion (compression or elongation) of octahedral environment of impurity ion is impurity-dependent, i.e., when the ionic radius of impurity is greater than that of the replaced Zn2+ion, the octahedral environment of impurity is compressed, whereas if the ionic radius of impurity is smaller than that of Zn2+, it is elongated. This point is similar to the case of isomorphous pure crystal where the paramagnetic ion is the host ion rather than the impurity.

ISSN:1042-0150    

DOI:10.1080/10420159708216857

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor