摘要:

A pure Pt sample and three different dilute Pt-Au alloys were simultaneously irradiated with thermal neutrons at 4,4 K. The influence of the varying gold concentrations on the isochronal recovery spectrum of Pt was investigated using a resistivity method. The characteristics of several additional substages observed in Stage II due to the gold alloying were comparable to the results of electron irradiation experiments. The observations made with regard to the impurity (gold) dependence of these substages could be interpreted in terms of the concentrations of the interstitials, vacancies and impurities present in the material. The interpretation of these substages was further found to be consistent if the recovery spectrum was investigated as a function of defect concentration.

ISSN:0033-7579    

DOI:10.1080/00337578008208422

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Some aspects of the molecular orbital methods are briefly received. The problems dealing with the evaluation of the total energy are discussed. The conditions of application to a cluster of atoms containing the defect are described. An example of calculation of the lattice distortion and relaxation around the vacancy in diamond, using semi empirical methods, is given.

ISSN:0033-7579    

DOI:10.1080/00337578008208423

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The growth of macroscopic radiolytic gas bubbles in reactor irradiated polymethyl methacrylate during subsequent heat treatment is studied.

ISSN:0033-7579    

DOI:10.1080/00337578008208424

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Accurate calculations for the correction of the Rutherford scattering cross section are presented, based on the potentials obtained from the Dirac-Fock electron distributions. The calculations have been tested against relative4He back- scattering measurements in Al, Cu, Ag, and Au in the energy range 200–2000 keV. Complete consistency has been found to within experimental error (0.5–1%). At 170° scattering angle, thecorrections found were in A10.1–1.5%, in Cu 0.5–4%, in Ag 0.7–8%:, and in Au 1.7–15%.

ISSN:0033-7579    

DOI:10.1080/00337578008208425

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The theory of interstitial loop nucleation and growth in metals at the beginning of irradiation is developed. After some transient time the loop concentration becomes constant and both interstitial and vacancy diffusion fluxes achieve their steady state values. At this stage vacancy cluster nucleation becomes possible. Analytical expressions for the loop concentration, the characteristic times of their growth and the start for vacancy clustering are obtained. It is shown that for given irradiation conditions some critical density of dislocation network exists. For higher densities the process of loop formation under irradiation is suppressed due to interstitial absorption in sinks.

ISSN:0033-7579    

DOI:10.1080/00337578008208426

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The behaviour of materials during irradiation is determined by the point defect concentrations which develop and the manner in which they evolve in time. The controlling factors are the production, recombination and loss to sinks and these are usually modelled with the help of first order (“bimolecular”) non-linear equations. In this paper we present exact solutions which are obtained by transforming them to a Riccati equation. Five cases have been considered and the corresponding models are pertinent to different irradiation conditions which exist at very low or high temperatures or arise due to self ion irradiation etc. The Lyapounov stability of the solutions are discussed together with the phase diagram plots. A general formalism has been given for the case of pulsed irradiation based on the structure of solution of the Riccati equation. The solution enables us to calculate the instantaneous and average value of the concentrations during any pulse cycle. The formalism also enables us to explicitly identify two time scales corresponding to the irradiation and annealing pulses from which the behaviour of the system can be obtained for a sequence of pulses. The formalism is applied to one of the models as an example. The paper concludes with a few general comments on the implication of stability due to diffusion and fluctuations. In particular it is shown that one of the models applicable to situations at very low temperature where recombination dominates and loss to sinks is unimportant the fluctuations will drive the mean square of the concentrations linearly in time.

ISSN:0033-7579    

DOI:10.1080/00337578008208427

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The contribution from vacancies to the expansion of graphite lattice along theCaxis and to its contraction along theaaxis has been calculated on the basis of the dependence of the spacings between the carbon atoms on the bond order. It is found that αvc= 1.32, αva= −0.46. Using the same model the effect of interstitials contained in various complexes on the graphite expansion along theCaxis has been estimated. The relationships obtained have been used for the analysis of experimental data on the change in theCandaparameters of graphite irradiated under various conditions. Comparison with other models is also made.

ISSN:0033-7579    

DOI:10.1080/00337578008208428

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Type-316 stainless steel was irradiated at room temperature with 14-MeV, Be(d,n), and fission-reactor neutrons. Highenergy neutron irradiations were carried out at the Rotating Target Neutron Source (RTNS-I) at the Lawrence Livermore Laboratory and the 1.93-m Isochronous Cyclotron at the University of California at Davis. Irradiations with fission-reactor neutrons were carried out in the Lawrence Livermore Pool Type Reactor (LPTR). Tensile properties after irradiation were determined at room temperature, and significant changes in strength and ductility were found. Irrddiation at all three neutron sources produced a very high density of defects 1 to 2 nm in diameter. The 14-MeV neutrons created more damage on a fluence basis, but the mechanical property and microstructure data could be correlated well on a damage energy basis. The deformation behavior was in accord with the dispersed barrier model of radiation hardening.

ISSN:0033-7579    

DOI:10.1080/00337578008208429

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Energy spectra of sputtered Na and Sm atoms investigated with a Doppler-Shift-Laser-Spectrometer (DSLS) are presented. The results obtained with Na and Sm targets are compared with former measurements with alkali halides. It can be shown than an increasing contribution of collision cascades to the energy spectrum results in a maximum of the sputtered flux at zero energy. We therefore suggest that an 1/(E+Eb)2distribution is relevant for collision cascades instead of anE/(E+Eb)3proposed by many authors. In this case the energy spectrum of sputtered Sm atoms can be explained by random collisions. The energy spectra of sputtered Na can be very well fitted if we assume that random collision cascades and slow thermal processes both contribute to sputtering. The slow thermal contribution strongly increases if the target is heated. A small thermal spike contribution can be found in the energy region from 0.2 to 0.5 eV. The binding energy of Na increases from 1.7 to 2.5 eV if the target is exposed to oxygen. In this case the slow thermal contribution is strongly reduced.

ISSN:0033-7579    

DOI:10.1080/00337578008208430

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The results of low energy ion scattering are presented and their application to the determination of surface crystallography is described. The focussing of surface wedges and surface lenses is evident from these results.

ISSN:0033-7579    

DOI:10.1080/00337578008208431

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor