摘要:

The spatial distribution of particles sputtered from the (001) face of Ni single-crystals is studied as a function of temperature. A significant increase in sputtering intensities both in the (011) directions and in random directions is found experimentally near the Curie point (Tc= 635 K). The temperature dependence of mean-square angular deviation ψ2of sputtered particles from close-packed (011) directions was determined both experimentally and by computer simulation. Except for a near-Tcregion, ψ2increases linearly with temperature in agreement with the result of the computer calculation. At the Curie point, the experimental ψ2has a sharp peak (corresponding to the value of ψ at 1200 K, determined by computer calculations). This result suggests a significant increase in displacement amplitude of surface atoms nearTc, and gives a method for its estimation from sputtering patterns.

ISSN:1042-0150    

DOI:10.1080/10420159708216838

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The following kinds of materials, which are potentially useful for CTR construction, namely: the 12KH18N10T, W-4541, W-4016 and SS-304 steels, Ni, Cu and Mo have been Cyclotron irradiated with 3.0, 4.7 and 6.8 MeV He ions with the aim of investigating the energy and the dose dependence of the induced surface deformation effects (blistering and flaking). We report the experimentally determined values for the blisters average diameter and for the critical fluences inducing blistering. We describe other observed features due to irradiation, as sponge-and wave-like structures, submicronic cracks, multilayer flaking, secondary blisters and microcraters. It is discussed the potential validity of the two main categories of explanations which could describe the reported phenomena: the gas driven (gas bubble coalescence) model and the stress-induced model of blistering.

ISSN:1042-0150    

DOI:10.1080/10420159708216839

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The convenience of parametrizing the screening charge density induced by a proton in a metal has been stressed by several authors. This parametrization simplifies the description of the charge density and ease its use in different applications. In this work we propose a simple fitting function characterized by a small number of parameters with physical significance. However simple, this function correctly describes charge normalization, asymptotic behavior and cusp condition. Our results compare favorably with previous parametrizations and numerical calculations.

ISSN:1042-0150    

DOI:10.1080/10420159708216840

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A study of the annealing of defects in CaHfO3produced by181Hf thermal neutron activation is presented. Two defect structures besides the undistorted lattice were detected. One of them characterized by well-defined hyperfine parameters disappears at 1243 K. The other one vanishing at 1343 K, is characterized by a very strong and unresolved hyperfine interaction. The temperature dependence of site-fractions follows an exponential lawe−δe/kT. The activation energies of 1.5 eV and 0.1163eV were obtained upon annealing those structures.

ISSN:1042-0150    

DOI:10.1080/10420159708216841

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Changes in the near-surface region of V-5Fe alloy after irradiation at room temperature with 50 keV V+ions to fluences in the range from 1019to 1021ion/m2have been investigated. Radiation-induced segregation profiles were measured by means of XPS with ion sputtering. Calculations of the segregation profiles were performed using diffusion equations modified for the case of ion irradiation at temperatures where the vacancies are immobile. The difference in the interstitial diffusion coefficients of alloy components were considered as the main driving force for the component redistribution. By fitting the experimental data the ratio of iron to vanadium interstitial diffusion coefficients δihas been evaluated. Assuming the equality of the pre-exponential factors in the diffusion coefficients, a temperature dependence of δihas been found. An analytical expression for δihas been derived.

ISSN:1042-0150    

DOI:10.1080/10420159708216842

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Experimental and theoretical study of the F absorption band were carried out in mixed ionic crystals as a function of temperature and molar composition. Both the point-ion and pseudopotential methods of Gourary–Adrian and Bartram–Stoneham–Gash, respectively, have been used to obtain the F band shift effect in KCl1−xBrxmixed crystals with molar fraction x and the temperatureTof the crystal. The theoretical values were compared with the experimental ones, and a good agreement between experimental and theoretical calculations has been found.

ISSN:1042-0150    

DOI:10.1080/10420159708216843

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The variations of the Hall constantRH, Seebeck coefficient α, reflectance spectra in the plasma-resonance frequency range and shift of the absorption edge due to the incorporation of Pb atoms into the crystal lattice of Bi2Se3single crystals, show that Pb impurities at low concentrations lead to an increase of the free charge carrier (electron) concentrationnin the crystals; at higher concentrations a decrease ofnvalues is observed. The anomaly in then=f(cPb) dependence is accounted for by a model based on the assumption that the arising Pb'Bisubstitution defects interact with native defects in the crystal lattice of undoped Bi2Se3; i.e. with antisite Bi'Sedefects and V−Sevacancies in the selenium sublattice. Fitting then=f(cPb) dependence allows us to conclude that the formation energy of Bi'Sedefects increases with increasing content of Pb content in the crystal lattice. It is shown that simultaneous changes of the concentration of the considered defects, Pb'Bi, Bi'Seand V−Se, are responsible for the maximum observed on then = f(cPb) dependence in the range of low Pb concentrations.

ISSN:1042-0150    

DOI:10.1080/10420159708216844

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Glasses with compositionxCoO · (0.3–x)Na2O · 0.70B2O3have been prepared over the range 0 ·x· 0.12 containing 1 mol%/2 mol% of V2O5. Electron paramagnetic resonance spectra of VO2+of the glasses have been measured at X-band (v· 9.3 GHz) at room temperature. Spin Hamiltonian parameters of the VO2+ions have been calculated. It is found that forx· 0.05 the octahedral symmetry is reduced when Na2O is replaced by CoO. d.c. conductivity of these samples has also been measured which shows that conductivity decreases and activation energy increases when Na2O is replaced by CoO.

ISSN:1042-0150    

DOI:10.1080/10420159708216845

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A study has been made of the temperature dependence of the d.c. conductivity of pure and borated low density polyethylene LDPE (4% and 8% borax). The above calculations were carried out before and after X-ray irradiation. The irradiation dose was varied from 0 to 1000 rad.

ISSN:1042-0150    

DOI:10.1080/10420159708216846

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor