0000000000297135
AUTHOR
G. Bujnarowski
Positron Annihilation in Metals Defected by Action of the Tensile Force
Results of experimental investigations of uniaxially elongated mono- and polycrystalline samples of several metals (Fe, Ta, Pd, Ag, and Au), performed using the positron annihilation methods, are reviewed. The dependences of the S-parameters and positron lifetimes on the relative elongation of the samples were presented. The data obtained for polycrystalline samples indicate that in the proportionality and limited proportionality regions the changes in the physical properties are governed mainly by generation of vacancies and by kinetics of formation and transformations of vacancy clusters occurring flrst of all on the grain boundaries of monocrystallites. In the region of plastic deformati…
In situ and postradiation analysis of mechanical stress in Al2O3:Cr induced by swift heavy-ion irradiation
Abstract Optical spectroscopy and TEM techniques have been applied to study the radiation damage and correlated mechanical stresses in Al2O3 and Al2O3:Cr single crystals induced by (1–3) MeV/amu Kr, Xe and Bi ion irradiation. Mechanical stresses were evaluated in situ using a piezospectroscopic effect through the shift of the respective lines in ionoluminescence spectra. It was found that dose dependence of the stress level for Xe and Bi ions, when ionization energy loss exceeds the threshold of damage formation via electronic excitations, exhibits several alternate stages showing the build-up and relaxation of stresses. The beginning of relaxation stages is observed at fluences associated …
Positron Annihilation in Steel Samples Deformed by Uniaxial Tension
Angular distributions of the positron annihilation quanta were measured for steel ST2 SAL samples deformed by uniaxial tension up to difierent deformation degrees. The dependences of the S parameter on the relative elongation of the samples are presented. The positron annihilation data for steel are compared with the results obtained previously for polycrystalline iron samples deformed by uniaxial tension up to difierent deformation degrees in the proportionality and limited proportionality regions.
Positron Lifetime in Hostaphan
Positron lifetime measurements in hostaphan RNK, used for encapsulation of Na positron sources, were performed. It was found that the parameter of positron lifetime spectra in hostaphan RNK differ markedly from those for other forms of polyethylene terephthalate. The maximum penetration depth of positrons from RNK hostaphan amounts 0.42 mm. The information gained in the present study is of great importance for experimenters using hostaphan RNK for encapsulation of positron sources.
Positron Annihilation in Polycrystalline Metals Deformed by Uniaxial Tension
Angular distributions of the positron annihilation quanta were measured for polycrystalline samples deformed by uniaxial tension up to difierent deformation degrees. The S parameter as a function of the W parameter was determined. The data obtained for samples elongated up to difierent elongation degrees indicate that in the proportionality and limited proportionality regions the changes in the physical properties of samples are governed mainly by generation of vacancies and formation and kinetics of transformations of vacancy clusters occurring flrst of all on the grains of monocrystallites. In the region of plastic deformations the dominant defects are dislocations and vacancies and their…
Piezospectroscopic study of mechanical stress in Al2O3:Cr under swift heavy ion irradiation
Abstract The spatial distribution of mechanical stresses in Al2O3:Cr single crystal irradiated with (1 ÷ 3) MeV/amu Kr, Xe and Bi ions has been studied by using laser confocal scanning microscopy technique. The stress level as a function of the ion penetration depth has been evaluated from depth-resolved photostimulated R-line luminescence spectra exploiting the piezospectroscopic method. As it was found, the stress field generated by swift heavy ion irradiation is composed of stresses with maximal magnitude comparable with the ultimate stress limit of ruby crystals. Experimental data are discussed in the framework of a model considering the Cr3+ atoms as individual piezosensors.