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Positron Annihilation Parameters (positron + annihilation_parameter)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Effect of magnetic field on the corrosion of iron and St20 steel as studied by positron annihilation

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2010
Ryszard Pietrzak
Abstract Lifetime spectra of positron annihilation in iron and St20 steel corroded in the water solution of HCl and in vapour above its surface have been investigated with emphasis on the effect of corrosion time and environment (solution or vapour) as well as of the presence and orientation of the magnetic field on the measured positron annihilation parameters. All the registered positron lifetime spectra consist of two components. For corroded samples the intensities of the two components as well as the corresponding values of the mean positron lifetime, differ from those for uncorroded material. The corrosion-induced changes in the positron annihilation parameters depend on the corrosion environment (solution or vapour) and on the presence and direction of external magnetic field. [source]

Irradiated polymethylmethacrylate studied by positron annihilation spectroscopy

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2007
Hamdy F. M. Mohamed
Abstract The effect of gamma irradiation dose on microscopic structure of polymethylmethacrylate (PMMA) has been studied using positron annihilation lifetime (PAL) and Doppler broadening of annihilation radiation (DBAR) techniques. The measurements were performed at room temperature as a function of the ,-irradiation doses from 60-1200 kGy. The observed lifetime spectra were resolved into three components. The size and the fraction of the o-Ps hole volume were estimated from the positron annihilation parameters. The effect of ,-irradiation was identified at lower doses to be cross-linking while at higher doses the chemical degradation of the polymer was observed. Moreover, the distribution of the free volume shifts from a large to small size as the irradiation increases and has very similar Gaussian-like distribution. The PAL results were confirmed with X-ray measurement. A correlation between the macroscopic mechanical properties Hv and positron annihilation parameters has been demonstrated. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Composition influence on positron annihilation parameters in ZnO-based nanocrystal semiconductor powders

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2007
L. C. Damonte
Abstract Zn1,xMgxO powders at various compositions were obtained by mechanical milling from the binary oxides. The progressive incorporation of Mg atoms into the ZnO lattice was monitored by X-ray diffraction (XRD). The evolution of annihilation parameters with milling time and composition were analyzed and related to the possible types of mechanical and substitutional induced defect present. It was concluded that the average lifetime constitute a useful parameter to sense the complete cation substitution in the wurtzite structure. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]