Results of investigations of the angular correlation of annihilation radiation and positron annihilation lifetime measurements are presented for polyethylene-carbon black composites. The inhibition of positronium formation due to the carbon black introduction is evidenced by a decrease in intensities of the narrow component in angular correlation of annihilation radiation curves and of the longest-lived components in positron annihilation lifetime spectra. A qualitative interpretation of the data in terms of the free-volumes model is proposed.
Positron lifetime measurements were performed on polyethylene probes of different densities under various atmspheric conditions within a Y-dose range from 0 kGy up to 1460 kGy. Ve present here experiments non destroying the sample. Four components could be resolved in each lifetime spectrum; the components consist each of a lifetime T and an intensity I. In the dose range investigated the behaviour of the lifetime parameters of the longestlived (74, 14) and the second long-lived (73, 13) component, respectively, could be explained by the y-induced recristallisation and the creation of hydroperoxides. The average free volume as a function of the dose m y be calculated out of the lifetime of the fourth component (7~).
One-dimensional angular correlation studies of the Ni73TM5Si10B12 (TM=V, Cr, Mn, Fe and Co) metallic glasses have been performed. The analysis of the angular correlation data, consisting of a deconvolution into one Gaussian and two parabolic curves, indicates the possibility that two 'species' of the nearly free electrons are present in the particular materials. We have attempted to verify the physical reliability of this fitting procedure by assuming that the crystalline embryos tend to localise the thermalised positrons. It is shown that some of the estimated parameters describing the shape of the angular correlation curves systematically change with changing the atomic number of the TM admixtures. It allows the effect of TM on the thermal stability to be precisely recognised.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.