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Positron annihilation lifetime spectroscopy(PALS) is applied toa series of bis(aniline)fluorene and bis(xylidine)fluorene-based cardopolyimide and bis(phenol)fluorene-based polysulfone membranes. Itwas found that favorable amounts of positronium (Ps, the positron-electronbound state) form in cardo polyimides with the 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) moiety and bis(phenol)fluorene-basedcardo polysulfone, but no Ps forms in most of the polyimides withpyromellitic dianhydride (PMDA) and 3,3′,4,4′-biphenyltetracarboxylicdianhydride (BTDA) moieties. A bis(xylidine)fluorene-based polyimidemembrane containing PMDA and BTDA moieties exhibits a little Ps formationbut the ortho-positronium (o-Ps,the triplet state of Ps) lifetime of this membrane anomalously shortenswith increasing temperature, which we attribute to chemical reactionof o-Ps. Correlation between the hole size (Vh) deduced from the o-Ps lifetimeand diffusion coefficients of O2and N2forpolyimides with the 6FDA moiety and cardo polysulfone showing favorablePs formation is discussed based on free volume theory of gas diffusion.It is suggested that o-Ps has a strong tendency toprobe larger holes in rigid chain polymers with wide hole size distributionssuch as those containing cardo moieties, resulting in deviations fromthe previously reported correlations for common polymers such as polystyrene,polycarbonate, polysulfone, and so forth. [ABSTRACT FROM AUTHOR]

Abstract: We present a microstructural study of a surveillance test specimen from a reactor pressure vessel steel of a Russian-type nuclear reactor after neutron irradiation, post-irradiation annealing and re-irradiation, using atom probe tomography (APT) and positron annihilation spectroscopy (PAS). The APT results showed the formation of Cu-rich solute nano-clusters (CRCs) during the initial irradiation and their subsequent coarsening during annealing. After re-irradiation, new CRCs have been observed. The irradiation-hardening almost recovered during annealing. However, by re-irradiation, hardening comparable to that by the initial irradiation was observed. The hardening due to the CRCs formed during the initial irradiation, estimated using the Russell–Brown model, was almost the same as that observed. However, the estimated hardening after the re-irradiation was about half of the measured one. The other hardening is attributed to the newly formed MDs by the re-irradiation, which was evidenced by PAS. [Copyright &y& Elsevier]