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Hypo-eutectic alloy of Zr 45 Cu 45 Al 10 was irradiated with 16 MeV and 200 MeV Au ions at room temperature. Before and after irradiation, effects of the irradiation on the structure and hardness of the alloy were investigated by using X-ray diffraction (XRD), Extended X-ray absorption fine structure (EXAFS), micro-Vickers hardness and positron annihilation measurements. As a result of the irradiation, amorphization was confirmed for both energies of the irradiations, but the behavior of hardness change strongly depends on the irradiation energy. That is, the hardness once decreases and increases with increasing the fluence in the case of 16 MeV irradiation, but in the case of 200 MeV irradiation, no decreasing trend was observed. The EXAFS measurement shows that the changing ratio of Cu-Cu and Cu-Zr bonds around each Cu atom is different between low energy and high energy Au ion irradiation. [ABSTRACT FROM AUTHOR]

Structural relaxation behavior of various composition for Zr-Cu-Al ternary bulk amorphous alloys (hyper-eutectic: Zr 45 Cu 45 Al 10 and Zr 49 Cu 41 Al 10 , eutectic: Zr 50 Cu 40 Al 10 , hypo-eutectic: Zr 55 Cu 35 Al 10 and Zr 60 Cu 30 Al 10 ) during isothermal annealing below glass transition temperature ( T g ) has been investigated by positron annihilation techniques (positron lifetime and coincidence Doppler broadening (CDB)), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and bulk density measurements. The annealing makes the positron lifetime decrease owing to the relaxation. However, maximum decreasing of positron lifetime after 10 ks annealing for eutectic alloy was observed. And different composition dependence of positron change between hypo- and hyper-eutectic alloys was confirmed. Especially, open-volume in hyper-eutectic alloys is hard to change by the annealing. We found that the trend of positron lifetime change Δτ with Zr concentration is not necessarily correlated with the change in bulk density consistently. On the other hand, the positron lifetime during annealing obeys a stretched exponential relaxation function. Also we found the relaxation parameter β , which indicates the distribution activation energy for open-volume relaxation, varies in Zr concentration. [ABSTRACT FROM AUTHOR]

Abstract: Positron annihilation lifetime (PAL) and Doppler broadening (DB) techniques have been performed to identify defects, such as vacancy clusters and dislocations, and to study their distributions on the sample in the early stage of fatigue cycle (0–10% of cycles to failure) in pure Fe. From two-lifetime component analysis, the component of the longer lifetime of about 130ps, corresponding to a mono-vacancy on edge dislocation, has been observed from 0.01% Nf fatigue. However, the long lifetime component of about 200ps appears in 10% Nf fatigue at a certain position of the sample. Vacancy clusters have possibly been formed to some extent at this fatigue life. The results suggest that the generation of micro-cracks during fatigue test is related to the formation of three-dimensional vacancy clusters. [Copyright &y& Elsevier]

The relations between vacancy-type defects in Fe-40, 45, and 50 at%Rh alloys and stress-induced phase transitions from a B2 phase have been examined by XRD, TEM, and positron annihilation experiments. The specimens were deformed at room temperature by a high-speed compression machine, and the natures of related vacancies and vacancy clusters were examined. The results reveal that structural Rh vacancies exist in non-stoichiometric FeRh alloys, and that lifetimes of the long-lifetime components of the introduced defects change in various manners, depending upon the deformation conditions. [ABSTRACT FROM AUTHOR]

Abstract: Binary Au–Pd nanoparticles were synthesized by ultrasonic irradiation of solutions containing Au3+ and Pd2+ ions (the ion ratio from 0.3:0.7 to 0.9:0.1mM) and cationic surfactant (SDS: sodium dodecyl sulfate). In each case the core–shell structure (Au core, Pd shell) was confirmed by scanning transmission electron microscopy (STEM). The mean diameters of them were all about 9nm, and the thickness of the Pd shell depends on the ratio of Pd2+ and Au3+ ions in solution. In order to study the electronic states of core–shell nanoparticles and their dependence on shell thickness, Doppler broadening measurements were performed for Au–Pd core–shell nanoparticles by using slow positron beam technique. The ratio curves of Au–Pd particles did not match with those of pure Pd and pure Au, but a small difference in the low electron momentum region was observed among nanoparticles depending on Pd shell thickness. [Copyright &y& Elsevier]

Abstract: Thermal vacancy formation was studied for the Heusler-type ferromagnetic alloys Co2MnZ (Z=Si, Ge, Sn) as a function of temperature (773–1273K) by the density, electrical resistivity and positron annihilation measurements. The vacancy concentration increased with increase in quenching temperature and particularly, a high vacancy concentration exceeding 2% was observed in Co2MnGe and Co2MnSn. Estimated vacancy formation and migration energies were comparable with those for B2-type FeAl and CoGa alloys with high vacancy concentration. Further, the vacancy type and the vacancy site were examined for alloys quenched from 773K. As a result, it was suggested that the mono-vacancies are randomly distributed over the lattice sites. [Copyright &y& Elsevier]