[en] A new isotope ²²⁰At has been identified among the mass-separated products of a spallation reaction of ThO₂. Its half-life has been found to be 3.71 ± 0.04 min. This isotope was identified through its β decay to four excited levels in ²²⁰Rn known previously from the α decay of ²²⁴Ra. (author)

[en] We have investigated the structures of the θ' and T₁ precipitates in Al-1.6wt%Li-3.2wt%Cu and Al-2.4wt%Li-3.2wt%Cu alloys aged at 220 deg. C. The θ' precipitates in the 1.6 wt%-Li alloy are those known for the Al-Cu binary system (a=0.40 and c=0.58 nm); whereas those in the 2.4 wt%-Li alloy exhibited two atypical structures. One, named a type I T_B' plate in this study, is isostructural to the known θ phase with a large c value of about 0.64 nm, having a habit plane parallel to the matrix {100}_α; the other, type II T_B', is characterized by a=0.41 and c=0.61 nm, having a habit plane inclined at about 20 deg. with {100}_α, while maintaining a coherent interface. Also images of {111} precipitates in the 1.6 wt%-Li alloy revealed a continuous change from the T₁ phase (c=0.935 nm), to a structure with c=0.87-0.90 nm. The image and small lattice parameter suggest that this {111} precipitate is likely to be the Ω phase

[en] CePd_1_-_xRh_x undergoes a continuous evolution from ferromagnetic order in CePd to an intermediate-valence (IV) ground state for CeRh. Close to the disappearance of magnetic order at x_c_r ∼ 0.87 unusual behavior of the ac susceptibility and the specific heat was observed. It was explained with a broad distribution of local Kondo temperatures T_K from below 2 K to above 50 K due to the disorder introduced by Pd-Rh exchange. The thermopower S is very sensitive to Kondo scattering even for diluted 4f systems. In Ce compounds a large positive maximum in S(T) is usually observed around T_K. We studied S(T) in CePd_1_-_xRh_x in order to evaluate the presence of Kondo scattering and the involved energy scales. Pure CeRh shows typical IV behavior with a large maximum at 220 K and small values at low T. Already 5 % Pd substitution leads to a strong enhancement of the low-T thermopower. Even larger values are found around x_c_r, while the high-T maximum shifts only moderately. Our results are in line with the existence of low (local) Kondo scales in the presence of IV behavior at high Rh content x > x_c_r. For lower Rh content a decreasing (average) Kondo scale is found.

[en] In this work, ultra-long ZnO nanorods (NRs) were grown on ZnO buffered Si substrates by using direct heat substrate-modified chemical bath deposition (DHS-MCBD) method. Initially, the growth temperature was varied in the range 140 °C to 250 °C while keeping the time fixed at 4h. In the second stage, the growth temperature was kept fixed at 220 °C and the time was changed from 4h to 8 h. The morphological, structural and optical properties of ZnO NRs at different growth temperatures were investigated by using field emission scanning electron microscope (FESEM), x-ray diffraction (XRD) and photoluminescence (PL) spectroscopy techniques. The surface morphology results revealed the formation of hexagonal-shaped, ultra-long and vertically-aligned ZnO NRs. The average length of the NRs was increased from 5.7 μm to 24.5 μm by increasing the growth temperature from 140 °C to 250 °C. The XRD results specified the formation of c-axis oriented diffraction peak corresponding to hexagonal ZnO NRs in all the samples. The intensity of this peak was increased by increasing the growth temperature up to 220 °C, however, on further increasing the temperature to 250 °C, the c-axis peak intensity was decreased. The PL analysis indicated higher UV to deep level emission intensity ratio (I_UV/I_DLE) of the NRs grown at 220 °C as compared to the others. Similarly, by changing the growth time from 4h to 8h, the length of ZnO NRs was also increased. The results obtained were correlated and the chemical reactions for ZnO NRs growth were discussed in this paper. (paper)

[en] Cleaning techniques for metallic first mirrors are needed in more than 20 optical diagnostic systems from ITER to avoid reflectivity losses. Plasma sputtering is considered as one of the most promising techniques to remove deposits coming from the main wall (mainly beryllium and tungsten). Previous plasma cleaning studies were conducted on mirrors contaminated with beryllium and tungsten where argon and/or helium were employed as process gas, demonstrating removal of contamination and recovery of optical properties. Still, both above-mentioned process gases have a non-negligible sputtering yield on mirrors. In this work, we explored the possibility to use a sputter gas having a small impact on mirrors while being efficient on Be deposits, e.g. deuterium. Two sputtering regimes were studied, on laboratory deposits as well as on mirrors exposed in JET-ILW, namely physical sputtering (220 eV ion energy) and chemically assisted physical sputtering (60 eV ion energy) using capacitively coupled plasma with radio frequency. The removal of Be and mixed Be/W contaminants, as well as the recovery of reflectivity, was achieved when deuterium was employed at 220 eV while cleaning at 60 eV was only fully efficient on laboratory beryllium deposits. On mirrors exposed in JET-ILW, the situation is more complex due to the presence of tungsten in the contaminant film, leading to the formation of a tungsten enriched surface that is not easily sputtered, especially at 60 eV. (paper)

[en] The room temperature fatigue properties of AZ91 magnesium alloy produced by high pressure die casting (HPDC) as cast, heat treated, friction stir processed (FSP) and FSP and heat treated were studied. The fatigue properties of the material were evaluated for the HPDC magnesium alloy in the as-received state and after a solution treatment at 415 deg. C for 2 h and an ageing treatment at 220 deg. C for 4 h. The heat treatment resulted in a significant increase in the fatigue properties of the HPDC material, while no significance influence of heat treatment was recorded in the FSP condition. The morphology of fracture surfaces was examined by employing a field emission gun scanning electron microscope (FEGSEM)

[en] The charge-exchange (p, n) reaction at 220 MeV has been measured to extract the strength distribution of Gamow-Teller transitions from the doubly magic unstable nucleus ¹³²Sn. A recently developed experimental technique of measuring the (p, n) reaction in inverse kinematics has been applied to the study of unstable nuclei in the mass region around A ∼ 100 for the first time. We have combined the low-energy neutron detector WINDS and the SAMURAI spectrometer at the RIKEN radioactive isotope beam factory (RIBF). The particle identification plot for the reaction residues obtained by the spectrometer provides the clear separation of the CE reaction channel from other background events, enabling us to identify kinematic curves corresponding the (p, n) reaction. Further analysis to reconstruct the excitation energy spectrum is ongoing. (authors)

[en] We have studied the effect of ion-beam irradiation on reducing the ordering temperature of FePt and FePtAu nanoparticles. FePt and FePt(Au14%) 4 nm particles dispersed on a Si-substrate were irradiated by 300 keV Al-ions with a dose of 1 x 10¹⁶ ions/cm² at 43 ^oC using a water-cooled flange in order to minimize the vacancy migration and voids formation within the collision cascades. Partial chemical ordering has been observed in as-irradiated particles with coercivity of 60-130 Oe. Post-irradiation annealing at 220 ^oC enhanced chemical ordering in FePt nanoparticles with coercivity of 3500 Oe, magnetic anisotropy of 1.5 x 10⁷ erg/cc, and thermal stability factor of 130. A much higher 375 ^oC post-irradiation annealing was required in FePtAu, presumably because Au atoms were trapped at Fe/Pt lattice sites at lower temperatures. As the annealing temperature increased, anomalous features in the magnetization reversal curves were observed that disappeared at higher annealing temperatures

[en] Nickel-coated silk composites (Ni/silk fiber) were prepared by electroless nickel-plating using a kind of natural silk as template in first stage. The silk templates were then removed to get Ni hollow fiber by annealing the Ni/silk fiber at 220 deg. C for 2 h in air or 700 deg. C for 1.5 h in nitrogen. The prepared Ni/silk fiber and Ni hollow fiber were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), field emission scanning electron microscope (FE-SEM) and differential thermal analysis and thermogravimetric analysis (TG-DTA). The values of complex permittivity, complex permeability, dielectric and magnetic loss of Ni/silk fiber and Ni hollow fiber were measured in the frequency range of 2-18 GHz by a reflection/transmission approach using a network analyzer. The results indicate that the dielectric loss of Ni/silk fiber and Ni hollow fiber is high up to 1 even at 18 GHz while the magnetic loss is low

[en] Sol-gel technique was used to prepare silica-supported copper chromite catalyst from acid hydrolysis of sodium silicate. The catalyst was characterized by BET surface area, FESEM, XRD, H₂-TPR and pyridine adsorption by FTIR. The catalyst was activated in a hydrogen atmosphere based on H₂-TPR result. The surface acidity of the catalyst was evaluated by NH₃-TPD and pyridine adsorption. XRD result of reduced catalyst showed the presence of Cu⁰, Cu¹⁺ and Cr₂O₃ in the catalyst. Glycerol dehydration was carried out at different temperature (180 °C to 240 °C) from aqueous glycerol solution with the reduced catalyst in a batch reactor. The glycerol conversion was reached 100% with maximum acetol selectivity of 70% for highest Copper chromite loaded (40 wt%) on silica at 220 °C in atmospheric pressure. The distilled liquid product was analyzed by high-performance liquid chromatography. Oxidized catalyst and spent catalyst showed lower glycerol conversion with low acetol selectivity than the reduced form of the catalyst. This is due to the cuprous ion in the reduced form of the catalyst, which acts as Lewis acid sites in glycerol dehydration.

Graphic abstract

Glycerol dehydration to acetol with reduced form of silica-supported copper chromite catalyst is reported. The reduced form of copper chromite (cuprous oxide) on silica surface acts as a lewis acid in glycerol dehydration. Cuprous oxide coordinates with terminal hydroxyl group of glycerol and forms low energy six-membered transition state in the dehydration reactions. .