[en] In order to prepare a pure Pu(VI) solution, the oxidation of Pu(IV) to Pu(VI) by cerium(IV) was investigated with a UV-Visible spectrophotometer equipped with a 0.5 m liquid core waveguide. The degree of the oxidation of Pu(IV) was studied as function of the Ce(IV) concentration and the reaction time. The study showed that in 1 M HNO_3 solution, 1.2 × 10"-"3 M Ce(IV) can oxidize Pu(IV) with concentration of 4.3 × 10"-"5 M to Pu(VI) completely within 40 min, while 2.4 × 10"-"3 M Ce(IV) can do it within 15 min. The oxidation reaction of Pu(IV) by Ce(IV) is a first order process with respect to Pu(IV) according to the data analysis. From a thermodynamic point of view, the reaction can proceed almost completely provided that amount of the Ce(IV) is greater than stoichiometric amount. (author)

[en] A radiochemical procedure is developed for the determination of ²³⁷Np in soil with multi-collector inductively-coupled plasma mass spectrometry (MC-ICP-MS) and gamma-spectrometry. ²³⁹Np (milked from ²⁴³Am) was used as an isotopic tracer for chemical yield determination. The neptunium in the soil is separated by thenoyl-trifluoracetone extraction from 1 M HNO₃ solution after reducing Np to Np(IV) with ferrous sulfamate, and then purified with Dowex 1 x 2 anion exchange resin. ²³⁹Np in the resulting solution is measured with gamma-spectrometry for chemical yield determination while the ²³⁷Np is measured with MC-ICP-MS. Measurement results for soil samples are presented together with those for two reference samples. By comparing the determined value with the reference value of the ²³⁷Np activity concentration, the feasibility of the procedure was validated. (author)

[en] Catalytic conversion of CO₂ to CO (reverse water-gas shift reaction, RWGS) is one of the most promising technologies for CO₂ resource utilization. In this work, a sulfur-containing zirconia supported nickel catalyst (Ni/ZrO₂) was prepared to improve the CO₂ conversion while adjusting the CO₂ hydrogenation selectivity from CH₄ to CO. The effect of support size (80 nm, 120 nm, 200 nm and 320 nm) on the catalytic performance of RWGS was investigated. The results showed that the Ni/ZrO₂-80 sample with a smaller support size of 80 nm exhibited higher Ni dispersion and oxygen vacancy concentration, which not only exposed more active sites but also enhanced the adsorption and activation capacity of CO₂. For these reasons, the CO₂ conversion of 27.6% with 100% selectivity of CO was achieved over Ni/ZrO₂-80, and no catalyst deactivation was observed during the stability test for 50 h. This work provides a new idea for designing the RWGS catalyst with an outstanding CO₂ hydrogenation performance. (authors)

[en] A method was developed for the determination of ²³⁷Np with liquid scintillation counting (LSC) in the batch experiment of neptunium sorption onto bentonite. Before we use the pulse shape analysis (PSA) technique to discriminate α/β emission, a new approach was developed to set the optimum PSA by measuring a mixed α/β emitters sample and a background sample. The mathematic treatment of neptunium spectrum indicated that at the selected PSA-level of 38 approximately 86 % of the total α emission is detected, which is suitable for the determination of samples in the batch sorption experiments. Moreover, we confirmed that, at mass to volume radio 0-10 g/L the bentonite suspension in samples has a little impact on LSC determination. Thus, sorption percentage can be easily obtained by counting equivalent amount of suspension and supernatant from the same sample. Therefore, ²³⁷Np samples of batch sorption experiments could be detected with LSC quickly and effectively. (author)

[en] W–3Re alloys reinforced with various HfC particles contents (0 wt%, 0.5 wt%, 1 wt%, 5 wt%, 10 wt%) were fabricated using spark plasma sintering (SPS) at 2050 °C for 10 min. Microstructure, Vickers hardness and high temperature compression properties of the sintered W-3Re-xHfC alloys were investigated. Spherical HfC nanoparticles and micron scale clusters are distributed at the grain boundaries of the W–Re matrix. These nanoscale HfC particles pin dislocations and grains boundary as well as refine grain, thus enhancing the strength of composites. Furthermore, the HfC-W interfaces are well bonded semi-coherently without apparent interfacial gaps. The high temperature strength and micro-hardness of sintered composites are significantly increased with an increase of HfC contents. The micro-hardness of W–3Re alloy was 659.4 HV when 10 wt % HfC was added, which is enhanced up to 92.5 % compared with matrix. Its compressive strength is 850 MPa, increased by ~286 % compared with that of W–Re matrix. Quantitative analysis indicates that the main strength mechanisms are grain refinement, Orowan strengthening and interfacial thermal mismatch strengthening, which are influenced significantly by the HfC contents. This study provides new insights into composites performance optimization, reinforcement designs and strengthening mechanisms of particles reinforced W matrix alloys.