[en] The reaction of uranium and its alloy with oxygen and water vapor has attracted widely attention as an important nuclear material. The oxidation process, reaction rate and products of uranium and its alloy with oxygen, water vapor and humid oxygen has been summarized and discussed. The process of uranium-oxygen systematic reaction includes the adsorption, solution of oxygen on the surface, diffuseness in the crystal lattice which is the determinative step and reaction at the interface of the metal and the oxide. However, the reaction mechanism of uranium-water system was dispersive on the diffuse ion. The uranium-oxygen-water systematic reaction is the result combines the uranium-oxygen and uranium-water reaction. (authors)

[en] A study was made on radiolysis of glycyrrhizic acid in dilute aqueous alkaline solution. Radiolysis of glycyrrhizic acid would be divided into two processes; (1) Chromophore (unsaturated ketones) was destroyed; (2) Structure of glycyrrhizic acid was destroyed due to hydrogen abstraction reaction, but chromophore was not destroyed. The G values of radiolysis of glycyrrhizic acid under different atmospheres have been determined. Four radiolytic products were separated by HPLC. Using scavenger method, it showed that glycyrrhetinic acid and unknown products are formed by OH attack. OH attack leads to glucosidic bond rupture. Unknown product is formed by OH and HO₂. Unknown III may be secondary product. Using competition kinetics k_OH-GAH ∼ 10¹⁰ dm³mol^-1s^-1 was got

[en] High current pulsed electron beam (HCPEB) surface treatment of a metastable β titanium alloy that initially consisted of an α + β double-phase microstructure has been employed with a various treating parameters. The parameters taken are as follows: accelerating voltage, 27 kV; pulse numbers, 5, 10 and 25, respectively; pulse duration, 2 μs. The microstructure and surface morphology changes occurring in the modified surface were investigated with optical microscopy, scanning electron microscopy, electron backscatter diffractometry and X-ray diffractometry techniques. We found that the sample surface showed a wavy aspect after 5 pulse treatment. After 25 pulses, the treated sample turned flatter and showed a lamellar structure. Meanwhile the initial α phase in the surface layer diminished gradually while increasing the number of pulses. On the contrary, the α'' martensite phase induced by the stress generated by the HCPEB treatment was found in melted layer of the treated samples. (authors)

[en] Highlights: • A Cr/Cr₂N film was prepared to improve corrosion resistance of uranium. • The Cr/Cr₂N film showed laminate structure, its modulation period was 40–50 nm. • The oxidized depth of Cr/Cr₂N film was less than 40 nm at 573 K for 120 min. • The corrosion resistance of uranium was improved after deposited the Cr/Cr₂N film. - Abstract: Depleted uranium is widely used in national defence and nuclear energy fields. However, the inferior corrosion resistance limits its application. A Cr/Cr₂N film was prepared by magnetron sputtering on the uranium to improve its corrosion resistance. The Cr/Cr₂N film exhibits modulation structure. The introduction of the Cr/Cr₂N increases the corrosion potential; the corresponding current density decreases about three orders of magnitude. After polarization corrosion, the surface morphology of the Cr/Cr₂N-coated on uranium keeps integrated. Only a thin layer of film (∼40 nm) is oxidized. The Cr/Cr₂N film shows great potential in improving oxidation and corrosion resistance of depleted uranium

[en] Highlights: •The Volta potential differences relative to the matrix are positive for both types of inclusions. •Both types of inclusions are cathodic in the “inclusion/matrix” microgalvanic couples. •The oxide-rich inclusions show a larger Volta potential value of about 115 mV than the carbo-nitride-rich inclusions. •The oxide-rich inclusions give stronger local galvanic coupling with the matrix. •The oxide-rich inclusions are more predisposed to initiate pitting corrosion. -- Abstract: The effects of carbo-nitride-rich and oxide-rich inclusions on the pitting susceptibility of depleted uranium were investigated by electrochemical corrosion measurements, optical microscopy, scanning Kelvin probe force microscopy (SKPFM), and SEM. The results of the potentiodynamic polarization tests suggest that oxide-rich inclusions are more likely to induce pitting corrosion than carbo-nitride-rich inclusions. This enhanced corrosion may be explained by the strong local galvanic coupling between the oxide-rich inclusion and the surrounding matrix, which, from the sight of SKPFM analysis, exhibits a 115 V higher Volta potential than the coupling between the carbo-nitride-rich inclusions and the matrix, respectively.

[en] ZrN films were prepared using microwave electron cyclotron resonance (MW-ECR) plasma enhanced unbalanced magnetron sputtering (PE-UMS) technique. The plasma characteristics near the holder were diagnosed by Langmuir probe for various deposition conditions and the films obtained were characterized by electron probe microanalysis x-ray diffraction and microhardness. As the N₂ flow rate increases from 2 to 20sccm, the ion density initially increases from 8.07 x 10⁹ to 8.31 x 10⁹ cm^-3 and then decreases to 7.52 x 10⁹ cm^-3, while the N₂⁺ ion density increases monotonically from 3.12 x 10⁸ to 3.35 x 10⁹ cm^-3 and the electron temperature does not vary much. The N concentration in the films increases and the grain size decreases as the N₂⁺ ion density increases. And the films become more and more amorphous as the N/Zr ratio is above 1.4. The corresponding microhardness of the deposited films increases from 22.5 GPa to the maximum of 26.78 GPa, and then decreases linearly to 19.82 GPa as the N₂ flow rate increases from 8 to 14sccm. The mechanism of the influence of the plasma characteristics on the microstructure and mechanical properties of the deposited films were discussed. (author)

[en] Multi-layered Ti/TiN films, single layer TiN films and gradient TiN films were deposited on uranium substrates by arc ion plating. The anodic polarization experiments in 50 μg/g Cl^- solution indicate that E_corr of the sample at a pulse bias of -800 V increases to about 714 mV, with an I_corr decrease of about two orders of magnitude. Studying on electrochemical corrosion mechanisms indicates that single layer films and gradient films become inactive by defect penetration through the substrate, hence decreased corrosion-resistance; while the inactivation of multi-layer films is due to layer malfunction, which makes it difficult for corrosive substances to reach the substrate. In this way the corrosion resistance is enhanced. (authors)

[en] The microwave ECR plasma in a cusp field has been diagnosed with the Langmuir probe. The plasma was generated in a novel multifunction PSII system with double symmetrical ECR chambers. The effects of gas pressure and microwave power on both the electron temperature and the plasma density are discussed. The plasma distribution in the process chamber has been detected. (authors)

[en] Luminescence sensing is an attractive approach for in-situ monitoring the health and integrity of multilayered surface protective coatings on highly active metals. In this work, we demonstrate the potential of erbium (Er) doped aluminum nitride (AlN) films to be applied as luminescence sensing layer in the Al/AlN multilayered coating system. The AlN:Er films were prepared by radio-frequency magnetron sputtering from Al targets doped with varied concentrations (from 0.5 at.% to 2.5 at.%) of Er. The chemical composition, surface morphology, crystal structure, chemical state and optical properties of the deposited AlN:Er films were investigated. We found that the crystal structure, surface roughness and optical properties of the AlN:Er films have strong correlations with the Er doping level. The as-deposited AlN:Er films showed the characteristic photoluminescence emission lines of the trivalent Er ions in the visible frequency range and quenching was observed when the Er doping level increased to 2.5 at.%. This work signifies the viability of AlN:Er film as luminescence sensing layer and the optimal Er doping concentration of the Al sputtering target is 2.0 at.% for practical applications. - Highlights: • AlN:Er film for luminescence sensing of multilayer Al/AlN coating health is proposed. • The properties of the AlN:Er films have strong correlations with the Er doping level. • The as-deposited AlN:Er films showed strong visible photoluminescence emission. • The optimal Er doping level of the Al target is 2.0 at.% for luminescence sensing.

[en] Multi-layer Ti/TiN films were prepared on U and Si by using arc ion plating in different bias voltages. The microstructure and cross section morphology were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results indicate that the pulse bias not only affects the diffraction peak strength, but also induces a new Ti₂N phase. The multi-layer films grow layer by layer or by island expansion. As the bias voltage is increased, the directional crystals become fine, and the films become denser. Corrosion tests in 50 μg/g Cl^- solution indicate that the multi-layer films are corroded by layers, which make it difficult for corrosion solution to reach the substrate. In this way the corrosion resistance is enhanced. (authors)