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Journal of Nuclear Materials
North-Holland
Journal of Nuclear Materials

North-Holland

0022-3115

Journal of Nuclear Materials/Journal Journal of Nuclear MaterialsSCIISTPEIAHCI
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    First-principles study on stability, adhesion and fracture properties of ZrO2/W interface in composite materials

    Liu J.Hou C.Zhang X.Zhang Y....
    5页
    查看更多>>摘要：© 2022 Elsevier B.V.Zirconia/tungsten (ZrO2/W) interface is easily formed during the preparation of W-Zr and W-ZrC composites for plasma-facing materials. But there is little information available about the stability, cohesion and bonding of ZrO2/W interface at the atomic scale. Therefore, the thermodynamic stability, mechanical properties and electronic structure of t-ZrO2(001)/W(001) interfaces have been calculated using first-principles calculations. Five kinds of interface bonding structures were considered, and it is found that the two sandwich-like interfaces with one or two stoichimetric ZrO2(001) layers between two W(001) slabs have lower interface energies and better stability than the three precipitate-like interfaces with a ZrO2(001) slab stacked on a W(001) slab, which means that an ultrathin zirconia film tends to form and may promote the grain refinement in W. The analyses of mechanical properties including the work of separation, fracture energy and tensile strengths show that the mechanical failure of the interfaces is inclined to initiate at the interfacial W-O and the O-O bonds, and the ZrO2(001)/W(001) interfaces are less stable against brittle fracture than bulk W and clean W grain boundaries, which implies that the precipitate of ZrO2 particles may act as the crack initiation sites during stretching. Furthermore, the electronic structures analysis indicates that the interfacial W-O bond has some property of covalent and ionic feature. This work could provide a deep understanding of stability, cohesion and fracture properties of ZrO2/W interfaces.
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    Effects of MoO3 and Nd2O3 on the structural features, thermal stability and properties of iron-boron-phosphate based glasses and composites

    Wang F.Wang Y.Hao Y.Liao Q....
    5页
    查看更多>>摘要：© 2021 Elsevier B.V.Three series of iron-boron-phosphate based glasses and composites as hosts for MoO3 and Nd2O3 were prepared by a melt-quenching process. The effects of MoO3 and Nd2O3 on phase composition, structural features, thermal stability and aqueous durability of the iron-boron-phosphate glasses and composites were investigated in detail. The results show that the 5∼15 mol% MoO3 containing samples with Nd2O3 content less than 3 mol% are fully amorphous, monazite NdPO4 phase is detected in their amorphous structure while more than 3 mol% of Nd2O3 incorporated. Generally, the incorporation of Nd2O3 and MoO3 enhances the crystallization of NdPO4 phase, and induces the decrease of Q0 units and the increase of [MoO4], Q1 and Q2 units. Thermal stability of glassy phase in the samples is enhanced with the increase in MoO3 content, although its thermal stability decreases due to the formation of NdPO4 phase. Moreover, the reasons on the variations of structure and thermal stability are discussed. LRMo are about 10−4 ∼ 10−3 g·m−2·d−1 for 14 days and LRNd are believed to be less than ∼10−6 g·m−2·d−1, indicating their good aqueous durability. The conclusions provide researchers with the roles of MoO3 and Nd2O3 in iron-boron-phosphate based glasses and composites as potential hosts for Mo- and Nd-containing nuclear waste.
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    Structural investigation and specific heat measurements on borosilicate, uranium and rare earths loaded borosilicate glasses

    Manivannan A.Jayaraman V.Saravanan G.Ravisankar P....
    5页
    查看更多>>摘要：© 2021Enthalpy increment data were acquired for borosilicate and doped borosilicate glasses containing oxides of uranium and surrogates of plutonium (CeO2, Nd2O3 and Gd2O3) using isoperibol drop calorimetry. The specific heat of borosilicate glasses were derived from these data and compared with doped glasses. The specific heat of the pristine glass is nearly similar to that of BSGU and found to show a dissimilar trend for BSGUCe and BSGRE. Internal network connectivity of the base glasses was investigated using micro-Raman spectrometer and compared with the glass containing high and low concentration of modifier (Na2O) for better understanding of thermal stability of the glasses. The Raman spectra reveal changes in the network structure with varying concentration of Na2O.
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    First-principles computational tensile tests of grain boundaries of zirconia with Cu segregation

    Xu C.-H.Xie Y.-P.Yao M.-Y.Hu L.-J....
    5页
    查看更多>>摘要：© 2021 Elsevier B.V.Zirconium alloys are widely used as nuclear cladding in pressured water reactor of nuclear power plant, and its corrosion resistance determines the service life of Zr alloys. Alloying can improve the corrosion resistance of Zr alloys, however, the mechanism of alloying element changing the corrosion resistance is still unclear. Since the properties of oxide of Zr alloys are critical to corrosion resistance, we use first-principles calculation to investigate the role of a typical alloying element Cu on the tensile strength of monoclinic zirconia grain boundary (GB) in oxide of Zr alloys. It is found that Cu atom can segregate at GB, and enhance the tensile strength of GB, leading to the improvement of corrosion resistance of Zr alloys. Moreover, we also check the results from calculations with various exchange-correlation functionals, we confirm that it is necessary to use generalized gradient approximation (GGA) plus a Hubbard U correction or hybrid functional instead of standard GGA to calculate the tensile strength of GB with Cu.
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    Xenon bubbles formed by ion implantation in zirconium alloy films

    Cummings R.B.Grunwald M.Minty A.Blackmur M.S....
    5页
    查看更多>>摘要：© 2021The xenon content of a Zircaloy-4 thin film was quantified in a spatially resolved way using high angle annular dark field (HAADF) images and DualEELS, a type of electron energy loss spectroscopy that takes spectra from the high- and low-loss regions in quick succession. The xenon in the films was implanted using a tandem accelerator. The HAADF images show that the xenon had coalesced into bubbles. A semi-empirical standard was used created for the quantification using pre-existing xenon data and experimental data scaled using a Hartree Slater cross-section. This standard was used to calculate the number of atoms in the xenon bubbles and their densities and pressures were then calculated. In total, 244 were bubbles were analysed. The mean diameter, density and pressure across all the bubbles were 21.2 Å, 2355 kg/m3 and 5.27 GPa respectively. Most of the bubbles were gaseous xenon. The separation of the bubbles was also analysed. This work is a good demonstration of a characterisation technique for end-of-life structural materials and the technique can be easily applied to small gas bubbles in other materials.
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    Change in nanoindentation hardness of polycrystalline tungsten irradiated with Fe ions or electrons by hydrogen gas charging

    Sato K.Kiyohara A.Hirabaru M.Kasada R....
    5页
    查看更多>>摘要：© 2021 Elsevier B.V.The effects of hydrogen atoms on the hardnesses of unirradiated, ion-irradiated, and electron-irradiated polycrystalline tungsten samples were investigated using nanoindentation tests. The bulk equivalent hardnesses of the unirradiated and electron-irradiated tungsten samples did not change upon hydrogen charging. The bulk equivalent hardness of the ion-irradiated tungsten increased upon the hydrogen charging. The number of hydrogen atoms trapped at dislocation loops was very small. We estimated that the hydrogen occupancy in vacancy clusters was 0.24−0.45 (in the case of tri-vacancies, the number of hydrogen atoms trapped per vacancy (H/V) is 1.04−1.95). Because of the irradiation temperature of 573 K, the density and size of irradiation-induced defects did not change during hydrogen charging at 543 K. Therefore, the hardening was mainly caused by an increase of approximately 8 − 11% in the obstacle strength α of vacancy clusters containing hydrogen atoms. The ion-irradiated area hardened upon the hydrogen charging and changed the configuration of the pile-up. Observation of the dislocation structure is required to clarify the mechanism of hardening caused by hydrogen charging.
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    Plasticity improvement and radiation hardening reduction of Y doped V-4Cr-4Ti alloy

    Zhang Y.Li R.Diao S.Zhan Q....
    5页
    查看更多>>摘要：© 2022 Elsevier B.V.In current work, V-4Cr-4Ti and V-4Cr-4Ti-2Y alloys are prepared using mechanical alloying and spark plasma sintering. Sequential-beam irradiation of 30 keV H+ and 50 keV He+ ions, are carried out at 450 ℃ to the peak damage of 0.18 dpa. The influence of Y on the microstructure, mechanical properties, radiation induced defect and radiation-hardening are investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), mechanical test, and nano-indentation test. Two kinds of Y-rich particles precipitated in Y added alloy, one is Y2O3 phase with a mean size of 60 nm, the other is YVO4 with a diameter of ∼10 nm, but no carbide of Y is observed. The results show that Y can significantly improve plasticity of V base alloy, reduce the size and number density of radiation induced dislocation loops, limit radiation hardening. Two different fitting process with different initial values and boundary conditions are used to analysis radiation hardening, the fitting results indicate a slight softening of matrix near damage layer which named softened layer. This softened layer can affect nanoindentation test results especially for shallow irradiation. A plausible explanation for the formation of this softened layer could be the oxygen diffuses from unirradiated region to damage layer.
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