| 1. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Yang, Xiaoyong, et al.
(författare)
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Investigating the solution and diffusion properties of hydrogen in alpha-Uranium by first-principles calculations
- 2020
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Ingår i: Progress in nuclear energy (New series). - : PERGAMON-ELSEVIER SCIENCE LTD. - 0149-1970 .- 1878-4224. ; 122
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Tidskriftsartikel (refereegranskat)abstract
- The stability, solution and diffusion properties of an interstitial hydrogen atom in uranium metal have been firstly investigated by first-principles calculations. In energy, the octahedral site is more favorable for hydrogen to occupy than tetrahedra site with neglectable anisotropic perturbation. Besides, the effects of temperature on solution energy are quantified, which demonstrate the solution energy decreases fast with temperature. The calculated density of states and electronic charge re-distribution are analyzed. It is found the conductivity of metal uranium remains well after hydrogen occupied the interstitial position with lower concentration. The minimum migration pathways of interstitial hydrogen in uranium lattice are characterized by the climbing image nudged elastic band (CINEB) method. The obtained energy barriers are 0.239 eV, 0.298 eV and 0.313 eV with respect to O <-> T, O <-> O and T <-> T pathways with feeble structural deterioration. We believe our results for hydrogen diffusion in such a complex f -electron system not only provide en evidence for uranium corrosion but also supports the future experiments on measuring the hydriding rate and their interpretations.
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| 3. |
- Yang, Xiaoyong, et al.
(författare)
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Structural, electronic, mechanical and thermodynamic properties of U-Si intermetallic compounds : A comprehensive first principles calculations
- 2022
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Ingår i: Progress in nuclear energy (New series). - : Elsevier BV. - 0149-1970 .- 1878-4224. ; 148, s. 104229-
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Tidskriftsartikel (refereegranskat)abstract
- Uranium silicides are proposed as the prominent accident tolerant fuels for the light water reactors (LWR) due to their high metal density and high thermal conductivity. Among the U-Si alloys, the alloy with high U:Si ratio is more favorable for nuclear fuel application due to the higher uranium density. Thus, the crystal structure, mechanical property, electronic structure, phonon band structure and thermodynamic property of U3Si, U3Si2 and USi compounds, along with the thermodynamic reaction between U-Si intermetallic compounds are systematically studied in our work. The optimized structural parameters of these U-Si alloys are comparable with previous results. Besides, all of them are metallic in nature. Since the calculated elastic constants satisfy the Born stability criteria, one can know U-Si alloys are mechanically stable. The phonon dispersion curves are obtained based on the density functional perturbation theory (DFPT). Accordingly, various thermophysical properties, such as Helmholtz free energy, heat capacity, internal energy and entropy are calculated. Furthermore, the reaction energies related to the formation of U3Si, U3Si2 and USi as well as transformation between them are calculated. It is revealed at the same chemical environment the reaction to form USi occurs more easily, whereas the high temperature and sufficient uranium environment are more in favor for fully silicification of uranium metal into U3Si. Theoretical investigation of this work is expected to provide some new insights for the application of uranium silicides as nuclear fuels and future exploration on the design and synthesis of new-type uranium silicides.
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| 4. |
- Fang, Xing, et al.
(författare)
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Microstructure and mechanical properties of the laser welded air-hardening steel joint
- 2024
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Ingår i: Materials Characterization. - : Elsevier BV. - 1044-5803 .- 1873-4189. ; 213
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Tidskriftsartikel (refereegranskat)abstract
- The decrease in mechanical properties of high-strength steel after welding is an important issue affecting the wide application of high-strength steel. Air-hardening steel is a high-strength steel suitable for lower body structural parts such as subframes. Its application process involves welding, hot forming and other processes. The present work investigates the microstructure and mechanical properties of the air-hardening steel laser welded joint that is air-cooled after hot forming in the two-phase zone (800 °C). The microstructure was characterized by electron backscattered diffraction (EBSD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that during hot forming, the welded joint transforms from martensite to ferrite and acicular martensite, and the base metal transforms from ferrite to polygonal martensite and ferrite. The difference in martensite morphology between the welded joint and the base metal is attributed to the nucleation positions of austenite. The structural evolution of the welded joint and the base metal is accompanied with the annihilation and reproduction of dislocations, which results in significant changes in hardness. The hardness value dropped from the highest 430 HV to 271 HV in the welded joint, while increased from the lowest 184 HV to 203 HV in the base metal. After hot forming, the tensile strength of the welded sample is reduced by only 36 MPa, and the total elongation is slightly decreased by about 1.5% compared with the unwelded sample. The welded joint and the base metal have similar plastic deformation capabilities, since the acicular martensite in the welded joint displays good plastic deformation ability, and the dislocation density of the welded joint and the base metal is similar. Overall, the microstructure and dislocation density of the air-hardening steel welded joint after hot forming are similar to those of the base metal, which is responsible for the good mechanical properties of air-hardening steel welded joint.
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| 5. |
- Fang, Zhiwei, et al.
(författare)
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Structural stability and aqueous durability of Cs incorporation into BaAl2Ti6O16 hollandite
- 2022
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 565, s. 153716-
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Tidskriftsartikel (refereegranskat)abstract
- Hollandite ceramics are well-recognized as a promising host for immobilizing radioactive cesium. In the present paper, the [BaxCsy][(Al3+,Ti3+)(2x +y)Ti-8-2x-y(4+)]O-16 (0.4 <= x, y <= 0.8) ceramics were fabricated to in-vestigate the effect of incorporated Cs on structural stability and durability of (Ba,Cs)(Al,Ti)(8)O-16 ceramics with Cs-incorporated. It was found that the sintered samples at 1250 degrees C show a pure hollandite phase with tetragonal structure (I4/m) and high Cs retention. Moreover, the synthesized (Ba,Cs)(Al,Ti)(8)O-16 ceramics exhibit an excellent aqueous stability and the normalized Cs release rate is 2.82 (+/- 0.27) x10(-3) g m(-2) d(-1) after 28 days. All these results reveal that (Ba,Cs)(Al,Ti)(8)O-16 is a promising candidate as a Cs-waste form.
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| 6. |
- Li, Shuyang, et al.
(författare)
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Efficient photoreduction strategy for uranium immobilization based on graphite carbon nitride/perovskite oxide heterojunction nanocomposites
- 2021
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Ingår i: Applied Catalysis B. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 298
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Tidskriftsartikel (refereegranskat)abstract
- The photoreduction conversion of soluble U(VI) to insoluble U(IV) is an economical strategy for the efficient removal of uranium from radioactive wastewater. A graphite carbon nitride and pemvskite oxide heterojunction composite (g-C3N4/LaFeO3) is designed for the photocatalytic reduction of U(VI) under simulated sunlight conditions from aqueous solution, the reduction-immobilization mechanism is interpreted with the aid of spectroscopic evidence. The proposed heterojunction structure exhibits efficient removal ability (460 mg/g) over a wide range of U(VI) concentrations due to the suppressed recombination of photogenerated electron-hole pairs and the prolonged lifetimes of the photogenerated carriers. The catalytic efficiency is maintained at a high level after five cycles of reuse. The electrons on LaFeO3 transferred to valence band of g-C3N4, U(VI) is reduced by the electrons and center dot O-2(-) on the surface of g-C3N4. The g-C3N4/LaFeO3 heterojunction provides a promising strategy for the feasible recovery of U(VI) resources with inexhaustible solar energy.
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| 7. |
- Ma, Jiang, et al.
(författare)
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Investigating hollandite-perovskite composite ceramics as a potential waste form for immobilization of radioactive cesium and strontium
- 2021
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Ingår i: Journal of Materials Science. - : Springer Nature. - 0022-2461 .- 1573-4803. ; 56:16, s. 9644-9654
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Tidskriftsartikel (refereegranskat)abstract
- Ceramic matrix containing zirconolite, hollandite, and perovskite phases is proposed as a potential host for HLW immobilization. Hollandite phase principally immobilizes Cs, while perovskite phase mainly immobilizes Sr. In this study, hollandite–perovskite composite ceramics are considered as a specialized waste form for immobilizing the separated Cs and Sr from HLW streams and synthesized by a solid-state reaction method at 1300 °C for 5 h. The phase compositions of the synthesized composites were characterized by XRD and BSE. The XRD results indicated that the as-prepared ceramics are composed of tetragonal hollandite Ba0.8Cs0.4Al2Ti6O16, cubic perovskite SrTiO3, alongside a lesser amount of TiO2. The BSE—EDX results confirm that Cs partitions into the hollandite matrix, while Sr incorporates into perovskite host with homogenous distribution. In addition, aqueous durability testing was carried out using the MCC-1 static leach test method. The normalized release rates of Cs and Sr in HP-3 sample (i.e., 75 wt% Ba0.8Cs0.4Al2Ti6O16 + 25 wt% SrTiO3) were < 10−2 g·m−2·d−1 after 42 days, exhibiting excellent chemical durability. These results indicate that the hollandite–perovskite ceramic matrix could be considered as a customized host matrix for immobilization of the separated Cs and Sr from HLW streams.
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| 8. |
- Wang, Xin-Xin, et al.
(författare)
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What is the Role of Nb on Preferential Hydriding of Double-Phased Uranium, Stabilizing gamma-U, or Avoiding Hydrogen Aggregation?
- 2021
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 125:17, s. 9364-9370
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Tidskriftsartikel (refereegranskat)abstract
- Uranium as the heaviest naturally occurring element plays important roles in nuclear industries. Hydrogen-caused corrosions and irradiation-caused structural damages are two critical degradations that threaten the safe storage and practical applications of uranium. Through alloying with transition metals like Nb, the gamma-phase of U can be stabilized at room temperature, which shows better performance against hydrogen-caused corrosions than the ground-state alpha-U. The underlying mechanisms have not been fully understood yet. To explain the preferential hydriding phenomenon observed on a specially fabricated double-phase U-2.5 wt % Nb alloy, we perform multiscale ab initio calculations and kinetic Monte Carlo (KMC) simulations. We find that because of different diffusion mechanisms, intrinsic alpha-U and gamma-U already show different hydrogen accumulation behaviors. The existence of random Nb atoms further inhibits hydrogen accumulation in gamma-U. Our work declares its contribution by pointing out the important role of crystal lattice architectures on hydrogen accumulations in metals.
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| 9. |
- Ba, Kun, et al.
(författare)
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Billiard Catalysis at Ti3C2 MXene/MAX Heterostructure for Efficient Nitrogen Fixation
- 2022
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Ingår i: Applied Catalysis B. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 317, s. 121755-
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Tidskriftsartikel (refereegranskat)abstract
- Electrocatalytic ammonia (NH3) conversion under ambient atmosphere is crucial to mimic the nature's nitrogen cycle. But currently it is always interrupted by the HER process which is more competitive. Herein, we tactically cultivate a series of incompletely etched Ti3AlC2 MAX / Ti3C2 MXene based heterostructure catalysts whose composition can be finely tuned through regulation of the LiF percentage in mixed chemical etching agent. Notably, the surface potential difference between MAX and MXene is ~40 mV, indicating that the electron can be readily transferred from MAX to MXene across the interfaces, which is favorable for N2 fixation, yielding an outstanding Faradic efficiency of 36.9%. Furthermore, density functional theory calculations reveal the billiard-like catalysis mechanism, where the intermediates are alternatively adsorbed on MAX or MXene surfaces. Meanwhile, the rate-determining step of *NH → *NH2 possesses an energy barrier of 0.96 eV on the hetero-interface which follows associative distal mechanism. This work opens a new frontier of heterostructured catalyst for balancing electrical conductivity and catalytic activity in electrocatalysis.
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| 10. |
- Chen, Xue, et al.
(författare)
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Co-Doped Fe3S4Nanoflowers for Boosting Electrocatalytic Nitrogen Fixation to Ammonia under Mild Conditions
- 2022
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Ingår i: Inorganic Chemistry. - : American Chemical Society. - 0020-1669 .- 1520-510X. ; 61:49, s. 20123-20132
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Tidskriftsartikel (refereegranskat)abstract
- Compared with the Haber Bosch process, the electrochemical nitrogen reduction reaction (NRR) under mild conditions provides an alternative and promising route for ammonia synthesis due to its green and sustainable features. However, the great energy barrier to break the stable NN bond hinders the practical application of NRR. Though Fe is the only common metal element in all biological nitrogenases in nature, there is still a lack of study on developing highly efficient and low-cost Fe-based catalysts for N2fixation. Herein, Co-doped Fe3S4nanoflowers were fabricated as the intended catalyst for NRR. The results indicate that 4% Co-doped Fe3S4nanoflowers achieve a high Faradaic efficiency of 17% and a NH3yield rate of 37.5 μg·h-1·mg-1cat.at-0.55 V versus RHE potential in 0.1 M HCl, which is superior to most Fe-based catalysts. The introduction of Co atoms can not only shift the partial density states of Fe3S4toward the Fermi level but also serve as new active centers to promote N2absorption, lowering the energy barrier of the potential determination step to accelerate the catalytic process. This work paves a pathway of the morphology and doping engineering for Fe-based electrocatalysts to enhance ammonia synthesis.
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