| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- Gao, Chan, et al.
(författare)
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Defect evolution behaviors from single sulfur point vacancies to line vacancies in monolayer molybdenum disulfide
- 2021
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 23:35, s. 19525-19536
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional monolayer transition metal dichalcogenides (TMDs) are promising candidates for many novel nanoelectronic and optoelectronic applications due to their exceptional electronic, optical, chemical and mechanical properties. Experimentally, single chalcogen point vacancies caused by electron beam irradiation are found to agglomerate into line vacancy defects in monolayer TMDs. Herein, the corresponding defect evolution behaviors from single sulfur point vacancies to line vacancies in the monolayer molybdenum disulfide (MoS2) have been systematically studied using molecular dynamics and first principles calculations. The experimental observations of the defect evolution from single sulfur point vacancies to line vacancies are reproduced at the atomic level. The results indicate that the di-vacancy line defect and a point vacancy separated by a sulfur atom in a line evolve into tri-vacancy line defects, and the di-vacancy line defects can rotate 60 degrees clockwise or counterclockwise. Moreover, two adjacent di-vacancy line defects with an angle of 120 degrees can evolve into tri-vacancy line defects. High temperature and large vacancy concentrations promote the defect evolution from point vacancies to line vacancies. Intriguingly, compared with the randomly distributed point vacancy defects, the line vacancy defects formed after the defect evolution significantly decrease the mechanical properties, such as the ultimate strength, ultimate strain and Young's modulus of monolayer MoS2. In addition, the mechanical properties decrease with increasing vacancy concentration and temperature for the final configurations after defect evolution in monolayer MoS2 with different vacancy concentrations at different temperatures. The band gaps of monolayer MoS2 with line vacancy defects are smaller than those with randomly distributed point vacancy defects. Therefore, our study clarifies the defect evolution behaviors from single sulfur point vacancies to line vacancies in monolayer MoS2 and opens an opportunity for the novel nanoelectronic and optoelectronic applications of monolayer TMDs.
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| 5. |
- Gao, Chan, et al.
(författare)
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Synergistic vacancy defects and mechanical strain for the modulation of the mechanical, electronic and optical properties of monolayer tungsten disulfide
- 2021
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 23:10, s. 6298-6308
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Tidskriftsartikel (refereegranskat)abstract
- Monolayer transition metal dichalcogenides (TMDs) are the potential candidate materials in nanoelectronic and optoelectronic applications due to their unique physical and chemical properties. Although both defect and strain greatly alter the structural, physical and chemical properties of monolayer TMDs, the defective monolayer TMDs under applied strain have not been adequately studied. In this paper, the synergistic effects of sulfur vacancy defects and mechanical strain on the mechanical, electronic and optical properties of monolayer tungsten disulfide (WS2) have been systematically studied using first principles density functional theory. The results indicate that the sulfur vacancy formation energy increases linearly with increasing sulfur vacancy concentration under different strains. The strain energy and stress of monolayer WS2 with different sulfur vacancy concentrations increase with increasing applied strain in the strain range of -10% to 10%. The band gap of monolayer WS2 decreases with increasing sulfur vacancy concentration under different strains. Moreover, compared with unstrained conditions, 5% compressive strain increases the band gap at a larger vacancy concentration and the case is just opposite at a smaller vacancy concentration, while 5% tensile strain decreases the band gap. The band gap of monolayer WS2 with different sulfur vacancy concentrations firstly increases and then shrinks with increasing applied strain under compressive strain, whereas it decreases monotonically under tensile strain in the strain range of -10% to 10%. In the visible-light wavelength region, the out-of-plane absorption coefficient under different strains increases with increasing sulfur vacancy concentration. Furthermore, 5% compressive strain enhances the absorption coefficient and 5% tensile strain decreases the absorption coefficient. Hence, the synergistic effects of sulfur vacancy defects and mechanical strain in monolayer TMDs can open new avenues for their applications in nanoelectronic and optoelectronic devices.
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| 6. |
- Yang, Xiaoyong, et al.
(författare)
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Enhanced overall water splitting under visible light of MoSSe vertical bar WSSe heterojunction by lateral interfacial engineering
- 2021
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Ingår i: Journal of Catalysis. - : Elsevier. - 0021-9517 .- 1090-2694. ; 404, s. 18-31
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Tidskriftsartikel (refereegranskat)abstract
- Photocatalytic splitting water is a promising method to obtain hydrogen energy. While design and synthesis of efficient and economical photocatalysts is one of the important contents. Janus MoSSe and WSSe monolayers are efficient and wide sunlight harvesting photocatalysts due to their intrinsic vertical electric fields. So how is the photocatalytic performance of lateral MoSSe vertical bar WSSe heterojunctions, which possesses an intra-plane interface and intrinsic vertical electric field? In the present work, the structural property, electronic characteristic, optical property, and photocatalytic application of MoSSe vertical bar WSSe lateral heterojunctions are systematically investigated. It is found that both zigzag and armchair configurations are semiconductors with suitable bandgaps of similar to 1.60 eV. Besides, they possess a type-II band alignment where electrons tend to accumulate at the coupling interface of MoSSe side and holes at WSSe side, giving rise to a paralleled electric field in heterojunctions, which can largely promote the separation of photo-generated carriers. More remarkably, these heterojunctions exhibit pronounced solar-spectrum absorption efficiency, proper valence, and conduction band positions by initializing the redox reactions of H2O and high carrier mobility. Intriguingly, the zigzag MoSSe vertical bar WSSe heterojunction has a better photocatalytic performance in an acidic environment, and the armchair MoSSe vertical bar WSSe prefers to produce H-2 and O-2 in a neutral environment. These fascinating properties render the intra-plane MoSSe vertical bar WSSe heterojunctions as the wide solar harvesting photocatalysts in further overall water splitting.
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