| 1. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Lu, Huayu, et al.
(författare)
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Chinese loess and the Asian monsoon : What we know and what remains unknown
- 2022
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Ingår i: Quaternary International. - : Elsevier. - 1040-6182 .- 1873-4553. ; 620, s. 85-97
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Tidskriftsartikel (refereegranskat)abstract
- The variability and dynamics of the Asian monsoon (AM, hereafter indicates both of the summer and winter monsoons.) at orbital and millennial timescales has attracted wide interest. Chinese loess deposits, covering an area of-500 x 10(3) km(2) and with a thickness of several tens to more than three hundred meters, is an ideal continental archive to reconstruct AM variations during the Quaternary epoch. Over the past thirty years, since the earliest paper published in an international journal that linked the Asian monsoon and Chinese loess deposits, many studies have been undertaken focusing on this research topic. These results have greatly deepened our understanding of the variations of the AM climate and their driving mechanisms during the past-2.6 Myr. In this paper, we emphasize recent progress on the AM variability and dynamics revealed by Chinese loess records; in particular, we discuss the reliability and precision of the timescale and the monsoon proxy indicators for the loess-paleosol sequences, which are two fundamental aspects for understanding AM behavior. We analyze what we know and discuss what we do not know about the AM. We refine the timescale for the typical loess-paleosol sequence in the central Chinese Loess Plateau (CLP), which can be used as a new timescale to study palaeoclimate and palaeoenvironmental changes in the monsoonal Asia. We conclude that low-latitude insolation changes induced by precession, and global ice volume, temperature at high-latitudes, as well as sea-level changes forced variations of the AM at orbital time scales. High-latitude cooling events and low-latitude hydroclimate process at millennial time scales, such as climate changes associated with Heinrich events and Dansgaard-Oeschger cycles in Northern Atlantic and Greenland, have also modulated AM variability. We suggest that high-latitude forcing of AM variations occurs through ocean and atmospheric circulation linkages, although the roles of atmospheric CO2, ocean and vegetation feedbacks need further investigation. In future study, high-resolution independent dating, novel proxy indices and transient numerical simulations are still basic tools to understand the loess deposition and AM variations that require considerably more work. Issues such as reliable spatial comparison and regional linkages of records (dependent on precise and accurate numerical chronologies), and quantitative reconstruction of the AM variations, should be given priority in the study the past climate change in Asia, and low-latitude hydroclimate process.
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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- Bai, Sai, et al.
(författare)
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Ethanedithiol Treatment of Solution-Processed ZnO Thin Films: Controlling the Intragap States of Electron Transporting Interlayers for Efficient and Stable Inverted Organic Photovoltaics
- 2015
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Ingår i: Advanced Energy Materials. - : Wiley-VCH Verlag. - 1614-6832 .- 1614-6840. ; 5:5, s. 1401606-
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Tidskriftsartikel (refereegranskat)abstract
- The surface defects of solution-processed ZnO films lead to various intragap states. When the solution-processed ZnO films are used as electron transport interlayers (ETLs) in inverted organic solar cells, the intragap states act as interfacial recombination centers for photogenerated charges and thereby degrade the device performance. Here, a simple passivation method based on ethanedithiol (EDT) treatment is demonstrated, which effectively removes the surface defects of the ZnO nanocrystal films by forming zinc ethanedithiolates. The passivation by EDT treatment modulates the intragap states of the ZnO films and introduces a new intragap band. When the EDT-treated ZnO nanocrystal films are used as ETLs in inverted organic solar cells, both the power conversion efficiency and stability of the devices are improved. The control studies show that the solar cells with EDT-treated ZnO films exhibit reduced charge recombination rates and enhanced charge extraction properties. These features are consistent with the fact that the modulation of the intragap states results in reduction of interfacial recombination as well as the improved charge selectivity and electron transport properties of the ETLs. It is further demonstrated that the EDT treatment-based passivation method can be extended to ZnO films deposited from sol-gel precursors.
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| 7. |
- 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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| 8. |
- Han, Zhiyong, et al.
(författare)
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Extreme monsoon aridity episodes recorded in South China during Heinrich Events
- 2015
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 440, s. 467-474
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Tidskriftsartikel (refereegranskat)abstract
- Geological records of climate change since the last glaciation in South China, a core area of the East Asian monsoon, are key to understanding secular variation in the monsoon system. However, with the exception of the speleothems, records from this area with independent age control are few. We investigated aeolian sand deposition on a sand hill on the shore of Poyang Lake in South China and reconstructed the chronological sequence of aeolian deposition using Optically Stimulated Luminescence (OSL) dating. Without exception, all aeolian sediments were deposited within seven periods that generally match the timing of Heinrich events and other cold periods in Greenland. We argue that aeolian sand accumulation in this region is most likely forced by extreme aridity driven by weakening of the summer monsoon, while the characteristics of this deposition are influenced by winter monsoon intensity. The monsoon shifts revealed here suggest a possible link between North Atlantic cooling and summer monsoon strength in South China, and support the intensities of cooling phases recorded in Greenland ice cores.
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| 9. |
- Liang, Xiaoyong, et al.
(författare)
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Colloidal metal oxide nanocrystals as charge transporting layers for solution-processed light-emitting diodes and solar cells
- 2017
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Ingår i: Chemical Society Reviews. - : ROYAL SOC CHEMISTRY. - 0306-0012 .- 1460-4744. ; 46:6, s. 1730-1759
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Forskningsöversikt (refereegranskat)abstract
- Colloidal metal oxide nanocrystals offer a unique combination of excellent low-temperature solution processability, rich and tuneable optoelectronic properties and intrinsic stability, which makes them an ideal class of materials as charge transporting layers in solution-processed light-emitting diodes and solar cells. Developing new material chemistry and custom-tailoring processing and properties of charge transporting layers based on oxide nanocrystals hold the key to boosting the efficiency and lifetime of all-solution-processed light-emitting diodes and solar cells, and thereby realizing an unprecedented generation of high-performance, low-cost, large-area and flexible optoelectronic devices. This review aims to bridge two research fields, chemistry of colloidal oxide nanocrystals and interfacial engineering of optoelectronic devices, focusing on the relationship between chemistry of colloidal oxide nanocrystals, processing and properties of charge transporting layers and device performance. Synthetic chemistry of colloidal oxide nanocrystals, ligand chemistry that may be applied to colloidal oxide nanocrystals and chemistry associated with post-deposition treatments are discussed to highlight the ability of optimizing processing and optoelectronic properties of charge transporting layers. Selected examples of solution-processed solar cells and light-emitting diodes with oxide-nanocrystal charge transporting layers are examined. The emphasis is placed on the correlation between the properties of oxide-nanocrystal charge transporting layers and device performance. Finally, three major challenges that need to be addressed in the future are outlined. We anticipate that this review will spur new material design and simulate new chemistry for colloidal oxide nanocrystals, leading to charge transporting layers and solution-processed optoelectronic devices beyond the state-of-the-art.
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| 10. |
- Liang, Xiaoyong, et al.
(författare)
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Synthesis of Unstable Colloidal Inorganic Nanocrystals through the Introduction of a Protecting Ligand
- 2014
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Ingår i: Nano letters (Print). - : American Chemical Society. - 1530-6984 .- 1530-6992. ; 14:6, s. 3117-3123
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a facile and general strategy based on ligand protection for the synthesis of unstable colloidal nanocrystals by using the synthesis of pure p-type NiO nanocrystals as an example. We find that the introduction of lithium stearate, which is stable in the reaction system and capable of binding to the surface of NiO oxide nanocrystals, can effectively suppress the reactivity of NiO nanocrystals and thus prevent their in situ reduction into Ni. The resulting p-type NiO nanocrystals, a highly demanded hole-transporting and electron-blocking material, are applied to the fabrication of organic solar cells and polymer light-emitting diodes, demonstrating their great potential as an interfacial layer for low-cost and large-area, solution-processed optoelectronic devices.
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