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First principles investigation of quantum emission from hBN defects

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arXiv

arXiv 2017年

作者： Tawfik, Sherif Abdulkader Ali, Sajid Fronzi, Marco Kianinia, Mehran Tran, Toan Trong Stampfl, Catherine Aharonovich, Igor Toth, Milos Ford, Michael J. School of Mathematical and Physical Sciences University of Technology Sydney UltimoNSW2007 Australia Department of Physics GC University Faisalabad Allama Iqbal Road Faisalabad38000 Pakistan International Research Centre for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi710049 China School of Physics University of Sydney NSW2006 Australia

Hexagonal boron nitride (hBN) has recently emerged as a fascinating platform for room-temperature quantum photonics due to the discovery of robust visible light single-photon emitters. In order to utilize these emitters, it is necessary to have a clear understanding of their atomic structure and the associated excitation processes that give rise to this single photon emission. Here we perform density-functional theory (DFT) and constrained DFT calculations for a range of hBN point defects in order to identify potential emission candidates. By applying a number of criteria on the electronic structure of the ground state and the atomic structure of the excited states of the considered defects, and then calculating the Huang-Rhys (HR) factor, we find that the CBVN defect, in which a carbon atom substitutes a boron atom and the opposite nitrogen atom is removed, is a potential emission source with a HR factor of 1.66, in good agreement with the experimental HR factor. We calculate the photoluminescence (PL) line shape for this defect and find that it reproduces a number of key features in the the experimental PL lineshape. Copyright © 201., The Authors. All rights reserved.

关键词： III-V semiconductors

Radiant performance of opacifiers in opcifier-loaded silica aerogel-based composites

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Yingyong Jichu yu Gongcheng Kexue Xuebao/Journal of Basic Science and engineering 2012年第SUPPL.期20卷 181-189页

作者： Sun, Duo Wang, Xiaodong Duan, Yuanyuan Zhao, Junjie State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Beijing 102206 China Department of Thermal Engineering University of Science and Technology Beijing Beijing 100083 China Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy North China Electric Power University Beijing 102206 China Key Laboratory for Thermal Science and Power Engineering of MOE Department of Thermal Engineering Tsinghua University Beijing 100084 China

Since the opacifier-loaded silica aerogel composites have strong ability to inhibit radiant heat transfer compared to the pure silica aerogel, they can improve effectively the insulation performance at high temperature conditions and have been used extensively as thermal insulation materials in a variety of industrial applications. This paper developed a theoretical model to predict the radiant performance of opacifiers by using the Mie scattering theory, Beer law and a radiant heat transfer equations. The model was used to calculate the radiant performance of carbon black opacifier with various particle diameters and the radiant performance of three opacifiers, carbon black, SiC and ZrO2. The results showed that the opacifier-loaded silica aerogel composites had much higher extinction coefficient than the pure silica aerogel in a range of 3-7.5 μm wave band or in medium and high temperature ranges, which significantly improved the insulation performance of composites. With a fixed opacifier mass fraction, the optimal particle diameter was 2-3 μm for carbon black opacifier. Among the three opacifiers, carbon black opacifier had better opaque property than that of SiC and ZrO2 opacifiers. Due to poor thermostability for carbon black opacifier at high temperature conditions, the optimal material design for opacifier-loaded silica aerogel composites should be as follows: SiC or ZrO2 are added on high temperature side of aerogel and carbon black is added on low temperature side.

关键词： Thermal conductivity

Particle-Scale Modelling of Injected Hydrogen and Coke Co-Combustion in the Raceway of an Ironmaking Blast Furnace

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SSRN 2022年

作者： Dianyu, E. Zhou, Peng Ji, Langyong Cui, Jiaxin Xu, Qiang Guo, Liejin Yu, Aibing International Institute for Innovation Jiangxi University of Science and Technology Ganzhou341000 China Jiangxi Provincial Key Laboratory for Simulation and Modelling of Particulate Systems Jiangxi University of Science and Technology Ganzhou341000 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China ARC Research Hub for Computational Particle Technology Department of Chemical Engineering Monash University VIC3800 Australia Centre for Simulation and Modelling of Particulate Systems Southeast University Monash University Joint Research Institute Suzhou215123 China

Hydrogen is an environmentally friendly fuel that does not produce greenhouse gas (GHG) emissions. Its applications have attracted significant attention from many industries, especially the ironmaking industry, which consumes massive amounts of fossil energy. The injection of hydrogen into a blast furnace (BF) is one of the most promising low-carbon ironmaking routines. In this study, an experimentally validated CFD-DEM model is adopted to investigate the dynamics, microstructure and thermochemical behaviours in the raceway of a BF with hydrogen injection operations (HIOs), which include raceway evolution, force distribution and the co-combustion characteristics of hydrogen and coke. Some significant features are obtained through comparison analyses between HIOs and air injection operations (AIOs). In particular, the effects of the hydrogen injection concentration on the raceway size, gas temperature and components are studied. The simulation results show that a smaller raceway is formed under HIOs in comparison with that of AIOs. In addition, the gas temperature is higher near the tuyere but lower along the tuyere axis, and the oxygen consumption is larger and produces more CO. As the hydrogen injection concentration increases: (i) the raceway size and gas temperature decrease;(ii) the CO is generated at the early stage and the maximum CO2 concentration moves to inlet direction along the tuyere axis. The results provide insights on the fundamental understanding of low-carbon ironmaking BF technology. © 2022, The Authors. All rights reserved.

关键词： Blast furnaces

Facile Synthesis of Bulk Au-Co-Coox-Ceox@Iron Ball and its Photocatalytic Application in 4-Nitrophenol Degradation

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SSRN 2023年

作者： Sun, Li Qiao, Zhili Zhi, Yuan Zhang, Hua Dou, Binlin Shan, Yuejin Huang, Weijia School of Energy and Power Engineering University of Shanghai for Science and Technology Jun Gong Road 516 Shanghai200093 China R&D Department Shanghai Minrula Biotechnology Co.Ltd Building 15 Haji Sixth Road 218 Shanghai201306 China Department of Material and Environmental Chemistry Research Division of Functional Materials Design Utsunomiya University Yoto 7-1-2 Utsunomiya321-8585 Japan Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering China

Bulk noble metal-semiconductor composites can be chosen as photocatalysts to carry out the continuous-flow (C-F) degradation of 4-nitrophenol (4-NP) whereas their preparation is complex and uncontrollable. Here, bulk Au/Co-CC@iron ball is designed and prepared by a facile and controllable route without any toxic chemical. The bulk Au/Co-CC@iron ball shows excellent photocatalytic activity and reusability for the 4-NP degradation, which can be ascribed to the synergistic action of active components and foliated iron ball surface. Furthermore, the highly active Au/Co-CC@iron ball is used as packing material to construct a new-type of packed reactor, by which the C-F degradation of 4-NP is successfully achieved. As-fabricated packed reactor and its tandem module exhibit superior photocatalytic performance for the C-F degradation of 4-NP. Noteworthy, based on the tandem module with six reactors, the removal rate of 4-NP can reach up to 2750 µmol/h. Meanwhile, the reactor and its module display satisfactory operational stability and reusability in the C-F degradation of 4-NP. Clearly, the provided route is effective for the preparation of bulk noble metal-semiconductor composites with exceptional performance, which can also be a prospective strategy to obtain bulk packing materials to serve for the C-F degradation. © 2023, The Authors. All rights reserved.

关键词： Precious metals

Theoretical investigation on heat-electricity decoupling technology of low-pressure steam turbine renovation for CHPs

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IOP Conference Series: Earth and Environmental Science 2019年第4期227卷

作者： Qingbo Hu Kun Wang Li Zhang Liansheng Zhou Rong Chen Shan Wang Yu Zhang Guohao Li Tianjin Electric Power Science & Research Institute Tianjin 300384 State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiao Tong University Xi'an 710049.

The power grid peaking capacity is insufficient due to the increasing installed capacity of renewable power. Moreover, it is also restricted by the operation mode of combined heat and power units (CHPs), the minimum electricity loads of which are determined by the heat load. It is significant to study the heat-electricity decoupling technologies for CHPs. Therefore, the low-pressure steam turbine renovation technology is studied in this paper with a 300MW unit as reference case. Results show that the minimum electric load rate and the coal consumption are decreased, and the heat-electricity ratio is increased significantly for CHP with low-pressure steam turbine renovation. When the heat load is 1.00 GJ/h, the minimum electric load rate and coal consumption with low-pressure steam turbine renovation can be reduced by 32.4 and 30.9 % respectively. The heat-electricity ratio can be increased by 68.8 % after renovation of low-pressure steam turbine.

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On-Line Measurement of Ultralow Mass Concentration Particulate Based on Light Scattering Coupled with Beta Ray Attenuation Method

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SSRN 2022年

作者： Liu, Xiaowei Huang, Yubo Wang, Zhaofeng Jiang, Meng Zhou, Zijian Xu, Minghou Han, Jinke Yang, Bin Fan, Xinfeng State Key Laboratory of Coal Combustion School of Energy and Power Engineering Huazhong University of Science and Technology 1037 Luoyu Road Wuhan430074 China JXIC Energy Technology Research Institure Nanchang330000 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Wuhan Tianhong Environmental Protection Industry Co. Ltd Yuhong Environmental Protection Science and Technology Industrial Park No.11 Huashiyuan North Road Miaoshan District Donghu high tech Development Zone Wuhan430074 China

Light scattering method is the most commonly used method for on-line measurement of ultralow particulate matter mass concentration. However, when the particle characteristics change, the effectiveness of the empirical relationship decreases, which would lead to a sizeable deviation. To accurately measure the mass concentration of particulate matter in real-time, a coupling measurement idea of light scattering and beta-ray attenuation is proposed. The beta-ray attenuation is little affected by particle properties and accurately reflects the average PM mass concentration in the measured period. The single calibration method (M1., periodic calibration method (M2), average calibration method (M3), and asymmetric factor calibration method (M4) are formed based on the coupling idea. The results of all methods are perfect when the particle size is unchanged. However, when the particle sizes fluctuate frequently, the results of M1. M2, and M3 deviate seriously from the actual value, and the applicable working conditions have limitations. The results of M4 are in good agreement with the actual value, and the effectiveness is not limited by the particle size. Finally, the prototype based on experimental exploration was developed and had been continuously operated for more than 528 hours at a 1.00 MW unit of a coal-fired power plant. © 2022, The Authors. All rights reserved.

关键词： Particle size

Current Density Regulating Lithium Metal Directional Deposition for Long Cycle Life Lithium Metal Batteries

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SSRN 2020年

作者： Mao, Heng Yu, Wei Cai, Zhuanyun Liu, Guixian Liu, Limin Wen, Rui Su, Yaqiong Xi, Kai Li, Benqiang Da, Xinyu Kou, Huari Yan, Wei Ding, Shujiang Xi'an Key Laboratory of Sustainable Energy Materials Chemistry School of Chemistry Xi’an Jiaotong University & Shaanxi Quantong Joint Research Institute of New Energy Vehicles Power Xi’an Jiaotong University Xi’an710049 China State Key Laboratory of Physical Chemistry of Solid Surfaces Department of Chemistry College of Chemistry and Chemical Engineering Xiamen University Xiamen361005 China Key Laboratory of Molecular Nanostructure and Nanotechnology Beijing National Laboratory for Molecular Sciences CAS Research/Education Center for Excellence in Molecular Sciences Institute of Chemistry Chinese Academy of Sciences Beijing100190 China Cambridge Graphene Centre Department of Engineering University of Cambridge CambridgeCB3 0FA United Kingdom Department of Mechanical Engineering University of Michigan-Dearborn DearbornMI48128 United States Department of Environmental Science and Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Uncontrolled dendrite formation in the high energy density of lithium metal batteries (LMBs) may pose serious safety risks. Numerous works have been reported to protect separator. However, these methods still couldn’t inhibit the dendrite upward growth to protect the separator, effectively. Here, we introduce a novel “orientated-growth” strategy that makes the depositional interface transfer to the anode/current collector interface from the anode/separator interface. We placed a layer of cellulose/graphene carbon composite aerogel (CCA) between the current collector and the anode (CCA-Li). This layer works as the charge organizer;it induces a higher current density distribution and makes Li prefer to deposit in the bottom CCA layer of CCA-Li electrode. Both in-situ and ex-situ images of the electrode demonstrate the anode part of the cell has been flipped;with the new deposited particles facing the current collector and smooth surface facing the separator. Electrochemical characterization of the electrode in half and full cells showed outstanding cyclic stability and rate capability, with the CCA-Li/LPF full cell able to maintain 94% of its initial capacity after 1.00 cycles. We believe that the innovative strategy would promote the leapfrog development for LMBs. © 2020, The Authors. All rights reserved.

关键词： Electric current collectors

Corrigendum to “Huge wave and drop entrainment mechanism in gas–liquid churn flow” [Chem. Eng. Sci. 1.8 (201.) 638–646]

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Chemical engineering Science 2017年 158卷 624-624页

作者： Ke Wang Bofeng Bai Weimin Ma State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi 710049 China Royal Institute of Technology (KTH) Stockholm 10691 Sweden

Erosion of water-based fracturing fluid containing particles in a sudden contraction of horizontal pipe

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Journal of Physics: Conference Series 2017年第1期916卷

作者： Jiarui Cheng Yinping Cao Yihua Dou Zhen Li State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China. Department of Mechanical Engineering Xi'an Shiyou University Xi'an China.

A lab experiment was carried out to study the effects of pipe flow rate, particle concentration and pipe inner diameter ratio on proppant erosion of the reducing wall in hydraulic fracturing. The results show that the erosion rate and erosion distribution are different not only in radial direction but also in circumferential direction of the sample. The upper part of sample always has a minimum erosion rate and erosion area. Besides, the erosion rate of reducing wall is most affected by fluid flow velocity, and the erosion area is most sensitive to the change in the diameter ratio. Meanwhile, the erosion rate of reducing wall in crosslinked fracturing fluid is mainly determined by the fluid flowing state due to the high viscosity of the liquid. In general, the increase in flow velocity and diameter ratio not only cause the expansion of erosion-affected flow region in sudden contraction section, but also lead to more particles impact the wall.

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