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Temperature evolution and grain defect formation during single crystal solidification of a blade cluster

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China Foundry 2017年第5期14卷 456-460页

作者： De-xin Ma Fu Wang Qiang Wu Jian-zheng Guo Fu-ze Xu Zhao-feng Liu Shou-zhu Ou Wedge Central South Research Institute Shenzhen 518045China Foundry Institute RWTH Aachen UniversityAachen 52072Germany ald vacuum technologies gmbh Hanau 63450Germany

In order to investigate the asymmetry of thermal conditions during directional solidification, the temperature evolution and correspondingly developed undercooling in a simplified single crystal blade cluster were numerically simulated. Simulation results demonstrate that the temperature distribution at the blade platforms is obviously asymmetrical. On the outside of the blade which directly faces the heating element, the liquidus(TL) isotherms progress relatively smoothly. On the inside of the blades facing the central rod, however, the TLisotherms are in concave shape and the slope goes upwards to the platform extremities. The average undercooling extent ?T and undercooling time ?t at the inside are much higher than those at the outside. It was then predicted that the inside platform extremities have significantly higher probabilities of stray grain formation compared to the outside ones. A corresponding experiment was carried out and the metallographic examination exhibited the same side-and height-dependence of stray grain formation in the blades as predicted. On the inside of the blades, all platforms are occupied by stray grains, while the platforms on the outside are nearly stray grain free. The simulation result agrees very well with the experimental observation.

关键词： superalloy directional solidification single crystal (SC) simulation stray grain (SG)

PRODUCTION METHODS AND APPLICATIONS FOR HIGH-QUALITY METAL POWDERS AND SPRAYFORMED PRODUCTS

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Acta Metallurgica Sinica(English Letters) 2005年第1期18卷 15-23页

作者： M. Hohmann S. Pleier ald Vacuuum technologies AG Wilhelm-Rohn-Strasse 35 D-63450 Hanau GermanyALD Vacuuum Technologies AG Wilhelm-Rohn-Strasse 35 D-63450 Hanau Germany

Metal powders of superlative quality, i.e. high cleanliness, rapidly solidified and spherical shape, have seen an increasing demand in the market. The leading technology for the production of such powders is the inert gas atomization of metal alloy melts. To fulfill these requirements, the metal alloy is usually produced in a vacuum induction melting furnace (VI-GA = vacuum induction melting/gas atomization) and poured by means of a preheated tundish system into a gas nozzle where the metal stream is disintegrated by a high kinetic energy inert gas jet. The produced micro-droplets solidify in a free fall inside the atomization tower. For special applications, super-clean and ceramic-free metal powders can be produced by using the EIGA (electrode induction melting/gas atomization) melting- and atomizing system. As an alternative to the metal powder route, the sprayforming technology allows to produce semi-finished products in one step. In this case, the metal droplets produced by the high-energy inert gas nozzle system are directly solidified on a substrate, allowing to form billets, rolls and tubes.

关键词： powder production atomization inert gas recycling ceramic-free powders sprayforming

Collective transport of Lennard-Jones particles through one-dimensional periodic potentials

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Chinese Physics B 2017年第7期26卷 7-14页

作者：何健辉温家乐陈沛荣郑冬琴钟伟荣 Siyuan Laboratory Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy MaterialsDepartment of Physics Jinan University

The surrounding media in which transport occurs contains various kinds of fields, such as particle potentials and external potentials. One of the important questions is how elements work and how position and momentum are redistributed in the diffusion under these conditions. For enriching Fick＇s law, ordinary non-equilibrium statistical physics can be used to understand the complex process. This study attempts to discuss particle transport in the one-dimensional channel under external potential fields. Two kinds of potentials—the potential well and barrier—which do not change the potential in total, are built during the diffusion process. There are quite distinct phenomena because of the different one-dimensional periodic potentials. By the combination of a Monte Carlo method and molecular dynamics, we meticulously explore why an external potential field impacts transport by the subsection and statistical method. Besides, one piece of evidence of the Maxwell velocity distribution is confirmed under the assumption of local equilibrium. The simple model is based on the key concept that relates the flux to sectional statistics of position and momentum and could be referenced in similar transport problems.

关键词： transport external potential collective diffusion Maxwell velocity distribution

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热处理中气体淬火采用的物理和工艺基础

传动技术 2001年第2期15卷 1-7页

作者： Friedrich Preisser ald vacuum technologies AG

与液体淬火介质相比 ,气体在生态和经济性方面有优势。为获得所需的质量 ,必须仔细选择和调整淬火气体和工厂的工艺。理论上讲 ,轻气体和“冷却室”将带来许多好处。

关键词：气体淬火热处理淬火介质

Collective diffusion in carbon nanotubes: Crossover between one dimension and three dimensions

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Chinese Physics B 2016年第8期25卷 308-311页

作者：陈沛荣徐志成古宇钟伟荣 Siyuan Laboratory Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy Materials Department of PhysicsCollege of Science and Engineering Jinan University

Using non-equilibrium molecular dynamics and Monte Carlo methods, we study the collective diffusion of helium in carbon nanotubes. The results show that the collective diffusion coefficient（CDC） increases with the dimension of the channel. The collective diffusion coefficient has a linear relationship with the temperature and the concentration. There exist a ballistic transport in short carbon nanotubes and a diffusive transport in long carbon nanotubes. Fick＇s law has an invalid region in the nanoscale channel.

关键词： transport carbon nanotube fluid

THAI experimental research on hydrogen risk and source term related safety systems

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Frontiers in Energy 2021年第4期15卷 887-915页

作者： Sanjeev GUPTA Martin FREITAG Gerhard POSS Becker technologies gmbh Rahmannstrasse 11Eschborn 65760Germany

In the defense-in-depth concept employed for the safety of nuclear installations,maintaining integrity of containment as the last barrier is of high importance to limit the release of radioactivity to the environment in case of a severe *** active and passive safety systems implemented in containments of light water reactors(LWRs)are designed to limit the consequences of such *** the performance and reliability of such systems under accident conditions is critical to the safety of nuclear *** the aftermath of the Fukushima accident,there has been focus on re-examining the existing safety systems to demonstrate their capabilities for a broader range of boundary conditions comprising both the early as well as the late phases of an *** addition to the performance testing of safety systems,their interaction with containment atmosphere needs detailed investigations to evaluate the effects of operation of safety systems on H2 risk and fission product(FP)behavior in containment,which may ultimately have an impact on the source term to the *** this context,an extensive containment safety related experimental research has been conducted in a thermalhydraulics,hydrogen,aerosols,and iodine test facility(THAI,60 m3,single vessel)/(THAI+,80 m3,two interconnected vessels).Related to the subject of this paper,experimental investigations covered performance testing of various safety and mitigation systems,i.e.,containment spray,passive autocatalytic recombiner(PAR),pressure suppression pool(water pools),and effects of their operation on H2 risk and in-containment FP *** experimental results have provided a better phenomenological understanding and database for validation and further improvement of a safety analysis tool based on computation fluid dynamic(CFD)and lumped parameter(LP)modeling *** paper summarizes the main insights obtained from the aforesaid THAI experimental research covering safety systems

关键词： severe accident containment safety mitigation H2 risk source term

Self-powered and broadband germanium/PEDOT:PSS heterojunction photodetectors for near-infrared biomedical imaging applications

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Science China(Technological Sciences) 2021年第11期64卷 2523-2531页

作者： WU QiuYue LIU YuJin HUANG XinYue ZHENG Xu HE JieZhong JI Zhong MAI WenJie Siyuan Laboratory Guangdong Provincial Engineering Technology Research Center of Vacuum Coating Technologies and New Energy MaterialsDepartment of PhysicsJinan UniversityGuangzhou 510632China

To develop high-performance photodetectors(PDs) as near-infrared(NIR) imaging sensors, researchers have either proposed new photoelectric materials, introduced complicated interface-processing steps, or created complex optical structures. In this study, we introduce a solution-processed organic material, PEDOT:PSS(PEDOT corresponds to a polymer of 3,4-ethylene dioxythiophene(EDOT), and PSS corresponds to a polystyrene sulfonate), to germanium(Ge) wafers using a convenient spincoating method to improve the photoresponse performance of Ge-based PDs. The Ge wafers and PEDOT:PSS form a heterojunction that reduces the dark current when compared with the Ge Schottky PD(Au/Ge/Ag PD). The experimental results show that the Au/PEDOT:PSS/Ge/Ag heterojunction PD with a bias voltage of 0 V at 1550 nm exhibits a responsivity(R) of 0.26 A/W,a detectivity(D*) of 6.5×1011 Jones, a linear dynamic range(LDR) of 124 d B, and a bandwidth(-3 dB) of 10 k Hz. This implies that the performance of the PD is comparable to that of previously reported Ge-based PDs. Subsequently, a biomedical imaging application of the PD is successfully demonstrated through foreign-body detection. Therefore, it is expected that the selfpowered Au/PEDOT:PSS/Ge/Ag PD will be highly suitable for NIR imaging.

关键词： gemanium photodetectors PEDOT:PSS heterojunction self-powered photodetectors near-infrared biomedical imaging

All-inorganic lead-free NiO_(x)/Cs_(3)Bi_(2)Br_(9) perovskite heterojunction photodetectors for ultraviolet multispectral imaging

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Nano Research 2022年第2期15卷 1094-1101页

作者： Yujin Liu Yuxin Gao Jingyi Zhi Rongqing Huang Wanjun Li Xinyue Huang Genghua Yan Zhong Ji Wenjie Mai Siyuan Laboratory Guangdong Provincial Engineering Technology Research Center of Vacuum Coating Technologies and New Energy MaterialsDepartment of PhysicsJinan UniversityGuangzhou 510632China.

Bismuth-based perovskites are considered to be promising candidates to substitute the toxic lead-based perovskite in optoelectronics due to their excellent optoelectronic properties,high environmental friendliness,and(moisture,light,and heat)***,there are still few reports about high performance bismuth-based perovskite ultraviolet photodetectors,and is more lacking in ultraviolet imaging ***,we reported a self-powered NiO_(x)/Cs_(3)Bi_(2)Br_(9) heterojunction photodetector with excellent photodetection performance by electrochemical depositing NiOx as the hole transport *** optimized NiO_(x)/CsaBi_(2)Brg heterojunction photodetector exhibits excellent ultraviolet detection performance with a fast response speed of 3.04/4.65 ms,wide linear dynamic range of 116.6 dB,decent responsivity of 4.33 mA·W^(-1) at 0 V bias,and high detectivity of 1.3×10^(11) *** outstanding performance of the optimized NiO_(x)/Cs_(3)Bi_(2)Br_(9) heterojunction photodetector is enough to meet the high-quality ultraviolet ***,we further integrated the optimized NiO_(x)/Cs_(3)Bi_(2)Br_(9) heterojunction photodetector to the transmission mode ultraviolet multispectral imaging system,achieving admirable imaging results at weak light *** work will play a positive role in promoting the development of bismuth-based ultraviolet photodetection and ultraviolet multispectral imaging.

关键词： bismuth perovskites heterojunction photodetectors multispectral imaging

In Situ Monitoring the Potassium‑Ion Storage Enhancement in Iron Selenide with Ether‑Based Electrolyte

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Nano-Micro Letters 2021年第11期13卷 294-307页

作者： Xiaodan Li Jinliang Li Wenchen Zhuo Zhibin Li Liang Ma Zhong Ji Likun Pan Wenjie Mai Siyuan Laboratory Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy MaterialsGuangdong Provincial Engineering Technology Research Center of Vacuum Coating Technologies and New MaterialsDepartment of PhysicsJinan UniversityGuangzhouGuangdong 510632People’s Republic of China Shanghai Key Laboratory of Magnetic Resonance School of Physics and Electronic ScienceEast China Normal UniversityShanghai 200241People’s Republic of China

As one of the promising anode materials,iron selenide has received much attention for potassium-ion batteries(KIBs).Nevertheless,volume expansion and sluggish kinetics of iron selenide result in the poor reversibility and stability during potassiation–depotassiation *** this work,we develop iron selenide composite matching ether-based electrolyte for KIBs,which presents a reversible specific capacity of 356 mAh g^(−1) at 200 mA g^(−1) after 75 *** to the measurement of mechanical properties,it is found that iron selenide composite also exhibits robust and elastic solid electrolyte interphase layer in ether-based electrolyte,contributing to the improvement in reversibility and stability for *** further investigate the electrochemical enhancement mechanism of ether-based electrolyte in KIBs,we also utilize in situ visualization technique to monitor the potassiation–depotassiation *** comparison,iron selenide composite matching carbonate-based electrolyte presents vast morphology change during potassiation–depotassiation *** changing to ether-based electrolyte,a few minor morphology changes can be *** phenomenon indicates an occurrence of homogeneous electrochemical reaction in ether-based electrolyte,which results in a stable performance for potassium-ion(K-ion)*** believe that our work will provide a new perspective to visually monitor the potassium-ion storage process and guide the improvement in electrode material performance.

关键词： Iron selenide Ether-based electrolyte In situ visualization technique Potassium-ion batteries