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Plasma spray coating on interconnector toward promoted solid oxide fuel cells and solid oxide electrolysis cells

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Frontiers in Energy 2024年第3期18卷 390-398页

作者： junwen CAO Yun ZHENG Wenqiang ZHANG Bo YU Institute of Nuclear and New Energy Technology(INET) Collaborative Innovation Center of Advanced Nuclear Energy TechnologyTsinghua UniversityBeijing 100084China Department of Chemical Engineering University of WaterlooWaterlooOntario N2L 3G1Canada Institute of New Energy Materials and Engineering School of Materials Science and EngineeringFuzhou UniversityFuzhou 350108China

Interconnector is a critical component to construct solid oxide cells (SOCs) stack. Oxidation of metallic interconnectors and Cr poisoning caused by oxidation are important factors that lead to long-term performance degradation of SOCs. Coating on the interconnector surface is an important approach to inhibit the oxidation and Cr migration of the interconnector. Herein, (La0.75Sr0.25)0.95MnO3–δ (LSM) and Mn1.5Co1.5O4 (MCO) are used to fabricate the coatings of interconnector. Two advanced thermal spray technology, atmospheric plasma spraying (APS) and low-pressure plasma spray (LPPS), are adopted for the coating preparation. The electrochemical performance, rising and cooling cycle stability, and Cr diffusion inhibition performance of the coatings are tested and evaluated. The result indicates that MCO can generate more uniform and denser coatings than LSM. In addition, MCO coatings prepared by LPPS shows the best electrochemical performance, rising and cooling cycle stability, and Cr diffusion inhibition. The initial area specific resistance (ASR) is 0.0027 Ω·cm2 at 800 °C. After 4 cooling cycle tests, the ASR increases to 0.0032 Ω·cm2 but lower than other samples. Meanwhile, the relative intense of Cr at the interface of SUS430 with MCO coatings fabricated by LPPS is lower than that of MCO fabricated by APS after 4 rising and cooling cycle operations, showing more favorable Cr diffusion inhibition performance.

关键词： interconnector coating plasma spray electrochemical performance Cr diffusion inhibition solid oxide cells(SOCs)

Multi-population particle swarm optimization algorithm for automatic design of steel frames

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Frontiers of Structural and Civil Engineering 2024年第1期18卷 89-103页

作者： Wenchen SHAN Jiepeng LIU Yao DING Y.Frank CHEN junwen ZHOU Institute of Smart City and Intelligent Transportation Southwest Jiaotong UniversityChengdu 610000China School of Civil Engineering Chongqing UniversityChongqing 400045China Department of Civil Engineering the Pennsylvania State UniversityMiddletownPA 17057USA

Steel structures are widely used;however,their traditional design method is a trial-and-error procedure which is neither efficient nor cost effective.Therefore,a multi-population particle swarm optimization(MPPSO)algorithm is developed to optimize the weight of steel frames according to standard design codes.Modifications are made to improve the algorithm performances including the constraint-based strategy,piecewise mean learning strategy and multi-population cooperative strategy.The proposed method is tested against the representative frame taken from American standards and against other steel frames matching Chinese design codes.The related parameter influences on optimization results are discussed.For the representative frame,MPPSO can achieve greater efficiency through reduction of the number of analyses by more than 65% and can obtain frame with the weight for at least 2.4%lighter.A similar trend can also be observed in cases subjected to Chinese design codes.In addition,a migration interval of 1 and the number of populations as 5 are recommended to obtain better MPPSO results.The purpose of the study is to propose a method with high efficiency and robustness that is not confined to structural scales and design codes.It aims to provide a reference for automatic structural optimization design problems even with dimensional complexity.The proposed method can be easily generalized to the optimization problem of other structural systems.

关键词： steel frame multi-population particle swarm optimization automatic structural optimization design

First-principles study on the electronic structure of Pb_(10−x)Cu_(x)(PO_(4))_(6)O(x=0,1)

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Journal of Materials Science & Technology 2024年第4期171卷 66-70页

作者： junwen Lai Jiangxu Li Peitao Liu Yan Sun Xing-Qiu Chen Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China

Recently,Lee et al.claimed the experimental discovery of room-temperature ambient-pressure super-conductivity in a Cu-doped lead-apatite(LK-99)(arXiv:2307.12008,arXiv:2307.12037).Remarkably,the claimed superconductivity can persist up to 400 K at ambient pressure.Despite the experimental im-plication,the electronic structure of LK-99 has not yet been studied.Here,we investigate the electronic structures of LK-99 and its parent compound using first-principles calculations,aiming to elucidate the doping effects of Cu.Our results reveal that the parent compound Pb_(10)(PO_(4))_(6)O is an insulator,while Cu doping induces an insulator-metal transition and thus volume contraction.The band structures of LK-99 around the Fermi level are featured by a half-filled flat band and a fully-occupied flat band.These two very flat bands arise from both the 2p orbitals of 1/4-occupied O atoms and the hybridization of the 3d orbitals of Cu with the 2p orbitals of its nearest-neighboring O atoms.Interestingly,we observe four van Hove singularities on these two flat bands.Furthermore,we show that the flat band structures can be tuned by including electronic correlation effects or by doping different elements.We find that among the considered doping elements(Ni,Cu,Zn,Ag,and Au),both Ni and Zn doping result in the gap opening,whereas Au exhibits doping effects more similar to Cu than Ag.Our work establishes a foundation for fu-ture studies to investigate the role of unique electronic structures of LK-99 in its claimed superconducting properties.

关键词： First-principles calculations Density functional theory Electronic structur e Superconductivity Flat bands Strongly correlated electrons

Recent advances and challenges of nitrogen/nitrate electro catalytic reduction to ammonia synthesis

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Frontiers in Energy 2024年第2期18卷 128-140页

作者： junwen CAO Yikun HU Yun ZHENG Wenqiang ZHANG Bo YU Institute of Nuclear and New Energy Technology(INET) Collaborative Innovation Center of Advanced Nuclear Energy TechnologyTsinghua UniversityBeijing 100084China Department of Chemical Engineering University of WaterlooWaterlooOntario N2L 3G1Canada Institute of New Energy Materials and Engineering School of Materials Science and EngineeringFuzhou UniversityFuzhou 350108China

The Haber-Bosch process is the most widely used synthetic ammonia technology at present.Since its invention,it has provided an important guarantee for global food security.However,the traditional Haber-Bosch ammonia synthesis process consumes a lot of energy and causes serious environmental pollution.Under the serious pressure of energy and environment,a green,clean,and sustainable ammonia synthesis route is urgently needed.Electrochemical synthesis of ammonia is a green and mild new method for preparing ammonia,which can directly convert nitrogen or nitrate into ammonia using electricity driven by solar,wind,or water energy,without greenhouse gas and toxic gas emissions.Herein,the basic mechanism of the nitrogen reduction reaction(NRR)to ammonia and nitrate reduction reaction(NO_(3)^(-))to ammonia were discussed.The representative approaches and major technologies,such as lithium mediated electrolysis and solid oxide electrolysis cell(SOEC)electrolysis for NRR,high activity catalyst and advanced electrochemical device fabrication for(NO_(3)^(-))RR and electrochemical ammonia synthesis were summarized.Based on the above discussion and analysis,the main challenges and development directions for electrochemical ammonia synthesis were further proposed.

关键词： electrochemical ammonia synthesis nitrogen nitrate nitrogen reduction reaction(NRR)to ammonia nitrate reduction reaction(NO_(3)^(-))RR

Effects of transgenic overexpression of diapause hormone and diapause hormone receptor genes on non-diapause silkworm

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Effects of transgenic overexpression of diapause hormone and...

Carbon reduction paths for Chinese oil companies under the carbon peaking and carbon neutrality goals

中国蚕学会第九届青年学术研讨会

作者： Chunying Gong Wenhui Zeng Tianyang Zhang Rongpeng Liu Yao Ou junwen ai Zhonghuai Xiang Hanfu Xu

Diapause is a state of developmental arrest that is most often observed in arthropods,especially insects.The domesticated silkworm,Bombyx mori,is a typical insect that enters diapause at an early embryonic stage.Previous studies have revealed that the diapause hormone（DH） signaling molecules,especially the core members DH and DH receptor 1（DHR1）,are crucial for the determination of embryonic diapause in diapause silkworm strains.However,whether they function in non-diapause silkworm strains remains largely unknown.Here,we generated two transgenic lines overexpressing DH or DHR1 genes in a non-diapause silkworm strain,Nistari.Our results showed that developmental expression patterns of DH and DHR1 are quite similar in transgenic silkworms:both genes are highly expressed in the mid to late stages of pupae and are most highly expressed in day-6 pupae but are expressed at very low levels in other developmental stages.Moreover,the overexpression of DH or DHR1 can affect the expression of diapause-related genes but is not sufficient to induce embryonic diapause in their offspring.This study provides new insights into the function of DH and DHR1 in a non-diapause silkworm strain.

关键词： DH DHR1 Transgene Overexpression Non-diapause silkworm

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Microstructure evolution, mechanical properties and fracture behavior of Al-xSi/AZ91D bimetallic composites prepared by a compound casting

Natural Gas Industry 2024年第4期44卷 180-189页

作者： Zhu, Hongjun Li, Yingmei Chen, junwen Hao, Hongtao Gao, Yue School of Petroleum Engineering Southwest Petroleum University Sichuan Chengdu 610500 China Southwest Branch of China Petroleum Engineering & Construction Corporation Sichuan Chengdu 610041 China

To cope with the global warming and achieve the carbon peaking and carbon neutrality goals, Chinese oil companies have taken a series of carbon reduction measures. This paper analyzes the current carbon emissions in China and the carbon reduction measures taken by oil companies, and clarifies the challenges in carbon reduction. Finally, some carbon reduction paths are proposed for the Chinese oil companies. The results indicate that in the process of oil and gas production and utilization, greenhouse gas is mainly emitted in the upstreams. The Chinese oil companies adopt carbon capture, carbon reduction, carbon substitution, and carbon emission trading methods to reduce the carbon emissions, while maintaining energy supply and improving quality and efficiency. Moreover, some companies have been developing wind energy, solar energy, geothermal energy, hydrogen energy and marine new energy according to local conditions, gradually promoting the green transformation of energy. According to the research results and the current situation of Chinese oil enterprises, some carbon reduction paths are proposed. First, a scientific and reasonable multi-energy complementation system should be built to realize the collaborative development of conventional energy and new energy. Second, low-cost and efficient technologies should be developed in fossil energy mining, clean energy development, and digital carbon neutrality, etc., and the initial innovation capability should be enhanced to address. Moreover, initiative actions should be taken in the new round of industrial revolution and technological transformation. Third, the exchange and cooperation with national/international enterprises, local governments, universities/colleges, and research institutes should be strengthened to ensure the advancement of associated technologies and to cultivate professional and technical talents. © 2024 Natural Gas Industry Journal Agency. All rights reserved.

关键词： Global warming

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Journal of Magnesium and Alloys 2024年第5期12卷 1944-1964页

作者： Guangyu Li Wenming Jiang Feng Guan junwen Zhu Yang Yu Zitian Fan State Key Laboratory of Materials Processing and Die & Mould Technology School of Materials Science and Engineering Huazhong University of Science and Technology

In this paper, the effect of the Si content on microstructure evolution, mechanical properties, and fracture behavior of the Al-xSi/AZ91D bimetallic composites prepared by compound casting was investigated systematically. The obtained results showed that all the Al-xSi/AZ91D bimetallic composites had a metallurgical reaction layer（MRL）, whose thickness increased with increasing Si content for the hypoeutectic Al-Si/AZ91D composites, while the hypereutectic Al-Si/AZ91D composites were opposite. The MRL included eutectic layer（E layer）,intermetallic compound layer（IMC layer） and transition region layer（T layer）. In the IMC layer, the hypereutectic Al-Si/AZ91D composites contained some Si solid solution and flocculent Mg2Si+Al-Mg IMCs phases not presented in the hypoeutectic Al-Si/AZ91D composites.Besides, increasing Si content, the thickness proportion of the T layer increased, forming an inconsistent preferred orientation of the MRL.The shear strengths of the Al-xSi/AZ91D bimetallic composites enhanced with increasing Si content, and the Al-15Si/AZ91D composite obtained a maximum shear strength of 58.6 MPa, which was 73.4% higher than the Al-6Si/AZ91D composite. The fractures of the Al-xSi/AZ91D bimetallic composites transformed from the T layer into the E layer with the increase of the Si content. The improvement of the shear strength of the Al-xSi/AZ91D bimetallic composites was attributed to the synergistic action of the Mg2Si particle reinforcement, the reduction of oxidizing inclusions and the ratio of Al-Mg IMCs as well as the orientation change of the MRL.

关键词： Al/Mg bimetallic composites Si content Mg 2 Si reinforcement Microstructure Mechanical properties Fracture behavior

Stability analysis of intermittently jointed rock slopes based on the stepped failure mode

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Journal of Mountain Science 2024年第3期21卷 1019-1035页

作者： LI Dejian FU junwen LI Hekai CHENG Xiao ZHAO Lianheng ZHANG Yingbin PENG Xinyan School of Civil Engineering Southwest Jiaotong UniversityChengdu 610031China Institute for Disaster Management and Reconstruction College of Architecture&EnvironmentSichuan UniversityChengdu 610065China School of Civil Engineering Key Laboratory of Heavy-Haul Railway Engineering StructureMinistry of EducationHunan Provincial Key Laboratory for Disaster Prevention and Mitigation of Rail Transit Engineering StructureCentral South UniversityChangsha 410075China

In practical engineering,due to the noncontinuity characteristics of joints in rock slopes,in addition to plane failure,stepped sliding failure may occur for intermittently jointed rock slopes.Especially for intermittently bedding jointed rock slopes,the correlation and difference in strength parameters between joints and rock bridges,along with the various failure modes and intermittency of rock bridges,contribute to the complexity of stepped failure modes and the unpredictability of failure regions.Based on the upper-bound limit analysis method and multi-sliders step-path failure mode,considering the shear and tensile failure of rock bridges and the weakened relationship between the strength parameters of rock bridges and jointed surfaces,by introducing the modified M-C failure criterion and the formula for calculating the energy consumption of tensile failure of rock bridges,two failure mechanisms are constructed to obtain the safety factor(F_(s))of intermittently jointed rock slopes.The sequential quadratic programming method is used to obtain the optimal upper-bound solution for F_(s).The influence of multiple key parameters(slope height H,horizontal distance L,Slope angleβ,shear strength parameters of the rock bridgeφr and cr,Dimensionless parameter u,weakening coefficients of the internal friction angle and cohesion between the rock bridges and joint surfaces Kφand Kc)on the stability analysis of intermittently jointed rock slopes under the shear failure mode of rock bridges as well as under the tensile failure mode is also explored.The reliability of the failure mechanisms is verified by comparative analysis with theoretical results,numerical results,and landslide cases,and the variation rules of F_(s)with each key parameter are obtained.The results show that F_(s) varies linearly withφr and cr of the rock bridge and with K_(φ)and K_(c),whereas F_(s)changes nonlinearly with H and L.In particular,with the increase in Kφand Kc,Fs increases by approximately 52.78%and 171.02%on average,respectively.For rock b

关键词： Jointed rock slopes Stepped sliding failure Weakening characteristics Modified M‒C failure criterion

Experimental and numerical study on atmospheric-pressure air dielectric barrier discharge via 50 Hz/5000 Hz dual-frequency excitation

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High Voltage 2024年第2期9卷 391-402页

作者： junwen He Bangfa Peng Guanglin Yu Ronggang Wang Nan Jiang Jie Li Yan Wu School of Electrical Engineering Dalian University of TechnologyDalianChina Canmax Technologies Co. Ltd.SuzhouChina

A dual-frequency(DF)dielectric barrier discharge,excited by the superposition of a 50 Hz low frequency(LF)and a 5000 Hz intermediate frequency(IF),is proposed to enhance discharge.The effect of the LF voltage component on the breakdown behaviour of the DF discharge during different periods has been studied both experimentally and numerically.The number of high-current pulses rises as the LF voltage increases.The statistical analysis shows that the number of the current pulse amplitude above 80 mA in the DF discharge reaches nearly 6 times that in the IF discharge.Additionally,the total discharge energy in the DF discharge is significantly higher than that in the IF discharge.The simulation re-produces the temporal variation of the breakdown behaviours in the DF discharge.The simulated results reveal that the maximal electric field strength of the breakdown process is greater in the DF discharge compared to the IF discharge during a half-period of DF.Finally,the comparison between the IF and DF discharges exhibits that the LF voltage regulates the accumulation of residual charged species on the dielectric surface after the breakdown by modulating the residual voltage between the air gap.

关键词： dielectric excitation excited