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Effects of longitudinal magnetic field on primary dendrite spacing and segregation of directionally solidified single crystal superalloy

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Progress in Natural Science:materials International 2024年第1期34卷 26-36页

作者： Congjiang Zhang Yilin Zhou Chen Shen Weili Ren Xiaotan Yuan Biao Ding Haibiao Lu Zuosheng Lei Yunbo Zhong Ang Zhang State key laboratory of advanced Special Steel College of Materials Science and Engineering Shanghai University National Engineering Research Center for Magnesium Alloys Natural Key Laboratory of Advanced Casting Technologies College of Materials Science and EngineeringChongqing University

The primary dendrite spacing(PDS) and segregation of directionally solidified single crystal(SC) superalloy under the longitudinal magnetic field(LMF) were investigated based on the analysis of the whole cross-sectional microstructure at different solidification distances. The results show that the PDS under the LMF remains basically unchanged at different solidification distances, and it is greater than that under no LMF. With the increase of magnetic field intensity, the PDS increases and the macrosegregation decreases. The increasing PDS and reducing segregation under the LMF can be attributed to the increase of solute boundary layer, which expands the non-equilibrium freezing temperature range and brings the effective partition coefficient closer to 1. The increase of the solute enrichment layer thickness could be caused by the downward secondary circulation generated by the thermoelectric magnetic convection(TEMC) near the interface, which drives the migration of solutes towards the interdendritic region. This work not only clarifies the mechanism of LMF controlling PDS and reducing segregation by TEMC, but also provides theoretical guidance for producing high-quality SC superalloys using magnetic fields.

关键词： Primary dendrite spacing Segregation Single crystal superalloy Directional solidification Magnetic field Thermoelectric magnetic convection

"Win-Win"Scenario of High Energy Density and Long Cycling Life in a Novel Na_(3.9)MnCr_(0.9)Zr_(0.1)(PO_(4))_(3)Cathode

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Energy & Environmental materials 2024年第1期7卷 83-90页

作者： Yao Wang Yukun Liu Pingge He Junteng Jin Xudong Zhao Qiuyu Shen Jie Li Xuanhui Qu Yongchang Liu Lifang Jiao Beijing advanced Innovation Center for materials Genome Engineering State Key Laboratory for Advanced Metals and MaterialsInstitute for Advanced Materials and TechnologyUniversity of Science and Technology BeijingBeijing 10083China Department of Chemistry and Biochemistry University of California1156 High StreetSanta CruzCA 95064USA Tianjin key laboratory for Photoelectric materials and Devices School of Materials Science and EngineeringTianjin University of TechnologyTianjin 300384China key laboratory of advanced Energy materials Chemistry(Ministry of Education) Nankai UniversityTianjin 300071China

The development of high-energy and long-lifespan NASICON-type cathode materials for sodium-ion batteries has always been a research hotspot but a daunting *** Na_(4)MnCr(PO_(4))_(3)has emerged as one of the most promising high-energy-density cathode materials owing to its three-electron reactions,it still suffers from serious structural distortion upon repetitive charge/discharge processes caused by the Jahn-Teller active Mn^(3+).Herein,the selective substitution of Cr by Zr in Na_(4)MnCr(PO_(4))_(3)was explored to enhance the structural stability,due to the pinning effect of Zr ions and the≈2.9-electron reactions,as-prepared Na_(3.9)MnCr_(0.9)Zr_(0.1)(PO_(4))_(3)/C delivers a high capacity retention of 85.94%over 500 cycles at 5 C and an ultrahigh capacity of 156.4 mAh g^(-1)at 0.1 C,enabling the stable energy output as high as 555.2 Wh kg^(-1).Moreover,during the whole charge/discharge process,a small volume change of only 6.7%was verified by in situ X-ray diffraction,and the reversible reactions of Cr^(3+)/Cr^(4+),Mn^(3+)/Mn^(4+),and Mn^(2+)/Mn^(3+)redox couples were identified via ex situ X-ray photoelectron spectroscopy *** intermittent titration technique tests and density functional theory calculations further demonstrated the fast reaction kinetics of the Na_(3.9)MnCr_(0.9)Zr_(0.1)(PO_(4))_(3)/C *** work offers new opportunities for designing high-energy and high-stability NASICON cathodes by ion doping.

关键词： high energy density mechanism investigation NASICON-type cathodes sodium-ion batteries structure modification

Synthesis and characterization of high entropy(TiVNbTaM)_(2)AlC(M=Zr,Hf)ceramics

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Journal of advanced Ceramics 2024年第2期13卷 237-246页

作者： Lei Cao Qiqiang Zhang Lijing Du Shuai Fu Detian Wan Yiwang Bao Qingguo Feng Chunfeng Hu key laboratory of advanced Technologies of materials Ministry of EducationSchool of Materials Science and EngineeringSouthwest Jiaotong UniversityChengdu 610031China State key laboratory of Green Building materials China Building Materials AcademyBeijing 100024China

The high-entropy design of MAX phases is expected to confer superior properties,but its study was hindered by the complex synthesis method and limited purity of *** this work,two noteworthy types of high-entropy MAX phase structural ceramics,high-entropy(TiVNbTaM)_(2)AlC(M=Zr,Hf),were designed and prepared by the in-situ synthesis using spark plasma sintering(SPS).The microstructure and lattice parameters of sintered samples were *** with the single-component MAX phases,the highly pure high-entropy(TiVNbTaZr)_(2)AlC sample had good physical and mechanical properties,including electrical conductivity of 0.96×106Ω^(-1)·m^(-1),thermal expansion coefficient of 3.65×10^(-6) K^(-1),thermal conductivity of 8.98 W·m^(-1)·K^(-1),Vickers hardness of 9.80 GPa,flexural strength of 507 MPa,fracture toughness of 5.62 MPa·m^(1/2),and compressive strength of 1364 MPa,which exhibited the remarkable hardening-strengthening effect.

关键词： MAX phase high-entropy ceramic microstructure physical properties mechanical properties

Experimental investigation of omnidirectional multiphysics bilayer invisibility cloak with anisotropic geometry

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Chinese Physics B 2024年第3期33卷 649-658页

作者：丰火雷张兴伟周利敏张悦凯倪玉山 Department of Aeronautics and Astronautics Fudan UniversityShanghai 200433China key laboratory of advanced Ship materials and Mechanics College of Aerospace and Civil EngineeringHarbin Engineering UniversityHarbin 150001China

Thermal-electric bilayer invisibility cloak can prevent the heat flux and electric current from touching the object without distorting the external temperature and electric potential fields *** this paper,we design an omnidirectional thermal-electric invisibility cloak with anisotropic *** on the theory of neutral inclusion,the anisotropic effective thermal and electric conductivities of confocal elliptical bilayer core-shell structure are derived,thus obtaining the anisotropic matrix material to eliminate the external disturbances *** inner shell of the cloak is selected as an insulating material to shield the heat flux and electric ***,the omnidirectional thermal-electric cloaking effect is verified numerically and experimentally based on the theoretical anisotropic matrix and manufactured composite structure,***,we achieve the thermal-electric cloaking effect under a specific direction of heat flux and electric current using the isotropic natural materials to broaden the selection range of *** method proposed to eliminate anisotropy and achieve the omnidirectional effect could also be expanded to other different physical fields for the metadevices with different functions.

关键词： omni-directionality multiphysics bilayer confocal ellipse invisibility cloak

pH Induced Self-assembly of AIE Fluorescent Probe for Tumor Imaging

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Chinese Journal of Polymer Science 2024年第1期42卷 7-13,I0005页

作者： Jing-Yuan Xiang Wen-Long Zhang He-Ting Li Ya-Ning He Department of Chemical Engineering Key Laboratory of Advanced Materials(MOE)Tsinghua UniversityBejing 100084China

This work reported an AIE fluorescent probe for tumor imaging based on the p H induced self-assembly strategy. The fluorescent probe was composed of an acid-responsive soluble copolymer PEG-b-PAMA-DMMA with a maleic acid amide group and an anionic soluble aggregation-induced emission fluorogen(AIEgen) TPE-2SO_(3)^(-). The polymer could be transformed into a protonated amine-containing polymer after the hydrolysis of maleic acid amide in acidic tumor microenvironment, which would be further self-assembled with TPE-2SO_(3)^(-)to form aggregated nanoparticles. The transition of TPE-2SO_(3)^(-)from dispersed state to aggregated state led to an obvious increase in fluorescence intensity due to its AIE characteristics.

关键词： p H-responsive Self-assembly Fluorescent probe AIE Tumor imaging

Revisiting the sodium-ion storage capability of hard carbon in carbonate-based electrolytes via a sodium-metal-free protocol

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Science China Chemistry 2024年第7期67卷 2240-2247页

作者： Gaopan Liu Yanbing Mo Jiawei Chen Yu Peng Xiao Zhu Fei Wang Xiaoli Dong Yongyao Xia Department of Chemistry and Shanghai key laboratory of Molecular Catalysis and Innovative materials Institute of New EnergyLaboratory of Advanced MaterialsFudan UniversityShanghai 200438China

Common evaluation methodology of sodium(Na)-containing two-electrode or three-electrode configurations overlooks the interference from highly reactive Na metal,leading to the underestimation or inconsistent performance of low-potential hard carbon(HC)***,the trap of Na metal was systematically investigated with or without applied current,uncovering its inadequacy as the reference or counter electrode in different configurations.A Na-metal-free three-electrode protocol is proposed for evaluating the actual Na^(+)-storage capability of the typical low-potential HC *** avoiding Na crosstalk and precisely controlling the working electrode's potential,the actual electrochemical performance of HC in the carbonate esterbased electrolyte can be recognized with high capacity of 222 mAh g^(-1)at 2 C and 113 mAh g^(-1)at 5 C,correcting the misunderstanding of the inferior performance of HC in coin-type half cells(68%and 50%undervaluation at 2 C and 5 C,respectively).The advanced protocol is expected to reduce misunderstandings or underestimation due to evaluation methods and to guide the development of high-performance battery materials.

关键词： highly reactive sodium potential drift carbonate ester sodium-metal-free protocol sodium storage capability

Synthesis of size-controlled and dispersible Sm2Fe17N3 magnetic particles by reduction diffusion process using molten salt

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Journal of Rare Earths 2024年第11期42卷 2105-2111页

作者： Junhua Xi Zhi Yang Muhammad Haseeb Yuanyuan Chen Xiaofeng Nie Liying Cong Qiong Wu Enfeng Fu Hongguo Zhang Weiqiang Liu Ming Yue Faculty of materials and Manufacturing Key Laboratory of Advanced Functional MaterialsMinistry of Education of ChinaBeijing University of Technology

The synthesis of size-controlled Sm2Fe17magnetic particles is a prerequisite for the fabrication of highperformance Sm2Fe17N3permanent magnetic ***,Sm2Fe17was synthesized using a costeffective reduction-diffusion *** calcium chloride molten salt was introduced to control the particle size and achieve a single phase of *** effects of reduction-diffusion reaction temperature and the amount of added calcium chloride on the phase constitution and microstructure of the final product of reduction-diffusion were systematically *** an appropriate amount of calcium chloride can effectively inhibit the overgrowth and sintering of the reduced *** employing the strategy of adding 20 wt% of calcium chlorides into the green compacts,we were able to successfully synthesize uniform Sm2Fe17particles that are well-dispersed,with an average size of 2.2 μ***,by combining the optimal reduction-diffusion conditions and the nitriding process,the hard magnetic Sm2Fe17N3material was successfully *** study could be useful for the development of high-performance Sm2Fe17N3magnetic materials utilizing reduction-diffusion technology.

关键词： Molten salt Permanent magnets Rare earths Reduction-diffusion Sm2Fe17N3

Chiral thermally activated delayed fluorescence materials for circularly polarized organic light-emitting diodes

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Science China Chemistry 2024年第4期67卷 1097-1116页

作者： Li Yuan Yi-Pin Zhang You-Xuan Zheng State key laboratory of Coordination Chemistry Collaborative Innovation Center of Advanced MicrostructuresJiangsu Key Laboratory of Advanced Organic MaterialsSchool of Chemistry and Chemical EngineeringNanjing UniversityNanjing 210023China

Chirality is an important natural characteristic of organic molecules,and chiral organic molecules have shown extensive application in areas such as pharmaceutical development and material *** from the ability to achieve circularly polarized luminescence(CPL),chiral luminescent materials have shown potential applications in anti-glare display,optical communication and,3D display,*** to the ability to harvest both singlet and triplet excitons by a fast reverse intersystem crossing process without involving noble metals,chiral thermally activated delayed fluorescence(TADF)materials with point chirality,axial chirality,planar chirality and helical chirality are regarded as the state-of-the-art materials for circularly polarized organic light-emitting diodes(CP-OLEDs).In recent years,the chiral TADF materials and CP-OLEDs have rapidly developed,but unfortunately,the dissymmetry factors(g)are far from the requirement of practical *** ideal emitters and devices should have both high efficiency and a g factor,or at least a balance between these two *** review gives an overview of recent progress in chiral TADF materials,with a particular focus on the chiral skeleton,CPL property and device ***,the molecular design concept,device structure and methods to improve the g factors of chiral materials and CP-OLEDs are also discussed.

关键词： chiral thermally activated delayed fluorescence material chiral skeleton circularly polarized luminescence circularly polarized organic light-emitting diodes dissymmetry factor

High-capacity dilithium hydroquinone cathode material for lithium-ion batteries

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National Science Review 2024年第6期11卷 206-213页

作者： Yong Lu Haoqin Han Zhuo Yang Youxuan Ni Zhicheng Meng Qiu Zhang Hao Wu Weiwei Xie Zhenhua Yan Jun Chen Frontiers Science Center for New Organic Matter Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education) State Key Laboratory of Advanced Chemical Power SourcesCollege of ChemistryNankai University

Lithiated organic cathode materials show great promise for practical applications in lithium-ion batteries owing to their Li-reservoir characteristics. However, the reported lithiated organic cathode materials still suffer from strict synthesis conditions and low capacity. Here we report a thermal intermolecular rearrangement method without organic solvents to prepare dilithium hydroquinone（Li2Q）, which delivers a high capacity of 323 m Ah g-1with an average discharge voltage of 2.8 V. The reversible conversion between orthorhombic Li2Q and monoclinic benzoquinone during charge/discharge processes is revealed by in situ X-ray diffraction. Theoretical calculations show that the unique Li–O channels in Li2Q are beneficial for Li+ion diffusion. In situ ultraviolet-visible spectra demonstrate that the dissolution issue of Li2Q electrodes during charge/discharge processes can be handled by separator modification, resulting in enhanced cycling stability. This work sheds light on the synthesis and battery application of high-capacity lithiated organic cathode materials.

关键词： lithium-ion batteries cathode materials lithiated organic materials dilithium hydroquinone separator modification