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One-step synthesis and electromagnetic absorption properties of high entropy rare earth hexaborides(HE REB6)and high entropy rare earth hexaborides/borates(HE REB6/HE REB03)composite powders

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Journal of Advanced Ceramics 2021年第1期10卷 62-77页

作者： Weiming ZHANG Biao ZHAO Huimin XIANG Fu-Zhi DAI shijiang wu Yanchun ZHOU Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China Henan Key Laboratory of Aeronautical Materials and Application Technology School of Material Science and EngineeringZhengzhou University of AeronauticsZhengzhou 450046China Zibo Firststar New Material Incorporated Co. Ltd.Zibo 255000China

Considering the emergence of severe electromagnetic interference problems,it is vital to develop electromagnetic(EM)wave absorbing materials with high dielectric,magnetic loss and optimized impedance ***,realizing the synergistic dielectric and magnetic losses in a single phase material is still a ***,high entropy(HE)rare earth hexaborides(REB6)powders with coupling of dielectric and magnetic losses were designed and successfully synthesized through a facial one-step boron carbide reduction method,and the effects of high entropy borates intermedia phases on the EM wave absorption properties were *** HE REB6 ceramics including(Ce0.2Y0.2Sm0.2Er0.2Yb0.2)B6,(Ce0.2Hu0.2Sm0.2Er0.2Yb0.2)B6,(Ce0.2Y0.2Eu0.2Er0.2Yb0.2)B6,(Ce0.2Ya2Sm0.2Eu0.2Yb0.2)B6,and(Nd0.2Y0.2Sm0.2Eu0.2Yb0.2)B6 possess CsCl-type cubic crystal structure,and their theoretical densities range from 4.84 to 5.25 g/cm^(3).(Ce02Y0.2Sm0.2Er0.2Yb02)B6 powders with the average particle size of 1.86 jim were found to possess the best EM wave absorption properties among these *** RLmin value of(Ce0.2Y0.2Sm0.2Er0.2Yb0.2)B6 reaches-33.4 dB at 11.5 GHz at thickness of 2 mm;meanwhile,the optimized effective absorption bandwidth(EAB)is 3.9 GHz from 13.6 to 17.5 GHz with a thickness of 1.5 *** introduction of HE REB03(RE=Ce,Y,Sm,Eu,Er,Yb)as intermediate phase will give rise to the mismatching impedance,which will further lead to the reduction of reflection ***,the HEREB6/HEREB03 still possess wide effective absorption bandwidth of 4.1 GHz with the relative low thickness of 1.7 *** the better stability,low density,and good EM wave absorption properties,HE REB6 ceramics are promising as a new type of EM wave absorbing materials.

关键词： high entropy rare earth hexaborides(HE REB6) one-step synthesis electromagnetic wave absorbing properties synergistic dielectric and magnetic losses wide effective absorption bandwidth

Achieving ultra-broadband electromagnetic wave absorption in high-entropy transition metal carbides (HE TMCs)

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Journal of Advanced Ceramics 2022年第4期11卷 545-555页

作者： Weiming ZHANG Huimin XIANG Fu-Zhi DAI Biao ZHAO shijiang wu Yanchun ZHOU Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China Henan Key Laboratory of Aeronautical Materials and Application Technology School of Material Science and EngineeringZhengzhou University of AeronauticsZhengzhou 450046China Zibo Firststar New Material Incorporated Co. Ltd.Zibo 255000China

Electronic devices pervade everyday life,which has triggered severe electromagnetic(EM)wave *** face this challenge,developing EM wave absorbers with ultra-broadband absorption capacity is critically ***,nano-composite construction has been widely utilized to realize impedance match and broadband ***,complex experimental procedures,limited thermal stability,and interior oxidation resistance are still unneglectable ***,it is appealing to realize ultra-broadband EM wave absorption in single-phase materials with good *** at this target,two high-entropy transition metal carbides(HE TMCs)including(Zr,Hf,Nb,Ta)C(HE TMC-2)and(Cr,Zr,Hf,Nb,Ta)C(HE TMC-3)are designed and synthesized,of which the microwave absorption performance is investigated in comparison with previously reported(Ti,Zr,Hf,Nb,Ta)C(HE TMC-1).Due to the synergistic effects of dielectric and magnetic losses,HE TMC-2 and HE TMC-3 exhibit better impedance match and wider effective absorption bandwidth(EAB).In specific,the exclusion of Ti element in HE TMC-2 endows it optimal minimum reflection loss(RL_(min))and EAB of−41.7 dB(2.11 mm,10.52 GHz)and 3.5 GHz(at 3.0 mm),***,the incorporation of Cr element in HE TMC-3 significantly improves the impedance match,thus realizing EAB of 10.5,9.2,and 13.9 GHz at 2,3,and 4 mm,*** significance of this study lays on realizing ultra-broadband capacity in HE TMC-3(Cr,Zr,Hf,Nb,Ta),demonstrating the effectiveness of high-entropy component design in tailoring the impedance match.

关键词： transition metal carbide(TMC) high-entropy ceramics electromagnetic(EM)wave absorption dielectric and magnetic loss coupling ultra-broadband absorption

High entropy rare earth hexaborides/tetraborides(HE REB_(6)/HE REB_(4)) composite powders with enhanced electromagnetic wave absorption performance

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Journal of Materials Science & Technology 2021年第28期87卷 155-166页

作者： Weiming Zhang Biao Zhao Na Ni Huimin Xiang Fu-Zhi Dai shijiang wu Yanchun Zhou Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing100076China Henan Key Laboratory of Aeronautical Materials and Application Technology School of Material Science and EngineeringZhengzhou University of AeronauticsZhengzhou450046China Key Lab of Education Ministry for Power Machinery and Engineering School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai200240China Zibo Firststar New Material Incorporated Co.Ltd. Zibo255000China

The increasing electromagnetic hazards including electromagnetic interference and electromagnetic pollution,which were stemmed from massive usage of electromagnetic technology,have triggered widespread *** cope with this challenge,electromagnetic wave absorbing materials with high performance are greatly *** construction has been widely applied in electromagnetic(EM)wave absorbing materials to achieve high permittivity,high permeability and impedance ***,high-temperature stability,oxidation and corrosion resistance are still unignorable ***,high entropy hexaborides/tetraborides(HE REB_(6)/HE REB_(4))composites with synergistic dielectric and magnetic losses were designed and successfully synthesized through a one-step boron carbide reduction *** five as-prepared(Y_(0.2) Nd_(0.2) Sm_(0.2) Eu_(0.2) Er_(0.2))B_(6)/(Y_(0.2) Nd_(0.2) Sm_(0.2) Eu_(0.2) Er_(0.2))B_(4),(Y_(0.2) Nd_(0.2) Sm_(0.2) Er_(0.2) Yb_(0.2))B_(6)/(Y_(0.2) Nd_(0.2) Sm_(0.2) Er_(0.2) Yb_(0.2))B_(4),(Y_(0.2) Nd_(0.2) Eu_(0.2) Er_(0.2) Yb_(0.2))B_(6)/(Y_(0.2) Nd_(0.2) Eu_(0.2) Er_(0.2) Yb_(0.2))B_(4),(Nd_(0.2) Sm_(0.2) Eu_(0.2) Er_(0.2) Yb_(0.2))B_(6)/(Nd_(0.2) Sm_(0.2) Eu_(0.2) Er_(0.2) Yb_(0.2))B_(4) and(Y_(0.2) Sm_(0.2) Eu_(0.2) Er_(0.2) Yb_(0.2))B_(6)/(Y_(0.2) Sm_(0.2) Eu_(0.2) Er_(0.2) Yb_(0.2))B_(4) contain two phases of HE REB_(6) and HE REB_(4).Among them(Y_(0.2) Nd_(0.2) Sm_(0.2) Eu_(0.2) Er_(0.2))B_(6)/(Y_(0.2) Nd_(0.2) Sm_(0.2) Eu_(0.2) Er_(0.2))B_(4)(HE REB_(6)/HE REB_(4)-1)and(Y_(0.2) Nd_(0.2) Sm_(0.2) Er_(0.2) Yb_(0.2))B_(6)/(Y_(0.2) Nd_(0.2) Sm_(0.2) Er_(0.2) Yb_(0.2))B_(4)(HE REB_(6)/HE REB_(4)-2)exhibit excellent EM wave absorption *** optimal minimum reflection loss(RL_(m in))and effective absorption bandwidth(E_(AB))of HE REB_(6)/HE REB_(4)-1 and HE REB_(6)/HE REB_(4)-2 are–53.3 dB(at 1.7 mm),4.2 GHz(at 1.5 mm)and–43.5 dB(1.3 mm),4.2 GHz(1.5 mm),*** combination of conducting HE REB_(4) with magnetism into HE REB_

关键词： High entropy ceramics Hexaborides/tetraborides composites One-step synthesis Electromagnetic wave absorption Synergistic dielectric and magnetic losses

Electromagnetic wave absorbing properties of TMCs(TM=Ti,Zr,Hf,Nb and Ta)and high entropy(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C

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Journal of Materials Science & Technology 2021年第15期74卷 105-118页

作者： Yanchun Zhou Biao Zhao Heng Chen Huimin Xiang Fu-Zi Dai shijiang wu Wei Xu Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing100076China Henan Key Laboratory of Aeronautical Materials and Application Technology School of Material Science and EngineeringZhengzhou University of AeronauticsZhengzhou450046China Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education School of Materials Science and EngineeringTianjin UniversityTianjin300072China Zibo Firstar New Material Incoqjorated Co.Ltd. Zibo255000China Shanghai Chenhua Science and Technology Coloration Ltd. Shanghai201804China

Electromagnetic wave(EMW)absorbing materials play a vital role in modern communication and information processing technologies to inhibit information leakage and prevent possible damages to environment and human ***,most of EMW absorbing materials are either composites of two or more phases or in the form of nanosheets,nanowires or nanofibers in order to enhance the EMW absorption performance through dielectric loss,magnetic loss and dielectric/magnetic loss ***,the combination of complex shapes/multi phases and nanosizes may compound the difficulties of materials processing,composition and interfaces control as well as performance maintenance during ***,searching for single phase materials with good stability and superior EMW absorbing properties is *** achieve this goal,the EMW absorbing properties of transition metal carbides TMCs(TM=Ti,Zr,Hf,Nb and Ta)and high entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C which belong to ultrahigh temperature ceramics,were investigated in this *** to the good electrical conductivity and splitting of d orbitals into lower energy t2glevel and higher energy eglevel in TMC6octahedral arrangement,TMCs(TM=Ti,Zr,Hf,Nb and Ta)exhibit good EMW absorbing ***,Hf C and Ta C exhibit superior EMW absorbing *** minimum reflection loss(RLmin)value of Hf C is-55.8 d B at 6.0 GHz with the thickness of 3.8 mm and the effective absorption bandwidth(E_(AB))is 6.0 GHz from 12.0 to 18.0 GHz at thickness of 1.9 mm;the RL_(minvalue)of Ta C reaches-41.1 d B at 16.2 GHz with a thickness of 2.0 mm and the EABis 6.1 GHz with a thickness of 2.2 ***,the electromagnetic parameters,i.e.,complex permittivity and permeability are tunable by forming single phase solid solution or high entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))*** R_(Lminvalue)of high entropy(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C is-38.5 d B at 9.5 GHz with the thickness of 1.9 mm,and the EA

关键词： Transition metal carbides High entropy ceramics Microwave absorption Electromagnetic parameters Electronic structure Crystal field theory

Enabling highly efficient and broadband electromagnetic wave absorption by tuning impedance match in high-entropy transition metal diborides (HETMB_(2))

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Journal of Advanced Ceramics 2021年第6期10卷 1299-1316页

作者： Weiming ZHANG Fu-Zhi DAI Huimin XIANG Biao ZHAO Xiaohui WANG Na NI Rajamallu KARRE shijiang wu Yanchun ZHOU Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China Henan Key Laboratory of Aeronautical Materials and Application Technology School of Material Science and EngineeringZhengzhou University of AeronauticsZhengzhou 450046China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Key Lab of Education Ministry for Power Machinery and Engineering School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai 200240China Zibo Firststar New Material Incorporated Co. Ltd.Zibo 255000China

The advance in communication technology has triggered worldwide concern on electromagnetic wave *** cope with this challenge,exploring high-performance electromagnetic(EM)wave absorbing materials with dielectric and magnetic losses coupling is urgently *** the EM wave absorbers,transition metal diborides(TMB2)possess excellent dielectric loss ***,akin to other single dielectric materials,poor impedance match leads to inferior ***-entropy engineering is expected to be effective in tailoring the balance between dielectric and magnetic losses through compositional ***,three HE TMB2 powders with nominal equimolar TM including HE TMB2-I(TM=Zr,Hf,Nb,Ta),HE TMB2-2(TM=Ti,Zr,Hf,Nb,Ta),and HE TMB2-3(TM=Cr,Zr,Hf,Nb,Ta)have been designed and prepared by one-step boro/carbothermal *** a result of synergistic effects of strong attenuation capability and impedance match,HE TMB2-1 shows much improved performance with the optimal minimum reflection loss(RL_(min))of-59.6 dB(8.48 GHz,2.68 mm)and effective absorption bandwidth(EAB)of 7.6 GHz(2.3 mm).Most impressively,incorporating Cr in HE TMB2-3 greatly improves the impedance match over 1-18 GHz,thus achieving the RLmin of-56.2 dB(8.48 GHz,2.63 mm)and the EAB of 11.0 GHz(2.2 mm),which is superior to most other EM wave absorbing *** work reveals that constructing high-entropy compounds,especially by incorporating magnetic elements,is effectual in tailoring the impedance match for highly conductive compounds,i.e.,tuning electrical conductivity and boosting magnetic loss to realize highly efficient and broadband EM wave absorption with dielectric and magnetic coupling in single-phase materials.

关键词： transition metal diboride(TMB2) high-entropy(HE)ceramics electronic structure microwave absorption dielectric and magnetic losses coupling

Theoretical predictions and experimental verification on the phase stability of enthalpy-stabilized HE TMREB_(2)s

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Journal of Materials Science & Technology 2022年第26期121卷 154-162页

作者： Ze Zhang Shizhen Zhu Fu-Zhi Dai Huimin Xiang Yanbo Liu Ling Liu Zhuang Ma shijiang wu Fei Liu Kuang Sun Yanchun Zhou School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials and Processing TechnologyBeijing 100076China National Key Laboratory of Science and Technology on Materials Under Shock and Impact Beijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120China Yangtze Delta Region Academy of Beijing Institute of Technology Jiaxing 314019China Zibo Firststar New Material Incorporated Co. Ltd.Zibo 255000China Shanghai Chenhua Science and Technology Corporation Ltd. Shanghai 201804China

Transition metal diborides(TMB_(2)s)are the materials of choice in extreme environments due to their excellent thermal and chemical ***,the degradation of oxidation resistance of TMB_(2)s at elevated temperature still hinders their *** cope with this challenge,it is effective to incorporate rare earth elements to form high-entropy transition and rare-earth metal diborides(HE TMREBs).To obtain thermodynamically stable single-phase structures for HE TMREB_(2)s,a“16×16 mixed enthalpy matrix”is constructed using first-principles calculations to predict the single-phase formation ability of120 two-component diborides(TCBs).Through the use of the“16×16 mixed enthalpy matrix”of TCBs,specific combinations of TMB_(2)s and REB_(2)s that are most likely to form single-phase HE TMREB_(2)s are ***,based on the energy distribution of the local mixing enthalpies of all possible configurations,the enthalpy and entropy descriptors of HE TMREB_(2)s(RE=Sc,Lu,Tm,Er,Ho and Dy)are *** is found that the mixing enthalpy plays a critical role in the stability of the single-phase HE TMREB_(2)s,i.e.,HE TMREB_(2)s are enthalpy-stabilized *** experimental results further confirm that enthalpy dominates the thermodynamic domain and drives the stability of REB_(2)s in HE TMREB_(2)*** study validates that enthalpy-stabilized HE TMREB_(2)s can further expand the compositional space of ultrahigh temperature ceramics(UHTCs)and is expected to further improve the oxidation resistance and high temperature properties of UHTCs.

关键词： High-entropy ceramics Ultrahigh temperature ceramics First-principles calculation Mixing enthalpy Transition and rare earth metal diborides

基于财政评审视角的EPC项目工程造价的合理确定

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建筑经济 2023年第S1期44卷 71-73页

作者：吴世将薛春平厦门市财政审核中心福建厦门361013 上海申元工程投资咨询有限公司上海200070

政府投资项目正在大力推进EPC模式,为确保政府资金的合法、合规、合理运用,财政评审中心作为政府的职能部门须对其进行恰当的监管。通过对EPC项目各阶段工程造价的评审,可以保障EPC项目工程造价的准确性、合理性,使参与各方的利益与目... 详细信息

政府投资项目正在大力推进EPC模式,为确保政府资金的合法、合规、合理运用,财政评审中心作为政府的职能部门须对其进行恰当的监管。通过对EPC项目各阶段工程造价的评审,可以保障EPC项目工程造价的准确性、合理性,使参与各方的利益与目标得以实现。

关键词： EPC项目工程造价财政评审

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大城市中心区道路收费问题研究

土木工程学报 2004年第8期37卷 106-109页

作者：吴世江史其信清华大学交通研究所

随着我国大城市交通需求总量的快速增加和交通供给总量增长的相对缓慢 ,我国大城市交通道路拥挤的情况越来越严重。本文主要分析在大城市中心区实施道路收费来缓解大城市中心区的交通拥挤的方法 ,首先建立了大城市中心区道路收费的双层... 详细信息

随着我国大城市交通需求总量的快速增加和交通供给总量增长的相对缓慢 ,我国大城市交通道路拥挤的情况越来越严重。本文主要分析在大城市中心区实施道路收费来缓解大城市中心区的交通拥挤的方法 ,首先建立了大城市中心区道路收费的双层规划模型 ,然后对模型的求解进行了分析。

关键词：道路收费城市中心区双层规划模型

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基于宽带激光拍频的瞬时束匀滑技术

光学学报 2023年第5期43卷 166-173页

作者：吴世江熊皓张寅瑞钟哲强张彬四川大学电子信息学院四川成都610065

针对高功率激光装置对靶面辐照均匀性的需求,提出了一种基于宽带激光拍频的瞬时束匀滑技术。激光集束采用宽带激光,利用连续相位板对焦斑包络进行控制,并结合共轭螺旋相位板使得集束中各子束在焦平面处拍频产生旋转周期不同、位置各异... 详细信息

针对高功率激光装置对靶面辐照均匀性的需求,提出了一种基于宽带激光拍频的瞬时束匀滑技术。激光集束采用宽带激光,利用连续相位板对焦斑包络进行控制,并结合共轭螺旋相位板使得集束中各子束在焦平面处拍频产生旋转周期不同、位置各异的快速运动散斑。合理选择宽带光参数可使得散斑的旋转周期在皮秒至亚皮秒量级,从而达到瞬时匀滑焦斑的目的。通过建立基于宽带激光拍频的瞬时束匀滑技术物理模型,模拟分析了关键参数包括激光带宽和谱线类型对焦斑束匀滑特性的影响和规律,并与双频单色激光拍频技术作了比较分析。研究结果表明,通过合理选取光源谱线类型或增大激光带宽,所提技术可在降低系统要求的基础上增强对激光等离子体不稳定性的抑制,使焦斑实现瞬时匀滑并获得较好的均匀性。

关键词：激光光学惯性约束聚变束匀滑宽带激光激光等离子体不稳定性