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Grain boundary segregation induced strong UHTCs at elevated temperatures:A universal mechanism from conventional UHTCs to high entropy UHTCs

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Journal of Materials Science & Technology 2022年第28期123卷 26-33页

作者： Fu-Zhi Dai Bo Wen Yinjie Sun Yixiao Ren Huimin Xiang yanchun zhou Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China DP Technology Beijing 100044China

Ultra-high temperature ceramics(UHTCs)exhibit a unique combination of excellent properties,including ultra-high melting point,excellent chemical stability,and good oxidation resistance,which make them promising candidates for aerospace and nuclear ***,the degradation of hightemperature strength is one of the main limitations for their ultra-high temperature ***,searching for mechanisms that can help to develop high-performance UHTCs with good high-temperature mechanical properties is urgently *** achieve this goal,grain boundary segregation of a series of carbides,including conventional,medium entropy,and high entropy transition metal carbides,i.e.,Zr_(0.95)W_(0.05)C,TiZrHfC_(3),ZrHfNbTaC_(4),TiZrHfNbTaC_(5),were studied by atomistic simulations with a fitted Deep Potential(DP),and the effects of segregation on grain boundary strength were *** all the studied carbides,grain boundary segregations are realized,which are dominated by the atomic size *** addition,tensile simulations indicate that grain boundaries(GBs)will usually be strengthened due to *** simulation results reveal that grain boundary segregation may be a universal mechanism in enhancing the high-temperature strength of both conventional UHTCs and medium/high entropy UHTCs,since GBs play a key role in controlling the fracture of UHTCs at elevated temperatures.

关键词： UHTCs High entropy ceramics Grain boundary segregation High-temperature strength Machine learning potential

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

Electronic structure and mechanical properties of layered compound YB_2C_2:A promising precursor for making two dimensional(2D) B_2C_2 nets

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Journal of Materials Science & Technology 2017年第9期33卷 1044-1054页

作者： yanchun zhou Huimin Xiang Xiaohui Wang Wei Sun Fu-Zhi Dai Zhihai Feng Science and Technology of Advanced Functional Composite Laboratory Aerospace Research Institute of Materials & Processing Technology Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

Layered compounds play pivotal roles as precursors for producing 2D materials through mechanical exfoliation(micro-mechanical cleavage) or chemical approaches. Therefore, searching for layered compounds with sharp anisotropic chemical bonding and properties becomes emergent. In this work, the stability, electronic structure, elastic properties, and lattice dynamics of YBCwere investigated. Strong anisotropy in elastic properties is revealed, i.e., high Young’s modulus in a-b plane but low Young’s modulus in c direction. The maximum to minimum Young’s modulus ratio is 2.41 and 2.45 for YBCwith P42/mmc and P4/mbm symmetry, respectively. The most likely systems for shear sliding or microdelaminating are(001)[100] and(001)[010]. The anisotropic elastic properties are underpinned by the anisotropic chemical bonding, i.e., strong bonding within the BCnets and weak bonding between Y atom layers and BCnets. YBCis electrically conductive and the contributions to the electrical conductivity are from delocalized Y 4deas well as Bpandpzelectrons. The layered crystal structure, sharp anisotropic mechanical properties, and metallic conductivity endorse YBCpromising as a precursor for new 2D BCnets.

关键词： YB2C2 Layered compounds Electronic structure Mechanical properties 2D graphite like materials

Phase pure and well crystalline Cr2AlB2:A key precursor for two-dimensional CrB

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Journal of Materials Science & Technology 2019年第8期35卷 1593-1600页

作者： Haiming Zhang Fu-Zhi Dai Huimin Xiang Xiaohui Wang Zhili Zhang yanchun zhou School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044 China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials & Processing TechnologyNo. 1 South Dahongmen Road Beijing 100076 China Shenyang National Laboratory for Materials Sciences Institute of Metal ResearchChinese Academy of Sciences72 Wenhua Road Shenyang 110016 China

Phase pure and well crystalline Cr2AlB2 powders are synthesized by heating the mixtures of CrB and Al powders at 900~℃.Cr2AlB2 exhibits nanolaminated morphology which transforms from flake-like crystallite to needle-like grain with the increase of holding *** morphology-structure relationships of Cr2AlB2 are delicately ***,as the precursor for fabrication of Cr2AlB2,high purity CrB powders are also prepared by high-temperature reaction of B and Cr elemental powders at 1800℃.CrB grains grow into regular plate-like *** Rietveld structure refinement,new sets of diffraction data are presented for both CrB and Cr2AlB2 and overlapped peak positions and intensities are revealed which make up for the deficiency of the existing data in ICDD PDF#32-0277(CrB)and ICDD PDF#72-1847(Cr2AlB2).Moreover,since MAB phases are precursors for preparing MBenes,2D-CrBnanosheets are successfully prepared by completely etching out Al atomic layers from Cr2AlB2.2D-CrB crystalizes in CrB structure with two-dimensional lamellar *** the formation mechanism of 2D-CrB is vividly depicted.A system of materials preparation from CrB to Cr2AlB2 and then to 2D-CrB is well established.

关键词： Cr2AlB2 CrB MAB phases 2D-CrB Ultrahigh temperature ceramics

Stabilizing MXene suspension with polyhydric alcohols

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Journal of Materials Science & Technology 2023年第34期165卷 219-224页

作者： Renfei Cheng Junchao Wang Tao Hu Yiming Zhao Yan Liang Xiaohui Wang yanchun zhou 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 Institute of Materials Science and Devices School of Materials Science and EngineeringSuzhou University of Science and TechnologySuzhou 215009China School of Materials Science and Engineering Zhengzhou UniversityZhengzhou 450001China

MXenes have promises in myriad applications by virtue of two-dimensional nature and adjustable functional *** achieve the applications,MXenes are always first prepared in the form of aqueous ***,fast degradation caused by the attack of dissolved oxygen and water molecules is the main obstacle to the application of *** has come to light that the degradation preferentially takes place at defective sites and edges where defects *** tackle this problem and increase the stability,herein,using Ti_(3)C_(2)T_(x)MXene as a model material,we report a simple yet efficient strategy for long term storage of MXene suspension by introducing glycerol,a typical polyhydric *** effectiveness of the strategy is evidenced by structural compositional and morphological *** protects the defective sites of MXene flakes through restricting water and/or oxygen molecules from reactive *** is supported by ab initio molecular dynamics simulations that form hydrogen bonds between MXene and glycerol molecules just over defective *** this mechanism,other polyhydric alcohols,such as ethylene glycol and propylene glycol,are also effective in stabilizing Ti_(3)C_(2)T_(x)MXene *** strategy based on polyhydric alcohols has the potential to be extended to other MXenes,solving the most urgent challenge in the field of MXene engineering.

关键词： MXene Stability Polyhydric alcohols Glycerol Ethylene glycol and propylene glycol

Application of high-throughput first-principles calculations in ceramic innovation

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Journal of Materials Science & Technology 2021年第29期88卷 143-157页

作者： Bin Liu Juanli Zhao Yuchen Liu Jianqi Xi Qian Li Huimin Xiang yanchun zhou School of Materials Science and Engineering Shanghai UniversityShanghai200444China Department of Materials Science and Engineering University of WisconsinMadisonWI53706USA Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Material&Processing TechnologyBeijing100076China

Recent technical progress in the industry has led to an urgent requirement on new materials with enhanced *** meet this multi-property requirement,the materials consisting of three and more elements have attracted increasing ***,facing to the nearly unknown huge multi-component materials system,the traditional trial and error method cannot provide sufficient data ***,an efficient material innovation strategy is *** first-principles calculation based on the density functional theory is a powerful tool for both the accurate prediction of material properties and the identification of its underlying thermodynamics and *** the same time,the advances of computational methods and computer calculation abilities that are orders of magnitude faster than before make the high throughput first-principles calculations *** present,the simulation-assisted material design has become a main branch in the material research field and a great many successes have been *** this article,the advances of the high throughput first-principles calculations are reviewed to show the achievements of the first-principles calculations and guide the future directions of its applications in ceramics.

关键词： First-principles calculations Ceramics Defect Dynamics Structure-property relationship

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

(La0.2Ce0.2Nd0.2Sm0.2Eu0.2)2Zr2O7:A novel high-entropy ceramic with low thermal conductivity and sluggish grain growth rate

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Journal of Materials Science & Technology 2019年第11期35卷 2647-2651页

作者： Zifan Zhao Huimin Xiang Fu-Zhi Dai Zhijian Peng yanchun zhou School of Engineering and Technology China University of GeosciencesBeijing 100083China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China

Fine grains and slow grain growth rate are beneficial to preventing the thermal stress-induced cracking and thermal conductivity increase of thermal barrier *** by the sluggish diffusion effect of high-entropy materials,a novel high-entropy(HE)rare-earth zirconate solid solution(La0.2Ce0.2Nd0.2Sm0.2Eu0.2)2 Zr2 O7 was designed and successfully synthesized in this *** as-synthesized(La0.2Ce0.2Nd0.2Sm0.2Eu0.2)2 Zr2 O7 is phase-pure with homogeneous rare-earth element *** thermal conductivity of as-synthesized(La0.2Ce0.2Nd0.2Sm0.2Eu0.2)2 Zr2 O7 at room temperature is as low as 0.76 W m^-1 K^-***,after being heated at 1500℃for 1-18 h,the average grain size of(La0.2Ce0.2Nd0.2Sm0.2Eu0.2)2 Zr2 O7 only increases from 1.69μm to 3.92μm,while the average grain size of La2Zr2O7 increases from 1.96μm to 8.89μ*** thermal conductivity and sluggish grain growth rate indicate that high-entropy(La0.2Ce0.2Nd0.2Sm0.2Eu0.2)2Zr2O7 is suitable for application as a thermal barrier coating material and it may possess good thermal stress-induced cracking resistance.

关键词： (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)2Zr2O7 High-entropy ceramics Thermal barrier coatings Slow grain growth rate

Crystal structure determination of nanolaminated Ti_(5)Al_(2)C_(3) by combined techniques of XRPD,TEM and ab initio calculations

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Journal of Advanced Ceramics 2012年第4期1卷 268-273页

作者： Hui ZHANG Xiaohui WANG Yonghui MA Luchao SUN Liya ZHENG yanchun zhou Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China Graduate School of Chinese Academy of Sciences Beijing 100039China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyNo.1 South Dahongmen RoadBeijing 100076China

Crystal structure of Ti_(5)Al_(2)C_(3)was determined by means of X-ray powder diffraction(XRPD),transmission electron microscopy(TEM)and ab initio *** contrast to the already known P63/mmc space group that the MAX phases crystallize,it was demonstrated that the R3_m space group could better satisfy the experimental *** lattice parameters are a=0.30564 nm,c=4.81846 nm in a hexagonal unit cell.

关键词： Ti_(5)Al_(2)C_(3) crystal structure layered carbides transmission electron microscopy(TEM)