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Regulating the formation ability and mechanical properties of high-entropy transition metal carbides by carbon stoichiometry

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Journal of Materials Science & Technology 2022年第26期121卷 181-189页

作者： Juntao Song Guiqing Chen Huimin Xiang Fuzhi Dai Shun Dong Wenbo Han Xinghong Zhang yanchun zhou Science and Technology on Advanced Composite in Special Environments Laboratory Harbin Institute of TechnologyHarbin150080China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing100076China

Tremendous efforts have been dedicated to promote the formation ability of high-entropy transition metal ***,the majority of methods for the synthesis of high-entropy transition metal carbides still face the challenges of high temperature,low efficiency,additional longtime post-treatment and uncontrollable *** cope with these challenges,high-entropy transition metal carbides with regulatable carbon stoichiometry(HE TMC)were designed and synthesized,achieving improved ability for single phase solid solutions formation,promoting of sintering and controllable mechanical *** typical composition series,i.e.,easily synthesized(ZrHfTaNb)C(ZHTNC)and difficultly synthesized(Zr_(0.25)Hf_(0.25)Ta_(0.25)Ti_(0.25))C(ZHTTC)are selected to demonstrate the promoting formation ability of single phase solid solutions from carbon stoichiometry *** phase high-entropy ZHTTC,which has been proven difficult in forming a single phase solid solution,can be prepared with the decrease of C/TM ratio under 2000℃;while the high-entropy ZHTNC,which has been proven easy in forming a single phase solid solution,can be synthesized at lower temperatures with the decrease of C/TM *** synergistic effect of entropy stabilization and reduced chemical bond strength gaining from carbon stoichiometry deviations is responsible for the formation of single phase solid solutions and the promoted sintering of HE *** example,the relative density of bulk(ZrHfTaNb)C(SPS-ZHTNC)increases from 90.98%to 94.25%with decreasing the C/TM atomic ratio from 0.9 to *** importantly,the room temperature flexural strength,fracture toughness and brittleness index of SPS-ZHTNCcan be tuned in the range of 384 MPa–419 MPa,4.41 MPam–4.73 MPamand 3.679μm–4.083μm,***,the HE TMCprepared by adjusting the ratio of carbon to refractory transition metal oxides have great potential for achieving low temperature synthesis,promoted sintering and tunable properties.

关键词： Carbon stoichiometry High-entropy ceramics Transition metal carbide Low temperature synthesis Tunable mechanical properties

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High porosity and low thermal conductivity high entropy(Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2C

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Journal of Materials Science & Technology 2019年第8期35卷 1700-1705页

作者： Heng Chen Huimin Xiang Fu-Zhi Dai Jiachen Liu Yiming Lei Jie Zhang yanchun zhou Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials & Processing Technology Beijing 100076 China Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education School of Materials Science and Engineering Tianjin University Tianjin 300072 China Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

Porous ultra-high temperature ceramics(UHTCs)are promising for ultrahigh-temperature thermal insulation ***,the main limitations for their applications are the high thermal conductivity and densification of porous structure at high *** order to overcome these obstacles,herein,porous high entropy(Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))C was prepared by a simple method combing in-situ reaction and partial *** high entropy(Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))C possesses homogeneous microstructure with grain size in the range of 100–500 nm and pore size in the range of 0.2–1μm,which exhibits high porosity of 80.99%,high compressive strength of 3.45 MPa,low room temperature thermal conductivity of 0.39 W·m^-1K^-1,low thermal diffusivity of 0.74 mm^2·s^-1and good high temperature *** combination of these properties renders porous high entropy(Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))Cpromising as light-weight ultrahigh temperature thermal insulation materials.

关键词： Ultrahigh temperature ceramics (UHTCs) High entropy ceramics (Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))C Thermal conductivity Porosity

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Tunnel-structured willemite Zn_(2)SiO_(4):Electronic structure,elastic,and thermal properties

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Journal of Advanced Ceramics 2022年第8期11卷 1249-1262页

作者： Ruqiao DAI Renfei CHENG Jiemin WANG Chao ZHANG Cuiyu LI Hailong WANG 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 Advanced Computing East China Sub-center Suma Technology Company LimitedKunshan 215300China School of Material Science and Engineering Zhengzhou UniversityZhengzhou 450001China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China

Willemite Zn_(2)SiO_(4)crystallizes in such a way that Zn and Si are tetrahedrally coordinated with O in an ionic–covalent manner to form ZnO_(4)and SiO_(4)tetrahedra as the building *** tetrahedra are corner-sharing,of which one SiO_(4)tetrahedron connects eight ZnO_(4)tetrahedra,and one ZnO_(4)tetrahedron links four ZnO_(4)tetrahedra and four SiO_(4)*** unique crystallographic configuration gives rise to parallel tunnels with a diameter of 5.7Åalong the c-axis *** tunnel structure of Zn_(2)SiO_(4)definitely correlates with its interesting elastic and thermal *** the one hand,the elastic modulus,coefficient of thermal expansion(CTE),and thermal conductivity are ***_(2)SiO_(4)has low Vickers hardness of 6.6 GPa at 10 N and low thermal conductivity of 2.34 W/(m·K)at 1073 *** the other hand,the elastic modulus and CTE along the c-axis are significantly larger than those along the a-and b-axes,showing obvious elastic and thermal expansion ***,the Young’s modulus along the z direction(Ez=179 GPa)is almost twice those in the x and y directions(Ex=Ey=93 GPa).The high thermal expansion anisotropy is ascribed to the empty tunnels along the c-axis,which are capable of more accommodating the thermal expansion along the a-and *** striking properties of Zn_(2)SiO_(4)in elastic modulus,hardness,CTE,and thermal conductivity make it much useful in various fields of ceramics,such as low thermal expansion,thermal insulation,and machining tools.

关键词： Zn_(2)SiO_(4) electronic structure elastic properties thermal expansion thermal conductivity

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Anti-perovskite carbides and nitrides A3BX: A new family of damage tolerant ceramics

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Journal of Materials Science & Technology 2020年第5期40卷 64-71页

作者： Wei Zhang Yuchen Liu yanchun zhou Wai-Yim Ching Qian Li Wenxian Li Jiong Yang Bin Liu School of Materials Science and Engineering Shanghai UniversityShanghai 200444China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials and Processing TechnologyBeijing 100076China Department of Physics and Astronomy University of Missouri-Kansas CityKansas CityMO 64110USA Materials Genome Institute Shanghai UniversityShanghai 200444China

Synergy effect of high stiffness and good damage tolerance is always the focus of the development of novel structural ***,a new strategy on the future damage tolerant material design is proposed to merge the strong covalent bonds into the easy shear deformed A3B metallic *** goal is realized by studying 126 A3BX phases and establishing a database on their mechanical properties through highthroughput first principles *** combination strategies of A3B metallic box and XA3 octahedra show intensive influences on the expected mechanical *** family includes 49 quasi-ductile *** them,four compounds(Ti3AlN,Mn3CuN,Ti3TlN and Ni3SnN)exhibit excellent damage tolerance and the other six compounds(Mn3NiN,Mn3GaC,Mn3GaN,Mn3SnC,Cr3SnN,Co3AlC)show both damage tolerance and high *** competitive high temperature properties are demonstrated through the detailed investigation on the typical cases of Co3Al C and Ti3 Tl *** study leads a novel direction for the design of the future quasi-ductile and high stiffness ceramics.

关键词： Ceramics High-throughput calculation A3BX phases Damage tolerance

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Improved thermal stability and infrared emissivity of high-entropy REMgAl_(11)O_(19)and LaMAl_(11)O_(19)(RE=La,Nd,Gd,Sm,Pr,Dy;M=Mg,Fe,Co,Ni,Zn)

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Journal of Materials Science & Technology 2022年第9期104卷 131-144页

作者： Haolin Zhu Ling Liu Huimin Xiang Fu-Zhi Dai Xiaohui Wang Zhuang Ma Yanbo Liu 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&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 Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

LaMgAl_(11)O_(19)(LMA),characterized by high melting point,low density and thermal conductivity as well as good infrared emissivity,is regarded as a potential candidate for the thermal protection of hypersonic ***,the unsatisfied phase stability at high temperature results in declining of the emissivity below 6μm,which limits the extensive applications of LaMgAl_(11)O_(19).In order to overcome this obstacle,three dense bulk high-entropy ceramics,(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Pr_(0.2))MgAl_(11)O_(19)(HE LMA-1),(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Dy_(0.2))Mg Al_(11)O_(19)(HE LMA-2)and La(Mg_(0.2)Fe_(0.2)Co_(0.2)Ni_(0.2)Zn_(0.2))Al_(11)O_(19)(HE LMA-3),were designed and successfully prepared through solid state reaction at 1700℃for 4 h in one *** analyses show that the phase compositions of HE LMA-1,HE LMA-2 and HE LMA-3 are single-phase solid solutions with the relative density of 95.61%,95.49%and 94.31%,*** treatment experiments demonstrate that the phase composition of HE LMA-1 remains a single phase after high-temperature heating,while second phase appears in other two *** stability of HE LMA-1 is attributed to small average size differenceδ(~4%)of constitute ***,the average emissivity of HE LMA-1 in the range of 3-6μm reaches 0.9,which is significantly higher than that of LMA and other two HE LMA *** emissivity of all samples remains above 0.95 from 6 to 10μ*** the far infrared region(10-14μm),although the emissivity of these specimens decreases slightly,it still exceeds *** UV-Vis absorption spectra indicate that the formation of many discrete impurity energy levels with small intervals in HE LMA-1 promotes the f electrons to transit between adjacent impurity energy levels and conduction band,which enhances the infrared emission of HE LMA-1 below 6μ*** a word,with improved phase stability and thermal emissivity in infrared range,high-entropy REMgAl_(11)O_(19),especially(La_(0.2)Nd_(0.2)

关键词： High-entropy ceramics LaMgAl_(11)O_(19) Thermal stability Infrared emissivity UV-Vis absorption

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(La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4: A high-entropy rare-earth phosphate monazite ceramic with low thermal conductivity and good compatibility with Al2O3

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Journal of Materials Science & Technology 2019年第12期35卷 2892-2896页

作者： Zifan Zhao Heng Chen Huimin Xiang Fu-Zhi Dai Xiaohui Wang Zhijian Peng yanchun zhou School of Engineering and Technology China University of GeosciencesBeijing100083China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing100076China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyangJ10016China

Low thermal conductivity, matched thermal expansion coefficient and good compatibility are general requirements for the environmental/thermal barrier coatings(EBCs/TBCs) and interphases for Al2O3 f/Al2O3 composites. In this work, a novel high-entropy(HE) rare-earth phosphate monazite ceramic (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 is designed and successfully synthesized. This new type of HE rare-earth phosphate monazite exhibits good chemical compatibility with Al2O3, without reaction with Al2O3 as high as 1600℃ in air. Moreover, the thermal expansion coefficient(TEC) of HE (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4(8.9 × 10^-6/℃ at 300–1000℃) is close to that of Al2O3. The thermal conductivity of HE (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 at room temperature is as low as 2.08 W·m^-1·K^-1, which is about 42% lower than that of La PO4. Good chemical compatibility, close TEC to that of Al2O3, and low thermal conductivity indicate that HE (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 is suitable as a candidate EBC/TBC material and an interphase for Al2O3 f/Al2O3 composites.

关键词： (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 High-entropy ceramics Al2O3f/Al2O3ceramic matrix composites Environmental barrier coating materials Interphase material Thermal expansion coefficient Thermal conductivity Solution synthesis Rare-earth phosphates Monazite

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Zr_(2)SeB and Hf_(2)SeB:Two new MAB phase compounds with the Cr_(2)AlC-type MAX phase(211 phase)crystal structures

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Journal of Advanced Ceramics 2022年第11期11卷 1764-1776页

作者： Qiqiang ZHANG yanchun zhou Xingyuan SAN Wenbo LI Yiwang BAO Qingguo FENG Salvatore GRASSO Chunfeng HU Key Laboratory of Advanced Technologies of Materials Ministry of EducationSchool of Materials Science and EngineeringSouthwest Jiaotong UniversityChengdu 610031China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China Hebei Key Lab of Optic–Electronic Information and Materials College of Physics Science and TechnologyHebei UniversityBaoding 071002China State Key Laboratory of Green Building Materials China Building Materials AcademyBeijing 100024China

The ternary or quaternary layered compounds called MAB phases are frequently mentioned recently together with the well-known MAX ***,MAB phases are generally referred to layered transition metal borides,while MAX phases are layered transition metal carbides and nitrides with different types of crystal structure although they share the common nano-laminated structure *** order to prove that MAB phases can share the same type of crystal structure with MAX phases and extend the composition window of MAX phases from carbides and nitrides to borides,two new MAB phase compounds Zr_(2)SeB and Hf_(2)SeB with the Cr_(2)AlC-type MAX phase(211 phase)crystal structure were discovered by a combination of first-principles calculations and experimental verification in this ***-principles calculations predicted the stability and lattice parameters of the two new MAB phase compounds Zr_(2)SeB and Hf_(2)*** they were successfully synthesized by using a thermal explosion method in a spark plasma sintering(SPS)*** crystal structures of Zr_(2)SeB and Hf_(2)SeB were determined by a combination of the X-ray diffraction(XRD),scanning electron microscopy(SEM),and high-resolution transmission electron microscopy(HRTEM).The lattice parameters of Zr_(2)SeB and Hf_(2)SeB are a=3.64398Å,c=12.63223Åand a=3.52280Å,c=12.47804Å,*** the atomic positions are M at 4f(1/3,2/3,0.60288[Zr]or 0.59889[Hf]),Se at 2c(1/3,2/3,1/4),and B at 2a(0,0,0).And the atomic stacking sequences follow those of the Cr_(2)AlC-type MAX *** work opens up the composition window for the MAB phases and MAX phases and will trigger the interests of material scientists and physicists to explore new compounds and properties in this new family of materials.

关键词： Zr_(2)SeB and Hf_(2)SeB MAB phase MAX phase first-principles calculations thermal explosion synthesis

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Advances on strategies for searching for next generation thermal barrier coating materials

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Journal of Materials Science & Technology 2019年第5期35卷 833-851页

作者： Bin Liu Yuchen Liu Changhua Zhu Huimin Xiang Hongfei Chen Luchao Sun Yanfeng Gao yanchun zhou School of Materials Science and Engineering Shanghai University Shanghai 200444 China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Material & Processing Technology Beijing 100076 China High-performance Ceramics Division Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

Thermal barrier coating(TBC) materials play important roles in gas turbine engines to protect the Nibased super-alloys from the high temperature airflow damage. High melting point, ultra-low thermal conductivity, large thermal expansion coefficient, excellent damage tolerance and moderate mechanical properties are the main requirements of promising TBC materials. In order to improve the efficiency of jet and/or gas turbine engines, which is the key of improved thrust-to-weight ratios and the energysaving, significant efforts have been made on searching for enhanced TBC materials. Theoretically, density functional theory has been successfully used in scanning the structure and properties of materials, and at the same time predicting the mechanical and thermal properties of promising TBC materials for high and ultrahigh temperature applications, which are validated by subsequent experiments. Experimentally,doping and/or alloying are also widely applied to further decrease their thermal conductivities. Now, the strategy through combining theoretical calculations and experiments on searching for next generation thermal insulator materials is widely adopted. In this review, the common used techniques and the recent advantages on searching for promising TBC materials in both theory and experiments are summarized.

关键词： Thermal barrier coatings Oxide First principles calculation Thermal properties Mechanical properties

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Temperature Fluctuation Synthesis/Simultaneous Densification and Microstructure Control of Titanium Silicon Carbide (Ti_3SiC_2) Ceramics

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Journal of Materials Science & Technology 2000年第5期16卷 461-465页

作者： Zhimei SUN and yanchun zhou (Ceramic and Composite Department, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, China) Ceramic and Composite Department Institute of Metal Research Chinese Academy of Sciences Shenyang 110015 China

A novel temperature fluctuation synthesis/simultaneous densification process was developed for the preparation of Ti3SiC2 bulk ceramics. In this process. Si is used as an in-situ liquid forming phase and it is favorable for both the solid-liquid synthesis and the densification of Ti3SiC2 rainies. The present work demonstrated that the temperature fluctuation synthesis/simultaneous densification process is one of the most effective and simple methods for the preparation of Ti3SiC2 bulk materials providing relatively low synthesis temperature. short reaction time; and simultaneous synthesis and densification. This work also showed the capability to control the microstructure, e.g., the preferred orientation, of the bulk Ti3SiC2 materials simply by applying the hot pressing pressure at different Stages of the temperature fluctuation process. And textured Ti3SiC2 bulk materials with {002} faces of laminated Ti3SiC2 grains normal to the hot pressing axis were prepared.

关键词： Ceramics Temperature Fluctuation Synthesis/Simultaneous Densification and Microstructure Control of Titanium Silicon Carbide Ti3SiC2 SiC

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Synthesis and mechanical and elevated temperature tribological properties of a novel high-entropy(TiVNbMoW)C_(4.375) with carbon stoichiometry deviation

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Journal of Advanced Ceramics 2023年第2期12卷 242-257页

作者： Jicheng LI yanchun zhou Yunfeng SU Shuna CHEN Qiuan SUN Hengzhong FAN Junjie SONG Litian HU Yongsheng ZHANG State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China

High-entropy carbides are a nascent group of ceramics that are promising for high-temperature applications due to the combination of good stability,high hardness(H),high strength,and superior creep resistance that they *** to high melting points and low lattice diffusion coefficients,however,the high-entropy carbides are usually difficult to consolidate to a nearly full *** cope with this challenge,herein,binary carbides including TiC,V_(8)C_(7),NbC,Mo_(2)C,and WC with different carbon stoichiometry were used to prepare dense high-entropy(TiVNbMoW)C_(4.375),and the influence of carbon vacancy on formation ability and mechanical properties of carbon-deficient high-entropy(TiVNbMoW)C_(4.375) were ***,although the starting binary carbides have different crystal structures and carbon stoichiometry,the as-prepared high-entropy material showed a rock-salt structure with a relatively high density(98.1%)and good mechanical properties with hardness of 19.4±0.4 GPa and fracture toughness(KIC)of 4.02 MPa·m^(1/2).More importantly,the high-entropy(TiVNbMoW)C_(4.375) exhibited low coefficient of friction(COF)at room temperature(RT)and 800℃.Wear rate(W)gradually increased with the temperature rising,which were attributed to the formation of low-hardness oxidation films at high temperatures to aggravate *** 800℃,lubricating films formed from sufficient oxidation products of V_(2)O_(5) and MoO_(3) effectively improved tribological behavior of the high-entropy(TiVNbMoW)C_(4.375).Wear mechanisms were mainly abrasive wear resulting from grain pullout and brittle fracture as well as oxidation wear generated from high-temperature *** results are useful as valuable guidance and reference to the synthesis of high-entropy ceramics(HECs)for sliding parts under high-temperature serving conditions.

关键词： high-entropy ceramics(HECs) transition metal(TM)carbides carbon stoichiometry deviation tribological performances wear

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