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Equiatomic 9-cation high-entropy carbide ceramics of the IVB,VB,and VIB groups and thermodynamic analysis of the sintering process

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Journal of Advanced Ceramics 2022年第7期11卷 1082-1092页

作者： Yuan QIN ji-xuan liu Yongcheng LIANG Guo-Jun ZHANG State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringDonghua UniversityShanghai 201620China Institute of Functional Materials Donghua UniversityShanghai 201620China College of Science Donghua UniversityShanghai 201620China

The preparation of high-entropy(HE)ceramics with designed composition is essential for verifying the formability models and evaluating the properties of the ***,inevitable oxygen contamination in non-oxide ceramics will result in the formation of metal oxide impurity phases remaining in the specimen or even escaping from the specimen during the sintering process,making the elemental compositions of the HE phase deviated from the designed *** this work,the preparation and thermodynamic analysis during the processing of equiatomic 9-cation HE carbide(HEC9)ceramics of the IVB,VB,and VIB groups were studied focusing on the removing of the inevitable oxygen impurity existed in the starting carbide powders and the oxygen contamination during the powder mixing *** results demonstrate that densification by spark plasma sintering(SPS)by directly using the mixed powders of the corresponding single-component carbides will inhibit the oxygen-removing carbothermal reduction reactions,and most of the oxide impurities will remain in the sample as(Zr,Hf)O_(2)*** of the mixed powders at high temperatures in vacuum will remove most part of the oxygen impurity but result in a remarkable escape of gaseous Cr owing to the oxygen-removing reaction between Cr_(3)C_(2)and various oxide *** is found that graphite addition enhances the oxygen-removing effect and simultaneously prevents the escape of gaseous *** the other hand,although WC,VC,and Mo2C can also act as oxygen-removing agents,there is no metal-containing gaseous substance formation in the temperature range of this *** using the heat-treated powders with added graphite,equiatomic HEC9 ceramics were successfully prepared by SPS.

关键词： high-entropy(HE)carbide oxygen impurity carbothermal reduction reaction phase composition thermodynamic analysi

High-entropy pyrochlores with low thermal conductivity for thermal barrier coating materials

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Journal of Advanced Ceramics 2019年第4期8卷 576-582页

作者： Fei LI Lin ZHOU ji-xuan liu Yongcheng LIANG Guo-Jun ZHANG State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and Engineering Institute of Functional Materials College of ScienceDonghua University

High-entropy pyrochlore-type structures based on rare-earth zirconates are successfully produced by conventional solid-state reaction method. Six rare-earth oxides(La2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, and Y2O3) and ZrO2 are used as the raw powders. Five out of the six rare-earth oxides with equimolar ratio and ZrO2 are mixed and sintered at different temperatures for investigating the reaction process. The results demonstrate that the high-entropy pyrochlores(5RE1/5)2 Zr2O7 have been formed after heated at 1000 ℃. The(5RE1/5)2Zr2O7 are highly sintering resistant and possess excellent thermal stability. The thermal conductivities of the(5RE1/5)2Zr2O7 high-entropy ceramics are below 1 W·m–1·K–1 in the temperature range of 300–1200 ℃. The(5RE1/5)2Zr2O7 can be potential thermal barrier coating materials.

关键词： thermal barrier coating(TBC) pyrochlore high-entropy ceramics thermal conductivity

Fast grain growth phenomenon in high-entropy ceramics:A case study in rare-earth hexaaluminates

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Journal of Advanced Ceramics 2023年第1期12卷 111-121页

作者： Lin ZHOU ji-xuan liu Tian-Zhe TU Yue WU Guo-Jun ZHANG State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringInstitute of Functional MaterialsDonghua UniversityShanghai 201620China

It is generally reported that the grain growth in high-entropy ceramics at high temperatures is relatively slower than that in the corresponding single-component ceramics owing to the so-called sluggish diffusion *** this study,we report a fast grain growth phenomenon in the high-entropy ceramics(La_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Gd_(0.2))MgAl_(11)O_(19)(HEMA)prepared by a conventional solid-state reaction *** results demonstrate that the grain sizes of the as-sintered HEMA ceramics are larger than those of the corresponding five single-component ceramics prepared by the same pressureless sintering process,and the grain growth rate of HEMA ceramics is obviously higher than those of the five single-component ceramics during the subsequent heat *** fast grain growth phenomenon indicates that the sluggish diffusion effect cannot dominate the grain growth behavior of the current high-entropy *** X-ray photoelectron spectroscopy(XPS)analysis reveals that there are more oxygen vacancies(OV)in the high-entropy ceramics than those in the single-component ceramics owing to the variable valance states of Eu *** high-temperature electrical conductivities of the HEMA ceramics support this *** is considered that the high concentration of OV and its high mobility in HEMA ceramics contribute to the accelerated migration and diffusion of cations and consequently increase the grain growth *** on this study,it is believed that multiple intrinsic factors for the high-entropy ceramic system will simultaneously determine the grain growth behavior at high temperatures.

关键词： high-entropy ceramics rare-earth hexaaluminate fast grain growth electrical conductivity

Mechanical properties of hot-pressed high-entropy diboride-based ceramics

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Journal of Advanced Ceramics 2020年第4期9卷 503-510页

作者： ji-xuan liu Xiao-Qin Shen Yue Wu Fei Li Yongcheng Liang Guo-Jun Zhang State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringCollege of SciencesInstitute of Functional MaterialsDonghua UniversityShanghai201620China

High-entropy ceramics attract more and more attention in recent ***,mechanical properties especially strength and fracture toughness for high-entropy ceramics and their composites have not been comprehensively *** this work,high-entropy(Ti0.2Zr0.2Hf0.2Nb0.2Ta 0.2)B2(HEB)monolithic and its composite containing 20 vol%SiC(HEB–20SiC)are prepared by hot *** addition of SiC not only accelerates the densification process but also refines the microstructure of HEB,resulting in improved mechanical *** obtained dense HEB and HEB–20SiC ceramics hot pressed at 1800℃exhibit four-point flexural strength of 339±17 MPa and 447±45 MPa,and fracture toughness of 3.81±0.40 MPa·m1/2 and 4.85±0.33 MPa·m1/2 measured by single-edge notched beam(SENB)*** deflection and branching by SiC particles is considered to be the main toughening mechanisms for the HEB–20SiC *** hardness Hv0.2 of the sintered HEB and HEB–20SiC ceramics is 23.7±0.7 GPa and 24.8±1.2 GPa,*** the increase of indentation load,the hardness of the sintered ceramics decreases rapidly until the load reaches about 49 N,due to the indentation size *** on the current experimental investigation it can be seen that the room temperature bending strength and fracture toughness of the high-entropy diboride ceramics are within ranges commonly observed in structure ceramics.

关键词： high-entropy ceramics high-entropy diboride flexural strength fracture toughness indentation size effect

Synergistic effects of high-entropy engineering and particulate toughening on the properties of rare-earth aluminate-based ceramic composites

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Journal of Advanced Ceramics 2023年第4期12卷 861-872页

作者： Tian-Zhe Tu ji-xuan liu Yue Wu Lin Zhou Yongcheng Liang Guo-Jun Zhang State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringCollege of ScienceInstitute of Functional MaterialsDonghua UniversityShanghai 201620China

Rare-earth aluminates(REAIOs)are potential thermal barrier coating(TBC)materials,but the relatively high thermal conductivity(ko,~13.6 W·m^(-1)·K^(-1))and low fracture toughness(K_(1c),-1.9 MPa·m^(1/2))limit their *** work proposed a strategy to improve their properties through the synergistic effects of high-entropy engineering and particulate ***-entropy(La_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Gd_(0.2)AlO_(3))(HEAO)-based particulate composites with different contents of high-entropy(La_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Gd_(0.2))_(2)Zr_(2)O_(7)(HEZO)were designed and successfully prepared by solid-state *** high-entropy feature of both the matrix and secondary phases causes the strong phonon scattering and the incorporation of the HEZO secondary phase,remarkedly inhibiting the grain growth of the HEAO *** a result,HEAO-xHEZO(x=0,5%,10%,25%,and 50%in volume)ceramic composites show low thermal conductivity and high fracture *** to the most commonly applied TBC material-yttria stabilized-zirconia(YSZ),the HEAO-25%HEZO particulate composite has a lower thermal conductivity of 0.96-1.17 W·m^(-1)·K^(-1)(298-1273 K),enhanced fracture toughness of 3.94±0.35 MPa-m,and comparable linear coefficient of thermal expansion(CTE)of 10.5×10^(-6)K^(-1).It is believed that the proposed strategy should be revelatory for the design of new coating materials including TBCs and environmental barrier coatings(EBCs).

关键词： high-entropy particulate composites thermal barrier coating(TBC) thermal properties mechanical properties fine grains

A high entropy silicide by reactive spark plasma sintering

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Journal of Advanced Ceramics 2019年第1期8卷 148-152页

作者： Yuan QIN ji-xuan liu Fei LI Xiaofeng WEI Houzheng WU Guo-Jun ZHANG State Key Laboratory for Modification of Chemical Fibers and Polymer Materials Institute of Functional Materials College of Materials Science and Engineering Donghua University Department of Materials Loughborough University

A high-entropy silicide(HES),(Ti_(0.2) Zr_(0.2) Nb_(0.2) Mo_(0.2) W_(0.2))Si_2 with close-packed hexagonal structure is successfully manufactured through reactive spark plasma sintering at 1300 ℃ for 15 *** elements in this HES are uniformly distributed in the specimen based on the energy dispersive spectrometer analysis except a small amount of zirconium that is combined with oxygen as impurity particles. The Young's modulus, Poisson's ratio,and Vickers hardness of the obtained(Ti_(0.2) Zr_(0.2) Nb_(0.2) Mo_(0.2) W_(0.2))Si_2 are also measured.

关键词： high-entropy ceramics high-entropy silicide spark plasma sintering silicide

Effect of native carbon vacancies on evolution of defects in ZrC_(1-x)under He ion irradiation and annealing

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Journal of Materials Science & Technology 2022年第24期119卷 87-97页

作者： Weichao Bao Xin-Gang Wang Ying Lu ji-xuan liu Shikuan Sun Guo-Jun Zhang Fangfang Xu State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of CeramicsShanghai 200050China State Key Laboratory for Modification of Chemical Fibers and Polymer Materials Institute of Functional MaterialsDonghua UniversityShanghai 201620China School of Material Science and Energy Engineering Foshan UniversityFoshan 528000China

The dynamic study of radiation-induced defects with annealing is critical for the material design for nextgeneration nuclear energy *** native vacancy could affect the development of defects,which lacks *** the present work,the as-hot pressed ZrC_(1-x)(x=0,0.15,0.3)ceramics which comprised crystallites of a few microns in size with different amounts of carbon vacancies were irradiated by 540 ke V He^(2+)ions at room temperature with a fluence of 1×10^(17)/cm^(2).The radiation-induced lattice expansion was found to be a common phenomenon in a sequence of ZrC_(0.85)≥ZrC_(1.0)>ZrC_(0.7).Both X-ray and electron diffractions confirmed maintenance of structural integrity without amorphization after *** the irradiated region,only“black-dot”type defects,i.e.,clusters of point defects were observed while no helium-induced cavities,cracks,or extended dislocations were *** as-irradiated ZrC_(1-x)were then annealed at different high *** annealing at 800℃,very tiny helium-induced cavities were found to be generated and the crystal lattice recovered to a great extent,especially for the sub-stoichiometric *** annealed at 1500℃,all the samples almost fully recovered the crystal lattices close to those of as-hot pressed ***,large cavities and extended dislocations were *** increasing amount of native carbon vacancies,the size of cavities increased while the length and density of extended dislocations *** changes of lattice parameters during irradiation and annealing processes have been interpreted by the kinetics of ***,the correlation between native vacancies and damage behavior is discussed.

关键词： Native carbon vacancies Zirconium carbide He ions irradiation Helium bubbles Dislocations

Structural integrity and damage of ZrB_(2) ceramics after 4 MeV Au ions irradiation

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Journal of Materials Science & Technology 2021年第13期72卷 223-230页

作者： Weichao Bao Stuart Robertson jia-Wei Zhao ji-xuan liu Houzheng Wu Guo-Jun Zhang Fangfang Xu State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of CeramicsShanghai 200050China State Key Laboratory for Modification of Chemical Fibers and Polymer Materials Institute of Functional MaterialsDonghua UniversityShanghai 201620China Department of Materials Loughborough UniversityLeicestershire LE113TUUnited Kingdom

Ultra-high temperature ceramics have been considered as good candidates for plasma facing materials due to their combination of high melting point,high strength and hardness,high thermal conductivity as well as good chemical *** this study,zirconium diboride has been chosen to investigate its irradiation damage *** by 4 MeV Au^(2+)with a total fluence of 2.5×10^(16)cm^(-2),zirconium diboride ceramic shows substantial resilience to irradiation-induced damage with its structural integrity well maintained but mild damage at lattice *** incident X-ray diffraction evidences no change of the hexagonal structure in the irradiated region but its lattice parameter a increased and c decreased,giving a volume shrinkage of 0.46%.Density functional theory calculation shows that such lattice shrinkage corresponds to a non-stoichiometric compound as *** energy-loss spectroscopy in a transmission electron microscope revealed an increase of valence electrons in zirconium,suggesting boron vacancies were indeed developed by the *** ng the irradiation depth,long dislocations were observed inside top layer with a depth of 750 nm where the implanted Au ions reached the peak *** the top layer,a high density of Frank dislocations is formed by the cascade collision down to a depth of 1150 *** the features show the potential of ZrB_(2) to be used as structural material in nuclear system.

关键词： Zirconium diboride Heavy ion irradiation Boron vacancy Dislocation Structure integration

Assessing inflammation in Chinese subjects with subtypes of heart failure: an observational study of the Chinese PLA Hospital Heart Failure Registry

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Journal of Geriatric Cardiology 2019年第4期16卷 313-319页

作者： Bo-Han liu Yan-Guang LI ji-xuan liu Xiao-jing ZHAO Qia jiA Chun-Lei liu Zhen-Guo XU Kun-Lun HE Beijing Key Laboratory of Chronic Heart Failure Precision Medicine Chinese PLA General HospitalBeijingChina Department of Cardiology Chinese PLA General HospitalBeijingChina

Background Inflammation is an important element of the pathophysiological process of heart failure (HF) and is correlated with subtypes of HF. The association between multiple biomarkers of inflammation and HF subtypes in Chinese subjects remains unclear. This study aimed to compare the differences in inflammation biomarkers among Chinese patients with different subtypes of HF who have been identified to date. Methods We included 413 consecutive patients with HF,including 262 with preserved ejection fraction (HFpEF),55 with middle-ranged ejection fraction (HFmrEF) and 96 with reduced ejection fraction (HFrEF). Ten inflammation biomarkers were analyzed and compared according to the HF subtypes. One hundred contemporary non-HF subjects were also recruited as the control group. Moreover,the correlations between the inflammatory biomarkers and left ventricular ejection fraction of the HF subtypes were assessed. Results The mean age of the HF patients was 65.0 ± 12.0 years,65.8% were male. Distinct subtypes of HF demonstrated different inflammation biomarker panels. IL-6,PTX-3,ANGPTL-4 and TNF-α were correlated with HFrEF;IL-1β and PTX-3 were correlated with HFmrEF;and IL-1β and IL-6 were correlated with HFpEF. The multivariable logistic regression showed that IL-1β[relative ratio (RR)= 1.08,95% CI: 1.02–1.15,P = 0.010],IL-6 (RR = 1.03,95% CI: 1.01–1.06,P = 0.016),PTX-3 (RR = 1.31,95% CI: 1.11–1.55,P = 0.001),and ANGPTL-4 (RR = 1.05,95% CI: 1.02–1.07,P < 0.001) were independently associated with HF,while IL-6 (RR = 1.03,95% CI: 1.01–1.04,P = 0.019),PTX-3 (RR = 1.23,95% CI: 1.06–1.43,P = 0.007),and ANGPTL-4 (RR = 1.03,95% CI: 1.01–1.06,P = 0.005) were independently associated with the HF subtype. Conclusions Diverse inflammation biomarkers have multifaceted presentations according to the subtype of HF,which may illustrate the diverse mechanisms of inflammation in Chinese HF patients. IL-6,PTX-3,and ANGPTL-4 were independent inflammation factors associated with HFrEF and H

关键词： Biomarkers Chinese patients Correlation Heart failure Inflammation