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PVA-ECC高温冷却后力学特性与微观损伤机理

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哈尔滨工业大学学报 2024年第9期56卷 140-149页

作者：武芳文何岚清段钧淇王广倩刘来君杨飞长安大学公路学院西安710064 长安大学建筑工程学院西安710061

为研究工程水泥基复合材料(engineered cementitious composite,ECC)高温后的力学性能和微观特征,对ECC进行了高温后材料力学性能试验和微观特征观测。对常温(25℃)、200℃、300℃、400℃及500℃自然冷却和喷水冷却后的ECC试件开展了抗... 详细信息

为研究工程水泥基复合材料(engineered cementitious composite,ECC)高温后的力学性能和微观特征,对ECC进行了高温后材料力学性能试验和微观特征观测。对常温(25℃)、200℃、300℃、400℃及500℃自然冷却和喷水冷却后的ECC试件开展了抗压和抗折性能试验,并结合扫描电镜分析了ECC微观结构损伤特征以及探究了ECC高温后损伤机理。实验结果表明:高温后ECC表面未发生剥落,500℃以内未见爆裂现象,随着温度升高,纤维由混凝土表面逐渐向内部熔化,且失水增多,最大烧失率13.9%;力学性能方面,ECC自然冷却后抗压强度随温度升高呈现先降低后升高再降低的现象,而喷水冷却后抗压强度随温度的升高单调降低,且强度降低显著;高温后抗折强度随温度升高逐步下降,自然冷却降低幅度较喷水冷却显著;结合微观结构变化,ECC经历高温时,纤维部分熔化导致纤维与基体的黏结性能减弱;随着温度升高水化产物之间逐渐呈现独立存在的分散体,但喷水冷却后未水化颗粒二次水化现象明显,使ECC抗折强度较自然冷却提升17%。ECC具有良好的热稳定性,且冷却方式影响ECC材料的表观特性、力学性能和微观特征。

关键词：桥梁工程力学特性高温试验 ECC 微观结构冷却方式

Entropy regulation in LaNbO_(4)-based fergusonite to implement high-temperature phase transition and promising dielectric properties

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Journal of Advanced Ceramics 2023年第5期12卷 1067-1080页

作者： Deqin Chen Na Yan Xuefeng Cao Fengrong Li laijun liu Qinghua Shen Huanfu Zhou Chunchun Li Guangxi University Key Laboratory of Non-ferrous Metal Oxide Electronic Functional Materials and Devices College of Material Science and EngineeringGuilin University of TechnologyGuilin 541004China Guangxi Key Laboratory of Embedded Technology and Intelligent System Guilin University of TechnologyGuilin 541004China

High-entropy effect is a novel design strategy to optimize properties and explore novel *** this work,(La_(1/5)Nd_(1/5)Sm_(1/5)Ho_(1/5)Y_(1/5))NbO_(4)(5RNO)high-entropy microwave dielectric ceramics were successfully prepared in the sintering temperature(S.T.)range of 1210–1290℃via a solid-phase reaction route,and medium-entropy(La_(1/3)Nd_(1/3)Sm_(1/3))NbO_(4) and(La_(1/4)Nd_(1/4)Sm_(1/4)Ho_(1/4))NbO_(4)(3RNO and 4RNO)ceramics were *** effects of the entropy(S)on crystal structure,phase transition,and dielectric performance were *** entropy increase yields a significant increase in a phase transition temperature(from monoclinic fergusonite to tetragonal scheelite structure).Optimal microwave dielectric properties were achieved in the high-entropy ceramics(5RNO)at the sintering temperature of 1270℃for 4 h with a relative density of 98.2%and microwave dielectric properties of dielectric permittirity(ε_(r))=19.48,quality factor(Q×f)=47,770 GHz,and resonant frequency temperature coefficient(τ_(f))=–13.50 ppm/℃.This work opens an avenue for the exploration of novel microwave dielectric material and property optimization via entropy engineering.

关键词： high-entropy ceramics microwave dielectric property ion disorder far-infrared

Giant electrocaloric effect in BiFeO_(3) and La codoped PbZr_(0.7)Ti_(0.3)O_(3) epitaxial thin films in a broad temperature range

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Journal of Materiomics 2022年第1期8卷 156-165页

作者： Miaomiao Zhang laijun liu Rusen Yang Ping Yu Qi Zhang Biaolin Peng Guangxi Key Laboratory of Processing for Non-ferrous Metal and Featured Materials Center on Nanoenergy ResearchGuangxi UniversityNanning530004China Guangxi Key Laboratory of Optical and Electronic Materials and Devices Guilin University of TechnologyGuilin541004China School of Advanced Materials and Nanotechnology Xidian UniversityXi'an710126China College of Material Science and Engineering Sichuan UniversityChengdu610064China BCMaterials Basque Centre for MaterialsApplications and NanostructuresUPV/EHU Science Park48940LeioaSpain IKERBASQUE Basque Foundation for SciencePlaza Euskadi5Bilbao48009Spain

Ferroelectric thin/thick films with large electrocaloric(EC)effect are critical for solid state cooling ***,large positive EC effects with two EC peaks in a broad temperature range(~100 K)were obtained in 0.95Pb_(0.92)La_(0.08)(Zr_(0.70)Ti_(0.30))_(0.98)O_(3)-0.05BiFeO_(3)(BFO-La-codoped PZT)epitaxial thin films deposited on the(100),(110)and(111)oriented SrTiO_(3)(STO)substrates by a sol-gel *** thin film deposited on the(111)oriented STO substrate exhibited a stronger EC effect(~20.6 K at 1956 kV/cm)near room ***,the thin films deposited on the(100)and(110)oriented STO substrates exhibited a stronger EC effect(~18.8 K at 1852 kV/cm and~20.8 K at 1230 kV/cm,respectively)around the peak of the dielectric permittivity(T_(m),~375 K).Particularly,as the direction of the applied electric field was switched(E<0),the DT of the(100)-oriented thin films around T_(m) was enhanced significantly from 18.8 K to 38.1 *** self-induced-poling during the preparing process maybe plays a key role on the magic *** can be concluded that the BFO-La-codoped PZT epitaxial thin films are promising candidates for application in the next solid-state cooling devices.

关键词： Sol-gel Epitaxial thin film Electrocaloric effect Self-induce-poled

Constructing Nanoscale Topology on the Surface of Microfibers Inhibits Fibroblast Fibrosis

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Advanced Fiber Materials 2022年第5期4卷 1219-1232页

作者： Yongjie Jiao Xiaojing Li Jinjie Chen Chaojing Li laijun liu Xingxing liu Fujun Wang Guang Chen Lu Wang Key Laboratory of Textile Science and Technology Ministry of EducationCollege of TextilesDonghua UniversityShanghai 201620China Healthcare Department of Taizhou Hospital Affiliated to Wenzhou Medical University(Zhejiang Province Taizhou Hospital) Taizhou 317000China Department of Vascular Surgery Taizhou Hospital Affiliated to Wenzhou Medical University(Zhejiang Province Taizhou Hospital)Taizhou 317000China

Fibrosis is a common problem in soft tissue regeneration,often caused by the differentiation of fibroblasts into *** of the nanoscale topology that regulates the mechanical transduction of cells,nanofibers or nanoparticles are commonly used to modulate fibroblast ***,the strength of nanofibers is insufficient,and the physi-ological toxicity of nanoparticles still remains to be *** this study,self-induced crystallization was used to construct nano-protrusions on the random and aligned polycaprolactone microfibers to regulate the behavior of *** results revealed that the mechanical properties of microfibers with a nanoscale topology were *** staining manifested that nano-protrusions impeded the activation of integrins and vinculins,thereby inhibiting the nuclear transfer of Yes-associated protein,resulting in a decrease in the expression ofα-smooth muscle *** topology of microfibers hampered the activation of the Rho/ROCK signalling *** general,we used a simple process to con-struct a fibrous scaffold with a micro-nano multilevel *** structure can hinder the transformation of fibroblasts into myofibroblasts on both random and aligned fibers,which is expected to prevent fibrosis.

关键词： Electrospinning Topology Fibroblast Fibrosis

Oxygen vacancy migration and its lattice structural origin in A-site non-stoichiometric bismuth sodium titanate perovskites

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Journal of Materiomics 2022年第3期8卷 719-729页

作者： Jing Shi Xiao liu Fangyuan Zhu Wenchao Tian Yuanhua Xia Tangyuan Li Rongrong Rao Tao Zhang laijun liu Key Laboratory of Electronic Equipment Structure Design(MOE) School of Mechano-Electronic EngineeringXidian UniversityXi'an710071China School of Materials Science and Engineering Xi'an University of Science and TechnologyXi'an710054China Shanghai Synchrotron Radiation Facility Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai201204China Institute of Nuclear Physics and Chemistry China Academy of Engineering PhysicsMianyang621900China Frontier Institute of Science and Technology Xi'an Jiaotong UniversityXi'an710049China College of Science Xi'an University of Science and TechnologyXi'an710054China Key Laboratory of Nonferrous Materials and New Processing Technology(MOE) College of Materials Science and EngineeringGuilin University of TechnologyGuilin541004China

Off-stoichiometry of perovskite structural Bi0.5Na0.5TiO3(BNT)ferroelectrics can give rise to considerable oxide-ion *** inherent structural characteristics are urgent to be resolved due to its particular sensitivity of the conduction mechanism to the nominal composition and synthesis ***,a thorough study of the temperature-dependent neutron,X-ray diffraction and Raman spectrum is carried out on a series of equivalently substituted A-site deficient non-stoichiometric and pristine *** transition and defect association are systemically investigated in these dominated rhombohedral phases at room temperature,associated with well saturated ferroelectric *** structural evolution identified by Rietveld refinements and the origin of the electrical performance are clarified at elevated temperatures,focusing on the subtle distortions of ionic displacements,oxygen octahedral tilts and local chemical environments for oxygen *** ion migration ability mediated by oxygen vacancies that are not energetically favorable in BNT mainly depends on the external substitutional disorder,and is strongly affected by the dopant *** with the lone pair substitution concept,superior oxide ionic conductivity is achieved,and an alternative strategy is provided in designing BNT based oxide ion conductors.

关键词： Ferroelectrics Bismuth sodium titanate Oxide ion conductors Neutron powder diffraction Oxygen vacancy

Phase engineering in NaNbO_(3) antiferroelectrics for high energystorage density

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Journal of Materiomics 2022年第4期8卷 753-762页

作者： Zhengu Chen Shuaifei Mao Li Ma Gengguang Luo Qin Feng Zhenyong Cen Fujita Toyohisa Xiuning Peng laijun liu Huanfu Zhou Changzheng Hu Nengneng Luo School of Chemistry&Chemical Engineering Guangxi UniversityNanning530004China Guangxi Key Laboratory of Processing for Non-ferrous Metallic and Featured Materials School of ResourcesEnvironment and MaterialsGuangxi UniversityNanning530004China Center on Nanoenergy Research School of ResourcesEnvironment and MaterialsGuangxi UniversityNanning530004China School of Civil Engineering and Architecture Guangxi UniversityNanning530004China College of Materials Science and Engineering Guilin University of TechnologyGuilin541004China

The NaNbO_(3) antiferroelectrics have been considered as a potential candidate for dielectric capacitorsapplications. However, the high-electric-field-unstable antiferroelectric phase resulted in low energystorage density and efficiency. Herein, good energy storage properties were realized in (1-x)NaNbO_(3)- xNaTaO_(3) ceramics, by building a new phase boundary. As a result, a high recoverable energy density(Wrec) of 2.2 J/cm3 and efficiency (h) of 80.1% were achieved in 0.50NaNbO_(3)-0.50NaTaO_(3) ceramic at300 kV/cm. The excellent energy storage performance originates from an antiferroelectric-paraelectricphase boundary with simultaneously high polarization and low hysteresis, by tailoring the ratio ofantiferroelectric and paraelectric phases. Moreover, the 0.50NaNbO_(3)-0.50NaTaO_(3) ceramic also exhibitedgood temperature and frequency stability, together with excellent charge-discharge performance. Theresults pave a good way of designing new NaNbO_(3)-based antiferroelectrics with good energy storageperformance.

关键词： NaNbO_(3)ceramics Antiferroelectrics Paraelectrics Energy storage density Dielectric capacitors

Probing thermally-induced structural evolution during the synthesis of layered Li-, Na-, or K-containing 3d transition-metal oxides

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eScience 2022年第2期2卷 183-191页

作者： Weibo Hua Xiaoxia Yang Nicola PMCasati laijun liu Suning Wang Volodymyr Baran Michael Knapp Helmut Ehrenberg Sylvio Indris School of Chemical Engineering and Technology Xi'an Jiaotong UniversityXi'anShaanxi710049China Institute for Applied Materials(IAM) Karlsruhe Institute of Technology(KIT)Hermann-von-Helmholtz-Platz 1D-76344Eggenstein-LeopoldshafenGermany College of Materials Science and Engineering Guilin University of TechnologyGuilin541004China Paul Scherrer Institut(PSI) WLGA/2295232Villigen PSISwitzerland Deutsches Elektronen-Synchrotron(DESY) Notkestr.85Hamburg22607Germany

Layered alkali-containing 3d transition-metal oxides are of the utmost importance in the use of electrode materials for advanced energy storage applications such as Li-,Na-,or K-ion batteries.A significant challenge in the field of materials chemistry is understanding the dynamics of the chemical reactions between alkali-free precursors and alkali species during the synthesis of these *** this study,in situ high-resolution synchrotron-based X-ray diffraction was applied to reveal the Li/Na/K-ion insertion-induced structural transformation mechanism during high-temperature solid-state *** in situ diffraction results demonstrate that the chemical reaction pathway strongly depends on the alkali-free precursor type,which is a structural matrix enabling phase *** phase analysis identifies for the first time the decomposition of lithium sources as the most critical factor for the formation of metastable intermediates or impurities during the entire process of Li-rich layered Li[Li_(0.2)Ni_(0.2)Mn_(0.6)]O_(2) *** the alkali ions have different ionic radii,Na/K ions tend to be located on prismatic sites in the defective layered structure(Na_(2/3-x)[Ni_(0.25)Mn_(0.75)]O_(2) or K_(2/3-x)[Ni_(0.25)Mn_(0.75)]O_(2))during calcination,whereas the Li ions prefer to be localized on the tetrahedral and/or octahedral sites,forming O-type structures.

关键词： In situ sXRD Structural evolution 3d transition-metal oxides Layered structure High-temperature solid-state reaction

Compositional modulation in ZnGa2O4 via Zn2+/Ge4+ co-doping to simultaneously lower sintering temperature and improve microwave dielectric properties

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Journal of Advanced Ceramics 2021年第6期10卷 1360-1370页

作者： Ying XIONG Hongyuan XIE Zhenggang RAO laijun liu Zhengfeng WANG Chunchun LI College of Information Science and Engineering Guilin University of Technology Guangxi Key Laboratory of Optical and Electronic Materials and Devices College of Material Science and Engineering Guilin University of Technology School of Materials Science and Engineering Nanchang University

AB2O4-type spinels with low relative permittivity（εr） and high quality factor（Q × f） are crucial to high-speed signal propagation systems. In this work, Zn2+/Ge4+co-doping to substitute Ga3+in ZnGa2O4was designed to lower the sintering temperature and adjust the thermal stability of resonance frequency simultaneously. Zn1+xGa2-2xGexO4（0.1 ≤ x ≤ 0.5） ceramics were synthesised by the conventional solid-state method. Zn2+/Ge4+co-substitution induced minimal variation in the macroscopical spinel structure, which effectively lowered the sintering temperature from 1385 to 1250 ℃. All compositions crystallized in a normal spinel structure and exhibited dense microstructures and excellent microwave dielectric properties. The compositional dependent quality factor was related to the microstructural variation, being confirmed by Raman features. A composition with x = 0.3 shows the best dielectric properties with εr≈ 10.09, Q × f ≈ 112,700 THz, and τ_f ≈-75.6 ppm/℃. The negative τ_f value was further adjusted to be near-zero through the formation of composite ceramics with TiO2.

关键词： ceramics spinel composition modulation dielectric properties

Structure evolution,dielectric,and conductivity behavior of(K_(0.5)Na_(0.5))NbO_(3)-Bi(Zn_(2/3)Nb_(1/3))O_(3) ceramics

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Journal of Advanced Ceramics 2021年第4期10卷 809-819页

作者： Tianxiang YAN Kaiyuan CHEN Chengqi LI Min liu Jie WANG Liang FANG laijun liu College of Mechanical and Control Engineering&College of Materials Science and Engineering Guilin University of TechnologyGuilin 541004China Institute of Fluid Engineering Equipment Jiangsu Industrial Technology Research InstituteJiangsu UniversityZhenjiang 212013China Key Laboratory for RF Circuits and Systems Ministry of Education&Key Laboratory of Large Scale Integrated DesignHangzhou Dianzi UniversityHangzhou 310018China

(1-x)K_(0.5)Na_(0.5)Nb0_(3-x)Bi(Zn_(2/3)Nb_(1/3))0_(3)((1-x)KNN-xBZN,x=0.010,0.015,0.020,0.025,and 0.030)lead-free ceramics were fabricated via a traditional solid-state *** crystal structure,microstructure,dielectric,and conductivity behavior of this system were *** with X-ray diffraction(XRD)patterns,Rietveld refinement,and dielectric spectroscopy,an orthorhombic phase was determined for x=0.010,an orthorhombic-tetragonal mixed phase was identified for x=0.015,and a rhombohedral symmetry appears in 0.020≤x≤*** 0.98KNN-0.02BZN and 0.975KNN-0.025BZN ceramics exhibit stable permittivity and low dielectric loss tangent(tan)in wide temperature ranges owing to the combination of rhombohedral-tetragonal step-like feature and the diffuse phase transition from tetragonal to *** activation energies of dielectric relaxation and conductivity behavior at high temperatures initially decrease slightly,then drop sharply,and finally decline slowly,which could be attributed to microstructure morphologies and the concentration of oxygen vacancies.

关键词： ceramic crystal structure dielectric spectroscopy oxygen vacancies