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Effects of microstructure on fatigue crack propagation behavior in a bi-modal TC11 titanium alloy fabricated via laser additive manufacturing

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Journal of Materials Science & Technology 2019年第2期35卷 403-408页

作者： Yafei Wang Rui Chen Xu Cheng yanyan zhu Jikui Zhang Huaming Wang National Engineering Laboratory of Additive Manufacturing for Large Metallic Components Beihang University School of Materials Science and Engineering Beihang University School of Aeronautic Science and Engineering Beihang University

In this study, the crack propagation behaviors in the equiaxed and equiaxed-columnar grain regions of a heat-treated laser additive manufacturing(LAM) TC11 alloy with a special bi-modal microstructure are investigated. The results indicate that the alloy presents a special bi-modal microstructure that comprises a fork-like primary α(αp) phase surrounded by a secondary α colony(αs) in the α phase matrix after the heat treatment is completed. The samples demonstrate a fast crack growth rate with larger da/d N values through the equiaxed grain sample versus across the equiaxed-columnar grain sample at low K values(<13.8). The differences that are observed between the crack propagation behaviors(in the crack initiation stage) of the samples can be mostly attributed to the different size and morphology of the αp lamellae and αscolony within the grains in the equiaxed and columnar grain regions rather than the grain boundaries. The cracks prefer to grow along the α/β boundary with a smooth propagation route and a fast propagation rate in the equiaxed grain region, where the αpand α clusters have a large ***, in the columnar grain region, small and randomly distributed αplamellae generate a zigzagshaped propagation path with a reduction in the da/d N value. Additionally, the change in the size of the αp lamellae in the equiaxed grains(heat affected bands, HAB) is also observed to influence the propagation behavior of the crack during the crack initiation stage.

关键词： Laser additive manufacturing TC11 titanium alloy Microstructure Fatigue crack propagation path Fatigue crack growth rate

Construction and analysis of a plant transformation binary vector pBDGG harboring a bi-directional promoter fusing dual visible reporter genes

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Journal of Genetics and Genomics 2008年第4期35卷 245-249页

作者： Chunxiao Zhang Ying Gai Wenqi Wang yanyan zhu Xuemei Chen Xiangning Jiang College of Bioscience and Bioengineering Hebei University of Science ＆ Technology Shijiazhuang 050018 China College of Life Sciences and Biotechnology Beijing Forestry University The Tree and Ornamental Plant Breeding and Biotechnology Laboratory of State Forestry Administration Beijing 100083 China Department of Science and Technology Yanshan University Qinhuangdao 066004 China

The constitutive promoter of cauliflower mosaic virus 35S （CaMV 35S） is a polar unidirectional promoter and is widely used in plant genetic engineering. In the present study, the unidirectional CaMV 35S promoter has been modified to a bi-directional promoter by fusing its minimal promoter element to the 5＇ end of CaMV 35S promoter in the opposite orientation. To qualitatively and quantitatively estimate its bi-directional transcriptional function and activity, two visible reporter genes, gusA （13-glucuronidase, GUS） and gfp （green fluorescent protein, GFP）, were fused to the two ends of the promoter in bi-orientations ending with NOS terminator sequences, respectively. Stable expression of gusA and gfp genes in transgenic tobacco （Nicotiana tabacum L.） was visulized by histochemically staining for GUS and fluorescence microscopic observation under UV for GFP in transgenic plants. The expression of two reporter genes showed that the constructed bi-directional promoter did have the bi-directional transcriptional function in both expected orientations. The quantitative estimation of GUS and GFP were determined on a HITACHI F1000 Fluorescence Spectrophotometer with various wavelengths of excitation and emission. The GUS activity varied from g to 250 pmol 4-MU/min/mg protein and the GFP content varied from 0.9 to 1.8 μg/ mg protein in various lines of transgenic tobacco plants. Higher GUS activity generally coupled with lower GFP content, and vice versa.

关键词： bi-directional promoter gusA gene gfp gene Nicotiana tabacum L. expression

Formation mechanism of ring-like segregation and structure during directional solidification under axial static magnetic field

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Journal of Materials Science & Technology 2022年第4期99卷 48-54页

作者： Qingdong Zhong Huaiyu Zhong Hongbo Han Mingyong Shu Long Hou yanyan zhu Xi Li Panzhihua University Panzhihua 417000China State Key Laboratory of Advanced Special Steels Shanghai UniversityShanghai 200072China Shanghai Key Lab of Advanced High-temperature Materials and Precision Forming Shanghai Jiao Tong UniversityShanghai 200240China

The effect of the axial static magnetic field on the macro-segregation and structure in the Al-Cu and NiMn-Ga alloys during directional solidification is investigated experimentally and *** is found that the ring-like segregation and structure in the above-mentioned two alloys form during directional solidification at a certain growth speed under a moderate magnetic *** the Al-Cu and Ni-Mn-Ga alloys,the moderate values of the magnetic field under which the ring-like structure forms are about 0.5 T and 1.0 T at respective growth speed of 10μm/s and 5μm/***,the distributions of the flow and solute in the Al-Cu alloy during directional solidification under the axial static magnetic field is numerically *** results reveal that the rotary thermoelectric(TE)magnetic convection forms in the mushy zone during directional solidification under an axial magnetic *** flow will induce the formation of the ring-like macro-segregation and *** in structures under the magnetic field in the experimental results are in good agreement with the distributions of the TE magnetic convection and solute in the numerical ***,the formation of the ring-like structure and segregation under the magnetic field should be attributed to the solute redistribution induced by the TE magnetic convection.

关键词： Ring-like segregation and structure Magnetic field Directional solidification

Dielectric and Magnetic Properties of (1-x)CaTiO3-xNi0.5Zn0.5Fe2O4 Composite Ceramics

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Journal of Wuhan University of Technology(Materials Science) 2016年第4期31卷 786-790页

作者：陈晨刘银 WANG Chuanchuang zhu yanyan CHENG Qian YI Zhiguo School of Materials Science and Engineering Anhui University of Science and Technology Huainan 232001 China Key Laboratory of Optoelectronic Materials Chemistry and Physics Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences Fuzhou 350002 China

（1-x）CaTiO3-xNi0.5Zn0.5Fe2O4（0 x 1.0） composite ceramics were synthesized by a conventional solid state reaction *** phase formation,microstructure,and dielectric and magnetic properties were investigated by X-ray diffraction,scanning electron microscopy,precision impedance analysis,and vibrating sample magnetometry,*** results indicate that the composite ceramics are composed of both perovskite phase Ca TiO3 and spinel phase *** maximal relative density for 0.5CaTiO3-xNi0.5Zn0.5Fe2O4 composite ceramics reaches 97.8%,as it has been sintered at the temperature of 1260 ℃ for 3 *** constant and loss tangent of（1-x）CaTiO3-xNi0.5Zn0.5Fe2O4 composite ceramics show dispersion in the low frequency *** phase transition temperature of the dielectric constant shifts to lower temperatures with the increase of Ni0.5Zn0.5Fe2O4 *** phenomenon is attributed to that the phase transition temperature of CaTiO3 is higher than that of *** saturation magnetization of （1-x）CaTiO3-xNi0.5Zn0.5Fe2O4 composite ceramics increases with the Ni0.5Zn0.5Fe2O4 ferrite content.

关键词： ceramics dielectric sintered magnetization vibrating impedance saturation attributed tangent perovskite

Pincer iridium(Ⅲ)-catalyzed enantioselective C(sp3)-H functionalization via carbenoid C–H insertion of 3-diazooxindoles with 1,4-cyclohexadiene

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Chinese Chemical Letters 2022年第5期33卷 2437-2441页

作者： Nan Li Xiaoyan Yang yanyan zhu Fang Wang Junfang Gong Maoping Song College of Chemistry Green Catalysis CenterZhengzhou UniversityZhengzhou 450001China

The asymmetric carbenoid C–H insertion of 3-diazooxindoles into 1,4-cyclohexadiene has been accomplished in the presence of chiral bis(imidazoline) NCN pincer iridium(Ⅲ) complexes as the catalysts. With a catalyst loading of 0.5 mol%, the reactions proceeded smoothly at 0℃ to afford a variety of chiral 3-substituted oxindoles in good yields with moderate to excellent enantioselectivities(up to 99% ee). The protocol exhibits good functional group tolerance with respect to 3-diazooxindoles and is readily scaled up to 2 mmol scale without any loss in activity and enantioselectivity. Density functional theory(DFT)calculations have been performed to better understand the reaction mechanism and to explain the stereochemical outcome of the reactions.

关键词： Asymmetric catalysis C–H functionalization Pincer iridium(III)catalyst Carbenoid C–H insertion 3-Diazooxindole Chiral 3-substituted oxindole

Fe-substituted Ba-hexaaluminate with enhanced oxygen mobility for CO_2 capture by chemical looping combustion of methane

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Journal of Energy Chemistry 2019年第2期28卷 50-57页

作者： Fei Huang Ming Tian yanyan zhu Xiaodong Wang Aiqin Wang Lin Li Jian Lin Junhu Wang Fujian Normal University State Key Laboratory of Catalysis Dalian Institute of Chemical PhysicsChinese Academy of Sciences College of Chemical Engineering Northwest University

While Fe-based oxygen carriers(OC) are regarded to be promising for chemical looping combustion(CLC),the decrease of CO_2 selectivity during deep reduction process and the severe agglomeration of Fe_2O_3 often occur after multiple redox cycles due to the low oxygen ***,Fe-substituted Bahexaaluminates(Ba Fe_xAl_(12)– xO_(19),denoted as BF_xA-H,x = 1 and 2) prepared by a modified two-step method exhibited not only higher amount of converted oxygen(Ot) and CH_4 conversion(77% and 81% vs.17%and 75%) than those prepared by the traditional co-precipitation method(BF_xA-C,x = 1 and 2) but also high CO_2 selectivity above 92% during the nearly whole reduction from Fe^(3+) to Fe^(2+).Furthermore,the BFxA-H exhibited the excellent recyclability during 50 *** better performance was ascribed to the markedly enhanced oxygen mobility which resulted from dominant occupancy of Fe cations in Al(5) sites(Fe^5: 71% and 70% vs.49% and 41%) in mirror planes of hexaaluminate leading to larger amount of lattice oxygen coordinated with Fe^5(O–Fe^5)(0.45 and 0.85 mmol/g vs.0.31 and 0.50 mmol/g).The improvement of oxygen mobility also favored the preservation of chemical state of Fe cations in hexaaluminate structure in the re-oxidation step,resulting in the excellent recyclability of BF_xA-H.

关键词： CO2 capture Chemical looping CH4 conversion Oxygen mobility Fe-based hexaaluminate

Microstructure evolution and mechanical behavior of Ni-rich Ni-Mn-Ga alloys under compressive and tensile stresses

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Journal of Materials Science & Technology 2022年第2期97卷 113-122页

作者： Yue Wang Siyuan Yang Ting Zhou Long Hou Lansong Ba Yves Fautrelle Zhongming Ren yanyan zhu Zongbin Li Xi Li State Key Laboratory of Advanced Special Steels Shanghai UniversityShanghai 200072China Shanghai Key Lab of Advanced High-temperature Materials and Precision Forming Shanghai Jiao Tong UniversityShanghai 200240China EPM-Madylam ENSHMG BP 38402St Martin d’Heres CedexFrance School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China Key Laboratory for Anisotropy and Texture of Materials Northeastern UniversityShenyang 110819China

The microstructure evolution and mechanical behavior in directionally solidified Ni-rich Ni-Mn-Ga alloys with nominal compositions of Ni_(58)Mn_(25)Ga_(17) and Ni_(60)Mn_(25)Ga_(15) under compressive and tensile stresses have been *** composition distribution shows the element Ni segregates in gamma phase,while elements Mn and Ga segregate in martensite ***,the microstructure orientation examined by electron backscatter diffraction(EBSD)indicates that beta phase has a preferred growth orientation of(001)_(A) in Ni_(58)Mn_(25)Ga_(17) alloys,while gamma phase has a preferred growth orientation of(001)_(γ) in Ni_(60)Mn_(25)Ga_(15) *** fracture morphology suggests that the existence of ductile y phase can reduce the crack propagation and promote fracture strain,particularly in the Ni_(60)Mn_(25)Ga_(15) ***,Schmid factor and deformation gradient tensor were calculated to well explain the crystallographic evolution during the detwinning under compressive and tensile *** present findings not only elucidate the mechanism ofγphase on the mechanical behavior of Ni-rich Ni-Mn-Ga alloys,but also shed light on the composition design of high temperature Ni-Mn-Ga shape memory alloys.

关键词： Ni-Mn-Ga Gamma phase Tensile Compressive EBSD

Rational design of novel ultra-small amorphous Fe_(2)O_(3)nanodots/graphene heterostructures for all-solid-state asymmetric supercapacitors

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Nano Research 2021年第4期14卷 953-960页

作者： Chenxiao Wu Zhifang Zhang Zhonghui Chen Zuimin Jiang Huiyu Li Haijing Cao Yongsheng Liu yanyan zhu Zebo Fang Xiangrong Yu College of Mathematics and Physics Shanghai University of Electric PowerShanghai 200090China Key Lab for Special Functional Materials of Ministry of Education School of Materials Science and EngineeringHenan UniversityKaifeng 475004China Department of Physics Fudan UniversityShanghai 200433China Department of Physics Shaoxing UniversityShaoxing 312000China Department of Medical Imaging Zhuhai Peoples HospitalZhuhai Hospital affiliated with Jinan UniversityZhuhai 519000China

Constructing graphene-based heterostructures with large interfacial area is an efficient approach to enhance the electrochemical performance of supercapacitors but remains great challenges in their ***,a novel ultra-small amorphous Fe_(2)O_(3)nanodots/graphene heterostructure(a-Fe_(2)O_(3)NDs/RGO)aerogel was facilely synthesized via excessive metal-ion-induced self-assembly and subsequent calcination route using Prussian blue/graphene oxide(PB/GO)composite aerogel as *** deliberately designed a-Fe_(2)O_(3)NDs/RGO heterostructure offers a highly interconnected porous conductive network,large heterostructure interfacial area,and plenty of accessible active sites,greatly facilitating the electron transfer,electrolyte diffusion,and pseudocapacitive *** obtained a-Fe_(2)O_(3)NDs/RGO aerogel could be used as flexible free-standing electrodes after mechanical compression,which exhibited a significantly enhanced specific capacitance of 347.4 F·g^(-1)at 1 A·g^(-1),extraordinary rate capability of 184 F·g^(-1)at 10 A·g^(-1),and decent cycling *** the as-prepared a-Fe_(2)O_(3)NDs/RGO as negative electrodes and the Co_(3)O_(4)NDs/RGO as positive electrodes,an all-solid-state asymmetric supercapacitor(a-Fe_(2)O_(3)NDs/RGO//Co_(3)O_(4)NDs/RGO asymmetric supercapacitor(ASC))was assembled,which delivered a high specific capacitance of 69.1 F·g^(-1)at 1 A·g^(-1)and an impressive energy density of 21.6 W·h·k·g^(-1)at 750 W·k·g^(-1),as well as good cycling stability with a capacity retention of 94.3%after 5,000 *** work provides a promising avenue to design high-performance graphene-based composite electrodes and profound inspiration for developing advanced flexible energy-storage devices.

关键词： graphene heterostructures amorphous Fe_(2)O_(3) Co_(3)O_(4) all-solid-state asymmetric supercapacitors

Microstructural,crystallographic,and mechanical characteristics in Ni-Mn-Ga alloys directionally solidified under a transverse magnetic field

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Journal of Materials Science & Technology 2023年第11期142卷 10-21页

作者： Xi Li Long Hou Siyuan Yang Ting Zhou Yue Wang Xing Yu Zongbin Li Daoyong Cong Yves Fautrelle Zhongming Ren yanyan zhu Shanghai Key Lab of Advanced High-Temperature Materials and Precision Forming Shanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Advanced Special Steels Shanghai UniversityShanghai 200072China Key Laboratory for Anisotropy and Texture of Materials Northeastern UniversityShenyang 110819China Beijing Advanced Innovation Center for Materials Genome Engineering State Key Laboratory for Advanced Metals and MaterialsUniversity of Science and Technology BeijingBeijing 100083China EPM-Madylam ENSHMG BPSt Martin d’Heres 38402 CEDEXFrance

In this study,the effect of transverse magnetic field-assisted directional solidification(MFADS)on the microstructures in Ni-Mn-Ga alloys has been *** results show that the magnetic field is capable of inducing transversal macrosegregation perpendicular to the magnetic field,causing the emergence of martensite clusters in the austenite ***,the magnetic field alleviates the microseg-regation on a dendritic scale and promotes the preferred growth of austenite *** the basis of the above investigation,several special samples are designed using the MFADS to study the crystallographic evolution and mechanical behavior during thermal/stress-induced martensite *** martensite cluster in the austenite matrix is used to investigate the martensite transformation and growth under cooling-heating *** crystallographic relationship and phase boundary microstructure between martensite and austenite have been *** addition,the microsegregation on a dendritic scale can significantly influence the martensite variant distribution,corresponding to the performance during compressive circles based on the analysis of the deformation gradient *** stress-induced superelasticity is closely dependent on orientation,well explained from the perspective of different resolved shear stress factors and correspondence variant pair formation transformation *** crystallographic evolution has been characterized during in-situ stress-induced *** findings not only deepen the understanding of martensite transformation and mechanical behavior under a thermal/stress field in Ni-Mn-Ga alloys but also propose a promising strategy to obtain microstructure-controllable functional alloys by MFADS.

关键词： Magnetic field-assisted directional solidification Segregation Orientation Martensite transformation Superelasticity