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Purification performance on molten steel of novel Al_(2)O_(3)-based ceramic filter prepared from microporous powder and nano-Al_(2)O_(3) powder

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Journal of Iron and Steel Research(International) 2024年第6期31卷 1535-1546页

作者： Zhe Chen Wen Yan Ying Liu Guang-qiang Li Shao-song Hong Nan Li The State key laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan 430081HubeiChina Jiangsu Shengnai New Materials Co. Ltd.Taizhou 225534JiangsuChina

Reticulated ceramic foam filters provide an effective way to purify molten steel by removing non-metallic *** proposed a novel strategy to improve the purification performance of Al_(2)O_(3)-based ceramic filters by using microporous corundum-spinel raw materials to replace dense raw *** kinds of Al_(2)O_(3)-based ceramic filters fabricated from dense α-Al_(2)O_(3) micro-powder or microporous corundum-spinel powder were selected to carry out the immersion tests with molten *** the one hand,the higher surface roughness of the filter skeleton prepared from microporous raw materials increased the adsorption capacity of skeleton surface on inclusions in molten *** the other hand,the higher apparent porosity and larger pore size of the filter skeleton were more beneficial to the penetration of molten steel in the micropores of *** reaction process at the solid-liquid interface also improved the wettability of the interface between skeleton and molten steel,resulting in a larger penetration depth and a better adsorption effect on the *** summary,the novel Al_(2)O_(3)-based ceramic filter prepared with microporous corundum-spinel powder and addition of 5 wt.% nano-Al_(2)O_(3) powder reduced the total oxygen content of the steel from 40.2×10^(-4) to 12.7×10^(-4) wt.% by 68.4% and the Al content from 0.46 to 0.18 wt.% by 60.9% after immersion test,presenting the most excellent purification performance on molten steel.

关键词： Al_(2)O_(3)-based ceramic filter Microporous corundum-spinel powder Non-metallic inclusion-microstructure Molten steel purification

Effect of Interface Form on Creep Failure and Life of Dissimilar Metal Welds Involving Nickel-Based Weld Metal and Ferritic Base Metal

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Chinese Journal of Mechanical Engineering 2024年第1期37卷 265-285页

作者： Xiaogang Li Junfeng Nie Xin Wang Kejian Li Haiquan Zhang Institute of Nuclear and New Energy Technology Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of EducationTsinghua UniversityBeijing 100084China Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China

For dissimilar metal welds(DMWs)involving nickel-based weld metal(WM)and ferritic heat resistant steel base metal(BM)in power plants,there must be an interface between WM and BM,and this interface suffers mechanical and microstructure mismatches and is often the rupture location of premature *** this study,a new form of WM/BM interface form,namely double Y-type interface was designed for the *** behaviors and life of DMWs containing double Y-type interface and conventional I-type interface were compared by finite element analysis and creep tests,and creep failure mechanisms were investigated by stress-strain analysis and microstructure *** applying double Y-type interface instead of conventional I-type interface,failure location of DMW could be shifted from the WM/ferritic heat-affected zone(HAZ)interface into the ferritic HAZ or even the ferritic BM,and the failure mode change improved the creep life of *** interface premature failure of I-type interface DMW was related to the coupling effect of microstructure degradation,stress and strain concentrations,and oxide notch on the WM/HAZ *** creep failure of double Y-type interface DMW was the result of Type IV fracture due to the creep voids and micro-cracks on fine-grain boundaries in HAZ,which was a result of the matrix softening of HAZ and lack of precipitate pinning at fine-grain *** double Y-type interface form separated the stress and strain concentrations in DMW from the WM/HAZ interface,preventing the trigger effect of oxide notch on interface failure and inhibiting the interfacial microstructure *** is a novel scheme to prolong creep life and enhance reliability of DMW,by means of optimizing the interface form,decoupling the damage factors from WM/HAZ interface,and then changing the failure mechanism and shifting the failure location.

关键词： Dissimilar metal weld Nickel-based weld metal Ferritic heat resistant steel Interface Creep strain microstructure Failure mechanism Creep life

Enhanced interlayer neutral excitons and trions in MoSe_(2)/MoS_(2)/MoSe_(2)trilayer heterostructure

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Nano Research 2022年第6期15卷 5640-5645页

作者： Biao Wu Haihong Zheng Shaofei Li Junnan Ding Jun He Zongwen Liu Yanping Liu School of Physics and Electronics Hunan Key Laboratory for Super-microstructure and Ultrafast ProcessCentral South UniversityChangsha 410083China State key laboratory of High-Performance Complex Manufacturing Central South UniversityChangsha 410083China School of Chemical and Biomolecular Engineering The University of SydneyNSW 2006Australia The University of Sydney Nano Institute The University of SydneyNSW 2006Australia Shenzhen Research Institute of Central South University Shenzhen 518057China

Van der Waals heterostructures have recently emerged,in which two distinct transitional metal dichalcogenide(TMD)monolayers are stacked vertically to generate interlayer excitons(IXs),offing new opportunites for the design of optoelectronic ***,the bilayer heterostructure with type-II band alignment can only produce low quantum ***,we present the observation of interlayer neutral excitons and trions in the MoSe_(2)/MoS_(2)/MoSe_(2)trilayer heterostructure(Tri-HS).In comparison to the 8 K bilayer heterostructure,the addition of a MoSe_(2)layer to the Tri-HS can significantly increase the quantum yield of *** is believed the two symmetrical type-II band alignments formed in the Tri-HS could effectively promote the IX radiation *** analyzing the photoluminescence(PL)spectrum of the IXs at cryogenic temperature and the power dependence,the existence of the interlayer trions was *** results provide a promising platform for the development of more efficient optoelectronic devices and the investigation of new physical properties of TMDs.

关键词： transitional metal dichalcogenide trilayer heterostructure enhanced interlayer exciton effect photoluminescence interlayer exciton

Dynamic control of moirépotential in twisted WS_(2)-WSe_(2)heterostructures

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Nano Research 2022年第8期15卷 7688-7694页

作者： Shaofei Li Haihong Zheng Junnan Ding Biao Wu Jun He Zongwen Liu Yanping Liu School of Physics and Electronics Hunan Key Laboratory for Super-microstructure and Ultrafast ProcessCentral South UniversityChangsha 410083China State key laboratory of High-Performance Complex Manufacturing Central South UniversityChangsha 410083China School of Chemical and Biomolecular Engineering The University of SydneyNSW 2006Australia The University of Sydney Nano Institute The University of SydneyNSW 2006Australia Shenzhen Research Institute of Central South University Shenzhen 518057China

Moirésuperlattices are formed by a lattice mismatch or twist angle in two-dimensional materials,which can generate periodical moirépotentials leading to strong changes in the band structure,resulting in new quantum ***,the experimental engineering of in-situ deformation of moiréheterostructures remains ***,we demonstrate a dynamic local deformation of the twisted heterostructures using a diamond anvil cell(DAC),enabling in-situ dynamic modulation of moirépotential in twisted WS_(2)–WSe_(2)heterostructures at room *** of the twisted heterostructure increases the moirépotential,causing a red shift of the moiréexciton resonance,and observed the red shift of the intralayer exciton resonance up to 16.3 meV(less than 1.1 GPa).The blue shift of the interlayer excitons of twisted WS_(2)–WSe_(2)heterostructures shows an evident transition of the pressure sensitive exciton,induced by the dominant effect of modifying the band structure on optical *** with the spectral changes of pressurized Raman,which further demonstrated that the DAC can efficiently regulate the interlayer *** results offer an effective strategy for in-situ dynamic modulation of moirépotential,providing a promising platform for the development of novel quantum devices.

关键词： moirésuperlattices twisted heterostructures moirépotential diamond anvil cell(DAC)

2,7-二辛基[1]苯并噻吩并[3,2-b]苯并噻吩(C8-BTBT)的真空沉积薄膜生长、形貌和界面电子结构

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Journal of Central South University 2022年第4期29卷 1041-1061页

作者：魏俊华牛冬梅高永立 hunan key laboratory of super microstructure and ultrafast process School of Physics and ElectronicsCentral South UniversityChangsha 410083China Department of Physics and Astronomy University of RochesterRochesterNY 14627USA

两种材料的界面是物质交换和能量交换的场点,在电子器件中起着关键作用。同种材料可在不同基底材料上形成多种不同的薄膜形态,并展现不同的器件性能。本文综述了高迁移率有机小分子半导体2,7-二辛基[1]苯并噻吩并[3,2-b]苯并噻吩(C8-BT... 详细信息

两种材料的界面是物质交换和能量交换的场点,在电子器件中起着关键作用。同种材料可在不同基底材料上形成多种不同的薄膜形态,并展现不同的器件性能。本文综述了高迁移率有机小分子半导体2,7-二辛基[1]苯并噻吩并[3,2-b]苯并噻吩(C8-BTBT)在不同的功能材料上的真空沉积薄膜生长、界面过程以及界面电子结构。C8-BTBT分子的薄膜生长取决于衬底与C8-BTBT以及C8-BTBT分子之间的相互作用。在原子级光滑衬底上,C8-BTBT薄膜一般以层状模式生长,而在粗糙衬底上,C8-BTBT薄膜倾向于岛状模式生长。在电介质、半导体和导电衬底上沉积的初始C8-BTBT分子层显示出略有不同的晶格结构。界面层C8-BTBT分子的取向取决于衬底与有机分子的相互作用,但是在厚膜情况下表面层终将改变为直立构型。C8-BTBT与电介质或高功函数导电材料接触时表现为电子供体,这通常会诱导出指向C8-BTBT的界面偶极层,以及C8-BTBT侧朝向界面的向上能带弯曲。尽管C8-BTBT具有空气稳定性,但仍会在某些过渡金属,如镍、钴和化合物界面发生化学反应。C8-BTBT界面电子结构与其薄膜形貌和分子取向有关,当膜厚增加、分子取向从平躺到直立时,C-H会形成表面偶极层,导致电离能减小。本文提供了C8-BTBT的界面物理和化学过程的机制分析,并为基于C8-BTBT的电子器件的优化设计和制造提供参考。

关键词：界面薄膜形貌组织构型生长模式电子结构化学反应界面偶极

Effect of Microstructural Characteristics on Fracture Toughness in Direct Energy Deposited Novel Ti-6Al-4V-1Mo Alloy

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Acta Metallurgica Sinica(English Letters) 2024年第1期37卷 119-131页

作者： Chao Xia Kexin Zhao Xin Zhou Yuqi He Panpan Gao Hengxin Zhang Guangrui Gao Fengying Zhang Hua Tan School of Material Science and Engineering Chang’an UniversityXi’an710064China Science and Technology on Plasma Dynamics laboratory Air Force Engineering UniversityXi’an710038China State key laboratory of Solidification processing Northwestern Polytechnical UniversityXi’an710072China Surface Material Protection Co. LtdXi’an710018China

Meeting the damage tolerance requirements for engineering-grade titanium alloys pose a significant challenge in achieving high fracture toughness in direct energy deposition(DED)titanium *** work primarily investigated the relationship between the microstructure and the fracture toughness of DED new Ti-6Al-4V-1Mo *** types of microstructures were designed via two process strategies:high-line energy density(HE)and low-line energy density(LE).Relative to LE samples,HE samples possess larger-sized microstructural characteristics(coarser grain boundaryα(α_(GB)),largerαcolonies,and coarserαlaths).Lessα/βphase boundaries were formed by coarserαlaths in the HE samples,increasing the movement of dislocations,resulting in tensile strength decreasing from 1007.1 MPa(LE)to 930.8 MPa(HE)and elongation increasing from 10.8%(LE)to 15.7%(HE).Also,HE samples exhibited an excellent fracture toughness of 114.0 MPa m^(1/2),significantly higher than that of LE samples(76.8 MPa m^(1/2)).An analysis of crack propagation paths was conducted to investigate the factors contributing to *** primary factor enhancing toughness is the frequent obstruction of cracks by coarseαGB and largeαcolonies in HE ***,the pretty large-angle deflections induced by the superposition effect of coarseαGB and largeαcolonies play a vital of significant *** factors induced the long and tortuous high-energy pathways,which resulted in ultimately improved fracture *** discovered microstructural toughening mechanisms can serve as a reference for future studies involving titanium alloys,offering insights on how to enhance fracture toughness by achieving similar characteristics.

关键词： Direct energy deposition Ti-6Al-4V-1Mo Tensile properties Fracture toughness Crack propagation

microstructure evolution and phase transformation of the mushy zone in a quenchedβ-solidifying TiAl alloy

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Journal of Materials Science & Technology 2024年第2期169卷 28-41页

作者： Fuqiang Zhang Xianfei Ding Leming Xu Xin Feng Hai Nan Jianping He Yongfeng Liang Junpin Lin State key laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China Cast Titanium Alloy R&D Center Beijing Institute of Aeronautical MaterialsBeijing 100095China

This study investigates the phase constitutions and transformations that occur in the mushy zone and in the adjacent phase fields of a directionally solidified Ti-44Al-8Nb-1Cr alloy via quenching *** results indicate that the mushy zone consists of unmeltedβdendrites and interdendritic liquid,whose formation can be attributed to the difference in melting point aroused by local heterogeneity in ***βdendrite is composed of numerous subgrains with various *** quenching,theβdendrite transforms into Widmanstättenαvia a precipitation reaction,owing to the decreasing cooling rate caused by heat transfer from the surrounding ***,after quenching,the interdendritic liquid is transformed intoγ*** the singleβphase field and the lower part of the mushy zone,a massive transformation ofβtoγ***,in theβ+αphase field,bothβandαphases are retained to ambient *** the heating process,the transformation ofα→βgives rise to the formation ofβvariants,which affects the orientation ofβdendrites in the mushy *** growth kinematics of theα→βtransformation was elucidated,revealing the preferential growth directions of111and112forβ***,this study presents an illustration of the formation process of the mushy zone and the microstructural evolution during the heating and quenching process.

关键词： Titanium aluminides Mushy zone Quenching Electron backscattering diffraction Phase transformation

Research on the mechanism of the two-dimensional ultrasonic surface burnishing process to enhance the wear resistance for aluminum alloy

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Friction 2024年第3期12卷 490-509页

作者： Zhen-Yu ZHOU Qiu-Yang ZHENG Yu LI Cong DING Guang-Jian PENG Zhong-Yu PIAO College of Mechanical Engineering Zhejiang University of TechnologyHangzhou 310023China key laboratory of Special Purpose Equipment and Advanced processing Technology Ministry of Education and Zhejiang ProvinceZhejiang University of TechnologyHangzhou 310014China

The gradient nanostructure is machined on the aluminum(Al)alloy by the two-dimensional ultrasonic surface burnishing process(2D-USBP).The mechanism of why the gradient nanostructure enhances wear resistance is *** mechanical properties and microstructure characterization for the gradient nanostructure are performed by operating a nanoindenter,transmission electron microscopy(TEM),and electron backscattered diffraction(EBSD).Dry wear tests are performed on the samples before and after machining to evaluate the wear resistance and *** effect of the gradient nanostructure on the wear resistance is explored by developing the crystal plasticity(CP)finite element and molecular dynamics(MD)*** characterization results show that the 2D-USBP sample prepared a gradient structure of~600μm thick on the aluminum surface,increasing the surface hardness from 1.13 to 1.71 GPa and reducing the elastic modulus from 78.84 to 70.14 *** optimization of the surface microstructure and the increase of the mechanical properties effectively enhance the wear resistance of the sample,with 41.20%,39.07%,and 54.58% of the wear scar areas for the 2D-USBP treated samples to the original samples under 5,10,and 15 N loads,*** gradient nanostructure hinders the slip of dislocations inside the sample during the wear process and reduces the size and scope of plastic deformation;meanwhile,the resistance to deformation,adhesion,and crack initiation and propagation of the sample surface is improved,resulting in enhanced wear resistance.

关键词： structural superlubricity lattice registry elastic deformation strained solitons crystal plasticity molecular dynamics simulations

Evidence for interlayer coupling and moiréexcitons in twisted WS_(2)/WS_(2)homostructure superlattices

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Nano Research 2023年第2期16卷 3429-3434页

作者： Haihong Zheng Biao Wu Shaofei Li Jun He Keqiu Chen Zongwen Liu Yanping Liu School of Physics and Electronics Hunan Key Laboratory for Super-microstructure and Ultrafast ProcessCentral South UniversityChangsha 410083China State key laboratory of High-Performance Complex Manufacturing Central South UniversityChangsha 410083China Department of Applied Physics School of Physics and ElectronicsHunan UniversityChangsha 410082China School of Chemical and Biomolecular Engineering The University of SydneyNSW 2006Australia The University of Sydney Nano Institute The University of SydneyNSW 2006Australia Shenzhen Research Institute of Central South University Shenzhen 518000China

The formation of moirésuperlattices in twisted van der Waals(vdW)homostructures provides a versatile platform for designing the electronic band structure of two-dimensional(2D)*** graphene and transition metal dichalcogenides(TMDs)moirésystems,twist angle has been shown to be a key parameter for regulating the moiré***,the effect of the modulation of the twist angle on moirépotential and interlayer coupling has not been the subject of experimental ***,we report the observation of the modulation of moirépotential and intralayer excitons in the WS_(2)/WS_(2)*** accurately adjusting the torsion angle of the homobilayers,the depth of the moirépotential can be *** confinement effect of the moirépotential on the intralayer excitons was further demonstrated by the changing of temperature and valley ***,we show that a detection of atomic reconstructions by the low-frequency Raman mapping to map out inhomogeneities in moirélattices on a large scale,which endows the uniformity of interlayer *** results provide insights for an in-depth understanding of the behaviors of moiréexcitons in the twisted van der Waals homostructure,and promote the study of electrical engineering and topological photonics.

关键词： moirésuperlattices moiréexcitons interlayer coupling moirépotential