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Experimental reconstructions of 3D atomic structures from electron microscopy images using a Bayesian genetic algorithm

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npj Computational Materials 2022年第1期8卷 2076-2083页

作者： Annick De Backer Sandra Van Aert Christel Faes Ece Arslan Irmak Peter DNellist Lewys Jones EMAT University of AntwerpGroenenborgerlaan 1712020AntwerpBelgium NANOlab Center of Excellence University of AntwerpGroenenborgerlaan 1712020AntwerpBelgium I-BioStat Data Science InstituteHasselt UniversityHasseltBelgium Department of Materials University of OxfordParks RoadOX13PHOxfordUK Advanced microscopy Laboratory Centre for Research on Adaptive Nanostructures and Nanodevices(CRANN)Dublin 2Ireland School of Physics Trinity College DublinThe University of DublinDublin 2Ireland

We introduce a Bayesian genetic algorithm for reconstructing atomic models of monotype crystalline nanoparticles from a single projection using Z-contrast *** number of atoms in a projected atomic column obtained from annular dark field scanning transmission electron microscopy images serves as an input for the initial three-dimensional *** algorithm minimizes the energy of the structure while utilizing a priori information about the finite precision of the atom-counting results and neighbor-mass *** results show promising prospects for obtaining reliable reconstructions of beam-sensitive nanoparticles during dynamical processes from images acquired with sufficiently low incident electron doses.

关键词： algorithm atomic utilizing

Positive Strain Rate Sensitivity and Deformation Behavior of a Fe–29Mn–3Al–3Si TWIP Steel

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Acta Metallurgica Sinica(English Letters) 2022年第11期35卷 1825-1836页

作者： Shucheng Shen Cuilan Wu Pan Xie Yuanrui Liu Center of High Resolution Electron microscopy College of Materials Science and EngineeringHunan UniversityChangsha 410082China

The Fe-29 Mn-3 Al-3 Si twin-induced plasticity(TWIP)steel is used to conduct quasi-static compression and dynamic impact deformation with strain rates ranging from 8.3×10^(-4) to 3800 s^(-1).The microstructures and properties of deformed samples under different strain rates were investigated *** results show that positive strain rate sensitivity was observed with the increase in strain rates and that there was a significant difference in strain rate sensitivity factor(m)between quasi-static compression(m=0.029)and dynamic impact deformation(m=0.190).Compared to the quasi-static compression,the dynamic impact deformation exhibited higher yield *** examination reveals that the primary twins were frequently found during the quasi-static compression process,and the secondary twins were rarely ***,the secondary and multi-fold deformation twins were florescent in the dynamic impact *** the initial stage of dynamic impact deformation,partial dislocations and staking faults on multiple conjugate{111}planes were simultaneously activated and produced a large number of Lomer-Cottrell dislocations,resulting in a large increase in yield strength during dynamic impact.

关键词： TWIP steel Dynamic deformation Strain rate sensitivity Multi-fold deformation twins

Improved Properties in Relation to Fine Precipitate Microstructures Tailored by Combinatorial Processes in an Al-Cu-Mg-Si Alloy

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Acta Metallurgica Sinica(English Letters) 2020年第11期33卷 1527-1534页

作者： Fengjiao Niu Jianghua Chen Cuilan Wu Jing Wu Xiandong Xu Pan Xie Xiongwei Yu Center for High-Resolution Electron microscopy College of Materials Science and EngineeringHunan UniversityChangsha 410082China

The 2xxx series Al alloys have been widely used in aerospace industry owing to their high strength,good plasticity and superior *** ensure a good control of shape,the quenched alloy sheets require a small pre-deformation before artificial ***,this pre-deformation considerably deteriorates the mechanical strength of the Al-3.0 Cu-1.8 Mg-0.5 Si(wt%)alloys due to the formation of unfavorable large-sized precipitates at *** tackle this issue,we designed a pre-aging process prior to the *** thermal-mechanical treatment,involving pre-aging,pre-deformation and subsequent aging,markedly enhanced the ultimate tensile strength up to 521 MPa compared to that(448 MPa)of the alloy without *** characterization revealed that the fine precipitates(~2 nm)with a uniform dispersion were promoted within the Al matrix,which in turn partly suppressed the formation of the unfavorable large-sized precipitate(~100 nm).Our findings provide a new clue for designing stronger Al alloys with age-hardenability.

关键词： Aluminum alloys Thermo-mechanical treatment Precipitation Age-hardenability

Abnormal orientation relation between fcc and hcp structures revealed in a deformed high manganese steel

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Journal of Materials Science & Technology 2021年第1期60卷 156-161页

作者： Pan Xie Shucheng Shen Cuilan Wu Jianghua Chen Center for High Resolution Electron microscopy College of Materials Science and EngineeringHunan UniversityChangsha 410082China

The crystallography of phase transformation is an important issue for studying metallic ***,we demonstrate an abnormal orientation relation between face-centered cubic(fcc) and hexagonal closepacked(hcp) phases due to the intersection of two ε_(hcp)-martensite variants in a high manganese *** corresponding crystallogra phic cha racteristics,including invariant line,habit plane and atomic steps,have been characterized by transmission electron micro scopy and the quasi-O-line *** addition,the models of phase transfo rmation about the intersection are proposed based on transmission mechanisms of *** findings enrich the theories of phase transformation and implicate the possibility to fabricate stro nger and tougher steel.

关键词： Phase transformation Invariant line Habit plane Interface High-manganese steels

Rolling-assisted direct energy deposited Inconel 718:Microstructural evolution and mechanical properties after optimized heat treatment

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Journal of Materials Science & Technology 2023年第13期144卷 118-127页

作者： Chen Li Peter Hodgson Michael Preuss Yu Chen Xinhua Wu Yuman Zhu Yang Tian Aijun Huang Department of Material Science and Engineering Monash UniversityClaytonVIC 3800Australia Monash centre for Additive Manufacturing(MCAM) 15-17 Normanby RdNotting HillVIC 3168Australia Institute for Frontier Materials Deakin UniversityGeelongVIC 3217Australia Monash centre for Electron microscopy Monash University10 Innovation WalkClaytonVIC 3800Australia

Post-heat treatment is a necessary and important step for additive-manufactured products to relieve residual stress and to further improve mechanical *** this work,the heat treatment strat-egy for Inconel 718 superalloy fabricated by rolling-assisted laser-directed energy deposition(L-DED)has been designed and systematically investigated for the first *** results show that the designed ho-mogenization heat treatment at 1080℃ for 10 min can effectively dissolve most of the detrimental Lave phases existing in the rolling-assisted L-DED ***,it results in a homogenous grain struc-ture through static recrystallization,while maintaining a similar prior-refined grain size of∼8μ*** this basis,a high number density ofγ″andγ′precipitates appear in the microstructure after applying a subsequent double-aging heat *** optimized microstructure through such effective post-heat treatment designed in this work has led to a significant increase in material strength at both the room and elevated temperatures while maintaining good ductility.

关键词： Additive manufacturing Nickel superalloy In-situ rolling Heat treatment Mechanical properties

Thermal stability of Mg_2 Si epitaxial film formed on Si(111) substrate by solid phase reaction

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Chinese Physics B 2009年第7期18卷 3079-3083页

作者：王喜娜王勇邹进张天冲梅增霞郭阳薛其坤杜小龙张晓娜韩晓东张泽 Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of Sciences Faculty of Physics & Electronic Technology Hubei University School of Engineering and centre for microscopy and Microanalysis The University of QueenslandSt LuciaQLD 4072Australia Beijing University of Technology

A single crystalline Mg2Si film was formed by solid phase reaction （SPR） of a Si（111） substrate with an Mg overlayer capped with an oxide layer（s）,which was enhanced by post annealing from room temperature to 100℃ in a molecular beam epitaxy （MBE） *** thermal stability of the Mg2Si film was then systematically investigated by post annealing in an oxygen-radical ambient at 300℃,450℃ and 650℃,*** Mg2Si film stayed stable until the annealing temperature reached 450℃ then it transformed into amorphous MgOx attributed to the decomposition of Mg2Si and the oxidization of dissociated Mg.

关键词： Mg2Si solid phase reaction thermal stability

Ni-induced stepwise capacity increase in Ni-poor Li-rich cathode materials for high performance lithium ion batteries

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Nano Research 2015年第3期8卷 808-820页

作者： Delai Ye Chenghua Sun Yu Chen Kiyoshi Ozawa Denisa Hulicova-JurcakovaI Jin Zou Lianzhou Wang Nanomaterials centre School of Chemical Engineering and Australian Institute of Bioengineering and Nanotechnology The University of Queensland Brisbane QLD 4072 Australia School of Chemistry Monash University Clayton Victoria 3800 Australia National Institute for Materials Science Tsukuba Ibaraki 305-0047 Japan centre for microscopy and Microanalysis and Material Engineering The University of Queensland Brisbane QLD 4072 Australia

Li-rich cathode materials have been considered as promising candidates for high-energy lithium ion batteries （LIBs）. In this study, we report a new series of Li-rich materials （Li[Li1/B-2x/BMn2/3-x/3Nix]O2 （0.09 ≤x≤ 0.2）） doped with small amounts of Ni as cathode materials in LIBs, which exhibited unusual phenomenon of capacity increase up to tens of cycles due to the continuous activation of the Li2MnO3 phase. Both experimental and computational results indicate that unlike commonly studied Ni-doped Li-rich cathode materials, smaller amounts of Ni doping can promote the stepwise Li2MnO3 activation to obtain increased specific capacity and better cycling capability. In contrast, excessive Ni will over-activate the Li2MnO3 and result in a large capacity loss in the first cycle. The Lil.25Mn0.625Ni0.12sO2 material with an optimized content of Ni delivered a superior high capacity of -280 mAh.g-1 and good cycling stability at room temperature.

关键词： Ni-doping capacity-increase Li-rich cathode materials lithium ion battery

Hierarchical Sb-Ni nanoarrays as robust binder-free anodes for high-performance sodium-ion half and full cells

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Nano Research 2017年第9期10卷 3189-3201页

作者： Liying Liang Yang Xu Liaoyong Wen Yueliang Li Min Zhou Chengliang Wang Huaping Zhao Ute Kaiser Yong Lei Institute of Physics & IMN MacroNano (ZIK) Ilmenau University of Technology Professor Schmidt Strasse 26 98693 Ilmenau Germany Central Facility for Electron microscopy Electron Microscopy Group of Materials Science UIm University Albert~Einstein-Allee 11 89081 UIm Germany

A novel hierarchical electrode material for Na-ion batteries composed of Sb nanoplates on Ni nanorod arrays is developed to tackle the issues of the rapid capacity fading and poor rate capability of Sb-based materials. The three-dimensional (3D) Sb-Ni nanoarrays as anodes exhibit the synergistic effects of the two-dimensional nanoplates and the open and conductive array structure as well as strong structural integrity. Further, their capacitive behavior is confirmed through a kinetics analysis, which shows that their excellent Na-storage performance is attributable to their unique nanostructure. When used as binder-free sodium-ion battery (SIB) anodes, the nanoarrays exhibit a high capacity retention rate (more than 80% over 200 cycles) at a current density of 0.5 A·g–1 and excellent rate capacity (up to 20 A·g–1), with their capacity being 580 mAh·g–1. Moreover, a P2-Na2/3Ni1/3Mn2/3O2//3D Sb-Ni nanoarrays full cell delivers a highly reversible capacity of 579.8 mAh·g–1 over 200 cycles and an energy density as high as 100 Wh·kg–1. This design strategy for ensuring fast and stable Na storage may work with other electrode materials as well.

关键词： hierarchical Sb-Ni nanoarrays binder-free anode capacitive charge storage Na-ion full cell

Quantitative HRTEM and its application in the study of oxide materials

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Chinese Physics B 2018年第5期27卷 22-32页

作者： Chun-Lin Jia[[ Shao-Bo Mi Lei Jin Ernst Ruska-centre (ER-C) for microscopy and Spectroscopy with Electrons Forschungszentrum Julich GmbH 52425 Julich Germany School of Microelectronics Xi'an Jiaotong University Xi'an 710049 China State Key Laboratory for Mechanical Behaviour of Materials Xi'an Jiaotong University Xi'an 710049 China

On the basis of a state-of-the-art aberration-corrected transmission electron microscope, the spherical aberration coefficient CSof the objective lens can be tuned to either a positive or a negative value. The use of a negative value of CS combined with an overfocus setting of the objective lens leads to the development of the negative CSimaging（NCSI） technique. Images obtained using the NCSI technique show superior contrast and signal intensity at atomic column positions than the corresponding positive CSimages, especially for weakly scattering oxygen columns that are in close proximity to strongly scattering cation columns in oxides. Based on the images obtained under the NCSI condition, quantification of the image contrast allows measurements of the atom positions with a precision of a few picometers and the local chemistry on atomic scale. In the present review, we discuss firstly the benefits of the NCSI technique in studies of oxide materials,and then show a procedure for quantitative analysis of the image based on the absolute value of contrast. In the last part,examples are given for the application of the quantitative high-resolution transmission electron microscopy（HRTEM） to the study of electric dipoles of oxide ferroelectrics and atomic-scale chemistry of interfaces.

关键词： quantitative high-resolution transmission electron microscopy (HRTEM) negative Cs imaging(NCSI) aberration-correction functional oxides