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Nanoscale materials transformations revealed by liquid phase TEM

Nano Research 2024年第10期17卷 9152-9165页

作者： Qiubo Zhang Daewon Lee haimei zheng Materials Sciences Division Lawrence Berkeley National LaboratoryBerkeleyCalifornia 94720USA Department of Materials Science and Engineering University of CaliforniaBerkeleyCalifornia 94720USA

Nanoscale materials often undergo structural,morphological,or chemical changes,especially in solution processes,where heterogeneity and defects may significantly impact the transformation *** phase transmission electron microscopy(TEM),allowing us to track dynamic transformations of individual nanoparticles,has become a powerful platform to reveal nanoscale materials transformation pathways and address challenging issues that are hard to approach by other *** the development of modern liquid cells,implementing advanced imaging and image analysis methods,and strategically exploring diverse systems,significant advances have been made in liquid phase TEM,including improved high-resolution imaging through liquids at the atomic level and remarkable capabilities in handling complex systems and *** the past more than a decade,we spent much effort in developing and applying liquid phase TEM to elucidate how atomic level heterogeneity and defects impact various physicochemical processes in liquids,such as growth,self-assembly of nanoparticles,etching/corrosion,electrodeposition of alkali metals,catalyst restructuring during reactions,and so *** article provides a brief review of the liquid phase TEM study of nanoscale materials transformations,focusing on the growth of nanomaterials with distinct shape/hierarchical structures,such as one-dimensional(1D)growth by nanoparticle attachment,two-dimensional(2D)growth with nanoparticles as intermediates,core-shell structure ripening,solid-liquid interfaces including those in batteries and electrocatalysis,highlighting the impacts of heterogeneity and defects on broad nanoscale transformation pathways.

关键词： liquid phase transmission electron microscopy(TEM) liquid cells nanomaterials growth transformations pathways solid-liquid interface heterogeneity and fluctuations

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Recent progress in thermoelectric nanocomposites based on solution-synthesized nanoheterostructures

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Nano Research 2017年第5期10卷 1498-1509页

作者： Wei zheng Biao Xu Lin Zhou Yilong Zhou haimei zheng Chenghan Sun Enzheng Shi Tanner Dale Fink Yue Wu Department of Chemical and Biological Engineering Iowa State University Ames IA 50011 USA Ames Laboratory Department of Energy Iowa State University Ames IA 50011 USA Material Science Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA

Thermoelectric materials, which can convert waste heat into electricity, have received increasing research interest in recent years. This paper describes the recent progress in thermoelectric nanocomposites based on solution-synthesized nanoheterostructures. We start our discussion with the strategies of improving the power factor of a given material by using nanoheterostructures. Then we discuss the methods of decreasing thermal conductivity. Finally, we highlight a way of decoupling power factor and thermal conductivity, namely, incorporating phase-transition materials into a nanowire heterostructure. We have explored the lead telluride-copper telluride thermoelectric nanowire heterostructure in this work. Future possible ways to improve the figure of merit are discussed at the end of this paper.

关键词： thermoelectrics nanoheterostructures phase change

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Incorporating topographic factors in nonlinear mixed-effects models for aboveground biomass of natural Simao pine in Yunnan,China

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Journal of Forestry Research 2016年第1期27卷 119-131页

作者： Guanglong Ou Junfeng Wang Hui Xu Keyi Chen haimei zheng Bo Zhang Xuelian Sun Tingting Xu Yifa Xiao Key Laboratory of Biodiversity Conservation in Southwest China of State Forest Administration Southwest Forestry University

A total of 128 Simao pine trees （Pinus kesiya var. langbianensis） from three regions of Pu＇er City, Yunnan Province, People＇s Republic of China, were destructively sampled to obtain tree aboveground biomass （AGB）. Tree variables such as diameter at breast height and total height, and topographical factors such as altitude, aspect of slope, and degree of slope were recorded. We considered the region and site quality classes as the ran- dom-effects, and the topographic variables as the fixed- effects. We fitted a total of eight models as follows： least- squares nonlinear models （BM）, least-squares nonlinear models with the topographic factors （BMT）, nonlinear mixed-effects models with region as single random-effects （NLME-RE）, nonlinear mixed-effects models with site as single random-effects （NLME-SE）, nonlinear mixed-ef- fects models with the two-level nested region and site random-effects （TLNLME）, NLME-RE with the fixed-ef- fects of topographic factors （NLMET-RE）, NLME-SE with the fixed-effects of topographic factors （NLMET-SE）, and TLNLME with the fixed-effects of topographic factors （TLNLMET）. The eight models were compared by modelfitting and prediction statistics. The results showed： model fitting was improved by considering random-effects of region or site, or both. The models with the fixed-effects of topographic factors had better model fitting. According to AIC and BIC, the model fitting was ranked as TLNLME 〉 NLMET-RE 〉 NLME-RE.〉 NLMET-SE 〉 TLNLMET 〉 NLME-SE 〉 BMT 〉 BM. The differences among these models for model prediction were small. The model pre- diction was ranked as TLNLME 〉 NLME-RE 〉 NLME- SE 〉 NLMET-RE 〉 NLMET-SE 〉 TLNLMET 〉 BMT 〉 BM. However, all eight models had relatively high prediction precision （〉90 %）. Thus, the best model should be chosen based on the available data when using the model to predict individual tree AGB.

关键词： Aboveground biomass Mixed-effectsmodels Regional effect Site quality effect Topographicfactors Pinus kesiya var. langbianensis

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In situ TEM observation of neck formation during oriented attachment of PbSe nanocrystals

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Nano Research 2019年第10期12卷 2549-2553页

作者： Yu Wang Xinxing Peng Alex Abelson Bing-Kai Zhang Caroline Qian Peter Ercius Lin-Wang Wang Matt Law haimei zheng Materials Sciences Division Lawrence Berkeley National LaboratoryBerkeleyCalifornia 94720USA Department of Materials Science and Engineering University of CaliforniaBerkeleyCalifornia 94720USA State Key Lab of Physical Chemistry of Solid Surfaces Collaborative Innovation Center of Chemistry for Energy MaterialsCollege of Chemistry and Chemical EngineeringXiamen UniversityXiamen 361005China Department of Chemistry University of CaliforniaIrvineCalifornia 92697USA National Center for Electron Microscopy Molecular FoundryLawrence Berkeley National LaboratoryBerkeleyCalifornia 94720USA

Oriented attachment of nanocrystals is an important route to constructing epitaxially-connected nanocrystal superlattices for various *** oriented attach me nt of semic on ductor nano crystals,neck can be formed betwee n nan ocrystals and it strongly influe nces the properties of the resulting ***,the neck formation mechanism is poorly ***,we use in situ liquid cell transmission electro n microscopy(TEM)to directly observe the initiatio n and growth of homoepitaxial n ecks betwee n PbSe nano crystals with atomic *** find that neck initiatio n occurs slowly(~10 s)whe n two nano crystals approach to each other within an edge-to-edge dista nee of 0.6 *** neck initiation,Pb and Se atoms defuse from other facets into the gap,forming"dynamic reversible"*** the filament(n eck)width is larger than a critical size of 0.9 nm,it gradually(15 s)widens into a 3-nm-wide n *** atomic structure of the neck is further obtained using ex situ aberration-corrected seanning TEM *** initiation and growth mechanisms are elucidated with density functional theory calculati *** direct unveiling of the atomic pathways of neck formatio n duri ng oriented attach me nt shed light into the fabrication of nanocrystal superlattices with improved structural order and electronic properties.

关键词： PbSe nanocrystals quantum dots superlattices necking oriented attachment liquid cell transmission electron microscopy(TEM)

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Precipitation of α″-Fe_(16)N_2 Phase

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Journal of Materials Science & Technology 1998年第5期14卷 473-474页

作者： haimei zheng Chunyang LI Jian WANG and Baoyn LI (Dept. of Material Science and Engineering, Tianjin University, Tianjin 300072, China) Tianjin Univ Tianjin China

Characteristics of the precipitate α″-Fe16N2 phase have been investigated by X-ray diffraction and TEM analysis. VSM measurements give the saturation magnetization of the α″ phase.

关键词： Fe Precipitation of N2 Phase

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Real time imaging of two-dimensional iron oxide spherulite nanostructure formation

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Nano Research 2019年第11期12卷 2889-2893页

作者： Wenjing zheng Matthew R.Hauwiller Wen-I Liang Colin Ophus Peter Ercius Emory M.Chan Ying-Hao Chu Mark Asta Xiwen Du A.Paul Alivisatos haimei zheng Institute of New-Energy Materials School of Materials Science and EngineeringTianjin UniversityTianjin300350China Materials Sciences Division Lawrence Berkeley National LaboratoryBerkeleyCA94720USA Department of Chemistry University of CaliforniaBerkeleyBerkeleyCA94720USA Department of Materials Science and Engineering “National Chiao Tung University”Hsinchu30010TaiwanChina The Molecular Foundry Lawrence Berkeley National LaboratoryBerkeleyCA94720USA Department of Materials Science and Engineering University of CaliforniaBerkeleyBerkeleyCA94720USA Kavli Energy NanoScience Institute University of California-Berkeley and Lawrence Berkeley National LaboratoryBerkeleyCA94720USA

The formation of complex hierarchical nanostructures has attracted a lot of attention from both the fundamental science and potential applications point of *** structures with radial fibrillar branches have been found in various solids;however,their growth mechanisms remain poorly ***,we report real time imaging of the formation of two-dimensional(2D)iron oxide spherulite nanostructures in a liquid cell using transmission electron microscopy(TEM).By tracking the growth trajectories,we show the characteristics of the reaction front and growth *** observations reveal that the tip of a growing branch splits as the width exceeds certain sizes(5.5–8.5 nm).The radius of a spherulite nanostructure increases linearly with time at the early stage,transitioning to nonlinear growth at the later ***,a thin layer of solid is accumulated at the tip and nanoparticles from secondary nucleation also appear at the growing front which later develop into fibrillar *** spherulite nanostructure is polycrystalline with the co-existence of ferrihydrite and Fe3O4 through-out the growth.A growth model is further established,which provides rational explanations on the linear growth at the early stage and the nonlinearity at the later stage of growth.

关键词： liquid cell transmission electron microscopy(TEM) in situ TEM iron oxide spherulite nanostructures

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共振:高校思政教育对马克思主义中国化创新理论的坚守

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江苏高教 2024年第12期 136-140页

作者：郑海妹王贵斌海南师范大学马克思主义学院海口571158 陕西师范大学马克思主义学院西安710062 陕西师范大学新闻与传播学院西安710062

坚守马克思主义中国化创新理论的指引,是高校思政教育始终与时代同频共振、牢牢把握正确政治方向和价值导向的具体表现。这种共振基础上的坚守体现在四个方面:一是思政教育历史演进中始终伴随着马克思主义中国化的铿锵步伐,从素材吸收... 详细信息

坚守马克思主义中国化创新理论的指引,是高校思政教育始终与时代同频共振、牢牢把握正确政治方向和价值导向的具体表现。这种共振基础上的坚守体现在四个方面:一是思政教育历史演进中始终伴随着马克思主义中国化的铿锵步伐,从素材吸收到学科融合、从话语表达到课程阐释、从理论集成到重大创新;二是思政教育初心使命中始终秉承着马克思主义中国化的人学理想,表现为人的完整性与全面性的教育统一、人的目的性与工具性的异化纠偏、人的成长性与社会性的重新融合;三是思政教育发展创新中始终保持马克思主义中国化的整体思想,有助于打造思政全过程教育链条、推进思政全场域教育服务、融合思政全学科教育资源;四是思政教育有序发展中始终坚持马克思主义中国化的时代导向,能够以马克思主义教育观推动现代思政教育支点形成,以马克思主义生态观推动现代思政教育群落形成,以马克思主义大众化推动现代思政教育效能提升。

关键词：马克思主义创新理论思政教育

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Controlled oxidative etching of gold nanorods revealed through in-situ liquid cell electron microscopy

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Science China Materials 2020年第12期63卷 2599-2605页

作者： Wen Wang Tao Xu Tingting Bai Chao Zhu Qiubo Zhang Hongtao Zhang Hui Zhang Zhirui Guo haimei zheng Litao Sun SEU-FEI Nano-Pico Center Key Lab of MEMS of Ministry of EducationSoutheast UniversityNanjing 210096China Materials Sciences Division Lawrence Berkeley National LaboratoryBerkeleyCA 94720USA Department of Geriatrics The Second Affiliated HospitalKey Laboratory for Aging&DiseaseNanjing Medical UniversityNanjing 210011China Department of Materials Science and Engineering University of CaliforniaBerkeleyCalifornia 94720USA

Oxidative etching can be a powerful approach to modify the morphology of nanoscale materials for various *** of the etching mechanisms and morphological evolution during etching is *** the liquid cell transmission electron microscopy,we investigate the etching behavior of gold nanorods under different electron beam dose rates:caseⅠ,3.5×10^9 Gy s^-1;caseⅡ,1.5×10^10 Gy s^-1;caseⅢ,4.5×10^10 Gy s^-*** Au nanorod develops facets at the tips(caseⅠ)or adopts a transit ellipsoid shape and eventually dissolves(caseⅡ),depending on the dose *** rapid etching under an even higher dose rate(caseⅢ)may lead to the formation of Au3+ion-rich intermediates around the nanorod,which further accelerates the lateral etching and unexpectedly increases the aspect ratio of the *** quantitative analysis shows that the critical size of the nanorod,below which the etching rate increases significantly with the reduction of nanorod size,may vary subject to the degree that the system is away from *** results provide significant insights into the oxidative etching mechanisms and shed light on the rational design and synthesis of nanostructures.

关键词： in-situ liquid transmission electron microscope oxidative etching etching mechanism electron dose rate gold

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Correlation between grain size,mechanical properties and deformed microstructure of Fe-20Mn-6Al-0.6C-0.15Si low-density steel

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Journal of Iron and Steel Research International 2025年第1期32卷 282-292页

作者： Qi Zhang Guang-hui Chen zheng-liang Xue zheng-kun Chen Guang Xu State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan430081HubeiChina Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education Wuhan University of Science and TechnologyWuhan430081HubeiChina Red Eagle Novel Refractory Materials Research Institute Zhejiang Red Eagle Group Co.Ltd.Huzhou313000ZhejiangChina

The effects of austenite grain size on the deformed microstructure and mechanical properties of an Fe-20Mn-6Al-0.6C-0.15Si(wt.%)low-density steel were *** microstructure of the experimental steel after solution treatment was single austenitic *** austenite grain size increased with solution temperature and time.A model was established to show the relationship between temperature,time and austenite grain size for the experimental *** addition,as the solution temperature increased,the strength decreased,while the elongation first increased and then *** decrease in elongation after solution treatment at 1100℃ for 90 min is contributed to the over-coarse austenite ***,after solution treatment at 900℃ for 90 min,the strength-elongation product reached the highest value of 44.4 GPa%.As the austenite grain size increased,the intensity of//tensile direction fiber *** was accompanied by a decrease in dislocation density,resulting in a lower fraction of low-angle grain boundaries and a lower work hardening ***,the austenite grain size has a critical influence on the mechanical properties of the low-density *** grains lead to a lower yield strength due to the Hall-Petch effect and a lower tensile strength because of lower dislocation strengthening.

关键词： Austenitic low-density steel Solution treatment Grain size Mechanical property Deformed microstructure

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An efficient conversion model between acceleration and pseudo-acceleration response spectra considering effects of magnitude,distance,and site class

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Earthquake Engineering and Engineering Vibration 2025年第1期24卷 15-30页

作者： Liu zheng Zhao Yan-Gang Zhang Haizhong Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education Beijing University of TechnologyBeijing 100124China Faculty of Agriculture Yamagata University1-23Wakaba-machiTsuruoka-shiYamagata 997-8555Japan

Both acceleration and pseudo-acceleration response spectra play important roles in structural seismic ***,only one of them is generally provided in most seismic ***,many studies have attempted to develop conversion models between the acceleration response spectrum(SA)and the pseudo-acceleration response spectrum(PSA).Our previous studies found that the relationship between SA and PSA is affected by magnitude,distance,and site ***,we developed an SA/PSA model incorporating these ***,this model is suitable for cases with small and moderate magnitudes and its accuracy is not good enough for cases with large *** paper aims to develop an efficient SA/PSA model by considering influences of magnitude,distance,and site class,which can be applied to cases not only with small or moderate magnitudes but also with large *** this purpose,regression analyses were conducted using 16,660 horizontal seismic records with a wider range of *** magnitude of these seismic records varies from 4 to 9 and the distances vary from 10 to 200 *** ground motions were recorded at 338 stations covering four site *** comparing them with existing models,it was found that the proposed model shows better accuracy for cases with any magnitudes,distances,and site classes considered in this study.

关键词： acceleration response spectrum pseudo-acceleration response spectrum magnitude distance site class

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