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nucleation mechanisms of dynamic recrystallization for G3 alloy during hot compression

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Rare Metals 2016年第7期35卷 543-550页

作者： Jue Wang Jian-Xin Dong Mai-Cang Zhang Jiangsu Key Laboratory of Advanced Structural Materials andApplication Technology Nanjing 211167China School of Materials Science and Engineering Nanjing Instituteof TechnologyNanjing 211167China School of Materials Science and Engineering University ofScience and Technology BeijingBeijing 100083China

Dynamic recrystallization （DRX） mechanisms of a nickel-based corrosion-resistant alloy, G3, were investigated by hot compression tests with temperatures from 1050 to 1200 ℃ and strain rates from 0.1 to 5.0 s-1. Deformation microstructure was observed at the strain from 0.05 to 0.75 by electron backscatter diffraction （EBSD） and transmission electron microscope （TEM）. Work hardening rate curves were calculated to analyze the effect of deformation parameters on the nucleation process. Results indicate that strain-induced grain boundary migration is the principal mechanism of DRX. Large annealing twins promote nucleation by accumulating dis- locations and fragmenting into cell blocks. Continuous dynamic recrystallization is also detected to be an effective supplement mechanism, especially at low temperature and high strain rate.

关键词： G3 alloy Dynamic recrystallization nucleation mechanism Annealing twins

Altering polythiophene derivative substrates to explore the mechanism of heterogeneous lithium nucleation for dendrite-free lithium metal anodes

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Journal of Energy Chemistry 2021年第8期30卷 63-68,I0003页

作者： Yanchen Fan Yi Zhao Shuang Li Yue Liu You Lv Yuan Zhu Rong Xiang Shigeo Maruyama Hao Zhang Qianfan Zhang School of Materials Science and Engineering Beihang University100191 BeijingChina Department of Mechanical Engineering The University of Tokyo113-8656 Japan School of Material Science and Engineering Beijing Institute of Technology100081 BeijingChina School of Chemistry and Biological Engineering University of Science and Technology100083 BeijingChina School of Microelectronics Southern University of Science and TechnologyShenzhen 518055China

Lithium metal batteries(LMBs)possess outstanding theoretical energy density and have attracted widespread attention as the next generation of energy storage devices for various crucial ***,the commercialization of LMBs has to simultaneously overcome numerous challenges,such as inferior Coulombic efficiency and cycling performance,high self-discharge,and complicated interfacial *** has traditionally been an enormous challenge about the uniform deposition of lithium on the surface of current collector to relieve the formation of lithium *** this study,a novel efficient strategy of plating uniform lithiophilic polythiophene derivatives substrates on Cu foils was developed and the nucleation mechanism of Li ions on polythiophene derivatives substrates was further *** first explored the interaction between polythiophene derivatives substrates and Li ions by firstprinciples calculations,and found shorter side chains of polythiophene derivatives can enhance the adsorption energy and promote the diffusion rate of Li *** derivatives substrates have a large number of dispersive lipophilic sites and Li ions diffusion channels in the main chain,which can effectively regulate the nucleation and growth stages of Li ions *** further found polythiophene derivatives with different side chains can induce the electrodeposition of Li ions with different morphology,while the polythiophene derivatives with the shortest side chains can contribute to the most excellent cycle efficiency,resulting in a uniform lithium deposition with less lithium dendritic growth experimentally.

关键词： First-principles calculations Lithium metal batteries nucleation mechanism

Theoretical investigation of lithium ions’ nucleation performance on metal-doped Cu surfaces

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Journal of Energy Chemistry 2019年第12期28卷 160-169页

作者： Yanchen Fan Tianshuai Wang Dominik Legut Qianfan Zhang School of Materials Science and Engineering Beihang UniversityBeijing 100191China IT4Innovations Center VSB-Technical University of Ostrava17.listopadu 15CZ-70833 OstravaCzech Republic

Lithium metal batteries(LMBs)of an ultrahigh theoretical energy density have attracted lots of attentions for a wide range of practical ***,there are still numerous challenges in LMBs system,such as poor cycling performance,complicated interfacial reactions,low Coulombic efficiency,and uncontrollable lithium *** Li^+ions’nucleation mechanism is essential to tackle the uncontrolled growth of lithium ***,the nucleation behavior of Li+ions is interfered by the structural complexities of existing substrates during the reduplicative plating/stripping process and the rational mechanism of uniform nucleation of Li^+ions has not been clearly understood from the theoretical point of *** our work,first-principles theoretical calculations are carried out to investigate the Li^+ions nucleation performance on metal-doped Cu surfaces(MDCSs)and the key descriptors that determines the properties of various MDCSs are systematically *** is found that the introduction of heterogeneous doping Ag and Zn atoms will induce a gradient adsorption energy on MDCSs,and such gradient deposition sites can reduce the diffusion barriers and accelerate the diffusion rates of Li+ions *** maneuvering the Li+ions nucleation on MDCSs,a dendrite-free lithium metal anode can be achieved without the use of porous matrixes and complex synthesis process,which can be attributed to suppress the uncontrollable lithium dendrites for realizing the high-efficiency LMBs.

关键词： First-principles calculations Metal-doped Cu surfaces Lithium metal anode nucleation mechanism Dendrite growth

The nucleation and growth of borophene on the Ag(111)surface

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Nano Research 2016年第9期9卷 2616-2622页

作者： Shaogang Xu Yujun Zhao Jihai Liao Xiaobao Yang Hu Xu Department of Physics South China University of TechnologyGuangzhou 510640China Department of Physics South University of Science and Technology of ChinaShenzhen 518055China

B sheets have been intently studied, and various candidates with vacancies have been reported in theoretical investigations, including their possible growth on metal surfaces. However, a recent experiment reported that the borophene formed on a Ag (111) surface consisted of a buckled triangular lattice without vacancies. Our calculations propose a novel nucleation mechanism of B clusters and emphasize the B–Ag interaction in the growth process of borophene, demonstrating the structural evolution of triangular fragments with various profiles and vacancy distributions. Compared with the triangular lattice without vacancies, we have confirmed that the sheet energetically favored during the nucleation and growth is that containing 1/6 vacancies in a stripe pattern, whose scanning tunneling microscopy image is in better agreement with the experimental observation. [Figure not available: see fulltext.] © 2015, Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

关键词： borophene hexagonal vacancy nucleation mechanism first-principles calculations

Effects of PVP on the preparation and growth mechanism of monodispersed Ni nanoparticles

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Rare Metals 2008年第6期27卷 642-647页

作者： LIU Xiaodan GUO Min ZHANG Mei WANG Xidong GUO Xiao CHOU Kuochih Department of Physical Chemistry University of Science and Technology Beijing Beijing 100083 China College of Engineering Peking University Beijing 100871 China

Monodispersed Ni nanoparticles were successfully prepared by chemical reduction with hydrazine hydrate in ethylene glycol. The effect of the amount of polyvinylpyrrolidone （PVP-K30） on the preparation of Ni nanoparticles was investigated. X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and high resolution transmission electron microscopy （HRTEM） were employed to characterize the nickel powders. The average nickel particle size can be controlled from 103 nm to 46 ran with increasing the mass ratio of PVP to NiCl2·6H2O. The particles are spherical in shape and are not agglomerated. A possible extensive mechanism of nickel nanoparticle formation has been suggested.

关键词： Ni nanoparticles nucleation mechanism chemical reduction PVP

Investigation of the coercivity mechanism for Nd-Fe-B based magnets prepared by a new technique of strip casting

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Rare Metals 2004年第2期23卷 152-156页

作者： LIBo HUJifan WANGDongling GUOBinglin WANGXinlin DepartmentofFunctionalMaterials CentralIron＆SteelResearchInstituteBeijing100081China DepartmentofPhysics ShandongUniversityJinan250100China

The coercivity mechanism of Nd-Fe-B based magnets prepared by a new techniqueof strip casting was investigated. Different from the traditional magnets, α-Fe phases aredifficult to be found in Nd-Fe-B magnets prepared by strip casting. Meanwhile, the rich-Nd phasesoccur not only near the grain boundaries of main phases, but also within the main-phase *** on the magnetizing field dependence of the coercivity for the(Nd_(0.935)Dy_(0.065))_(14.5)Fe_(79.4)B_(6.1) magnet and the temperature dependence of thecoercivity for the Nd_(14.5)Fe_(79.4)B_(6.1) magnet hav been done. Results show that coercivitiesfor strip casting magnets are controlled by the nucleation mechanism.

关键词： NdFeB magnet coercivity mechanism nucleation mechanism strip casting

Dynamic recrystallization behaviour of H13-mod steel

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Journal of Iron and Steel Research(International) 2020年第9期27卷 1073-1086页

作者： Chang-min Li Yuan-biao Tan Fei Zhao College of Materials and Metallurgy Guizhou UniversityGuiyang 550025GuizhouChina

H13-mod steel developed after optimizing the composition and heat treatment process exhibits good hardness and impact toughness and can be used as a shield machine *** on the Avrami equation,the dynamic recrystallization(DRX)behaviour of H13-mod steel during hot compression was studied in the temperature of 900-1150°C and strain rate ranges of 0.01-10 s^-1.A DRX model and finite element software were used to study DRX behaviour of H13-mod *** DRX was found at both low and high strain *** backscatter diffraction and optical microscopy analyses found different DRX nucleation mechanisms at low and high strain rates under different *** a low strain rate,the nucleation was dominated by the strain-induced grain boundary migration,whereas the subgrain coalescence mechanism was dominant at a high strain ***,dynamic recovery occurred in both *** addition,it was easier to obtain small and uniform equiaxed grains at high strain rates than at low strain rates.

关键词： H13-mod steel Dynamic recrystallization Dynamic recrystallization volume fraction model Finite element simulation nucleation mechanism

Investigation of Coercivity mechanism for Nd-Fe-B Magnets Prepared by Combination of Strip-Casting with Hydrogen Decrepitation Techniques

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Journal of Rare Earths 2003年第5期21卷 555-557页

作者：李波胡季帆王东玲郭炳麟王新林 Department of Functional Materials Central Iron & Steel Research Institute Department of Physics Shandong University

The coercivity mechanism of Nd Fe B magnets prepared by combination of strip casting with hydrogen decrepitation techniques was investigated. The microstructure of (Nd 0.935 Dy 0.065 ) 14.5 Fe 79.4 B 6.1 magnet was observed. The average grain size is about 6～12 μm. The magnetizing field dependence of the hardmagnetic properties for the (Nd 0.935 Dy 0.065 ) 14.5 Fe 79.4 B 6.1 and the temperature dependence of the coercivity for the Nd 14.5 Fe 79.4 B 6.1 were investigated. Results show that the coercivity for magnets prepared by the combination of strip casting with hydrogen decrepitation techniques is controlled by the nucleation mechanism.

关键词： metal materials NdFeB magnet strip casting hydrogen decreipitation nucleation mechanism rare earths

STUDY ON THE POLYMERIZATION KINETICS AND STABILITY OF P(UA)/MMA MICROEMULSION

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Chinese Journal of Polymer Science 2001年第1期19卷 45-51页

作者： Hong-tao Zhang Tian-bin Ren Zhao-hui Yin Faculty of Chemistry and Material Science Hubei University Wuhan 430062 China Faculty of Chemistry and Material Science Hubei University Wuhan 430062 China Faculty of Chemistry and Material Science Hubei University Wuhan 430062 China

Urethane acrylate anionomer (APUA) as a kind of new type polymerizable emulsifier was synthesized using 2,4-toluene diisocyanate (TDI), polypropylene glycol (PPG), 2-hydroxyethyl methacrylate (HEMA) and dimethylolpropionic acid (DMPA). The critical micelle concentration (CMC) of APUA was measured by the methods of conductance and surface tension. The comparative studies between polymerizable emulsifier AUPA and conventional emulsifier sodium dodecyl sulfate (SDS) were carried out in the emulsion polymerization of methyl methacrylate (MMA). Polymerization kinetics, stability, size and morphology of the latex particles were investigated. It was found that in APUA both water soluble initiator potassium persulfate (KPS) and oil soluble initiator 2,2'-azobisisobutyronitrile (AlBN) can start the reaction of MMA, and the polymerization rate and yield were very high. On using AlBN as an initiator, the conversion-time behavior of MMA with APUA as emulsifier was different to that of SDS as emulsifier, signifying a different nucleation mechanism of the polymer latex particle. The average size of the two kinds of particles is about 50 nm. The particle size decreases with increasing emulsifier concentration. On using KPS as the initiator, APUA as emulsifier, cross-linking hydrogel of PMMA would be formed, but SDS was used as emulsifier and the hydrogel of PMMA was not present.

关键词： polymerizable emulsifiers urethane acrylate polymerization kinetics stability nucleation mechanism