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Multi-physics multi-scale simulation of unique equiaxed-to-columnar-to-equiaxed transition during the whole solidification process of Al-li alloy laser welding

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Journal of materials science & technology 2024年第4期171卷 235-251页

作者： chu Han Ping Jiang Shaoning Geng liangyuan Ren School of Mechanical science and Engineering Huazhong University of Science&Technology(HUST)Wuhan430074China

In this study,a novel multi-physics multi-scale model with the dilute multicomponent phase-field method in three-dimensional(3D)space was developed to investigate the complex microstructure evolu-tion in the molten pool during laser welding of Al-li *** accurately compute mass data within both two and three-dimensional computational domains,three efficient computing methods,including central processing unit parallel computing,adaptive mesh refinement,and moving-frame algorithm,were *** was placed on the distinctive equiaxed-to-columnar-to-equiaxed transition phenomenon that occurs during the entire solidification process of Al-li alloy laser *** results indi-cated that the growth distance of columnar grains that epitaxially grew from the base metal(BM)de-creased as the nucleation rate *** the nucleation rate increased,the morphology of the newly formed grains near the fusion boundary(FB)changed from columnar to equiaxed,and newly formed equiaxed grains changed from having high-order dendrites to no obvious dendrite *** the nucleation rate was sufficiently high,non-dendritic equiaxed grains could directly form near the FB,and there was nearly no epitaxial growth from the ***,simulation results illustrated the com-petition among multiple grains with varying orientations that grow in 3D space near the ***,how equiaxed grain bands develop was *** equiaxed band not only hindered the growth of early columnar grains but also some of its grains could grow epitaxially to form new columnar *** predicted results were in good agreement with experimental measurements and observations.

关键词： Laser welding Al-li alloy Equiaxed-to-columnar-to-equiaxed transition Multi-physics multi-scale model Multicomponent alloys 3D phase-field model

Fractal Nature of Crack Growth under Different Temperature

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Journal of materials science & technology 1996年第2期12卷 143-148页

作者： Qunsheng CAO (dept. of physics, Wuhan Yejin university of science & technology, Wuhan 430081, china) dept. of physics Wuhan Yejin University of Science and Technology Wuhan 430081 China

We have studied numerically a simple crack growth model in a two-dimensional triangular lattice of bonds and nodes which incorporates the surface of a growing crack bond-breaking probability P-i similar to exp{(-V-i+E(i))phi(T)}, where E(i) is elastic energy stored in the i-th bond. Different energy temperature factors phi(T) are employed during crack formation and propagation process with a uniform dilation strain case and a shear case and with periodic boundary condition in the horizontal direction. Our results show that the patterns of the cracks generated are fractal structure and the effective fractal dimensionalities decrease with the increase of the temperature factor phi(T)(the absolute temperature T decreasing). In the paper we also discuss the relation between the effective fractal dimension D-eff (the radius R(g) of gyration) and the fractal dimensions D (the radius R of circular), and also give their modification values Omega about two kinds of methods in the lattice model.

关键词： Nature Fractal Nature of Crack Growth under Different Temperature

INTERFACE REACTION IN MAGNETIC MULTILAYERS

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Acta Metallurgica Sinica(English Letters) 2001年第6期14卷 479-484页

作者： G.H. Yu, M.H li, F. W Zhu, X.F. Cui and J.L. Jin ( Department of materials physics, university of science and technology beijing, beijing 100083, china) ( State key laboratory for Advanced Metals and materials, university of science and technology beijing dept. of Mat. Phys. Univ. of Sci. and Technol. Beijing Beijing 100083 China

Ta/NiO/NiFe/Ta multilayers were prepared by rf reactive and dc magnetron sputtering. The exchange coupling field (Hex) between NiO and NiFe reached 120O e. The composition and chemical states at the interface region of NiO/NiFe were studied using the X-ray photoelectron spectroscopy (XPS) and peak decomposition technique. The results show that there are two thermodynamically favorable reactions at NiO/NiFe interface: NiO+Fe=Ni+FeO and 3NiO+2Fe=3Ni+Fe2O3. The thickness of the chemical reaction as estimated by angle-resolved XPS was about 1-1.5 nm. These interface reaction products are magnetic defects, and we believe that the Hex and the coercivity (Hc) of NiO/NiFe are affected by these defects. Moreover, the results also show that there is an intermixing layer at the Ta/NiO (and NiO/Ta) interface due to a thermodynamically favorable reaction: 2Ta+5NiO+Ta2O5. This interface reaction has an effect on the exchange coupling as well. The thickness of the intermixing layer as estimated by XPS dept.-profiles was about 8-10 nm.

关键词： Fabrication Interfaces (materials) Magnetic materials Magnetrons Reaction kinetics Sputtering

Preparation and Structure-Property Regulation Mechanism of Reversible Thermochromic Polydiacetylene

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Chinese Journal of Polymer science 2024年第8期42卷 1111-1121页

作者： Zhi-Qing Ge Shuo Yan Zu-Xiong Pan Shan Lei Xuan-Zhi Mao chu Zhao Mo-Zhen wang Xue-Wu Ge Key Laboratory of Precision and Intelligent chemistry Department of Polymer Science and EngineeringUniversity of Science and Technology of ChinaHefei 230026China Marshall Laboratory of Biomedical Engineering International Cancer CenterLaboratory of Evolutionary Theranostics(LET)School of Biomedical EngineeringShenzhen University Medical SchoolShenzhen UniversityShenzhen 518055China Shanghai Institute of Applied physics Chinese Academy of SciencesShanghai 201800China university of Chinese Academy of sciences Beijing 100049China

The thermochromic mechanism and the structure-property regulation principle of reversible thermochromic polydiacetylene(PDA)materials have always been a challenging *** this work,a series of diacetylene monomers(m-PCDA)containing phenyl and amide or carboxyl groups were synthesized from 10,12-pentacosadiynoic acid(PCDA)through the esterification or amidation *** effects of the number and the distribution of the functional groups in m-PCDA molecules on their solid-state polymerization capability,and the thermochromic mechanism of their corresponding polymers(m-PDA)were investigated and discussed in *** results show that the m-PCDA monomers containing both benzene ring and groups that can form hydrogen bonding interactions have strong intermolecular interaction,and are easy to carry out the solid phase polymerization under 254-nm UV irradiation to obtain the corresponding new thermochromic m-PDA *** thermochromic behavior of m-PDA depends on its melting *** initial color-change temperature(blue to red)is determined by the onset melting tem perature,and the temperature range in which reversible color recovery can be achieved by repeat heating-cooling treatment is determined by its melting *** to the proposed thermochromic mechanism of PDA,various new PDA materials with precise thermochromic temperatu res and reversible thermochromic temperature ra nges can be designed and synthesized through the appropriate introduction of benzene ring and groups that can form hydrogen bonding interactions into the molecular structure of linear diacetylene *** work provides a perspective to the precise molecular structure design and the property regulation of the reversible thermochromic PDA materials.

关键词： Polydiacetylene Thermochromism Hydrogen bonding Chemical modification

Pulse-doubling perovskite nanowire lasers enabled by phonon-assisted multistep energy funneling

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light(science & Applications) 2024年第8期13卷 1645-1654页

作者： chunhu Zhao Jia Guo Jiahua Tao Junhao chu Shaoqiang Chen Guichuan Xing Hunan Provincial Key Laboratory of Carbon Neutrality and Intelligent Energy School of Resource&EnvironmentHunan University of Technology and Business410205 ChangshaChina Engineering Research Center for Nanophotonics and Advanced Instrument Ministry of EducationSchool of Physics and Electronic ScienceEast China Normal University200241 ShanghaiChina Joint Key Laboratory of the Ministry of Education Institute of Applied Physics and Materials EngineeringUniversity of Macao999078 MacaoChina

Laser pulse multiplication from an optical gain medium has shown great potential in miniaturizing integrated optoelectronic *** multiple quantum wells(MQWs)structures have recently been recognized as an effective gain media capable of doubling laser pulses that do not rely on external optical *** the light amplifications enabled with pulse doubling are reported based on the perovskite MQWs thin films,the micronanolasers possessed a specific cavity for laser pulse multiplication and their corresponding intrinsic laser dynamics are still ***,a single-mode double-pulsed nanolaser from self-assembled perovskite MQWs nanowires is realized,exhibiting a pulse duration of 28 ps and pulse interval of 22 ps based on single femtosecond laser pulse *** is established that the continuous energy building up within a certain timescale is essential for the multiple population inversion in the gain medium,which arises from the slowing carrier localization process owning to the stronger exciton–phonon coupling in the smaller-n ***,the double-pulsed lasing is achieved from one fast energy funnel process from the adjacent small-n QWs to gain active region and another slow process from the spatially separated *** report may shed new light on the intrinsic energy relaxation mechanism and boost the further development of perovskite multiple-pulse lasers.

关键词： doubling energy phonon

Hydrogenation and Anisotropic Expansions in R_3Fe_(29-x)T_x (R=Y, Ce, Nd, Sm, Gd, Tb and Dy; T=V and Cr)

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Journal of materials science & technology 1999年第1期15卷 5-9页

作者： Xiufeng HAM and Lanyng liN(materials science Center, Institute of Semiconductors, Chinese Academy of sciences, beijing 100083, china)T.Miyazaki(dept. of Applied physics, Faculty of Engineering, Tohoku university, Sendai 980-77, Japan)Fuming YANG(Institute materials science Center Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 China dept. of Applied physics Faculty of Engineering Tohoku University Sendai 980-77 Japan Institute of physics Chinese Academy of Sciences Beijing 100080 China materials Department Zhejiang University Hangzhou 310027 China

A systematic study of the phase formation, structure and magnetic properties of the R3Fe29-xTxcompounds (R=Y, Ce, Nd, Sm, Gd, Tb, and Dy; T=V and Cr) has been performed uponhydrogenation. The lattice constants and the unit cell volume of R3Fe29-xTxHy decrease withincreasing R atomic number from Nd to Dy, except for Ce, reflecting the lanthanide *** anisotropic expansions mainly along the a- and b-axis rather than along the c-axis areobserved for all of the compounds upon hydrogenation. Hydrogenation leads to an increase inthe Curie temperature and a corresponding increase in the saturation magnetization at roomtemperature for each compound. First order magnetization processes (FOMP) occur in theexternal magnetic fields for Nd3Fe24.5Cr4.5H5.0, Tb3Fe27.0Cr2.0H2.8, and Gd3Fe28.0Cr1.0H4.2compounds

关键词： Hydrogenation and Anisotropic Expansions in R3Fe x)T_x R=Y Ce Sm Gd Nd

Fluorescence Associated with Impurities in Nanostructured Al_2O_3

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Journal of materials science & technology 1996年第1期12卷 19-24页

作者： lide ZHANGt and GuoZhong wang(Institute of Solid State physics, Chinese Academy of sciences, Hefei 230031, china)Chimei MO(dept. of materials science and Engineering, university of science and technology of china, Hefei 230026, china)Tienan ZHAO(Institute Institute of Solid State physics Chinese Academy of Sciences Hefei 230031 China dept. of materials science and Engineering University of Science and Technology of China Hefei 230026 China Institute of physics Chinese Academy of Sciences Beijing 100080 China

The fluorescent spectra of nanostructured Al2O3 after heat-treating at different temperatureshave been systematically investigated. The results show that for η-Al2O3 and γ-Al2O3, two broadfluorescent bands P1 and P2 appear in the wavenumber range of 20000 cm-1 to 11500 cm-1,and P1 and P2 bands are located in the wavenumber range of 20000 cm-1 to 14500 cm-1 and14500 cm-1 to 11500 cm-1, respectively The P1 band can be attributed to the impurity Cr3+luminescence. This is consistent with other author's result for the Cr doped Al2O3. The P2band is a new fluorescent phenomenon, which has not been reported previously. In this paper,the condition of the appearance of P2 and its mechanism is discussed in detail.

关键词： Al Cr der OO Fluorescence Associated with Impurities in Nanostructured Al2O3

PRECIPITATION BEHAVIOR OF Co PHASES IN B2-ORDERED(Ni,Co)Al COMPOUND

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Acta Metallurgica Sinica(English Letters) 2002年第3期15卷 253-259页

作者： W.H. Tian, A.L. Fan and M. NemotoDepartment of materials physics and chemistry, university of science and technology beijing, beijing 100083, chinaSasebo National College of technology, Okishin 1-1, Sasebo 857-1193, Japan Manuscript received 4 July 2001 dept. of Mat. Phys. and Chem. Univ. of Sci. and Technol. Beijing Beijing 100083 China

The precipitation behavior of Co phases in B2-ordered (Ni,Co)Al has been investigated in terms of transmission electron microscopy. Fine precipitation of fcc-Co occurs in (Ni,Co)Al by aging at temperature over 973K. The orientation relationship between the fee-Co precipitates and the B2-(Ni,Co)Al matrix follows the Kurdjumow-Sachs (K-S) orientation relation. But when the aging temperature is under 873K the Co precipitates have a hcp crystal structure. The orientation relationship between the hep-Co precipitates and the B2-(Ni,Co)Al matrix follows the Burgers orientation relation. (Ni,Co)Al is hardened appreciably by the fine precipitation of both the fee-Co and hep-Co phases. The temperature dependence of the yield strength of precipitate-containing BS-ordered (Ni, Co)Al was investigated by compression tests over the range of 298-1273K. The fine precipitation of Co phases enhances greatly the low and intermediate temperature yield strength. When the deformation temperature was over 87SK, the strength of precipitate-containing (Ni, Co)Al is comparable to ternary dual-phase (Ni,Co)Al+Ni3Al alloy.

关键词： nickel aluminides age-hardening mechanical properties precipitates

Metallic Sb-stabilized porous silicon with stable SEI and high electron/ion conductivity boosting lithium-ion storage performance

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Rare Metals 2024年第9期43卷 4234-4242页

作者： Jia-Guo Deng Hao-Qin Feng Yu-Long Xu Si-Guang Guo Jian-Ping li Kai-Fu Huo Ji-Jiang Fu Biao Gao Pual-K.chu The State Key Laboratory of Refractories and Metallurgy and Institute of Advanced materials and Nanotechnology Wuhan University of Science and Technology Wuhan National Laboratory for Optoelectronics (WNLO) School of Optical and Electronic InformationHuazhong University of Science and Technology Department of physics Department of Materials Science & Engineeringand Department of Biomedical EngineeringCity University of Hong Kong

Silicon （Si） has mild discharge potential and high theoretical capacity,making it a highly desirable material for lithium-ion batteries （liBs）.Nevertheless,the excessive volume expansion,poor ion/electron conductiv ity and unstable solid electrolyte interface （SEI） hinde practical application to ***,the metallic antimony（Sb） stabilized porous Si （SiDSb） composite was prepared by magnesiothermic reduction of Sb2O3and Mg2Si and chemical etching to remove the by-product of *** highly conductive Sb nanodots embedded in the Si liga ments promote not only the formation of conductive and stable liF-rich SEI,but also the electron/ion transpor ability of *** to the outstanding bulk/interface stability,excellent conductivity,as well as ideal porous structure,the SiDSb electrode demonstrates a capacity of820 mAh·g-1after undergoing 320 turns at 1000 mA·***,it exhibits a stable capacity of 675 m Ah·g-1when tested at a higher current density of 5000 m A·*** results reveal a viable solution to solve three problems at the same time,namely the poor conductivity,inferior SEI and excessive volume expansion of Si,boding well for the design of Si-based materials for high-energy liBs.

关键词： Anodes Antimony lithium-ion batteries Silicon Solid electrolyte interphase