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Diffusion mechanism of immiscible Fe-Mg system induced by high-density defects at the steel/Mg composite interface

Journal of Materials Science & Technology 2023年第13期144卷 150-160页

作者： Yanlan Sun Xuefeng Liu Wenjing Wang Yaohua Yang Weiliang Zhang Beijing Advanced Innovation Center for Materials Genome Engineering University of Science and Technology BeijingBeijing 100083China Beijing Laboratory of Metallic Materials and Processing for Modern Transportation University of Science and Technology BeijingBeijing 100083China Key Laboratory for Advanced Materials Processing of Ministry of Education University of Science and Technology BeijingBeijing 100083China

Due to positive mixing heat between Fe and Mg,it is difficult to diffuse for Fe-Mg at the interface of steel/Mg laminated composites,resulting in the inability to achieve high-strength metallurgical bonding.In this paper,20#steel/Mg laminated composites were prepared by large deformation rolling and subse-quent diffusion heat treatment process.The interfacial bonding strength was improved by constructing high-density crystal defects at the interface to promote element diffusion.The mechanisms of interface morphology evolution and element diffusion were analyzed by finite element simulation and theoretical calculation.The results show after diffusion heat treatment,the bond strength of the large deformation rolled interface was increased from 14 to 30 MPa.Fe-Mg transition layer with about 80 nm thickness as well as high-density vacancies,dislocations and grain boundaries were formed in the large deforma-tion rolled interface region.During diffusion heat treatment,Mg elements diffused into grain interior and grain boundary regions of 20#steel under the effect of heat-force coupling,and the thickness of Fe-Mg transition layer increased to 150 nm,forming an Fe-based supersaturated solid solution.The in-terface with high-density defects constituted a non-equilibrium interface.The 20#steel internal energy in the non-equilibrium interface is able to overcome positive mixing heat of immiscible Fe-Mg system and provide the driving force for Mg elements diffusion.Promoting elemental diffusion by constructing high-density defects can be a new concept to achieve metallurgical bonding at the interface of immiscible metal laminated composites.

关键词： Steel/Mg composite interface Immiscible Fe-Mg system Non-equilibrium interface Diffusion mechanism

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Multi-electron reaction and fast Al ion diffusion of δ-MnO_(2) cathode materials in rechargeable aluminum batteries via first-principle calculations

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Chinese Chemical Letters 2024年第4期35卷 248-254页

作者： Lumin Zheng Ying Bai Chuan Wu School of Materials Science&Engineering Beijing Institute of TechnologyBeijing 100081China Yangtze Delta Region Academy of Beijing Institute of Technology Jiaxing 314019China

Rechargeable aluminum batteries with multi-electron reaction have a high theoretical capacity for next generation of energy storage devices. However, the Diffusion mechanism and intrinsic property of Al insertion into MnO_(2) are not clear. Hence, based on the first-principles calculations, key influencing factors of slow Al-ions diffusion are narrow pathways, unstable Al-O bonds and Mn^(3+) type polaron have been identified by investigating four types of δ-MnO_(2)(O3, O'3, P2 and T1). Although Al insert into δ-MnO_(2) leads to a decrease in the spacing of the Mn-Mn layer, P2 type MnO_(2) keeps the long(spacious pathways)and stable(2.007–2.030 A) Al-O bonds resulting in the lower energy barrier of Al diffusion of 0.56 e V. By eliminated the influence of Mn^(3+)(low concentration of Al insertion), the energy barrier of Al migration achieves 0.19 e V in P2 type, confirming the obviously effect of Mn^(3+) polaron. On the contrary, although the T1 type MnO_(2) has the sluggish of Al-ions diffusion, the larger interlayer spacing of Mn-Mn layer,causing by H_(2)O could assist Al-ions diffusion. Furthermore, it is worth to notice that the multilayer δ-MnO_(2) achieves multi-electron reaction of 3|e|. Considering the requirement of high energy density, the average voltage of P2(1.76 V) is not an obstacle for application as cathode in RABs. These discover suggest that layered MnO_(2) should keep more P2-type structure in the synthesis of materials and increase the interlayer spacing of Mn-Mn layer for providing technical support of RABs in large-scale energy storage.

关键词： Rechargeable aluminum batteries δ-MnO_(2) First-principles calculations Multi-electron reaction Diffusion mechanism

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CO_2 adsorption performance of different amine-based siliceous MCM-41 materials

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Journal of Energy Chemistry 2015年第3期24卷 322-330页

作者： Zhilin Liu Yang Teng Kai Zhang Honggang Chen Yongping Yang Beijing Key Laboratory of Emission Surveillance and Control for Thermal Power Generation North China Electric Power University

A series of amine-based adsorbents were synthesized using siliceous MCM-41 individually impregnated with four different amines（ethylenediamine（EDA）,diethylenetriamine（DETA）,tetraethylenepentamine（TEPA） and pentaethylenehexamine（PEHA）） to study the effect of amine chain length and loading weight on their CO2 adsorption performances in detail.The adsorbents were characterized by FT-IR,elemental analysis,and thermo-gravimetric analysis to confirm their structure properties.Thermo-gravimetric analysis was also used to evaluate the CO2 adsorption performance of adsorbents.Longer chain amine-based materials can achieve higher amine loadings and show better thermal stability.The CO2 adsorption capacities at different temperatures indicate that the CO2 adsorption is thermodynamically controlled over EDAMCM41 and DETA-MCM41,while the adsorption over TEPA-MCM41 and PEHA-MCM41 is under kinetic control at low temperature.The chain length of amines affects the CO2 adsorption performance and the adsorption mechanism significantly.The results also indicate that CO2 adsorption capacity can be enhanced despite of high operation temperatures,if appropriate amines（TEPA and PEHA） are applied.However,adsorbents with short chain amine exhibit higher adsorption and desorption rates due to the collaborative effect of rapid reaction mechanisms of primary amines and less diffusion resistance of shorter chain length amines.

关键词： amine-based MCM-41 CO2adsorption chain length adsorption mechanism Diffusion mechanism

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Simulation of the neck growth of non-isometric biosphere during initial sintering

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Acta Metallurgica Sinica(English Letters) 2009年第4期22卷 263-274页

作者： Jixiang DU Shuhua LIANG Xianhui WANG Zhikang FAN Department of Material Science ＆ Engineering Xi＇an University of Technology Xi＇an 710048 China

Because powders are mostly non-isometric during the sintering process, copper powders were chosen to study the effects of four material transport mechanisms, including surface diffusion, grain-boundary diffusion, volume diffusion, and multi-couplings. These material transport mechanisms were studied with respect to sintering neck growth of a non-isometric biosphere during initial sintering. The evolution of the neck growth in the four transport mechanisms was simulated by Visual C＋＋ as well based on the model of different particles. The results show that the increase of the sintering temperature, both the grain-boundary diffusion and volume diffusion play primary roles in neck growth, while surface diffusion gradually becomes the secondary mechanism. Both the sintered neck and the shrinkage of the two centers increase with increasing temperature by means of the coupling Diffusion mechanism. The radius of the sintering neck decreased, and the shrinkage rate of the two centers increased with an increase of the diameter ratio of the two spheres.

关键词： Sintering simulation Non-isometric biosphere model Diffusion mechanism Sintering neck

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Variational Data Assimilation Method Using Parallel Dual Populations Particle Swarm Optimization Algorithm

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Wuhan University Journal of Natural Sciences 2024年第1期29卷 59-66页

作者： WU Zhongjian LI Junyan Detroit Green Institute of Technology Hubei University of TechnologyWuhan 430068HubeiChina School of Information Management Central China Normal UniversityWuhan 430079HubeiChina

In recent years,numerical weather forecasting has been increasingly emphasized.Variational data assimilation furnishes precise initial values for numerical forecasting models,constituting an inherently nonlinear optimization challenge.The enormity of the dataset under consideration gives rise to substantial computational burdens,complex modeling,and high hardware requirements.This paper employs the Dual-Population Particle Swarm Optimization(DPSO)algorithm in variational data assimilation to enhance assimilation accuracy.By harnessing parallel computing principles,the paper introduces the Parallel Dual-Population Particle Swarm Optimization(PDPSO)Algorithm to reduce the algorithm processing time.Simulations were carried out using partial differential equations,and comparisons in terms of time and accuracy were made against DPSO,the Dynamic Weight Particle Swarm Algorithm(PSOCIWAC),and the TimeVarying Double Compression Factor Particle Swarm Algorithm(PSOTVCF).Experimental results indicate that the proposed PDPSO outperforms PSOCIWAC and PSOTVCF in convergence accuracy and is comparable to DPSO.Regarding processing time,PDPSO is 40%faster than PSOCIWAC and PSOTVCF and 70%faster than DPSO.

关键词： parallel algorithm variational data assimilation dual-population particle swarm optimization algorithm Diffusion mechanism

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Transitions between Single-File and Fickian Self-diffusion for Fluids Confined in Carbon Nanotubes,Bundles and Activated Carbons

Transitions between Single-File and Fickian Self-Diffusion f...

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第十届全国计算(机)化学学术会议

作者： Joshua D.Moore Jeremy Palmer Keith E.Gubbins Department of Chemical ＆ Biomolecular Engineering and Center for High Performance Simulation（CHiPS） North Carolina State UniversityRaleighNC 27695-7905 U.S.A

＜正＞Carbon nanotubes are important building blocks for nanocomposite materials and nanomachinery due to their unique physical properties（electronic,optical,thermal,mechanical, etc.） and have received extensive interest in materials science.One possible application is the use of carbon nanotubes as host structures for gas separation as they yield faster diffusion rates of fluid molecules than other widely used materials（e.g.,zeolites）.Several Diffusion mechanisms are possible in narrow cylindrical pores,but these are still poorly understood.Among the most important are ballistic motion,Fickian diffusion,and single-file diffusion.Ballistic motion occurs for very short times,before the molecule has had a chance to collide with anything. For longer times the motion becomes either Fickian or single-file.If the pore is large enough, the molecules will diffuse in 3-dimensions as they would in a bulk fluid（Fickian diffusion）,but if the pore diameter becomes small enough the diffusion will crossover from Fickian to single-file diffusion,where the molecules can no longer pass each other.Clearly single-file motion is much slower than Fickian,which is much slower than ballistic.

关键词： single-file Fickian carbon nanotubes bundle Diffusion mechanism bimodal diffusion

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OBSERVATION OF EPITAXIAL OVERLAYER OF METALS AT ATOMIC LEVEL

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Acta Metallurgica Sinica(English Letters) 1989年第4期2卷 231-236页

作者： T.T.TSONG The Pennsylvania State University U.S.A.

Observation of epitaxial overlayer of metals at atomic level has been successfully observed in field ion microscope with 5 ns pulsed-laser heating.The condition of superlattice layer growth depends on the surface free energy and the lattice misfit.Many defects,such as vacancies,va- cancy clusters,voids,dislocations and twins are produced during epitaxial growth because of the lattice misfit even though the condition of surface free energy is satisfied.Alloying is ob- served to occur on the surface of the metal during the epitaxial growth.diffusion is probably via the exchange mechanism.

关键词： field ion microscope epitaxial growth crystal defect Diffusion mechanism superlattice

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EFFECTS OF CONVECTIVE FLUID MOTION UPON OXIDE CRYSTAL GROWTH IN HIGH TEMPERATURE SOLUTION

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空间科学学报 2002年第Z1期22卷 159-159页

作者： JIN Weiqing CAI Lixia LIANG Xinan PAN Zhilei Shanghai Institute of Ceramics The Chinese Academy of Sciences Shanghai 200050 P.R. China Shanghai Institute of Ceramics The Chinese Academy of Sciences Shanghai 200050 P.R. China Shanghai Institute of Ceramics The Chinese Academy of Sciences Shanghai 200050 P.R. China Shanghai Institute of Ceramics The Chinese Academy of Sciences Shanghai 200050 P.R. China

　　For understanding of the influence of convective flow on crystal growth, space high temperature in situ observation instrument (SHITISOI) is dedicated to visualize and record the whole growth process of oxide crystals in high temperature up to 1000°C. Model experiments using transparent liquids such as KNbO3 and a mix ture of Li2B4O7+KNbO3 were chosen to investigate effects on ground and in space.On the earth, an investigation of growth kinetics of KNbO3 crystal related to two different states of convection: diffusive-advective flow and diffusive-convective flow,has been performed. The per unit length of a step e is calculated from the exper imental data for two different states of convection. Analyses of these data show the effect of buoyancy convection is to enhance the sharpness of the interface. The growth of KNbO3 crystals from solution of KNbO3+Li2B4O7 was investigated in space. The streamlines of the steady thermocapillary convection in Li2B4O7 solvent was observed. Due to thermocapillary convection, KNbO3 crystal grains grew and filled the whole solution homogeneously. Earth-based quenching experiments are de signed in order to study polyhedral instability of KNbO3 crystal, which is controlled by Diffusion mechanism limitation. In all cases, when the crystal was nucleated near air/solution surface, it lost its polyhedral stability and varied from polyhedrons to dedrites. The thickness of Diffusion mechanism limitation layer is about 60μm.……

关键词： HIGH TEMPERATURE thermocapillary convection Diffusion mechanism high temperature polyhedral instability in situ observation growth kinetics oxide crystals crystal growth the earth in order

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