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Relationship between lattice mismatch and ionic conduction of Grain boundary in YSZ

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Progress in Natural Science:Materials International 2014年第1期24卷 83-86页

作者： Fei Ye Chunyu Yin Dingrong Ou Toshiyuki Mori School of Materials Science and Engineering Dalian University of Technology Key Laboratory of Materials Modification by Laser Ion and Electron BeamsDalian University of TechnologyMinistry of Education Laboratory of Fuel Cells Dalian Institute of Chemical PhysicsChinese Academy of Sciences Fuel Cell Materials Group Battery Materials UnitNational Institute for Materials Science

The Grain boundary plays an important role in the electrical behaviors of solid oxide electrolytes for solid state fuel cells. To reveal the relationship between the structure and the ionic conductivity of Grain boundary,the conductive properties of {1 1 1} and {1 1 0} twist grain boundaries in 8 mol% yttria-stabilized zirconia have been examined. These boundaries have a series of Σ values defined by the coincident site lattice model. It has been found that the activation energy of {1 1 1} twist Grain boundary increases and then decreases with the Σ value,while that of the {1 1 0} boundary shows an opposite trend. It is suggested that the properties can reflect the balance of the effects of lattice mismatch on the diffusion ability of oxygen vacancies and the segregation of oxygen vacancies and Y3 tions. Therefore,the properties in polycrystalline electrolyte can be adjusted by controlling the Grain boundary structures.

关键词： Yttria-stabilized zirconia Grain boundary Ionic conduction Mismatch

Computing Grain boundary“phase”diagrams

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Interdisciplinary Materials 2023年第1期2卷 137-160页

作者： Jian Luo Department of Nanoengineering Program of Materials Science and EngineeringUniversity of California San DiegoLa JollaCaliforniaUSA

grain boundaries(GBs)can be treated as two-dimensional(2-D)interfacial phases(also called“complexions”)that can undergo interfacial phase-like transitions.As bulk phase diagrams and calculation of phase diagram(CALPHAD)methods serve as a foundation for modern materials science,we propose to extend them to GBs to have equally significant impacts.This perspective article reviews a series of studies to compute the GB counterparts to bulk phase diagrams.First,a phenomenological interfacial thermodynamic model was developed to construct GB lambda diagrams to forecast high-temperature GB disordering and related trends in sintering and other properties for both metallic and ceramic materials.In parallel,an Ising-type lattice statistical thermodynamic model was utilized to construct GB adsorption(segregation)diagrams,which predicted first-order GB adsorption transitions and critical phenomena.These two simplified thermodynamic models emphasize the GB structural(disordering)and chemical(adsorption)aspects,respectively.Subsequently,hybrid Monte Carlo and molecular dynamics atomistic simulations were used to compute more rigorous and accurate GB“phase”diagrams.Computed GB diagrams of thermodynamic and structural properties were further extended to include mechanical properties.Moreover,machine learning algorithms were combined with atomistic simulations to predict GB properties as functions of four independent compositional variables and temperature in a 5-D space for a given GB in high-entropy alloys or as functions of five GB macroscopic(crystallographic)degrees of freedom plus temperature and composition for a binary alloy in a 7-D space.Other relevant studies are also examined.Future perspective and outlook,including two emerging fields of high-entropy grain boundaries(HEGBs)and electrically(or electrochemically)induced GB transitions,are discussed.

关键词： CALPHAD Grain boundary interfacial transition phase diagram

Non-equilibrium grain-boundary Segregation of Phosphorus in an Fe-17Cr Alloy

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Journal of Iron and Steel Research(International) 2014年第12期21卷 1136-1139页

作者： Kai WANG Hong SI Central Iron and Steel Research Institute Research Institute for Special Steel Dongbei Special Steel Group Co.Ltd.

In order to confirm the segregation characteristic of phosphorus in an Fe-17Cr alloy at Grain boundary, the phosphorus segregation was obtained by Auger electron spectroscopy. The results show that a maximum phosphorus segregation appeared at 450 ℃ for all specimens aged for 30 rain at 350, 400, 450, 500, and 600 ℃ after being solution-treated at 1 000 ℃ for 1 h. These results were analyzed by the characteristics of segregation peak temperature of non-equilibrium segregation.

关键词： Grain boundary non-equilibrium segregation ferritic steel

Temperature coefficients of Grain boundary resistance variations in a ZnO/p-Si heterojunction

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Journal of Semiconductors 2010年第12期31卷 11-15页

作者：刘秉策刘磁辉徐军易波 Department of Physics University of Science and Technology of China

Heteroepitaxial undoped ZnO films were grown on Si （100） substrates by radio-frequency reactive sputtering, and then some of the samples were annealed at N2-800℃ （Sample 1, S1） and 02-800℃ （Sample 2, S2） for 1 h, respectively. The electrical transport characteristics of a ZnO/p-Si heterojunction were investigated. We found two interesting phenomena. First, the temperature coefficients of Grain boundary resistances of S 1 were positive （positive temperature coefficients, PTC） while that of both the as-grown sample and S2 were negative （negative temperature coefficients, NTC）. Second, the I-V properties of S2 were similar to those common p-n junctions while that of both the as-grown sample and S 1 had double Schottky barrier behaviors, which were in contradiction with the ideal p-n heterojunction model. Combined with the deep level transient spectra results, this revealed that the concentrations of intrinsic defects in ZnO grains and the densities of interfacial states in ZnO/p-Si heterojunction varied with the different annealing ambiences, which caused the Grain boundary barriers in ZnO/p-Si heterojunction to vary. This resulted in adjustment electrical properties ofZnO/p-Si heterojunction that may be suitable in various applications.

关键词： ZnO/p-Si heterojunction Grain boundary temperature coefficients of Grain boundary resistances intrinsicdefects

Uniaxial Strain-Induced Grain boundary Migration in Titanium

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Acta Metallurgica Sinica(English Letters) 2021年第12期34卷 1715-1720页

作者： Tao Sun Aidong Tu Hao Wang Shu-Jun Li Hui Peng Jian-Ping Li State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Shanghai for Science and TechnologyShanghai 200093China National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid PhysicsMianyang 621900China

The mechanical response of a bi-crystal model with a 90°Grain boundary under external compressive and tensile loading parallel to the boundary plane normal was investigated with molecular dynamics simulations.The Grain boundary was found to migrate along two opposite directions upon compressive and tensile straining,with the formation of inter-connected coherent twin boundary and basal/prismatic boundary.The atomic details of such Grain boundary migration were unraveled,which indicated the role of interface dislocations.The temperature effect was also discussed.

关键词： Grain boundary Titanium Migration Dislocation Twinning

Effects of hydrogen on a tungsten Grain boundary:A first-principles computational tensile test

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Progress in Natural Science:Materials International 2011年第3期21卷 240-245页

作者： Hong-bo ZHOU,Shuo JIN,Ying ZHANG,Guang-hong LU Department of Physics,Key Laboratory of Micro-nano Measurement-Manipulation and Physics(Ministry of Education),Beijing University of Aeronautics and Astronautics,Beijing 100191,China Department of Physics Key Laboratory of Micro-nano Measurement-Manipulation and Physics (Ministry of Education) Beijing University of Aeronautics and Astronautics Beijing 100191 China

A first-principles computational tensile test has been preformed to investigate the effects of hydrogen on a tungsten Grain boundary.Ft has been found that the maximum ideal tensile strength of the tungsten Grain boundary with hydrogen atom segregation was 32.85 GPa,which was about 9%lower than that of the clean tungsten Grain boundary(36.23 GPa).This indicated that the theoretical strength of the tungsten Grain boundary became weaker in the presence of the hydrogen atom.Atomic configuration analysis showed that the Grain boundary fracture was caused by the interfacial bond breaking.The Griffith fracture energy was calculated to be 161 meV/A~2(2.58 J/m~2) and 155 meV/A~2(2.48 J/m~2) for the tungsten Grain boundary without and with the hydrogen atom segregation,respectively.The solution energy of the hydrogen atom in a fracture free surface was -0.31 eV,which was 0.08 eV lower than that of the hydrogen atom in a tungsten Grain boundary.This indicated that hydrogen was a Grain boundary embrittler according to the Rice-Wang thermodynamic theory.The Bader charge analysis suggested that the physical origin for hydrogen-induced embrittlement was the charge transfer induced by hydrogen in the tungsten Grain boundary.

关键词： tungsten hydrogen Grain boundary tensile strength first-principles

A molecular dynamics study on the tribological behavior of molybdenum disulfide with Grain boundary defects during scratching processes

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Friction 2021年第5期9卷 1198-1212页

作者： Boyu WEI Ning KONG Jie ZHANG Hongbo LI Zhenjun HONG Hongtao ZHU Yuan ZHUANG Bo WANG School of Mechanical Engineering University of Science and Technology BeijingBeijing 100083China School of Mechanical Materials&Mechatronics EngineeringUniversity of WollongongWollongongNSW 2522Australia Beijing Institute of Spacecraft System Engineering Beijing 100094China

The effect of Grain boundary(GB)defects on the tribological properties of MoS_(2) has been investigated by molecular dynamics(MD)simulations.The GB defects‐containing MoS_(2) during scratching process shows a lower critical breaking load than that of indentation process,owing to the combined effect of pushing and interlocking actions between the tip and MoS_(2) atoms.The wear resistance of MoS_(2) with GB defects is relevant to the misorientation angle due to the accumulation of long Mo-S bonds around the GBs.Weakening the adhesion strength between the MoS_(2) and substrate is an efficient way to improve the wear resistance of MoS_(2) with low‐angle GBs.

关键词： MoS_(2) Grain boundary tribological behavior molecular dynamics misorientation angle

Nonequilibrium Grain boundary Segregation of Sulfur and Its Effect on Intergranular Corrosion for 304 Stainless Steel

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Journal of Iron and Steel Research(International) 2011年第6期18卷 61-66页

作者： WANG Kai XU Ting-dong SHAO Chong YANG Chun Superalloy Department Central Iron and Steel Research Institute Beijing 100081 China National Analysis Center of Iron and Steel Central Iron and Steel Research Institute Beijing 100081 China

The data obtained by bending tests for intergranular embrittlement after 45 h and 450 h exposure to Strauss solution have been reported for 304 stainless steel. The results show that an embrittlement peak appears at 650℃ for all samples quenched from 1260℃ and then sensitized for 150 h at 480, 565, 650, 730, 815 and 900℃ respectively. The temperature corresponding to the embrittlement peak is decreased to 565℃ when the sensitizing time is prolonged to 1 500 h. In this paper, these data are analyzed with an isothermal kinetic model of nonequilibrium Grain boundary segregation, indicating that the embrittlement peak is related to the critical time for nonequilibrium Grain boundary segregation of sulfur.

关键词： stainless steel intergranular corrosion nonequilibrium segregation Grain boundary sulfur

Nonequilibrium Grain boundary Segregation of Phosphorus in Ni-Cr-Fe Superalloy

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Journal of Iron and Steel Research(International) 2011年第1期18卷 61-67页

作者： WANG Kai SI Hong YANG Chun XU Ting-dong Superalloy Department Central Iron and Steel Research Institute Beijing 100081 China National Analysis Center of Iron and Steel Central Iron and Steel Research Institute Beijing 100081 China

In virtue of Auger electron spectroscopy, the Grain boundary concentrations of phosphorus in Ni-Cr-Fe superalloy are measured after solution treatment at 1 180 ℃ for 45 min. The results show that a peak of phosphorus concentration occurs at about 180 min during isothermal ageing at 500 ℃, and a maximum concentration of phosphorus appears also at about 500 ℃ for all specimens aged for 20 min at temperatures of 200, 400, 500, 700 and 800 ℃. The results are analyzed with the laws of nonequilibrium Grain boundary segregation. It is found from the analysis that peaks are related to critical time for nonequilibrium Grain boundary segregation of phosphorus.

关键词： nonequilibrium segregation Grain boundary phosphorus nickel based superalloy