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Nano Research 2021年第6期14卷 1625-1649页

作者： Hui Cai Yiling Yu Yu-Chuan Lin Alexander A.Puretzky David B.Geohegan Kai Xiao Center for Nanophase Materials Sciences Oak Ridge National LaboratoryOak RidgeTN37831USA

Two-dimensional(2D)materials hold great promise for applications in optoelectronics,quantum information science,and energy conversion due to their remarkable properties imbued by their physical characteristics.Although heterogeneities in their intrinsic structure are the major challenges limiting their synthesis and predictable properties,they also provide a pathway to controllably tune the properties and broaden the potential of 2D materials.Heterogeneities that can be tailored,including defects,dopants,strain,edges,and layer stackings offer transformative opportunities in heterogeneous 2D materials through the introduction of novel properties for technological applications.This article provides a review of recent progress in studying heterogeneities in 2D materials.The review uses examples from our work to develop a strategy to understand the heterogeneities across multiple length scales to link the effect of heterogeneity at the nanoscale with the macroscale properties of 2D materials.We describe specific types of heterogeneities and explore novel synthesis and processing methods for their controlled production with example of the potential impact and applications enabled by their intriguing properties.Finally,we provide a perspective on how to extend the range of tunable properties through further engineering the heterogeneities in 2D materials.

关键词： wo-dimensional(2D)materials heterogeneity defect strain Grain boundary heterostructures phase

Regulation of Active Oxygen Species by grain Boundaries to Optimize Reaction Paths toward Aerobic Oxidations

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Energy & Environmental Materials 2021年第3期4卷 444-450页

作者： Zicheng Xie Jie Zhang Yu Xiao Yangcenzi Xie Wenkun Zhu Shuyi Yu Tingting Hou Shuquan Liang Liangbing Wang State Key Laboratory for Powder Metallurgy Key Laboratory of Electronic Packing and Advanced Functional Materials of Hunan ProvinceSchool of Materials Science and EngineeringCentral South UniversityChangsha 410083China State Key Laboratory of Environment-friendly Energy Materials Southwest University of Science and TechnologyMianyang 621010China

Aerobic oxidation by using molecular oxygen(O_(2))as the oxidant is highly attractive,in which activating O_(2)to reactive oxygen species(ROS)is a prerequisite.Although some progress has been achieved in regulating ROS by heterogeneous catalysts,the strategies to efficiently control ROS in aerobic oxidation are still urgently desired.Herein,grain boundaries(GBs)in metal oxides are discovered to be able to facilely regulate ROS.Impressively,MoO_(3)nanocrystals with high density of GBs(MoO_(3)-600)deliver a mass activity of 83 mmol g^(-1)h^(-1)in aerobic oxidation of benzyl alcohol,7 and 8 times as high as that of MoO_(3)nanoparticles without GBs and Pt/C,respectively.In addition,the selectivity of benzoic acid is 100%during whole reaction process over MoO_(3)-600.Mechanistic studies reveal that the oxygen atoms at GBs in MoO_(3)-600 are highly active to form·OH radicals with the generation of oxygen vacancies,while the oxygen vacancies are replenished by O_(2).The reaction path directly contributes to the excellent catalytic performance.

关键词： molybdenum oxide aerobic oxidation Grain boundary reactive oxygen species benzyl alcohol

Capture efficiency and bias from the defect dynamics near grain boundaries in BCC Fe using mesoscale simulations

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Journal of Materials Science & Technology 2021年第34期93卷 169-177页

作者： Jun Chai Shuo Jin Ziang Yu Haixuan Xu Guang-Hong Lu School of Physics.Beihang University Beijing 100191China Beijing Key Laboratory of Advanced Nuclear Materials and Physics Beihang UniversityBeijing 100191 China Department of Materials Science and Engineering University of TennesseeKnoxville.TN 37996United States Joint Institute for Advanced Materials KnoxvilleTN 37996United States

The capture efficiency describes the capability of a sink,such as a Grain boundary(GB),dislocation,and void,to absorb point defects(PDs).The bias defines the difference in capture efficiency between the absorption of a vacancy and dumbbell at a sink.Complete kinetic information on PDs,including diffusion barriers and diffusion orientations,as well as accurate saddle points,are needed to determine the capture efficiency and bias at a sink accurately,which is computationally demanding.In the present study,the Self-Evolving Atomistic Kinetic Monte Carlo(SEAKMC)method was used to investigate the defect dynamics of PDs near different types of grain boundaries(GBs)(with both 100 and 110 families)accurately in body-centered cubic(BCC)iron(Fe).The capture efficiency,sink strength,and bias factor of different types of GBs were determined in Fe,which,different from traditional rate theory estimation,showed a distinct capture efficiency,sink strength,and bias in different GBs.The results demonstrate a strong positive correlation between the capture efficiency and the GB strain width,instead of the GB misorientation,GB energy,or GB-PD binding energy,which have been investigated previously.This work provides valuable insight into the radiation-induced microstructural evolution of GBs.

关键词： Iron Grain boundary Capture efficiency Bias SEAKMC

INFLUENCE OF Grain boundary MORPHOLOGY ON CREEP AND FRACTURE BEHAVIOURS OF SUPERALLOYS IN SULFUR-CONTAINING ENVIRONMENT

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Acta Metallurgica Sinica(English Letters) 1991年第2期4卷 118-122页

作者： ZHANG Yuanhu SUN Jian XIANG Yi HU Gengxiang Shanghai Jiaotong University,Shanghai,ChinaLI Tiefan Institute of Corrosion and Protection of Metals,Academia Sinica,Shenyang,China Yuanhu,Department of Materials Science and Engineering,Shanghai Jiaotong University,Shanghai,200030

Studies on the high temperature creep and fracture behaviours in air or in SO_2 contaminated environment for the Fe-base superalloy GH302 with flat or zigzag grain boundaries(GB) and the Ni-base superalloy Rene 80 were carried out.Although the creep rupture properties of the GH302 with zigzag GB was remarkably superior to that of flat GB in air,the properties of both droped dramatically in 10% SO_2-air environment,the creep rupture properties of the directional solidified Rene 80 were much better than that of the conventionally cast alloy in air,and also kept the same property in SO_2 contaminated environment as in air.Owing to the interaction between creep and sulphidation,the failure mechanism relates to the formation of molten Ni-Ni-3S_2 eutectic along GB,led to the premature failure of the alloy.

关键词： superalloy Grain boundary sulphidation oxidation creep rupture

Thermal conductivity prediction of MgAl2O4:a non-equilibrium molecular dynamics calculation

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Journal of Iron and Steel Research(International) 2020年第5期27卷 500-505页

作者： Cheng-ming Ni Hua-wei Fan Xu-dong Wang Man Yao School of Materials Science and Engineering Dalian University of TechnologyDalian 116000LiaoningChina

Magnesium aluminate spinel(MgAl2O4)is widely used in steel metallurgy industry.Thermal conductivity at high temperature signifcantly infuences the cooling process of blast furnace and the heat preservation of steel converter.The efect of external(temperature)and internal(antisite defect and Grain boundary)factors on the thermal conductivity of MgAl2O4 was studied with non-equilibrium molecular dynamics.The main factors afecting the thermal conductivity of MgAl2O4 were summarized.In the temperature range of 100-2000 K,the results showed that the thermal conductivity of MgAl2O4 changed from 11.54 to 4.95 W/(m K)with the increase in temperature and was relatively stable at the temperature above 1000 K.The thermal conductivity of MgAl2O4 declined frst and then rose with the increase in the antisite defects,and the minimum value was 6.95 W/(m K)at the inversion parameter i=0.35.In addition,grain boundaries reduced the thermal conductivity of MgAl2O4 by 20%-30%at temperature below 1000 K comparing with the non-Grain boundary system.The Grain boundary rotation angle at temperature above 1000 K had less efect on the thermal conductivity than that below 1000 K.Present simulation scheme for thermal conductivity of MgAl2O4 can also be applied to the study of other nonmetallic ceramics.

关键词： Non-equilibrium molecular dynamics Thermal conductivity Magnesium aluminate spinel Antisite defect Grain boundary

Enhanced tensile ductility of tungsten microwires via high-density dislocations and reduced grain boundaries

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Journal of Materials Science & Technology 2021年第36期95卷 193-202页

作者： Chaoqun Dang Weitong Lin Fanling Meng Hongti Zhang Sufeng Fan Xiaocui Li Ke Cao Haokun Yang Wenzhao Zhou Zhengjie Fan Ji-jung Kai Yang Lu Department of Mechanical Engineering City University of Hong KongHong KongChina Department of Materials Science and Engineering Southern University of Science and TechnologyShenzhenChina School of Physical Science and Technology ShanghaiTech UniversityShanghaiChina Nano-Manufacturing Laboratory(NML) Shenzhen Research InstituteCity University of Hong KongShenzhenChina State Key Laboratory for Manufacturing Systems Engineering Xi'an Jiaotong UniversityXi'anChina Centre for Advanced Nuclear Safety and Sustainable Development City University of Hong KongHong KongChina

Despite being strong with many outstanding physical properties,tungsten is inherently brittle at room temperature,restricting its structural and functional applications at small scales.Here,a facile strategy has been adopted,to introduce high-density dislocations while reducing grain boundaries,through electron backscatter diffraction(EBSD)-guided microfabrication of cold-drawn bulk tungsten wires.The designed tungsten microwire attains an ultralarge uniform tensile elongation of~10.6%,while retains a high yield strength of~2.4 GPa.in situ TEM tensile testing reveals that the large uniform elongation of tungsten microwires originates from the motion of pre-existing high-density dislocations,while the subsequent ductile fracture is attributed to crack-tip plasticity and the inhibition of Grain boundary cracking.This work demonstrates the application potential of tungsten microcomponents with superior ductility and workability for micro/nanoscale mechanical,electronic,and energy systems.

关键词： Tungsten Dislocation Grain boundary Ductility In situ TEM Nanomechanics

Effects of Heat Treatment and Additive LiF on the Properties of Solid-State Electrolyte of Li_(1.5)Al_(0.5)Ge_(1.5)(PO_(4))_(3)

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Energy & Environmental Materials 2021年第2期4卷 208-212页

作者： Jinhang Lv Ruilin Zheng Peng Lv Wei Wei College of Electronic and Optical Engineering Nanjing University of Posts and Telecommunications9 Wenyuan RoadNanjing Jiangsu 210023China

A solid electrolyte of LAGP[Li_(1.5)Al_(0.5)Ge_(1.5)(PO_(4))_(3)]contained 0.5 wt%Li F was prepared by using low-volatile raw materials.The effects of different heat treatment conditions(750–900°C,4–10 h)and additive(Li F)on the ionic conductivity,structural morphology,and crystal transformation process were investigated in detail.EIS(electrochemical impedance spectroscopies)showed that the ionic conductivity of LAGP contained 0.5 wt%Li F had a highest value of 3.17×10^(-4)S cm^(-1)with low activation energy(0.31 e V)after treating 825°C for 6 h,more than LAGP of 2.45×10^(-4)S cm^(-1).DSC analysis and SEM images indicated that adding a small amount of Li F to LAGP not only can lower the glass transition temperature(from 513°C to507°C)and crystallization temperature(from 622°C to 605°C),but also can modify the Grain boundary and increase the relative density of LAGP(from 95.8%to 97.7%).

关键词： glass ceramics Grain boundary ionic conductivity LAGP solid-state electrolytes

Influence of grain size on strength of polymineralic crystalline rock: New insights from DEM grain-based modeling

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第4期13卷 755-766页

作者： Jun Peng Louis Ngai Yuen Wong Cee Ing Teh Department of Earth Sciences The University of Hong KongHong KongChina School of Civil and Environmental Engineering Nanyang Technological UniversitySingapore Shenzhen Institute of Research and Innovation The University of Hong KongShenzhenChina

grain size effect on rock strength is a topic of great interest in geotechnical engineering.A consensus obtained from earlier laboratory tests is that rock strength generally decreases with the increase of grain size for both silicate and carbonate rocks;however,some recent numerical results conflict with such laboratory test results.To address this intriguing issue,the effect of grain size on strength of polymineralic crystalline rock with low porosity is investigated numerically using the grain-based modeling(GBM)approach in discrete element method(DEM)by interpreting micro-cracking process in response to loading.In agreement with some previous DEM simulation results,the simulated rock strength is found to increase with increasing grain size for both homogeneous and heterogeneous models,even when the number of assembled disks in one mineral grain changes.The mechanism of strength increase with increasing grain size is mainly associated with the number of assembled smooth-joint contacts along grain interfaces and the generation of Grain boundary cracks in response to loading.The grain interfaces significantly weaken the integrity of the rock model,which is similar to effects of inherent defects in real rock.As the grain size increases,fewer grain interfaces are built in the model and the rock strength becomes much higher.Hence,by solely changing the mineral grain size in a model,the mechanism of grain size effect as observed in laboratory tests cannot be replicated.To address this issue,a method of degradation of Grain boundary strength parameters is used to mimic the possible mechanism of grain size effect.The simulated strength using the method becomes comparable with those obtained from laboratory tests when the heterogeneity in the rock is considered.Degradation of Grain boundary parameters with increasing grain size provides a plausible explanation for the grain size effect on rock strength.

关键词： grain size Rock strength grain-based modeling(GBM)approach Grain boundary Micro-cracking behavior

Texture modification and mechanical properties of AZ31 magnesium alloy sheet subjected to equal channel angular bending

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Journal of Materials Science & Technology 2021年第8期67卷 211-225页

作者： Shuai-Feng Chen Hong-Wu Song Ming Cheng Ce Zheng Shi-Hong Zhang Myoung-Gyu Lee Institute of Metal Research Chinese Academy of SciencesShenyang110016China Department of Materials Science and Engineering&Research Institute of Advanced Materials(RJAM) Seoul National UniversitySeoul08826Republic of Korea University of Chinese Academy of Sciences Beijing100049China

Analysis of the recently proposed equal channel angular bending(ECAB)process is provided on thin hotrolled AZ31 magnesium alloy sheets.In particular,effects of deformation temperature and strain path on the texture evolution and mechanical properties are systematically investigated under single pass ECAB at various temperatures and multi-pass ECAB process that involves changes in strain paths.It is found that simultaneous activation of multiple twinning types is successfully introduced during ECAB,which results in obvious tilted component of basal texture.Attributed to the domination of extension twins,weaker basal textures are detected after both single pass ECAB at 150℃and three cross passes ECAB at 200℃.After annealing,the basal texture is further weakened via twin-related recrystallization and the annealed microstructure is featured with mixture of basal and non-basal orientated grains.Additionally,the effect of grain orientation on the mode of plastic deformation and the roles of grain orientation and Grain boundary on the local strain accommodation are coherently studied.This study reveals that over 60%increase of uniform elongation with marginal reduction of tensile strength less than 5%can be achieved for single pass ECAB at 150℃and three cross passes ECAB at 200℃,which is the result of larger fraction of grains favored with extension twinning and better local strain accommodation.

关键词： Equal channel angular bending Magnesium alloy Thin sheet Texture Grain boundary Mechanical properties

Effects of post-sinter annealing on microstructure and magnetic properties of Nd–Fe–B sintered magnets with Nd–Ga intergranular addition

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Chinese Physics B 2021年第6期30卷 559-563页

作者：朱金豪金磊金哲欢丁广飞郑波郭帅陈仁杰闫阿儒 CAS Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application TechnologyNingbo Institute of Materials Technology and EngineeringChinese Academy of Sciences(CAS)Ningbo 315201China University of Chinese Academy of Sciences Beijing 100049China

We investigate the effects of post-sinter annealing on the microstructure and magnetic properties in B-lean Nd–Fe–B sintered magnets with different quantities of Nd–Ga intergranular additions. The magnet with fewer Nd–Ga additions can enhance 0.2 T in coercivity, with its remanences nearly unchanged after annealing. With the further increase of the Nd–Ga addition, the annealing process leads coercivity to increase 0.4 T, accompanied by a slight decrease of remanence. With the Nd–Ga addition further increasing and after annealing, however, the increase of coercivity is basically constant and the change of remanence is reduced. Microstructure observation indicates that the matrix grains are covered by continuous thin Grain boundary phase in the magnets with an appropriate Nd–Ga concentration after the annealing process. However, the exceeding Nd–Ga addition brings out notable segregation of Grain boundary phase, and prior formation of part RE6 Fe13 Ga phase in the sintered magnet. This prior formation results in a weaker change of remanence after the annealing process.Therefore, the diverse changes of magnetic properties with different Nd–Ga concentrations are based on the respective evolution of Grain boundary after the annealing process.

关键词： Nd–Fe–B magnet magnetic properties Grain boundary microstructures