三模晶体相场法研究应变诱导石墨烯晶界位错演化  

Strain induced dislocation evolution at graphene grain boundary by three-mode phase-field crystal method

作　　者：高丰 李欢庆 宋卓 赵宇宏[1,2,3] Gao Feng;Li Huan-Qing;Song Zhuo;Zhao Yu-Hong(School of Materials Science and Engineering,North University of China,Taiyuan 030051,China;Beijing Advanced Innovation Center for Materials Genome Engineering,University of Science and Technology Beijing,Beijing 100083,China;Liaoning Laboratory of Materials,Institute of Materials Intelligence Technology,Shenyang 110004,China)

机构地区：[1]中北大学材料科学与工程学院,太原030051 [2]北京科技大学北京材料基因工程高精尖创新中心,北京100083 [3]材料智能技术研究所,辽宁材料实验室,沈阳110004

出　　处：《物理学报》2024年第24期227-237,共11页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:52074246,52275390,52205429,52201146);国防基础科研项目(批准号:JCKY2020408B002);山西省重点研发计划(批准号:202102050201011);中央引导地方计划(批准号:YDZJSX2022A025,YDZJSX2021A027)资助的课题.

摘　　要：晶界结构在石墨烯变形过程中的演变规律及作用机制对理解石墨烯变形行为具有重要意义.本文采用三模晶体相场模型,在原子尺度上深入研究了石墨烯小角对称倾侧晶界处位错在应变作用下的演化机理.结果发现,随着晶界角的增大,晶界位错密度降低,特定类型的位错(5|8|7位错和5|7位错)数量上升.在与晶界平行的应力加载下,晶界处位错因C-C键断裂或旋转,转化为5|7或5|9型位错,这是由于较大自由能的位错在拉伸下演化为小能量的位错,这有利于石墨烯性能的提高.拉伸载荷下,含不同角度晶界的体系自由能变化呈现相同趋势:初始下降至拐点后出现异常上升,位错行为不能有效缓解体系因持续加载造成的应力集中,导致失效.本工作有助于从原子尺度理解石墨烯微观力学行为.The evolution law and mechanism of grain boundary structure in the deformation process of graphene are of great significance for understanding the deformation behavior of graphene and optimizing its mechanical properties.In this work,single-layer graphene is taken as the research object and a double crystalline graphene model is established by using the three-mode phase-field crystal method,thereby in depth ascertaining the evolution mechanism of dislocations at small-angle symmetrical tilt grain boundaries in graphene under strain.In view of the relaxation and deformation process,the relationship between the number of multiple dislocations and the grain boundary angle of graphene is studied on an atomic scale,and the deformation and failure mechanism of double crystalline graphene under tensile load are revealed,and also discussed from the perspective of the free energy.It is found that,after relaxation,with the increase of grain boundary angle,the density of dislocations at the grain boundary decreases,and the number of specific types of dislocations(5|8|7 and 5|7 dislocations)increases.Under stress loading parallel to the grain boundary,the changes of free energy of the systems containing grain boundaries with different angles show the same trend:at first,they fall to the inflection point and then rise abnormally,and the dislocation behavior cannot effectively alleviate the stress concentration caused by continuous loading in the system,leading to failure finally.Under tensile load,the free energy changes of the systems are divided into four stages,they being stage(I),in which the dislocations at grain boundaries are slightly deformed but do not change their structure,stage(II),in which dislocations at the grain boundaries are transformed into 5|7 or 5|9 dislocation due to C-C bond fracture or rotation,and the dislocations that are“incompatible”have higher energy,making them more conducive to improving the tensile properties of graphene,stage(III),in which the 5|7 and 5|9 dislocations begin to fail,and the

关 键 词：晶体相场方法 石墨烯 晶界 位错 

分 类 号：TQ127.11[化学工程—无机化工]