石墨烯台阶处摩擦特性的分子动力学模拟
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摘要
为了深入探讨硅探针在石墨烯台阶边缘的摩擦力变化特性及其微观摩擦机制,利用分子动力学方法建立模型,重点研究了不同的台阶层数、正压力作用下摩擦力变化规律,并利用x和z方向的应变云图分析摩擦特性.结果表明:正压力对石墨烯台阶边缘的摩擦力变化特性的影响不大,但台阶层数对石墨烯台阶边缘的摩擦力变化特性将产生较大影响;在压头爬上台阶的过程中,出现了明显挤压应力聚集的现象,在压头爬上多层台阶的过程中还伴随着挤压应力的释放;x方向的挤压应变以及z方向压坑中心圆的完整度是衡量摩擦力的重要指标.
In order to further investigate the frictional force characteristics of the silicon probing at the edge of graphene and its microscopic friction mechanism,a model was established by using molecular dynamics method,focusing on the variation of frictional force under different levels and positive pressure.The friction characteristics were also analyzed by using the strain cloud in the xand z directions.The results show that the positive pressure has little effect on the frictional characteristics of the graded edge of graphene,but the change of the number of steps will have a great influence on the frictional characteristics.In the process of pressing on the step,the phenomenon of compressive stress accumulation is accompanied by the release of compressive stress in the process of multi-step climbing.The compressive strain in the xdirection and the integrity of the center of the crater in the zdirection are important indexes to measure the friction force.
In order to further investigate the frictional force characteristics of the silicon probing at the edge of graphene and its microscopic friction mechanism,a model was established by using molecular dynamics method,focusing on the variation of frictional force under different levels and positive pressure.The friction characteristics were also analyzed by using the strain cloud in the xand z directions.The results show that the positive pressure has little effect on the frictional characteristics of the graded edge of graphene,but the change of the number of steps will have a great influence on the frictional characteristics.In the process of pressing on the step,the phenomenon of compressive stress accumulation is accompanied by the release of compressive stress in the process of multi-step climbing.The compressive strain in the xdirection and the integrity of the center of the crater in the zdirection are important indexes to measure the friction force.
引文
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[2]CHO D H,WANG L,KIM J S,et al.Effect of surface morphology on friction of graphene on various substrates[J].Nanoscale,2013,5(7):3063-3069.
[3]BERMAN D,ERDEMIR A,SUMANT A V.Few layer graphene to reduce wear and friction on sliding steel surfaces[J].Carbon,2013,54:454-459.
[4]BERMAN D,DESHMUKH S A,SANKARANARAYANAN S K,et al.Macroscale superlubricity enabled by graphene nanoscroll formation[J].Science,2015,348:1118-1122.
[5]唐文来,彭倚天,倪中华.基于有限元分析的石墨烯弹性性能和振动特性[J].东南大学学报(自然科学版),2013,43(2):345-349.TANG Wenlai,PENG Yitian,NI Zhonghua.Elastic properties and vibration characteristics of graphene using finite element method[J].Journal of Southeast University(Natural Science Edition),2013,43(2):345-349.
[6]DONG Y,LI Q,MARTINI A.Molecular dynamics simulation of atomic friction:A review and guide[J].Journal of Vacuum Science&Technology,2013,31(3):030801.
[7]VILHENA J G,PIMENTEL C,PEDRAZ P,et al.Atomic-scale sliding friction on graphene in water[J].Acs Nano,2016,10(4):4288-4293.
[8]BAI Q S,HE X,BAI J X,et al.An atomistic investigation of the effect of strain on frictional properties of suspended graphene[J].Aip Advances,2016,6(5):055308-1-8.
[9]YOON H M,JUNG Y,JUN S C,et al.Molecular dynamics simulations of nanoscale and sub-nanoscale friction behavior between graphene and a silicon tip:Analysis of tip apex motion[J].Nanoscale,2015,7(14):6295-6303.
[10]DONG Y,LIU X Z,EGBERTS P,et al.Correlation between probe shape and atomic friction peaks at graphite step edges[J].Tribology Letters,2013,50(1):49-57.