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CN  62-1224/O4

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孔然, 邹鲲. 不同厚度石墨烯表面的纳米摩擦各向异性研究[J]. 摩擦学学报, 2023, 43(3): 283-292. DOI: 10.16078/j.tribology.2021277
引用本文: 孔然, 邹鲲. 不同厚度石墨烯表面的纳米摩擦各向异性研究[J]. 摩擦学学报, 2023, 43(3): 283-292. DOI: 10.16078/j.tribology.2021277
KONG Ran, ZOU Kun. Nanofriction Anisotropy of Graphene Surface with Different Thickness[J]. TRIBOLOGY, 2023, 43(3): 283-292. DOI: 10.16078/j.tribology.2021277
Citation: KONG Ran, ZOU Kun. Nanofriction Anisotropy of Graphene Surface with Different Thickness[J]. TRIBOLOGY, 2023, 43(3): 283-292. DOI: 10.16078/j.tribology.2021277

不同厚度石墨烯表面的纳米摩擦各向异性研究

Nanofriction Anisotropy of Graphene Surface with Different Thickness

  • 摘要: 考察石墨烯表面的纳米摩擦各向异性,研究厚度对其摩擦各向异性的影响. 采用原子力显微镜和高精度旋转台分析不同厚度石墨烯表面在不同方向的纳米摩擦特性. 结果表明:厚度为3.6 nm的石墨烯表面纳米摩擦表现出显著的各向异性但无周期性规律,原因是褶皱效应的产生增大了摩擦力. 厚度为7.5和14.7 nm的石墨烯表面纳米摩擦呈现180°和90°的周期性各向异性规律,归因于晶格结构取向和褶皱效应的共同作用. 厚度为24.5 nm的石墨烯主要受到晶格结构取向的作用,表面纳米摩擦呈现60°的周期性各向异性规律且沿扶手椅型晶格取向的摩擦力大于锯齿型晶格取向的摩擦力.

     

    Abstract: Graphene has a wide range of potential applications in micro/nano electromechanical systems (MEMS/NEMS) due to its excellent lubrication properties. In this paper, the nanofriction anisotropy of graphene surface with different thicknesses was investigated as the tip slides on graphene surface along with different directions by atomic force microscopy (AFM) and high-precision rotating table. The results showed that due to the extremely low out-of-plane stiffness of graphene with a thickness of 3.6 nm, a strong friction strengthening effect was generated in the stick-slip characteristic experiment after the tip sliding on the graphene surface. Then, graphene produced a great out-of-plane deformation and formed a puckering, which increased the contact area between the tip and graphene and thus increased the friction force. As a result, the nanofriction on the surface of graphene exhibited significant anisotropy with a large friction anisotropy ratio. The friction anisotropy ratio was the maximum friction in different angles divided by the minimum friction, and the great out-of-plane deformation leaded to the non-periodic friction of the tip along with all directions. The stiffness of graphene increased with the increase of the thickness leading to an enhanced effect of stick-slip characteristics experiment of small friction due to the weakened out-off-plane deformation, but the out-of-plane deformation did not disappear completely. The zigzag lattice spacing decreased and the armchair lattice spacing increased, which began to close two lattice structures of graphene itself, indicating that the lattice structure began to dominate friction anisotropy. Furthermore, the effect of out-of-plane deformation and lattice structure resulted in periodic anisotropy of 180° and 90° of nanofriction on the surface of graphene with 7.5 nm and 14.7 nm thickness. Due to the large out-of-plane stiffness of graphene with a thickness of 24.5 nm, the lateral force tended to be stable in the stick-slip characteristic experiment, and the friction strengthening effect disappeared, indicating the out-of-plane deformation disappears. Moreover, the spacing between the zigzag lattice and the armchair lattice was almost consistent with the spacing of graphene itself. The results indicated that the frictional anisotropy was inhibited by the increased thickness of graphene and the frictional anisotropy dominated by the lattice structure orientation, resulting in a 60° periodic anisotropy of the surface nanofriction. Also, the friction along the armchair lattice orientation was greater than that along with the sawtooth lattice orientation. The coupling of structural anisotropy and thickness was the main factor of nanofriction anisotropy on the graphene surface. This work revealed the relationship between the different thicknesses of graphene and the anisotropy of surface nanofriction, which provided a theoretical basis for the design and application of graphene in micro and nanomechanical and electrical devices lubrication.

     

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