Shi Kunming, Chai Bin, Zou Haiyang, Min Daomin, Li Shengtao, Jiang Pingkai, Huang Xingyi
Department of Polymer Science and Engineering, Shanghai Key Laboratory of Electrical Insulation and Thermal Aging, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China.
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245, USA.
Research (Wash D C). 2022 Feb 1;2022:9862980. doi: 10.34133/2022/9862980. eCollection 2022.
Surface charge density has been demonstrated to be significantly impacted by the dielectric properties of tribomaterials. However, the ambiguous physical mechanism of dielectric manipulated charge behavior still restricts the construction of high-performance tribomaterials. Here, using the atomic force microscopy and Kelvin probe force microscopy, an in situ method was conducted to investigate the contact electrification and charge dynamics on a typical tribomaterial (i.e., BaTiO/PVDF-TrFE nanocomposite) at nanoscale. Combined with the characterization of triboelectric device at macroscale, it is found that the number of transferred electrons increases with contact force/area and tends to reach saturation under increased friction cycles. The incorporated high permittivity BaTiO nanoparticles enhance the capacitance and electron trapping capability of the nanocomposites, efficiently inhibiting the lateral diffusion of electrons and improving the output performance of the triboelectric devices. Exponential decay of the surface potential is observed over monitoring time for all dielectric samples. At high BaTiO loadings, more electrons can drift into the bulk and combine with the induced charges on the back electrode, forming a large leakage current and accordingly accelerating the electron dissipation. Hence, the charge trapping/storing and dissipating, as well as the charge attracting properties, should be comprehensively considered in the design of high-performance tribomaterials.
表面电荷密度已被证明会受到摩擦材料介电性能的显著影响。然而，介电调控电荷行为的物理机制尚不明确，这仍然限制了高性能摩擦材料的构建。在此，利用原子力显微镜和开尔文探针力显微镜，采用原位方法在纳米尺度上研究了典型摩擦材料（即钛酸钡/聚偏氟乙烯-三氟乙烯纳米复合材料）上的接触起电和电荷动力学。结合宏观尺度上摩擦电器件的表征，发现转移电子的数量随接触力/面积增加而增加，并且在增加的摩擦循环下趋于达到饱和。掺入的高介电常数钛酸钡纳米颗粒增强了纳米复合材料的电容和电子俘获能力，有效抑制了电子的横向扩散并提高了摩擦电器件的输出性能。在监测时间内，所有介电样品的表面电位均呈现指数衰减。在高钛酸钡负载量下，更多电子可漂移到本体中并与背电极上的感应电荷结合，形成大的漏电流，从而加速电子耗散。因此，在设计高性能摩擦材料时，应综合考虑电荷俘获/存储与耗散以及电荷吸引特性。
