Abstract
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., BaTiO3/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 BaTiO3 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 BaTiO3 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.
Highlights
Contact electrification brings about charge transfer between two materials during contact or friction process [1,2,3], and this universally existing phenomenon is considered to be derived from the difference of work functions or surface potentials between the contacting materials [4,5,6]
As contact electrification can be affected by mechanical conditions [38, 39], Figure 1(c) shows the ΔCPD of PVDFTrFE sample under different contact forces
An in situ method was demonstrated to characterize the contact electrification and charge dynamics of a metal-dielectric case at nanoscale via the combination of Polymer matrix BTO nanoparticles Electrons Electrons combined with positive charges Leakage current
Summary
Contact electrification brings about charge transfer between two materials during contact or friction process [1,2,3], and this universally existing phenomenon is considered to be derived from the difference of work functions or surface potentials between the contacting materials [4,5,6]. Incorporating high permittivity (high-k) fillers into the polymer matrix has been demonstrated to be efficient to improve the surface charge density and triboelectric performance [27,28,29,30,31] Though this strategy has been well established in the construction of tribomaterials, the physical interpretation of dielectric manipulated charge dynamics (charge transfer, charge distribution, and charge dissipation) still remain ambiguous, which restricts. To figure out the mechanism of dielectric manipulation, quantitative investigation of the in situ contact electrification and charge dynamics on the tribomaterials surface at nanoscale is required, as the regular macroscopic experiments cannot accurately control the electrification process or directly reveal the electrification interface [32]. A proposed mechanism is exhibited to elucidate the dielectric manipulated charge dynamics and surface charge density
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