Investigation of the Effect of Atmospheric Plasma Treatment in Nanofiber and Nanocomposite Membranes for Piezoelectric Applications

Abstract

In this work, we report the effect of steady-state atmospheric plasma (Corona discharge) in nanofibers and nanocomposite membranes for piezoelectric applications. The investigation was performed in PVDF (Poly vinylidene fluoride) nanofibers, CNT (Carbon Nanotubes)-reinforced PVDF nanocomposites, and PAN (Poly acrylonitrile) nanofiber membranes. Steady-state plasma was generated with a high voltage power source with 1 mA discharge current output and 6 kV discharge voltage, and the gap between tip and the material was maintained to be 1 cm. For the fabrication of nanofibers and nanocomposite membranes, an electrospinning method was used. The electrospinning parameters, such as flow rate and voltage, were optimally tuned for obtaining uniform nanofibers and nanomembranes. Along with the plasma treatment, heat treatment above the glass transition temperature was also conducted on the nanofiber membranes. Using a Scanning Electron Microscope (SEM), the morphology of the nanofibers was observed. X-Ray Diffraction (XRD) demonstrated the polycrystallinity of the nanofibers. Fourier Transform Infrared Spectroscopy (FTIR) analysis of the PVDF nanofibers shows a peak at 796 cm−1 representing α-phase (C-H rocking) in the control sample which is absent in the treated samples. Raman spectroscopy of PVDF nanofibers identifies a Raman shift from 873 cm−1 to 877 cm−1 (denoting β-phase) for plasma-treated samples only. Electron Paramagnetic Resonance (EPR) concludes that the intensity of the free radicals increases from 1.37 to 1.46 (a.u.) after plasma treatment. Then, sensors were fabricated from the PVDF nanofibers, MWCNT-reinforced PVDF nanofibers, and PAN nanofibers to characterize their piezoelectric properties. The impact test results showed that the atmospheric plasma and heat-treated samples had 86%, 277%, and 92% increases of the d33 value (piezoelectric coefficient) in the case of PVDF nanofibers, MWCNT-reinforced nanofibers, and PAN nanofibers, respectively. It was also observed that the capacitance of the nanofiber membranes has increased due to the plasma treatment.

A Review of Plasma-Synthesized and Plasma Surface-Modified Piezoelectric Polymer Films for Nanogenerators and Sensors

“…As depicted in Figure 18e, the piezoelectric charges of the untreated and plasma-treated composite film samples (Ar LPP, C 2 H 4 -CO 2 LPP, and N 2 LPP) were 2.7, 22, 25.7, and 23.1 pC for 1 N force, respectively. Sultana et al [47] investigated the effect of APP corona discharge treatment on various piezoelectric polymer samples, including PVDF nanofibers, carbon nanotubes (CNT)-PVDF nanocomposites, and PAN nanofiber membranes. These samples were fabricated by electrospinning.…”

“…Fathollahzadeh et al [48] investigated PVDF/BaTiO3 composites prepared by solution casting using nanoparticles and microparticles of BaTiO3. To increase the β−phase of Sultana et al [47] investigated the effect of APP corona discharge treatment on various piezoelectric polymer samples, including PVDF nanofibers, carbon nanotubes (CNT)-PVDF nanocomposites, and PAN nanofiber membranes. These samples were fabricated by electrospinning.…”

“…This increase in d 33 was attributed to the increased capacitance caused by plasma treatment. Sultana et al [47] investigated the effect of APP corona discharge treatment on vari ous piezoelectric polymer samples, including PVDF nanofibers, carbon nanotubes (CNT)-PVDF nanocomposites, and PAN nanofiber membranes. These samples were fabricated by electrospinning.…”

“…(a) Experimental set-up for APP corona discharge treatment, by Sultana et al (b) Capac itance and (c) d33 of all nanofiber membranes and films. Reproduced with permission from ref [47].…”