We improved the piezoelectric properties of poly(vinylidene fluoride) (PVDF) by employing multi-walled carbon nanotubes (MWCNTs) as nanofillers. The MWCNT/PVDF nanocomposite was prepared by the solution casting method with MWCNT content ranging from 0.0 to 0.3 wt%. To induce the piezoelectric β-phase crystal structure, the nanocomposite films were drawn to 400%-500% elongation and polarized with a step-wise poling method. To evaluate the piezoelectric properties, the output voltages of the nanocomposite films were measured through extensive experimental vibration tests. The experimental results show that the nanocomposite film with 0.05 wt% MWCNT loading possesses the highest output voltage, around two times higher than that of pure PVDF film, as compared to the other loadings. The main reason for this phenomenon is that more β-crystalline phase can be formed at this MWCNT loading, as confirmed by x-ray diffraction and Fourier transform infrared spectroscopy spectral analysis and polarized optical microscopy observations.
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