Study on preparation process and enhanced piezoelectric performance of pine-needle-like ZnO@PVDF composite nanofibers

The effect of hydrothermal process on the morphology and piezoelectric performance of zinc oxide/polyvinylidene fluoride (ZnO@PVDF) composite nanofibers is rarely studied. In this work, highly aligned ZnO nanorods were epitaxially grown on the electrospun PVDF nanofibers to form ZnO@PVDF composite nanofibers with a pine-needle-like bionic structure. Nanofibers before and after hydrothermal reaction were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and piezoelectric analysis. Results demonstrated that hydrothermal reaction conditions, including mass ratio of ZnCL2 to HMTA, ammonium hydroxide volume, hydrothermal reaction time and temperature should be carefully controlled and cooperated with each other to produce ZnO nanorods with ideal microstructure and piezoelectric performance. FTIR and XRD results confirmed the transformation of 1 phase in PVDF nanofibers from a phase in PVDF powder due to the elongation under strong electric field during electrospinning. Results of SEM and XRD certified the successful growth of ZnO nanorods with hexagonal wurtzite structure, which plays an important role in facilitating the percentage of 1 phase and the resulted piezoelectric capacity of ZnO@PVDF composite nanofibers. All of these characterizations suggest that the proposed pine-needle-like ZnO@PVDF composite nanofibers demonstrate promising potential in the wide application of electromechanical energy conversion.