The piezoelectric response of electrospun PVDF nanofibers with graphene oxide, graphene, and halloysite nanofillers: a comparative study

Abstract

Although, many efforts were performed to develop piezoelectric systems with high energy conversion rate, but they still show insufficient performance. In this study, the effect of three nanofillers with different morphology and their concentration on macro/micro structure and piezoelectric properties of polyvinylidene fluoride (PVDF) nanofibers were investigated and compared. Graphene oxide (GO) and graphene (Gr) as planner nanofillers, and halloysite (Hal) nanotube were introduced into a PVDF solution in different concentrations (0.05–3.2 wt/wt%). The prepared solutions were fabricated into nanofibers through electrospinning method. The electroactive phase (β-phase) of nanofibrous PVDF mat increased up to ~49% in comparison with PVDF powder. The presence of nanofiller in PVDF matrix also increased it more up to 10%. Gr nanofiller had least effect on piezoelectric properties attributed to its low interaction with PVDF chains. PVDF/Hal nanocomposite with low filler content concentration (<0.1 wt/wt%) and PVDF/GO with high content of filler concentration (>0.4 wt/wt%) caused higher polar phase. Hal nanotubes with a rod like morphology caused more oriented and finer nanofibers than PVDF/GO and PVDF/Gr nanofibers. However, PVDF/0.8 Hal showed higher output voltage (0.1 V), despite of its lower β-phase in compared with PVDF/0.8GO nanocomposites. It was concluded that the piezoelectric response cannot be just evaluated with dielectric constant of nanofiller or β-phase percentage in an electrospun PVDF nanocomposite, but there are some other important factors like orientation and fineness of electrospun nanofibers.