2D Nanomaterials Incorporated Poly(vinylidene fluoride) Nanocomposites: Morphology, Crystalline Structure, and Dielectric, Ferroelectric, and Piezoelectric Properties

Two-dimensional layered nanomaterials (hexagonal boron nitride (h-BN) and expanded graphite (EG)) incorporated poly­(vinylidene fluoride) (PVDF) nanocomposites were fabricated via high-shear solution mixing accompanied by compression molding. “Ultrasonication” followed by “centrifugation” was employed to “de-stack” h-BN and EG, which exhibited a decrease in “agglomerate” size in PVDF/h-BN and PVDF/EG nanocomposites. Further, the PVDF/h-BN nanocomposite showed a polar fraction of ∼57% at 0.50 wt % of h-BN concentration with an increased β-phase content, whereas the PVDF/EG nanocomposite showed a higher content of γ-phase as compared to β-phase. Moreover, dielectric investigations indicated that the “ultrasonicated” and “centrifuged” h-BN- and EG-based PVDF nanocomposites exhibit the highest dielectric properties owing to improved interfacial and dipolar polarizations. The piezoelectric strain coefficient of PVDF/0.16BN and PVDF/0.17EG nanocomposites exhibited d 33 values of ∼99 and ∼91 pm/V, respectively. Finally, sensor devices were fabricated based on PVDF/EG and PVDF/h-BN nanocomposite films, which showed a maximum peak-to-peak voltage of ∼24 V (at 0.17 wt % EG) and ∼14 V (at 0.16 wt % h-BN), respectively. A systematic investigation was carried out to relate the influence of finely dispersed h-BN and EG on the interfacial interactions, polar phase formation, and the piezoelectric property of PVDF/h-BN and PVDF/EG nanocomposites.