2D Nanomaterials Incorporated Poly(vinylidene fluoride) Nanocomposites: Morphology, Crystalline Structure, and Dielectric, Ferroelectric, and Piezoelectric Properties
Akanksha Adaval, Bharat Bhushan Bhatt, Shiva Singh, Dipti Gupta, Pradip K. Maji, M. Aslam, Terence W. Turney, George P. Simon, Arup R. Bhattacharyya
Abstract
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.