Remarkable Enhancement of Thermal and Dielectric Properties of Layered Double Hydroxides and Graphene Fillers Reinforced Poly(vinyl alcohol) Nanocomposite for Energy Applications

In this work, we have synthesized the zinc-aluminum layered double hydroxide (ZnAl LDH) nanostructures using cost-effective hydrothermal technique. The ZnAl LDH and graphene-based poly(vinyl alcohol) (PVA) nanocomposites are fabricated. The crystal structure, morphology, thermal, and dielectric properties of pristine PVA and ZnAl LDH and graphene-based PVA nanocomposites films were investigated using X-ray diffraction, HR-transmission electron microscopy, thermo gravimetric analysis, and impedance analyzer. HRTEM analysis reveals the hexagonal nanoplates shape-like morphology of Zn-Al layered double hydroxides with an average thickness of 40-50nm and size of 400-600nm. High thermal stability was observed from ZnAl LDH and graphene-reinforced nanocomposite. Enhanced thermal stability of 250°C and low weight loss was observed from ZnAl LDH reinforced PVA-based nanocomposites compared to pristine PVA. Zn-Al LDH nanoplates-graphene-PVA based nanocomposites showed ultra-high dielectric constant of 794 as compared to the ZnAl LDH-PVA nanocomposites (334) and pristine PVA sample (35). Low dielectric loss of 0.27, 0.18, 0.38 was observed for pristine PVA, ZnAl-LDH-PVA and ZnAl-LDH-graphene-PVA nanocomposites. The large enhancement of the dielectric constant and thermal stability were discussed in terms of improved crystallinity, interfacial polarization and formation of nanodipoles in the matrix. This study reveals a significant role of LDH-graphene-based hybrid nanocomposites in optoelectronics, energy storage, sensors, energy conversion and thermally stable devices.