S. K. Khadheer Pasha

Highly dispersible graphene oxide reinforced polypyrrole/polyvinyl alcohol blend nanocomposites with high dielectric constant and low dielectric loss

In the present study, we report the fabrication and characterizations of flexible dielectric nanocomposites consisting of water soluble polypyrrole (WPPy)/polyvinyl alcohol (PVA)/graphene oxide (GO) at different GO loadings (0.5–3 wt%). The WPPy/PVA/GO nanocomposites were characterized using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, UV-vis spectroscopy (UV), X-ray diffraction (XRD), thermogravimetric analysis (TGA), polarized optical microscopy (POM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). FTIR studies indicate the strong chemical interaction between GO and polymer systems. SEM results confirm that GO was homogeneously dispersed within the polymer matrix. The nanocomposites exhibit significant enhancement in the dielectric constant with low dielectric loss values as a function of GO loading which resulted from the fine dispersion of GO in the polymer matrix. The dielectric constant increases from (e = 27.93, 50 Hz, 150 °C) for WPPy/PVA (50/50) blend to (e = 155.18, 50 Hz, 150 °C) for nanocomposites with 3 wt% GO loading and the dielectric loss increases from (tan δ = 2.01, 50 Hz, 150 °C) for WPPy/PVA (50/50) blend to (tan δ = 4.71, 50 Hz, 150 °C) for nanocomposites with 3 wt% GO loading. Thus, these high-κ WPPy/PVA/GO nanocomposites are potential flexible high-performance dielectric materials for electronic devices such as high-frequency capacitors or embedded capacitors.

Influence of K2CrO4 Doping on the Structural, Optical and Dielectric Properties of Polyvinyl Alcohol/K2CrO4 Composite Films

ABSTRACT Polyvinyl alcohol/potassium chromate (K2CrO4) composite films were prepared by solution casting technique using distilled water as a solvent, and were further investigated using Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, X-ray diffraction, thermogravimetric analysis, optical microscopy, scanning electron microscopy, and dielectric measurements. Microscopic studies reveal that K2CrO4 was homogenously mixed with polyvinyl alcohol matrix due to interfacial interaction between polyvinyl alcohol and K2CrO4. The composite films showed very high dielectric constant and relatively low dielectric loss. Hence, such composite materials with improved dielectric properties could be useful for fabrication of electrical charge storage device. GRAPHICAL ABSTRACT

Eco-Friendly Synthesis of Graphene Oxide Reinforced Hydroxypropyl Methylcellulose/Polyvinyl Alcohol Blend Nanocomposites Filled with Zinc Oxide Nanoparticles for High-k Capacitor Applications

ABSTRACT Polymer/inorganic nanocomposites comprising of hydroxypropyl methylcellulose and polyvinyl alcohol as a polymer matrix and unique combination of graphene oxide and zinc oxide nanoparticles as fillers have been prepared using colloidal processing technique and characterized using various analytical methods. The dielectric properties of the nanocomposites are investigated using impedance analyzer. The nanocomposites show improvement in the dielectric properties compared to hydroxypropyl methylcellulose/polyvinyl alcohol (50/50) blends, which results from the homogeneous dispersion of fillers into the polymer matrix. The results indicate that these nanocomposites have a potential to meet the technological demands of high-k dielectrics and/or embedded capacitors. GRAPHICAL ABSTRACT

A High Sensitivity Isopropanol Vapor Sensor Based on Cr2O3-SnO2 Heterojunction Nanocomposites via Chemical Precipitation Route.

Cr2O3-SnO2 heterojunction nanocomposites were prepared via chemical precipitation method. The prepared samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectra and Field Emission Electron Microscopy (FESEM). The XRD spectrum confirms the presence of both tetragonal rutile SnO2 and rhombohedral corundum Cr2O3 structure. Further investigation into the gas sensing performances of the prepared Cr2O3-SnO2 nanocomposites exhibited an enhanced sensitivity towards VOPs such as isopropanol, acetone, ethanol and formaldehyde. Especially, isopropanol vapor sensor shows excellent sensitivity at an operating temperature of 100 °C. The highest sensitivity for Cr2O3-SnO2 heterojunction nanocomposites indicate that these materials can be a good candidate for the production of high-performance isopropanol sensors.

Biodegradable Nanocomposites for Energy Harvesting, Self-healing, and Shape Memory

This review aims to survey the rapidly expanding field of energy harvesting, self-healing, and shape-memory biodegradable composites by reviewing the major successful autonomic designs developed over the last decade. We have discussed the characterization of the composite and dispersion of the filler by different methods such as grafting, chemical modifications. Also, we have highlighted the recent work on polymers and blends, hydrogels of biocomposites and their controllable approach for adjusting desired properties. In addition to above, the design considerations critical to the successful integration of these components in the commercial applications have been discussed. These materials have huge demand in the development of robust modeling and design tools based on a fundamental understanding of the complex and time-variant properties of the material and mechanization structure in diverse environments. The potential directions for future advancement in this field are also discussed.

Biopolymer Composites With High Dielectric Performance: Interface Engineering

In recent years, there is a growing interest in studying the dielectric behavior of biopolymer composites due to their potential application as a dielectric material in various electronic devices such as microchips, transformers, and circuit boards. Conducting electroactive polymer composites have also been investigated for various potential applications which include biological, biomedical, flexible electrodes, display devices, biosensors, and cells for tissue engineering. In this chapter, the preparation and dielectric behavior of various biopolymer composites is presented. These biopolymer composites generally consist of nanoscale metal nanoparticles and carbon-based nanofillers such as carbon nanotubes, graphene, graphene oxide (GO), etc., dispersed into the polymer matrix. The physical and chemical properties of these fillers and their interactions with polymers have a significant effect on the microstructure and the final properties of nanocomposites. The biopolymer composites with excellent dielectric properties show great promise as an energy storage dielectric layer in high-performance capacitor applications such as embedded capacitors. This chapter highlights some of the examples of such biopolymer composites; their processing and dielectric behavior will be discussed in detail.

Studies on the Electrical Properties of Graphene Oxide-Reinforced Poly (4-Styrene Sulfonic Acid) and Polyvinyl Alcohol Blend Composites

In the present study, graphene oxide (GO)-reinforced poly (4-styrenesulfonic acid) (PSSA)/polyvinyl alcohol (PVA) blend composite films were prepared using colloidal blending technique at various concentrations of GO (0–3wt.%). The morphological investigations of the prepared composites were carried out using polarized optical microscopy and scanning electron microscopy. The electrical properties of composites were evaluated using an impedance analyzer in the frequency range 50Hz to 20MHz and temperature in the range 40–150∘C. Morphological studies infer that GO was homogeneously dispersed in the PSSA/PVA blend matrix. Investigations of electrical property indicate that the incorporation of GO into PSSA/PVA blend matrix resulted in the enhancement of the impedance (Z) and the quality factor (Q-factor) values. A maximum impedance of about 4.32×106Ω was observed at 50Hz and 90∘C for PSSA/PVA/GO composites with 3wt.% GO loading. The Q-factor also increased from 8.37 for PSSA/PVA blend to 59.8 for PSSA/PVA/GO...