Kalim Deshmukh

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

Morphology, Ionic Conductivity, and Impedance Spectroscopy Studies of Graphene Oxide-Filled Polyvinylchloride Nanocomposites

Graphene oxide was synthesized using modified Hummers method. The preparation of polyvinylchloride/graphene oxide nanocomposites was carried out using colloidal processing. The morphology of polyvinylchloride/graphene oxide nanocomposite confirms that graphene oxide was uniformly distributed within the polyvinylchloride matrix indicating complete exfoliation of graphene oxide. Significant improvement in the microhardness of the nanocomposite was observed as compared to neat polyvinylchloride. The impedance spectroscopy of nanocomposites was carried out in the frequency range (50 Hz to 35 MHz) and temperature range (80–150°C). Thus, based on the results obtained, we found that polyvinylchloride/graphene oxide nanocomposites hold great promise in many potential applications such as an electrode material for supercapacitors. GRAPHICAL ABSTRACT

Optical Analysis of Iron-Doped Lead Sulfide Thin Films for Opto-Electronic Applications

Iron-doped lead sulfide thin films were deposited on glass substrates using successive ionic layer adsorption and reaction method (SILAR) at room temperature. The X-ray diffraction pattern of the film shows a well formed crystalline thin film with face-centered cubic structure along the preferential orientation (1 1 1). The lattice constant is determined using Nelson Riley plots. Using X-ray broadening, the crystallite size is determined by Scherrer formula. Morphology of the thin film was studied using a scanning electron microscope. The optical properties of the film were investigated using a UV–vis spectrophotometer. We observed an increase in the optical band gap from 2.45 to 3.03eV after doping iron in the lead sulfide thin film. The cutoff wavelength lies in the visible region, and hence the grown thin films can be used for optoelectronic and sensor applications. The results from the photoluminescence study show the emission at 500–720nm. The vibrating sample magnetometer measurements confirmed that the lead sulfide thin film becomes weakly ferromagnetic material after doping with iron.

Ceramic-Based Polymer Nanocomposites as Piezoelectric Materials

Piezoelectric ceramics receive high interest due to their wide range of applications/usage in fabricating sensors, frequency filters, actuators, and many other electronic devices. Moreover, generating energy is the need of the hour. This chapter is written as a review of ceramic polymer composites that exhibit piezoelectric properties. A few synthesis methods for the ceramic particles as well as the polymer composites are discussed, followed by the core content of the chapter, the piezoelectric properties of the material.

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.

Conjugated polymer/graphene oxide nanocomposite as thermistor

We demonstrated the synthesis and measurement of temperature dependent electrical resistivity of graphene oxide (GO) reinforced poly (3, 4 - ethylenedioxythiophene) - tetramethacrylate (PEDOTTMA)/Polymethylmethacrylate (PMMA) based nanocomposites. Negative temperature coefficient (NTC) was observed for 0.5, 1 % GO loading and the positive temperature coefficient (PTC) was observed for 1.5 and 2 % Go loading in the temperature (40 to 120 °C). The GO inducted nanocomposite perform as an excellent thermistor and suitable for electronic and sensor domain.

Stretchable quaternary phasic PVDF-HFP nanocomposite films containing graphene-titania-SrTiO3 for mechanical energy harvesting

AbstractIntegrating efficient energy harvesting materials in to soft, flexible, and eco-friendly substrates could yield significant breakthroughs in wearable and flexible electronics. Substantial advances are emerged in fabricating devices which can conform to irregular surfaces in addition to integrating piezoelectric polymer nanocomposites in to mechanical generators and bendable electronics. Here, we present a tri-phasic filler combination of one-dimensional titanium dioxide (TiO2) nanotubes, two-dimensional reduced graphene oxide, and three-dimensional strontium titanate (SrTiO3), introduced in to a semi-crystalline polymer, poly(vinylidene fluoride-co-hexafluoropropylene). Simple mixing method was adopted for the composite fabrication after ensuring a high interaction between the various fillers. The prepared films were tested for their piezoelectric responses and mechanical stretchability. The results showed that the piezoelectric constant has increased due to the change in the filler concentration and reached a value of 7.52 pC/N at 1:2 filler combination. The output voltage obtained for the same filler composition was about 10.5 times that of the voltage generated by the neat polymer. Thus, we propose integration of these materials in fabricating energy conversion devices that can be useful in flexible and wearable electronics. Graphical abstractᅟ

Chapter 10 – Dielectric Spectroscopy

In this chapter, an attempt has been made to review dielectric spectroscopy (DS) as a technique for the characterization of nanomaterials. DS involves the study of the response of a material to an electric field, which furnishes structural information, i.e., molecular structure, physical arrangement, and behavior of the molecules within the structure. DS is a well-established technique in the fields of physics, polymers, and colloidal science and also in pharmaceutics. It is used to measure the dielectric and electric properties of a medium as a function of frequency. Nanomaterials have been known by the term nanodielectric, mainly because of their gradual evolution as excellent functional materials for dielectric and electrical insulation applications. DS has been validated as a powerful technique for appraising the structural and molecular dynamics of nanomaterials. DS in nanomaterial systems is specifically used to probe structure–property relationships, which helps to optimize composition and synthesis/processing conditions, which is useful in the design of new functional materials with envisioned properties. General perspectives such as the principle of DS, dielectric mechanisms such as polarization and relaxation, and dielectric formalisms such as permittivity, electrical modulus, and impedance are described in this chapter.