H. Devendrappa

Effect of 8 MeV electron irradiation on the optical properties of doped polymer electrolyte films

The effect of electron beam (EB) irradiation on the optical properties of cadmium chloride (CdCl2)-doped polyethylene oxide (PEO) is studied. The films are characterized using Fourier transform infrared spectroscopy (FTIR) in KBr medium. The morphology study of the films is conducted using a scanning electron microscope. The optical absorption study is carried out with the help of ultraviolet‐visible absorption spectroscopy. The doped films are exposed to a beam of 8 MeV electron at 25, 50, 75, 100 kGy doses. The FTIR results of the films after EB irradiation shows the appearance of new peaks, and shifts in the position of peak prove the formation of hydrogen bonding. The optical absorption edges shift towards higher frequency upon EB irradiation, which indicates a lowering of the energy gap. This can be evidenced by the formation of carbonaceous clusters, which are estimated using the modified Tauc’s equation. The optical parameters, namely absorption coefficient, optical direct and indirect band gaps (Eg), band edges and optical activation energy (Ea), are determined for different EB doses. These results reveal that the optical properties of the irradiated doped films are attributable to changes in the linear electronic polarizability of the material rather than its band gap or electronic structure. The obtained tunability in the optical properties of the EB-irradiated doped polymer electrolytes makes it of considerable interest in a number of optical applications.

Structural, thermal studies and ionic conductivity of doped polymer electrolytes

In this paper we present, the structural, thermal studies and ionic conductivity of cadmium chloride (CdCl2) doped polyethylene oxide (PEO). The XRD, FTIR, SEM and DSC were used to confirm the structural, chemical, morphology and thermal studies of doped PEO. The ionic conductivity measurement was done at different temperatures. The polymer electrolyte observed a maximum ionic conductivity of the order of 2.5×10−7 Sm/cm at 303K. The obtained results suggest that, these polymer systems are suitable candidates for solid state battery, optoelectronics display & electro chromic devices etc.

Increased porous morphology and thermal degradation of electron beam-irradiated PVDF-HFP/LiCLO4 polymer electrolyte

ABSTRACT The effect of 8 MeV energy electron beam radiation at 40, 80 and 120 kGy dosage on surface morphology and thermal properties of lithium perchlorate-doped poly (vinylidene fluoride-co-hexafluoropropylene) polymer electrolyte films have been studied. The field emission scanning electron microscopic image shows small-porous structured morphology for unirradiated film, but it changed drastically into large and deep porous structure as well as the size of spherulites is reduced for 120 kGy confirming the influence of irradiation on morphology. The atomic force microscope reveals the significantly changed surface roughness of unirradiated film from 116.8 to 123.4 nm with a hill-like pattern morphology for 120 kGy confirming the increased amorphousity after irradiation. The thermal study confirmed that the decrease in the melting point of unirradiated film 160.86–155.24°C for 120 kGy doses is attributed to the formation of defects by the chain scissioning process resulting in the degradation of polymer electrolytes at high dose.

Optical properties and ionic conductivity studies of an 8 MeV electron beam irradiated poly(vinylidene fluoride-co-hexafluoropropylene)/LiClO4 electrolyte film for opto-electronic applications

The influence of 8 MeV energy electron beam (EB) irradiation on optical properties and ionic conductivity of PVDF–HFP/LiClO4 (90 : 10 PHL10) electrolyte film with 40, 80 and 120 kGy doses. The FT-IR results show that CO bond stretching at 1654 cm−1 is due to the degradation of polymer chains and the CH2 bond wagging intensity at 1405 cm−1 corresponds to C–H bond scissioning in the 120 kGy dose irradiated film. 1H and 13C NMR spectroscopy was performed and the 13C NMR spectra confirm the effect of EB irradiation of the PHL10 polymer electrolyte by sharpening and splitting the spectral lines with increasing EB dose and revealing a new spectral line at 162.80 ppm with a 120 kGy EB dose. The size and shape of the porous morphology was drastically changed, becoming deeply porous with a visible inner hollow shaped structure, suggesting increased amorphous character upon irradiation. The absorption band of the unirradiated film observed at 202 nm in the ultraviolet region is shifted to 274 nm after irradiation due to inter band transition of electrons from the valence band to the conduction band and the optical band gap decreasing from 3.49 eV in the unirradiated film to 2.64 eV with a 120 kGy EB dose. Segmental motion in the polymer matrix leads to a decrease in the local viscosity by increasing the mobility of ions upon irradiation. Nyquist plots show semicircles at high frequency due to Li-ion migration through the porous surface of the electrolyte film. A maximum ionic conductivity of 8.28 × 10−4 S cm−1 was obtained with a 120 kGy EB dose and the observed cyclic voltammetry of the irradiated polymer electrolyte suggests it is electrochemically stable.

Flexible and high energy density solid-state asymmetric supercapacitor based on polythiophene nanocomposites and charcoal

An asymmetric supercapacitor (ASC) was constructed using a polythiophene/aluminium oxide (PTHA) nanocomposite as an anode electrode and charcoal as a cathode electrode. The highest specific capacitance (Csp) of the PTHA electrode was found to be 554.03 F g−1 at a current density (CD) of 1 A g−1 and that of the charcoal electrode was 374.71 F g−1 at 1.4 A g−1, measured using a three electrode system. The maximum Csp obtained for the assembled PTHA//charcoal asymmetric supercapacitor (ASC) was 265.14 F g−1 at 2 A g−1. It also showed a high energy density of 42.0 W h kg−1 at a power density of 735.86 W kg−1 and capacitance retention of 94.61% even after 2000 cycles. Moreover, it is worth mentioning that the asymmetric device was used to illuminate a light emitting diode (LED) for more than 15 minutes. This PTHA//charcoal ASC also possesses stable electrochemical properties in different bending positions and hence finds a promising application in flexible, wearable and portable energy storage electronic devices.

Characterization, Electrical Conductivity and Electrochemical Performance of Polyaniline-LiClO4-CuO Nano Composite for Energy Storage Applications

ABSTRACT Polyaniline (PANI), PANI/LiClO4 composite with 5% & 10% of salt and PANI/LiClO4/CuO NPs (PLC) nanocomposite were synthesized by chemical method and characterized them with help of fourier transform infrared spectrometer (FT-IR) spectrometer to investigate the chemical interaction between salt and confirmed the composite formation. Field emission scanning electron microscope (FESEM) is used to study the morphological changes in the composite due to effect of salt and formation of long fiber structures. provide the conducting path between the polymer matrix and the Li+ ions helps to increase conductivity. The absorbance study reveals shifting of absorption wavelength towards higher end with increasing salt content in PANI is attributed to the π→π* electron transition in the benzenoid and quinoid rings. The optical band gap (Eg) found decreasing from 2.88 to 2.35 eV for 10% of salt and 2% CuO nano NPs due to forming delocalized charges in host polymer. The dielectric parameters, and AC conductivity against frequency at different temperatures were studied. The PANI/LiClO4 composites are electrochemically stable upto 1000th cycle with 213.08 F/g specific capacitance at 3mA/g current density for10% of salt.

The change in dielectric constant, AC conductivity and optical band gaps of polymer electrolyte film: Gamma irradiation

The effects of gamma (γ) irradiation on dielectric and optical properties of polymer electrolyte film were investigated. The dielectric constant and ac conductivity increases with γ dose. Also optical band gap decreased from 4.23 to 3.78ev after irradiation. A large dependence of the polymer properties on the irradiation dose was noticed. This suggests that there is a possibility of improving polymer electrolyte properties on gamma irradiation.

AC conductivity and dielectric relaxation of polymer complexes

The ac conductivity and dielectric relaxations of PEO-CdS system were studied using impedance at different frequency & temperatures. The Fourier Transform Infra red (FTIR) used for confirm the complexation. The dielectric constants & modulus (real & imaginary) have been determined. It was observed that the dielectric constant decreases with increasing of frequency. The frequency dependence of ac conductivity slowly increases in lower frequency, whereas rapidly increases at the high frequency and it obey power law.