Browsing by Author "P.N. Gupta"

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50 MeV Li3+ ion irradiation effect on structural, electrical, and dielectric properties of PVA-based nanocomposite polymer electrolytes
(2014) Govind K. Prajapati; P.N. Gupta
Nanocomposite polymer electrolyte thin films of polyvinyl alcohol (PVA)-orthophosphoric acid (H3PO4)-Al2O3 have been prepared by solution cast technique. Films are irradiated with 50 MeV Li3+ ions having four different fluences viz. 5 × 1010, 1 × 1011, 5 × 1011, and 1 × 1012 ions/cm2. The effect of irradiation on polymeric samples has been studied and characterized. X-ray diffraction spectra reveal that percent degree of crystallinity of samples decrease with ion fluences. Glass transition and melting temperatures have been also decreased as observed in differential scanning calorimetry. A possible complexation/interaction has been shown by Fourier transform infrared spectroscopy. Temperature-dependent ionic conductivity shows an Arrhenius behavior before and after glass transition temperature. It is observed that ionic conductivity increases with ion fluences and after a critical fluence, it starts to decrease. Maximum ionic conductivity of ~2.3 × 10-5 S/cm owing to minimum activation energy of ~0.012 eV has been observed for irradiated electrolyte sample at fluence of 5 × 1011 ions/cm2. The dielectric constant and dielectric loss also increase with ion fluences while they decrease with frequency. Transference number of ions shows that the samples are of purely ionic in nature before and after ion irradiation. © 2013 Springer-Verlag Berlin Heidelberg.
Characterization and electrical properties of polyvinyl alcohol based polymer electrolyte films doped with ammonium thiocyanate
(Elsevier Ltd, 2014) N. Kulshrestha; B. Chatterjee; P.N. Gupta
In this communication, films of polyvinyl alcohol (PVA) polymer complexed with ammonium thiocyanate (NH4SCN) salt were studied. XRD (X-ray diffraction) was used to study the complexation of salt with the polymer matrix and amorphicity in the films. DSC (differential scanning calorimetry) studies showed that the glass transition temperatures (Tg) of the PVA:NH 4SCN complexed films were less than pristine PVA. Raman analysis was analyzed in order to study the change in the vibrational bands due to the complexation of salt with PVA. Optical micrographs confirm the fractal formation in 75:25 and 70:30 PVA:NH4SCN films. Ionic transference number was estimated by Wagner's polarization method and its large value indicates that conduction takes place mainly due to mobile ionic species. Maximum conductivity ∼10-3 S/cm at room temperature was obtained for 70:30 ratio of PVA: NH4SCN polymer electrolyte films. © 2014 Elsevier B.V.
Characterization of H3PO4 based PVA complex system
(Elsevier, 1996) P.N. Gupta; K.P. Singh
In this communication, thin films of polyvinyl alcohol (PVA) complexed with H3PO4 of different stoichiometric ratios have been characterized using various experimental techniques, namely IR, NMR and X-Ray Diffraction. Comparing the characteristic behaviour of pure and complexed PVA, it is observed that there is appearance of a new spectral band (IR), some new atomic planes in addition to variation in relative intensity (X-ray diffraction) and change in chemical shift along with change in intensity (NMR) which all confirm the formation of PVA-H3PO4 complexes. It is found that the amorphous character of PVA complexes increases with H3PO4 concentration which governs the magnitude of conductivity of polymer complexes. The ionic transference number of mobile ions has been estimated by Wagner's polarization method and the value is reported to be tion ≃ 0.97. The Transient Ionic Current (TIC) measurement technique has been used to detect the type of mobile species and to evaluate their mobilities. The mobility of H+ cation has been calculated and found to be μH . ≃ 1.3 × 10-4 cm2 V-1 s-1.
Collision frequency effect on plasma-filled transversely magnetized rectangular waveguide characteristics
(1972) Dinesh Singh; P.N. Gupta; S.K. Tolpadi
The characteristics of a rectangular waveguide filled with homogeneous lossy plasma in the presence of a strong magnetic field are discussed. The B-ω curves are drawn from the dispersion relation for different values of collision frequency and the results are compared with the characteristics of transversely magnetized plasma-filled rectangular waveguides without including the effect of collisions. It is found that the effect of the collision frequency is that the non-propagating region is limited to a point dependent on wave-number in the direction of the magnetic field and independent of values of collision frequency. © 1972 Taylor and Francis Group, LLC.
Comparative study of the electrical and dielectric properties of PVAPEGAl2O3MI (M=Na, K, Ag) complex polymer electrolytes
(2011) G.K. Prajapati; P.N. Gupta
Plasticized nanocomposite polymer electrolytes (PNCPEs) based on poly(vinyl alcohol) (PVA)MI (M=Na, K, Ag) dispersed with nanofillers Al2O 3 and plasticized with poly(ethylene glycol) (PEG) have been prepared by solution cast technique. The structural properties of the samples have been characterized using various experimental techniques such as XRD, DSC, FTIR and B-G spectroscopy. The ionic conductivity and dielectric constant of the samples have been estimated using a LCZ meter in a wide temperature range, i.e. from 30 to 170 °C. It has been observed that the presence of water molecules in polymer electrolytes significantly affects the mobility of ionic species. The temperature dependent ionic conductivity shows the Arrhenius type behavior separated in three distinct regions. The ionic transference number for all PNCPE samples is found to be ≈1, which strongly suggests their ionic nature. © 2011 Elsevier B.V.
Conduction mechanism in un-irradiated and γ-irradiated PVA-H3PO4 polymer electrolytes
(2009) G.K. Prajapati; P.N. Gupta
The a.c. conductivity and the dielectric properties of both un-irradiated and γ-irradiated PVA-H3PO4 complexed electrolytes are investigated as a function of frequency and temperature. The dielectric constant and dielectric loss have been studied in the frequency range of 10 kHz-1 MHz and in the temperature domain of 303-383 K. The a.c. conductivity is found to obey the "Universal power law". The variation of frequency exponent with temperature obtained from experimental results has been used to explain the mechanism of ion transport. It has been shown that correlated barrier hopping is the suitable model to study the electrical conduction mechanism of the complexed system. According to this model the maximum barrier height was calculated to be 0.31 eV for un-irradiated sample while for γ-irradiated, it was 0.28 eV. Moreover, the frequency exponent, which is a function of temperature, decreases slowly in the lower temperature range and at a faster rate in higher temperature range. The electrical activation energy at various frequencies was estimated in the range of 0.44-0.80 eV in two distinct temperature ranges. © 2009 Elsevier B.V. All rights reserved.
Dispersion Relations for Parallel-Plane Waveguide Containing Transversely Magnetized Uniaxial and Warm Plasma in Relative Motion
(1973) P.K. Jain; Dinesh Singh; P.N. Gupta; S.K. Tolpadi
Starting from the dispersion relation corresponding to TM modes in the rest system and relativistic transformations, dispersion relation corresponding to TM mode, is derived in the moving system. The plasma is assumed to be homogeneous, compressible, and uniaxial in the presence of strong TM field. From the wave equation corresponding to TE modes in the moving system, it is concluded that the dispersion relation corresponding to TE modes is independent of the temperature of plasma and is the same as that for ordinary air-filled parallel-plane waveguide in the presence of strong TM field. The magnetic field has no effect on air filled guide. The dispersion relation corresponding to TEM modes is also derived. © 1973, IEEE. All rights reserved.
Effect of Li3+ ion irradiation on ionic transport properties of complexed polymer electrolytes
(Materials Research Society, 2010) P.N. Gupta; G.K. Prajapati; R. Roshan
Swift heavy ion (SHI) irradiation effects on ionic conduction in the PVA-H3PO4 polymer electrolyte films have been investigated due to its variety of applications in electrochemical devices. Polymer electrolytes films are irradiated with 50 MeV Li3+ ions having five different fluences viz. 5×1010, 1011, 5×1011, 1012 and 5×1012 ions/cm2. It is observed that irradiation of the polymer electrolyte films with swift heavy ions shows enhancement in conductivity at lower fluences and decrease in conductivity at higher fluences. It appears that below the critical fluence, swift heavy ion irradiation increases the diffusivity of Li+ ion in the polymer electrolyte which provides larger pathways for ionic transport throughout the system. The temperature dependence of electrical conductivity variation has been used to compute the activation energy involved in conduction process. © 2010 Materials Research Society.
Effect of nanoparticles on complexed polymer electrolytes
(Apple Academic Press, 2012) P.N. Gupta; G.K. Prajapati; R. Roshan
Thin films of Nano-Composite Polymer Electrolyte (NCPE) consisting of poly (vinyl alcohol) (PVA), ortho phosphoric acid (H3PO4), and Al2O3 nanoparticles (size ~50 nm) have been prepared by solution cast technique. Solid Polymer Electrolytes (SPE) (PVA-H3PO4: 70:30 wt%) as first phase host matrix and nanoparticles of Al2O3 as second phase dispersed in different wt. ratios are utilized for the preparation of thin films of NCPE. The DSC result shows that both glass transition and melting temperatures of SPE films decreases with addition of Al2O3 nanoparticles. The FTIR spectra give indication about possible interactions between host matrix and dopants for its complexation. It has been found that ionic conductivity (σ = 2.7 x 10-4 S/cm) of the NCPE film having 2 wt% of nanoparticles is enhanced by one order of magnitude over the conventional SPE system at room temperature. The ionic transport behaviors in both SPE and NCPE films have been characterized and compared in terms of ionic conductivity (σ) and ionic transference number (tion) responsible for ionic conduction. The temperature dependent conductivity behavior has been used to compute the activation energy (Ea) involved in the conduction process. © 2012 by Apple Academic Press, Inc.
Effect of plasticizer on ionic transport and dielectric properties of PVAH3PO4 proton conducting polymeric electrolytes
(2010) G.K. Prajapati; R. Roshan; P.N. Gupta
Solid polymer electrolytes have attracted considerable attention due to their wide variety of electrochemical device applications. The present paper is focused on the effect of plasticizer to study the structural, electrical and dielectric properties of PVAH3PO4 complex polymer electrolytes. XRD results show that the crystallinity decreases due to addition of plasticizer up to particular amount of polyethylene glycol (PEG) and thereafter it increases. Consequently, there is an enhancement in the amorphicity of the samples responsible for process of ion transport. This characteristic behavior can be verified by the analysis of the differential scanning calorimetry results. FTIR spectroscopy has been used to characterize the structure of polymer and confirms the complexation of plasticizer with host polymeric matrix. Electrical and dielectric properties have been studied for different wt% of plasticizer and their variations have been observed. The addition of PEG has significantly improved the ionic conductivity. The optimum ionic conductivity value of the plasticized polymer electrolyte film of 30 wt% PEG has been achieved to be of the order of 10-4 S cm-1 at room temperature and corresponding ionic transference number is 0.98. The minimum activation energy is found to be 0.25 eV for optimum conductivity condition. © 2010 Elsevier Ltd.
Electrical properties of starch-PVA biodegradable polymer blend
(Institute of Physics Publishing, 2015) B. Chatterjee; N. Kulshrestha; P.N. Gupta
Solid polymer electrolyte films were prepared by adding different contents of potassium chloride (KCl) in a polymer matrix composed of two versatile biodegradable polymers: starch and polyvinyl alcohol (PVA), using the solution cast method. The complexation of the added salt (KCl) with the polymer matrix was confirmed from an x-ray diffraction study (XRD). The evolution of a smooth and uniform morphology with the increasing content of KCl was confirmed from scanning electron microscopy (SEM). The transference number measurement established ions as the dominant charge carriers in the system. The maximum ionic conductivity ∼5.44 × 10-5 S cm-1 at ambient conditions was obtained for the film with 1.5 wt% of KCl using complex impedance spectroscopy. The ionic conductivity and dielectric constant increased with the salt content, thus affirming the amplification in the number of charge carriers. The noteworthy aspect of the investigation is the observation of appreciable ionic conductivity at a relatively low salt content. Low values of activation energy obtained from temperature-dependent ionic conductivity could be favorable from the point of view of the application. Electric modulus studies confirmed the absence of electrode polarization effects in the polymer electrolyte films. The scaling of the electric modulus shows a distribution of relaxation times in the polymer electrolyte films. The study unveils the efficiency of the starch-PVA blend, with glycerol and citric acid as additives, as a hopeful material for preparing biodegradable solid polymer electrolyte films. © 2015 The Royal Swedish Academy of Sciences.
Erratum:Characterization and electrical properties of polyvinyl alcohol based polymer electrolyte films doped with ammonium thiocyanate(Materials Science and Engineering B (2014)184(49-57)DOI: 10.1016/j.mseb.2014.01.012)
(Elsevier Ltd, 2015) N. Kulshrestha; B. Chatterjee; P.N. Gupta
[No abstract available]
Influence of pre-harvest application of calcium and alar on post-harvest changes in cv. 'Sardar' guava fruits
(1999) R. Chandra; P.N. Gupta; C.B.S. Rajput
Three consecutive sprays of calcium chloride (1 or 2%) or calcium nitrate (1 or 2%) were applied 18, 12, and 6 days before harvest and one spray of alar (500 or 1000 ppm) was applied 18 days before harvest on cv. 'Sardar' guava (Psidium guajava L.) trees. The fruits were stored under ambient conditions [12 ± 3°C and 74-87% relative humidity (RH)]. Calcium and alar treatments delayed ripening and had a favourable effect on the quality of the fruits during storage. In general, the treated fruits exhibited a higher calcium level in the fruit pulp, a lower cumulative physiological loss in weight, and had lower invertase and pectinase activities. Calcium nitrate was better than calcium chloride in prolonging the storability and quality of guava fruits. Alar (1000 ppm) or calcium nitrate (2%) was most efficient in maintaining the edible quality and marketability of guava fruits up to eight days of storage.
Ion dynamics and dielectric relaxation behavior of PVA-PVP-NaI-SiO2 based nano-composites polymer blend electrolytes
(Elsevier B.V., 2020) Pankaj Singh; P.N. Gupta; A.L. Saroj
In this paper we have reported the loading effect of SiO2 nano-particles on the electrical transport properties and dielectric relaxation behavior of the PVA-PVP-NaI based nano composite polymer blend electrolytes (NCPBEs). Solution cast technique has been used for the preparation of PVA-PVP-NaI-SiO2 based NCPBE films. AC impedance spectroscopic technique is used for the study of electrical conductivity and dielectric properties. The frequency dependence of AC conductivity with different SiO2 concentration for all prepared NCPBEs obeys the Jonscher power law (JPL) with exponent, n ≥ 1. The dielectric permittivity (ε′&ε″), electric modulus (M′&M″) vs. frequency plots at different concentrations and temperatures were reported. Mobility (μ), dc conductivity (σdc) and total number of charge carriers (N) were estimated and found that mobility varies with the SiO2 concentration. Sample containing 0.6 wt% of SiO2 shows optimum dc conductivity, σdc ~5.07 × 10−6 S/cm with μ ~4.60 × 10−7 and N ~6.98 × 1021. Dielectric relaxation peaks have been observed for all samples and relaxation time (τ) is minimum for 0.6 wt%SiO2 based NCPBE film. © 2019 Elsevier B.V.
Ion transport in proton conducting solid polymer electrolytes
(Institute for Ionics, 1998) P.N. Gupta; K.P. Singh; R.K. Yadav
In this communication the ion transport properties of polyvinyl alcohol complexed with orthophosphoric acid (H3PO4) have been investigated. The proton conduction is confirmed by hydrogen gas evolved at the cathode of the coulometer and the transference number of H+ ion has been determined. The transient ionic current (TIC) technique has been used to detect the mobile ionic species and their mobilities are evaluated. The ionic mobility was found to be of the order of 10-4 cm2.V -1.s-1 for H+ ions. It is observed that the bulk electrical conductivity increases with the temperature following the Arrhenius type behaviour. Variation of charge carrier concentration with the molar ratio of H3PO4 in the sample reveals that the carrier concentration is largely affected by the amount of dopant in the complexes.
Ion transport studies in hydrazine dihydrochloride
(2000) P.N. Gupta
Electrical conductivity, coulometric, IR, TIC, TGA, DTA and DSC of the material have been investigated. Electrical conductivity has been measured in pressed pellets in the frequency range 100 Hz to 0.1 MHz at different temperatures. Proton conduction is confirmed by hydrogen gas evolved at the cathode of the coulometer. A comparison of the IR spectra of original and electrolysed sample indicates that a part of N2H6++ changes to N2H5++ confirming the removal of a part of hydrogen, TGA, DTA and DSC studies have been carried out to detect and interpret various transition temperatures and weight loss with temperature. Transient ionic current (TIC) technique has been used to detect mobile ionic species and their ionic mobilities can also be determined.
Nano composite solid polymer electrolytes based on biodegradable polymers starch and poly vinyl alcohol
(Elsevier B.V., 2016) B. Chatterjee; Niharika Kulshrestha; P.N. Gupta
An attempt has been made to prepare nano composite solid polymer electrolytes by adding nano fumed silica in different weight ratios in a polymer matrix composed of biodegradable polymers Starch and Poly Vinyl Alcohol (PVA) to get high ionic conductivity with good mechanical strength. Fourier Transform InfraRed spectroscopy (FTIR) was used to confirm the complexation and interaction of the nano filler with the polymer matrix. From the FTIR investigations it could be established that the formation of C-O-Si bonds by nano fumed SiO2 with Starch and PVA lead to the crucial structural modification that finally increase the conductivity of the sample. Dielectric and frequency dependent measurements substantiate the sharp increase in number of charge carriers as the major factor contributing to the enhancement of the conductivity for 3 wt% nano fumed silica. Electric modulus studies confirmed the ionic nature and indicate absence of electrode polarization in the system. Maximum ionic conductivity ∼10-3 S/cm could be realized for 3 wt% silica at ambient condition. © 2016 Elsevier Ltd. All rights reserved.
Nanocomposite films dispersed with silica nanoparticles extracted from earthworm humus
(2012) B. Chatterjee; P.N. Gupta
Research in the field of polymer electrolytes in recent years has been focused in achieving maximum conductivity at ambient conditions. Addition of ceramic nanoparticles to polymer matrices has been found to be an effective way to realize large ionic conductivity. A cost effective method of extracting silica nanoparticles from earthworm humus has been reported. To prepare polymer electrolyte films of PVA-PVP blend in 50:50 ratio by weight was taken as the polymer matrix and orthophosphoric acid (H 3PO 4) was added to the polymer blend solution. Nanocomposite polymer electrolytes were prepared by adding known amounts of SiO 2 nanoparticles to polymer electrolyte solution. XRD scans of the polymer electrolyte films reveal a well dispersed state of the nanoparticles in the polymer matrix. DSC studies have shown a reduction in Tg of the polymer electrolytes with addition of SiO 2 nanoparticles. The highest conductivity has been found to be 2.4 × 0 - 4 S/cm at 2 wt.% silica doping at room temperature. Transference number measurements have shown that the conductivity of the samples is mainly dominated by the motion of the ions. © 2012 Elsevier B.V.
Polymer based solid state electrochromic display device using PVA complex electrolytes
(1995) K.P. Singh; R.P. Singh; P.N. Gupta
Electrochromic display device has been fabricated using poly vinyl alcohol (PVA) films complexed with H3PO4 and H2SO4, as electrolyte and WO3 film as electrochromic material. The device response such as colouration and bleaching times are determined from the variation of transmitted light intensity measurement at 450 nm wavelength. Various device parameters such as colouration efficiency, transmissive contrast ratio and transmittance modulation have been evaluated and results are analysed. The complex electrolyte (H+/VA = 0.12) of PVA-H2SO4 shows maximum change in optical density (ΔOD = 0.13) due to its high conductivity value. It is observed that transmissive contrast ratio is dependent on acid concentration and increases with injected charge density. © 1995.
PROPAGATION OF ELECTROMAGNETIC WAVES IN SEMICONDUCTOR PLASMA UNDER THE INFLUENCE OF CROSSED ELECTRIC AND MAGNETIC FIELDS.
(1987) P.N. Gupta
This paper presents an investigation of characteristics of an electromagnetic wave propagating through semiconductor plasma in the presence of externally applied electrostatic and magnetostatic fields. The directions of propagating electromagnetic wave and an externally applied static magnetic field in the semiconductor are chosen to be in the same direction. The presence of electrostatic field applied in a direction perpendicular to the direction of static magnetic field establishes a current and the interaction of propagating wave and transverse current has been taken into account. With the determination of propagation constant from the dispersion relation, the variation of phase and attenuation constants for various frequencies in the microwave range have been computed and results are discussed. Such investigations are used as a diagnostic technique to study the transport properties of semiconductor.