Solid Polymer Electrolytes (SPEs) lack better conducting properties at ambient temperatures. Various methods to enhance their ionic conductivity like irradiation with swift heavy ions, γ-rays, swift electrons and quenching at low temperature etc., have been explored in the literature. Among these, one of the oldest methods is incorporation of different conducting species into the polymer matrix and/or addition of nano-sized inert particles into SPEs. Various new salts like LiBr, Mg(ClO4)2, NH4I etc., have already been tried in the past with some success. Also various nanoparticles like Al2O3, TiO2 etc., have been tried in the past. In this article, we have investigated an SPE containing Rubidium as a conducting species. Rubidium has a larger ionic size compared to lithium and sodium ions which have been investigated in the recent past. In the present article, we have investigated the conductivity of large sized conducting species and shown the enhancement in the ionic conductivity by addition of nano-sized inert particles.
Supercapacitors, as promising energy storage devices, have gained significant attention due to their ability to deliver high power and efficient charge storage mechanism. In this work, we report the synthesis and electrochemical characterization of pristine NiO and Ni1-xCexO(x=0.01, 0.02, 0.03) nanoparticles using a single-step auto ignition combustion method. Preliminary investigations indicate that Ni1-xCexO(x=0.02) nanoparticles (2% Ce doping) exhibit superior specific capacitance compared to other compositions. Therefore, we focused on structural, morphological, and optical studies on pristine and 2% Ce-doped NiO, and further electrochemical investigations were conducted solely on the 2% Ce-doped NiO. XPS and BET techniques were explored to assess the electronic state and porosity of the samples. Subsequent electrochemical performance evaluations included Cyclic Voltammetry (CV) at various scan rates, Galvanostatic Charge-Discharge (GCD), and Electrochemical Impedance Spectroscopic (EIS) techniques. From CV at a scan rate of 5 mVs-1, specific or gravimetric capacitance values of 412 Fg-1 and 967 Fg-1 were obtained for pristine and 2% Ce-doped NiO, respectively. GCD studies revealed a specific capacity of 1252 Fg-1 for 2% Ce-doped NiO at a current density of 1 Ag-1, while EIS demonstrated a capacitance retention of 95.1% over 3000 GCD cycles for a current density of 4 Ag-1. DFT calculations suggest that the Ce doping significantly alters the electronic and structural features of pristine NiO due to lattice strain. Our work highlights the enhanced electrochemical performance of 2% Ce-doped NiO and its potential as a good-quality supercapacitor material
PEG LTMS based polymer composites were prepared and studied for dielectric constant variation with frequency and temperature as a potential candidate with better dielectric properties. Solution cast technique is used for the preparation of polymer composite with five different compositions. Samples show variation in dielectric constant with frequency and temperature. Dielectric constant is large at low frequencies and higher temperatures. Samples with larger space charges have shown larger dielectric constant. The highest dielectric constant observed was about 29244 for PEG25LTMS sample at 100Hz and 312 K.
We have used optical V and R band observations from the Massive Compact Halo Object (MACHO) project on a sample of 59 quasars behind the Magellanic clouds to study their long term optical flux and colour variations. These quasars, lying in the redshift range of 0.2 < z < 2.8 and having apparent V band magnitudes between 16.6 and 20.1 mag, have observations ranging from 49 to 1353 epochs spanning over 7.5 yr with frequency of sampling between 2 to 10 days. All the quasars show variability during the observing period. The normalised excess variance (Fvar) in V and R bands are in the range 0.2% < FVvar < 1.6% and 0.1% < FRvar < 1.5% respectively. In a large fraction of the sources, Fvar is larger in the V band compared to the R band. From the z-transformed discrete cross-correlation function analysis, we find that there is no lag between the V and R band variations. Adopting the Markov Chain Monte Carlo (MCMC) approach, and properly taking into account the correlation between the errors in colours and magnitudes, it is found that the majority of sources show a bluer when brighter trend, while a minor fraction of quasars show the opposite behaviour. This is similar to the results obtained from another two independent algorithms, namely the weighted linear least squares fit (FITEXY) and the bivariate correlated errors and intrinsic scatter regression (BCES). However, the ordinary least squares (OLS) fit, normally used in the colour variability studies of quasars, indicates that all the quasars studied here show a bluer when brighter trend. It is therefore very clear that the OLS algorithm cannot be used for the study of colour variability in quasars.
The work reports the effect of 80MeV 6+ Oxygen ion irradiation on the performance of DSSCs. TiO2 coated FTO were subjected to ion irradiation of fluences 1 × 1012 to 1 × 1014 ions/cm2. TiO2 coated FTOs were characterized with XRD for structural analysis and have shown anatase phase. Irradiated films were used as electrodes for DSSCs. We have observed that the irradiated light conversion efficiency of the cells was highest for fluence of 1 × 1013ions/cm2 and at the same fluence the cell parameters showed to be the best. The reason may be due to the surface modification of the TiO2 coated films due to irradiation. However lower fluences than 1 × 1013 ions/cm2 show less effect while higher fluence shown degrading effect on the cell performance which may be due to the worsening of contact between electrode and dyes.
Polymers are known to be better materials for dielectric applications. Various polymers with different molecular weights are being studied for dielectric applications. In the present paper, we report the dielectric measurements of Poly(Ethylene Oxide) {PEO} using Impedance spectroscopy studies. The dielectric studies of PEO were carried out on pellets as a function of temperature. It was found that the dielectric constant seems to be negligibly varying with increase in temperature at high frequencies, however, at low frequencies, dielectric constant varies increases with temperature. This may be due to the fact that with the thermal energy provided to the system, more and more dipoles participate and hence the net dielectric constant of the material is also higher at higher temperature. Also at very high frequencies, due to many non-responsive dipoles for fast switching of the applied signal, net dielectric constant of the material also does vary much with temperatures.
Sodium alginate (SA) and graphene oxide (GO) composite pellets are prepared by one step simple procedure. The composites are found to be thermally stable up to 220°C in nitrogen atmosphere. The composite was studied for impedance analysis with varying temperature ranging from room temperature to 170°C. Dielectric constant of the samples was measured using the impedance data using standard formulae. It was found that the dielectric constant of the composites is high at low frequencies which may be due to the contribution from all the dipoles responding to the applied signal. However, at high frequencies, may be due to non-participating dipoles, the dielectric constant of the composites is lower.
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