Papers by Keyword: Conductivity

Abstract: Green composites of Glucose-reduced graphene oxide (GrGO) and manganese (IV) oxide (MnO₂) were prepared in a typical chemical synthesis route assisted with ultrasonic irradiation. Conductivity studies conducted via 2-point probe method shows GrGO/MnO₂ (4:1) possessed electrical conductivity of 30.29 S cm^-1 with energy band gap of 8.47×10^-1 eV. The increase of D/G intensity ratio of GrGO with increase MnO₂ loading indicates more disorder carbon or defects are introduced from the reaction of carbon with MnO₄^-.

Abstract: This study deals with the ionic conduction mechanism of carboxymethyl cellulose (CMC) – NH₄Br biopolymer electrolytes (BPEs) plasticized with ethylene carbonate (EC) prepared via solution-casting technique. The ionic conductivity of BPEs system was characterized by using impedance spectroscopy and shows the highest conductivity at ambient temperature for CMC–NH₄Br BPEs is 1.12 x 10^-4 S/cm and enhanced to 3.31 x 10^-3 S/cm with the addition of 8 wt. % EC. The conductivity–temperature plot of the BPEs system obeys Arrhenius law where R²~1. The dielectric values were found to increase with increasing temperature thus divulged that the BPEs system to be non-Debye type. The temperature dependence of the power law exponent shows the CMC–NH₄Br–EC BPEs system follows the quantum mechanical tunneling (QMT) model of conduction mechanism, where the enhanced protonation of NH₄Br with addition of EC makes the charge transfer (polarons) able to tunnel through the potential barrier that exists between the lone pair electrons in carboxyl group of CMC and NH₄Br.

Abstract: We measured the resistivity and conductivity behavior of activated carbon and an activated carbon – graphene oxide (GO – AC) hybrid using two point probe method. As graphene oxide is well known as insulator, the effects of different ratio of activated carbon on conductivity of hybrid GO – AC was investigated.

Abstract: The lattice energy of the doping salt for a polymer electrolyte is crucial because it affects the ionic conductivity of the polymer electrolyte system. It is also known that the lattice energy of a salt depends on the size of the anion. The larger the anion the lower the lattice energy of the salt. Therefore, in this study the effect of the anion size of various doping salts; LiNO₃ and LiN(CF₃SO₂)₂ with lattice energy of 848 kJ/mol and 489.4 kJ/mol, respectively were investigated and compared with LiCF₃SO₃ salt (735 kJ/mol) on the electrical properties of poly (methyl methacrylate) (PMMA) / epoxidised natural rubber (ENR 50) blend film. All the doped PMMA/ENR 50 films were prepared by solvent casting technique. Surprisingly, though LiN(CF₃SO₂)₂ exhibited the lowest lattice energy, it displayed the lowest ionic conductivity value of 10^-8 S/cm at room temperature as compared to LiNO₃ and LiBF₄ due to its poor coordinating power with the polymer. This was confirmed from the FTIR analyses. Further investigation on the dielectric behaviour of the doped PMMA/ENR 50 films were also reported.

Abstract: In this work, solid polymer electrolyte compose of blended 30% poly (methyl methacrylate) grafted natural rubber (MG30)-poly (ethyl methacrylate) (PEMA) polymer blend doped with Lithium trimethasulfonate (LiCF₃SO₃) films were prepared by solution casting technique. . FTIR analysis showed that the interactions between lithium ions and oxygen atoms occur at the carbonyl functional group C=O where there is shifting in wavenumber from 1728 cm^-1 of pure blend to lower wavenumber of blended MG30-PEMA on the MMA structure in both MG30 and PEMA. DSC analysis showed miscibility of polymer blend. From Electrochemical Impedance Spectrocopy analysis, ionic conductivity increase with the increasing of salt concentration. Maximum conductivity at room temperature is 9.20 x 10^-6 Scm^-1 was obtained when 30 wt% of LiCF₃SO₃ was added into the system. Ionic conductivity temperature dependence plots found obeys the Arrhenius rule.

Abstract: This paper reports on the conductivity-temperature studies of gel polymer electrolytes (GPEs) based on 49% poly (methyl methacrylate) grafted-natural rubber (MG49) doped with lithium triflate salt (LiTf) and plasticized with ethylene carbonate (EC). The GPE films are prepared by solution cast technique. The X-ray diffraction (XRD) studies reveal the polymer electrolyte systems are amorphous. AC impedance spectroscopy is carried out in the temperature range between 303 and 373 K. The magnitudes of conductivity observed are strongly dependent on salt concentration and temperature. The high ionic conductivity at elevated temperatures of GPE is attributed to the high ionic mobility of charge carriers. The ionic migration is seen to follow the VTF behavior and approaches to Arrhenius rule at high and low at temperature. Ionic conductivity relaxation appears to be a characteristic of the ionic polarization and the modulus formalism studies confirmed the GPEs in the present investigation are ionic conductors.

Abstract: Carboxyl methylcellulose (CMC) doped with oleic acid (OA) and plasticized with glycerol was able to be produced into solid biopolymer electrolytes using the solution cast technique. The CMC-OA-glycerol solid polymer electrolyte obtained the highest conductivity of 1.64 x 10^-4 S cm^-1 at room temperature for sample Gly 40 wt. %. Within the temperature range investigated, the conductivity– temperature relationship of the biopolymer electrolytes is characteristically Arrhenius behaviour, suggesting that the conductivity is thermally assisted. Fourier Transform Infrared studies was carried out to determine the dissociation of free protons (H⁺) from the carboxyl group (–COOH) of glycerol.

Abstract: The objective of this work is to study the structural, morphological and electrical characteristics of lithium triflate-alumina composite electrolytes which were prepared via sol-gel technique. For this purpose, the composite electrolyte pallet samples which were sintered at 300 °C for four hours were subjected to X-ray diffraction, scanning electron microscopy, impedance spectroscopy and transference number measurement. X-ray diffraction spectra and scanning electron micrographs indicated that the crystalline alumina was distributed over the amorphous lithium triflate phase implying that the two-phases of microstructure (lithium triflate and alumina) interspersed each other. The highest ionic conductivity of 2.86 × 10^-3 S cm^-1 at room temperature was obtained for the sample with 60 mol % alumina. Temperature dependence of conductivity study was performed in the 303 K to 423 K temperature range and the trend of conductivity-temperature plot suggested that the increase in conductivity was due to the increase in migration rate of ions with temperature. The non-Arrhenius plot of the conductivity-temperature was due to continuous freezing of cations within the amorphous triflate medium. The value of ionic transference number indicated that the majority charge carriers in this composite electrolyte were ions while the value of Li⁺ transference number suggested that the majority of the ions were anions.

Abstract: In this research, solid biopolymer electrolytes (SBEs) based on carboxy methylcellulose (CMC) has been prepared by doping different concentration of salicylic acid (SA) via solution casting technique. Fourier Transform Infrared spectroscopy was used to study the interaction between the host and ionic dopant. New peaks were observed at 1700, 2890, 2920 cm^-1.The highest ionic conductivity achieved at room temperature is 9.50 × 10⁸ S cm¹ for CMC incorporated with 7 wt. % SA. In addition, the temperature dependence of the SBEs exhibit Arrhenius behavior.

Abstract: The possibility of formation of coatings based on co-polymers 2-hydroxyethylmethacrylate with polyvinylpirrolidone on different nature surfaces is determined. It is investigated, that adsorption of liquid compositions components to surface-base affects the formation of coating from such compositions. The composite metal-filled coatings are obtained on the basis of synthesized polymers. Such coatings are characterized by variable conductivity dependently on moisture content, pH and low-molecular substances availability.