Papers by Keyword: Ionic Conductivity

Abstract: Kinetic Monte Carlo simulations are a useful tool to predict and analyze the ionic conductivity in crystalline materials. We present here the basic functionalities and capabilities of our recently published Monte Carlo software for solid state ionics called MOCASSIN, exemplified by simulations of several model systems and real materials. We address the simulation of tracer correlation factors for various structures, the correlation in systems with complex migration mechanisms like interstitialcy or vehicle transport, and the impact of defect interactions on ionic conductivity. Simulations of real materials include a review of oxygen vacancy migration in doped ceria, oxygen interstitial migration in La-rich melilites, and proton conduction in acceptor doped fully hydrated barium zirconate. The results reveal the impact of defect interactions on the ionic conductivity and the importance of the defect distribution. Combinations of these effects can lead to unexpected transport behavior in solid state ionic materials, especially for multiple mobile species. Kinetic Monte Carlo simulations are therefore useful to interpret experimental data which shows unexpected behavior regarding the dependence on temperature and composition.

Abstract: The present work highlights on the structural and conduction properties of the solid biopolymer electrolytes (SBPE) based carboxymethyl cellulose (CMC) doped dodecyltrimethyl ammonium bromide (DTAB) and plasticized with ethylene carbonate (EC). The SBPE exhibits high ionic conductivity at room temperature where the highest value reaching 1.0 x 10^-3 S cm^-1 for sample containing with 10 wt. % of EC and increases the ionic conductivity when temperature was increased. Complexation within the SBPE has been confirmed by the FTIR analysis where the intermolecular interaction has improvised the coordination between CMC-DTAB and EC resulting in better structural and conductivity ability. The findings suggest that the great potential of CMC and make it promising to serve as an electrolyte for electrochemical devices.

Abstract: This work focuses on the electrical properties study of solid biopolymer electrolyte (SBE) based plasticized carboxy methylcellulose (CMC) doped dodecyltrimethyl ammonium bromide (DTAB). Different weight percentage of ethylene carbonate (EC) which acts as plasticizer was incorporated into SBE system and were successfully prepared via solution casting technique. The conduction properties of SBE was investigated by using electrical impedance spectroscopy (EIS). The incorporation of 10 wt.% EC was found to achieve the highest ionic conductivity with 1.00 10^-3 S cm^-1 at room temperature. All SBE samples shows the ionic conductivity increased proportionally with temperature thus obeys to Arrhenius behaviour with regression value almost close to unity (R²~1). The electrical conduction behaviour of the CMC-DTAB-EC SBE reveals non-Debye behaviour without single relaxation properties.

Abstract: Sodium-ion batteries (SIBs) as low-cost alternatives to expensive lithium-ion batteries become a hot R&D topic in the recent days due to the natural abundancy of sodium in the Earth’s crust and also in the oceans. As far as solid electrolytes for SIBs are concerned, larger size of Na⁺ ions compared to that of Li⁺ ions hinders the ionic mobility resulting to insufficient ionic conductivity for practical applications. Development of quasi-solid state gel-polymer electrolytes (GPEs) would be a feasible solution to overcome this challenge. In this work, we developed Poly (methyl methacrylate) (PMMA) based GPEs with six different compositions dissolved in EC:PC (ethylene carbonate and propylene carbonate, 1:1 wt%) mixture. Among six different GPE samples investigated by Electrochemical Impedance Spectroscopic and Raman Spectroscopic techniques, the best ambient temperature ionic conductivity of 4.2 mS cm^-1 was obtained for 9PMMA:9NaPF₆:41EC:41PC (wt%). Variation of ionic conductivity with inverse temperature showed Arrhenius behavior with almost constant activation energies. The best conducting GPE showed an activation energy of 0.14 eV. In the Raman spectra, very sharp crystalline peaks (400-850 cm^-1 wave number range) of NaPF₆ disappear in the gel state of the electrolytes confirming the non-crystalline nature of the GPEs. Boson modes remain almost constant in intensity for all the six different compositions. The best conducting GPE seems to be highly suitable for practical applications in SIBs as it has sufficient ambient temperature ionic conductivity.

Abstract: The purpose of the work is influence investigation of modifying Nd₅Mo₃O_16+δ oxygen-conducting fluorite-related compound by lead at the crystal structure and conductivity. The substitution of lead for neodymium was studied by XRD (with structure refinement), scanning electron microscopy, FTIR-spectroscopy and conductivity measurements. The compositions Nd_5-xPb_xMo₃O_16+δ (x = 0 – 1.6) were obtained by a solid state reaction from the oxides. It was determined that single-phase solid solution Nd_5-xPb_xMo₃O_16+δ is formed up to x ≈ 0.82. The Rietveld structure refinement shows that lead is statistically located in the Ln1 and Ln2 positions. The introduction of lead does not significantly affect the nature and values of conductivity.

Abstract: The complex oxide BaLaIn_0.9Nb_0.1O_4.1 with Ruddlesden-Popper structure was obtained for the first time. It was found that the introduction of niobium into indium sublattice leads to the increase in the cell volume. Hydration processes and electrical properties have been investigated. For BaLaIn_0.9Nb_0.1O_4.1 it was proved the capability for water uptake and the appearance of proton current carriers. It was established that niobium doping leads to the increase of conductivity compared to undoped composition BaLaInO₄ at ~1 order of magnitude in whole temperature range.

Abstract: The aim of these comparative studies consists of synthesis and characterization of membrane assemblies from cellulose acetate (CelAc) and acrylic acid (AA), using as dopant in-situ generated pyrrole–aniline (Py–AN) copolymer intended for use in fuel cells fabrication. The synthesis was conducted through free radical polymerization in a semi-homogeneous system and the casting method was used to form the solid polymer membranes. In selecting the optimal compositional parameters, the influence of the molecular size of the majority matrix component was also observed. These membrane assemblies were studied using FT-IR spectroscopy, UV-Vis spectroscopy, and X-Ray diffraction analysis which highlighted the structure–composition dependence. With the electrochemical impedance spectroscopy the ionic conductivity of the membrane was determined, in order to evaluate the PEM fuel cell performance. In case of thicker membranes, there is an increase in ionic conductivity values over those of lower thickness, which is due to short-order structural order. Also, a superunitary Py:AN is more favorable to conductivity increase than a less than one ratio.

Abstract: In crystalline solids, during such processes as chemical interdiffusion in alloys, ionic conductivity and the annealing out of radiation damage there will inevitably be a net flux of vacancies. In most cases, when different species of atoms have different jump rates with vacancies within a net flux of vacancies, the phenomenon of the vacancy-wind effect will occur. This effect was first discovered in the 1960s by the late Dr John Manning. It is a subtle phenomenon that comes about because of the local redistribution of the equilibrium concentration of vacancies with respect to two or more species of drifting atoms in a driving force. The effect is captured in various ‘vacancy-wind factors’ (some of which are now sometimes called Manning factors) which formally arise from non-zero off-diagonal Onsager phenomenological transport coefficients and non-unity values of the tracer correlation factors. In this paper, the effect is reviewed and discussed.

Abstract: Chitosan-Starch blend biopolymer electrolyte system doped with different percentage of BMIMNO₃ was prepared via solution casting technique. The crystalinity of the system was calculated using data extracted from x-ray diffraction (XRD). The film was characterized by impedance spectroscopy HIOKI 3531-01 LCR Hi-Tester to measure its ionic conductivity over a wide range of frequency between 50Hz-5MHz and at temperatures between 298 K and 378 K. The result exhibit the advantages of ionic liquid as a charge carrier and also revealed that addition of 5% of BMIMNO₃ shows the highest conductivity of (2.26 +-0.96) x 10^-4 Scm^-1 .Conductivity-temperature relationship indicate that the system seems to obey the Vogel-Tamman-Fulcher (VTF) behaviour.

Abstract: Waste cooking oil (WCO) is an under-utilized, highly abundant raw material from food industry. In this study, WCO was used to prepare solid polymer electrolyte (SPE) films via solvent-free method. WCO was first pretreated and converted into polyol using epoxidation and hydroxylation reaction. Then, WCO-based polyol was combined with diisocyanate, LiCF₃SO₃ and carboxymethyl cellulose (CMC) to obtain polyurethane SPE films. CMC was added to SPE as bio-filler to observe the effect on ionic conductivity and mechanical properties of SPE. SPE films were characterized using Fourier transformed infrared spectroscopy, electrochemical impedance spectroscopy, x-ray diffraction spectrometer (XRD), differential scanning calorimetry and tensile strength. Addition of CMC resulted in increase of ionic conductivity up to 1.19 x 10^-5 S/cm for 15% CMC. The ionic conductivity supported with reduced crystalline peaks intensity in XRD to show that the amorphous nature of SPE increased as more CMC added. Tensile strength also increased with addition of CMC and peaked at 10% CMC (34.17 MPa) due to effective hydrogen bond interaction between CMC and PU or salt. However, increased CMC amount further to 15% reduced tensile strength due to agglomeration of CMC particles. As a conclusion, addition of CMC is a viable method to improve both ionic conductivity and mechanical property of SPE.