Search

The present work focuses on the synthesis of a proton exchange membrane to be assembled in a microbial fuel cell (MFC) for simultaneous bioelectricity production and domestic wastewater treatment. The indigenous membrane was prepared by ionizing irradiation-induced graft copolymerization of glycidyl methacrylate (GMA) and vinyl acetate (VAc) onto low-density polyethylene and subsequently, the prepared grafted sheets were sulfonated via epoxy ring-opening of PGMA moieties. Parameters affecting the grafting degree were investigated and the prepared membranes were characterized by investigating their structural, thermal, mechanical, and electrical properties. Some physicochemical characteristics including ion exchange capacity, sulfonation density, and proton conductivity were also evaluated. The data confirmed the success of the preparation protocol to obtain a suitable membrane for the proposed application. Moreover, the performance of the assembled MFC was thoroughly investigated through the evaluation of its electrochemical behaviour including cyclic voltammetry, electrochemical impedance spectroscopy, columbic efficiency, and wastewater treatment capability. The sulfonated LDPE-g-P(GMA-co-VAc) membrane of 80% grafting degree shows substantial removal of chemical oxygen demand up to about 90% with columbic efficiency of 10.1%, columbic recovery of 8.7%, rate of energy harvest of 2.1 C/h and power density of 2.72 W m−2. However, the use of 10 mM of KMnO4 as electron acceptor drastically increase the harvested power density to reach 356.4 W m−2 [ABSTRACT FROM AUTHOR]

Recently, solid polymer electrolytes (SPEs) are of great current interest as substitutes to conventional liquid type electrolytes. Although the SPEs significantly alleviate the safety issues of the lithium-ion batteries based on conventional liquid electrolytes, they intrinsically exhibit low ion conductivity. In this study, a bicontinuous solid polymer electrolyte containing polyacrylonitrile (PAN) membrane and a mixture of succinonitrile (SN) and lithium bis(trifluoromethanesulfonyl)imide was prepared with different molarities of the lithium salt. Porous PAN membrane was fabricated via a thermally induced phase separation method (TIPS). The PAN-based SPE exhibited the maximum ionic conductivity of ∼5.0 × 10−3 S/cm at the salt molarity of 1.0 M. [ABSTRACT FROM AUTHOR]

Wetlands form part of a diverse range of habitats and play an important role in the ecology and hydrological cycle but are amongst the most threatened ecological systems. It is therefore critical to understand the hydrology of wetlands, and their contributing water sources in particular, to ensure appropriate management of these systems. Land use activities not only alter the runoff characteristics of catchments, but also often result in modified flow regimes in watercourses. Wetlands often develop accidentally in anthropogenic landscapes and are not uncommon. However, these wetlands are poorly documented and researched. An accidental wetland formed in the Kgaswane Mountain Reserve, Rustenburg, due to leaking water infrastructure. The aim of this project was to categorise the wetland and confirm its origin, focussing on the role of the leakage. Methods included hydrogeomorphic classification, water ion composition analysis, as well as infield temperature and electrical conductivity measurements. Historical satellite imagery was used to study the evolution of the wetland over time. The electrical conductivity and ionic composition results suggest an unnatural water source, providing support that a leaking pipe caused the wetland to form. Management of accidental wetlands is discussed and the potential for future, related research is contemplated. [ABSTRACT FROM AUTHOR]

Composite films were prepared by using polyvinyl alcohol – polyvinyl acetate copolymer (PVA/Ac) blended with polyvinyl pyrrolidone (PVP) as the host polymeric material and titania (TiO2) nanoparticles (NPs) as the filler, by using ultrasonic dispersion of the filler in PVA/Ac-PVP blend solution, followed by solution casting method. Free standing films of this composite were characterized by using powder x-ray diffraction (XRD) technique, differential scanning calorimetry (DSC), thermo-gravimetric (TG) analysis, transference number determination, as well as DC and dielectric measurements. XRD patterns confirmed the incorporation of titania NPs within the polymer blend (PVA/Ac-PVP). DSC and TG techniques show that the glass transition temperature of the composite decreased, whereas its thermal stability increased on incorporating TiO2 NPs in PVA/Ac - PVP blend. Wagner's polarization technique, which was employed to determine the transference number revealed that ions were the majority mobile charge carriers. The activation energy (Ea) has been determined from DC electrical measurements by using the Arrhenius equation; Ea was found to decrease with an increase in the filler level (FL) of titania NPs in the polymeric blend. Dielectric studies revealed maximum ionic conductivities of 7.4 × 10−5 Sm−1 and 8.63 × 10−3 S m−1 for the composite film with FL 4.90 Wt%, at temperatures 303 K and 363 K, respectively. [ABSTRACT FROM AUTHOR]

With very fast polymerization in mild reaction conditions and unique characteristic of double bonds in its synthesized polymer skeleton for further modification and functionalization, ring opening metathesis polymerization (ROMP) becomes one typical processing method to obtain anion exchange membrane (AEM) for fuel cells. In this paper, AEMs prepared by ROMP are reviewed. Polycyclooctene and polynorbornene AEMs with both good stability and high conductivity are achieved with different ion exchange groups such as quaternary ammonium, phosphorus and metal cations (such as bis(terpyridine)-ruthenium(II) and cobaltocenium). Polymer structure and ion channels are mainly constructed in the polymer skeleton to form the "ion channel" microphase-separated structure to improve its chemical stability and ionic conductivity. On the basis of selected ion exchange groups and optimized polymer skeleton, performances obtained in these ion exchange membranes (IEMs) and their corresponding fuel cell performances are summarized. These polycyclooctene and polynorbornene AEMs have excellent properties and promising performances in fuel cells. We believe that further exploration of this class of AEM may lead to practical applications. [ABSTRACT FROM AUTHOR]

Ionogels is a kind of hybrid materials composed of ionic liquids (ILs) and solid polymer network matrix, has been extensively investigated in the most recent decade. Due to the excellent mechanical properties and ionic conductivity, their promising applications in flexible stress and strain sensors have been proposed and explosively developed. In this review, we briefly summarize research progresses on ionogel based flexible stress and strain sensors (IFSSs) from five aspects, including material synthesis, device fabrication, working principles, characteristics and performances, and potential applications. Some outlooks and perspectives are also proposed at the end of review. The review is expected to provide reference and new insights into the research of IFSS. [ABSTRACT FROM AUTHOR]

The aim of this study is to prepare Er and Sm co-doped CeO2 electrolytes via the Pechini method and investigate the effects of simultaneous addition of Sm and Er on the structural and electrical features of CeO2. The structural, functional group analysis, microstructures, and electrical properties of the electrolyte samples are conducted by X–ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and impedance spectroscopy (IS). All the calcined and sintered electrolytes were obtained with cubic fluorite crystal structure without secondary oxide phases. After sintering at 1400 °C, highly dense electrolytes were achieved (> 90%). The IS measurements indicated that the highest ionic conductivity was observed for the singly doped Ce0.80Sm0.20O1.90 (σ750 °C = 3.86 x 10−2 S/cm) electrolyte. σ750°C was found to be 3.82 x 10−2, 1.73 x 10−2, 0.61 x 10−2 S/cm for Ce0.80Er0.05Sm0.15O1.90, Ce0.80Er0.10Sm0.10O1.90 and Ce0.90Er0.10O1.95, respectively. [ABSTRACT FROM AUTHOR]

In this report, the relationship between the ionic conduction properties of alginate (AL) based biopolymer electrolyte (BE), and the amount of NH4Cl dopant and ethylene carbonate (EC) plasticizer is discussed. The BE was prepared via a solution casting method and characterized by using Fourier transform infrared (FTIR) and electrical impedance spectroscopy (EIS), respectively. The highest ionic conductivity attained for the AL-NH4Cl BE was 3.18 × 10−8 S cm−1 for 8 wt.% of NH4Cl. Nonetheless, an increased optimum value of 1.46 × 10−6 S cm−1 was obtained when plasticized with 4 wt.% of EC. It was observed that with the addition of the EC content between the range of 1 wt.% and 7 wt.% into the AL-NH4Cl with 8 wt.% salt content increased the flexibility of the AL chains to facilitate free H+ ion transport. The weak bonding created through EC - NH4+ allows higher dissociation of proton ions (H+), allowing more interaction to occur on the AL polymer backbone. These ions will hop from one complex site of AL to another, as revealed by FTIR analysis. Through the deconvolution analysis of the BE systems, it was demonstrated that the ionic conductivity for both systems was governed by the enhancement of the free ions fraction which, in turn, increased the number of mobile ions upon the addition of NH4Cl. [ABSTRACT FROM AUTHOR]

The effect of single-walled carbon nanotubes (SWCNTs) on the dielectric and conductivity properties of smectic A liquid crystal 4-nitrophenyl-4'- decyloxybenzoic acid has been studied. It was shown that the additive of SWCNTs with concentration of 0.5% leads to a decrease in the order parameter of the liquid crystal. In this case, the clearing point and the longitudinal component of the dielectric permittivity decreases while the transverse component increases. The incipient percolation effect promotes to the dominance of hopping electron conductivity over ionic conductivity, leading to an increase in specific conductance. [ABSTRACT FROM AUTHOR]

A solid polymer blend electrolyte was prepared by using Polyvinyl alcohol (PVA) and Methacrylic Acid Ethyl acrylate (MAA: EA) polymers with different weight percentages (Wt%) of Potassium Chloride (KCl) by using solution casting technique, with water as a solvent. The structural, thermal, optical, and electrical properties of the prepared samples were studied. The X-ray diffraction pattern shows the decreasing trend in the degree of crystallinity due to the incorporation of KCl into the polymeric matrix. From the FTIR analysis, some peak intensities were decreasing and shifted in the case of KCl complexed films, which results in the complexation between the polymer blend and dopant ions. The TGA analysis reveals that the thermal stability of the KCl complexed films increases as dopant concentration increases. The SEM images reveal the structural reorganisation of polymer chains in the KCl complexed polymer blend electrolytes. UV-VIS spectra show that the optical constants such as absorption edge and band gap (both direct and indirect) values are decreased with an increase in KCl concentration. From conductivity data, it was noticed that the conductivity increased with the increase in the K+ ion concentration. The maximum ionic conductivity of 1.85 × 10−7 S/cm was obtained for the sample having 15 wt% of KCl salt. [ABSTRACT FROM AUTHOR]

XRD measurements revealed that the investigated NaLiMnP2O7 compound consists of two phases: Na2Mn3(P2O7)2 and LiMnPO4. We found by XRD measurements that at 313 K Na2Mn3(P2O7)2 shows the triclinic symmetry of the compound (space group P-1), while LiMnPO4 phase showed the orthorhombic crystal symmetry (space group Pnma). The phase change between 773 K and 813 K was proved by thermal XRD, impedance spectroscopy and DTA analysis. No evident changes of peak intensities in thermal XRD were observed for LiMnPO4 phase. The impedance of NaLiMnP2O7 ceramics was measured at different temperatures and the total ionic conductivity of the compound was found to be of 5.3 × 10−9 S/m at 400 K on heating stage and only slightly higher on cooling stage. However, the conductivity value at 800 K was much higher – about 1.45 S/m on both stages. The step-like phase transition resulted in the conductivity increase of about 3 orders of magnitude in a narrow range of temperature. The ionic transference number was found to be 0.91 at room temperature. The XRD spectra and conductivity analysis of synthesised two separate phases showed that the phase transition takes place only in Na2Mn3(P2O7)2 ceramics. [ABSTRACT FROM AUTHOR]

Impact of Sodium Bromide salt on the microstructural properties of Poly (Vinyl Alcohol) and Sodium salt Carboxymethyl cellulose (PVA/NaCMC:70/30) blend biopolymer electrolyte films were investigated. The films were prepared by conventional solution casting method and were subjected to UV-Visible, XRD, SEM, AC, & DC conductivity studies. Microstructural properties of PVA/NaCMC blend system got affected due to complex-formation. Amorphosity of the poly blend-system increased upon doping indicating rearrangement of polymer chain due to the interaction of Na+with the functional group of PVA/NaCMC blend system. It is found that the degree of crystallinity of the PVA/NaCMC blend films decreased upon doping, due to molecular chain disorderness that facilitates the migration of ions due to enhancement in the free volume as observed from SEM. [ABSTRACT FROM AUTHOR]

The calamitic nematic liquid crystal generally exhibits a discontinuous weakly first-order isotropic-nematic (I-N) phase transition. We found that, on the incorporation of CdS nanowire in the nematic host, the weakly first-order discontinuous I-N phase transition evolved as a continuous phase transition. The parallel and perpendicular components of dielectric permittivity and bulk conductivity of nanocomposites of CdS nanowires of a nematic liquid crystal (NLC) are found to follow continuous I-N phase transition in contrast to the discontinuous weakly first-order transition of the pure host nematic liquid crystal. This was further confirmed from scattered iGntensity measurements on the CdS nanocomposite samples of nematic liquid crystal in homeotropically aligned cells. Such measurements indicate a continuous phase transition for the nanocomposites of NLC having concentrations less than 0.2 wt% of CdS nanowires in NLC. The dielectric anisotropy, birefringence, threshold voltage of nanocomposites of CdS nanowire in a calamitic nematic liquid crystal with varying concentration of the nanowire have been measured. The ionic conductivity of nanocomposites of CdS nanowires of NLC increases with increasing concentration of CdS nanowires. [ABSTRACT FROM AUTHOR]

Gadolinia-doped ceria (GDC) is widely used as an interlayer for preventing the formation of SrZrO3 between yttria-stabilized zirconia (YSZ) electrolyte and lanthanum strontium cobalt iron oxides (LSCF) cathode for solid oxide fuel cells (SOFCs). However, the diffusion of Gd ions to YSZ electrolyte results in the decrease in ionic conductivity due to the formation of Gd2(Zr, Ce)2O7. In the present work, we focus on lanthanum-doped ceria (LDC) as an interlayer between YSZ electrolyte and LSCF cathode. The ionic conductivity of YSZ/LDC composite was higher than that of YSZ/GDC composite in spite of the lower conductivity of LDC than GDC. The maximum power density for the microtubular SOFC with LDC interlayer was better than that with GDC interlayer. While the ohmic resistance decreased by the change from GDC to LDC interlayers, the polarization resistance for oxygen reduction reaction slightly increased as a result of distribution of relaxation times (DRT) analysis. The chemical compositions of Zr, Ce and La was gradually varied at the interface between YSZ electrolyte and LDC interlayer, which affected the both of ohmic and polarization resistances. [ABSTRACT FROM AUTHOR]

Sm0.2Ce0.8O1.9 electrolytes were prepared using a novel chitosan templating method. To examine the sintering kinetics of the materials, 5 minutes, 1 hour, and 6 hours of sintering processes were carried out at 1200, 1300, and 1400 ⁰C. The phase structure of the sintered samples was clarified by XRD analysis. The morphological structure was examined by SEM and the average grain sizes were calculated with the Linear Intercept Method. The dominant diffusion mechanism and grain growth activation energies during sintering were calculated for the SDC20 electrolytes synthesized by the chitosan templating method for the first time. In addition to the sintering study, the ionic conductivities of the samples were determined by electrochemical impedance spectroscopy. The maximum O2- conductivity value for the 1300–6 sample was found to be 0.052 S.cm−1. The study showed that the chitosan templating method is an effective way of synthesizing SDC20 materials. [ABSTRACT FROM AUTHOR]

The glass of lithium-sodium tetragermanate LiNaGe4O9 was prepared by fast quenching the melt. The glass was devitrified on heating under the control of differential scanning calorimetry. It was shown that the glass crystallized through a single stage. Electrical properties were measured on heating in the interval including the characteristic temperatures of the glass devitrification. It was shown that electrical conductivity increased on approaching glass transition temperature Tg from below and sharply dropped down after the glass crystallization. Charge transfer in LiNaGe4O9 glass and polycrystal was attributed to Li ions motion. The data obtained can be used for the preparation of the nanometer sized LiNaGe4O9 glass ceramics with increased ionic conductivity. [ABSTRACT FROM AUTHOR]

The glass of lithium-sodium tetragermanate LiNaGe4O9 was prepared by fast quenching the melt. The glass was devitrified on heating under the control of differential scanning calorimetry. It was shown that the glass crystallized through a single stage. Electrical properties were measured on heating in the interval including the characteristic temperatures of the glass devitrification. It was shown that electrical conductivity increased on approaching glass transition temperature Tg from below and sharply dropped down after the glass crystallization. Charge transfer in LiNaGe4O9 glass and polycrystal was attributed to Li ions motion. The data obtained can be used for the preparation of the nanometer sized LiNaGe4O9 glass ceramics with increased ionic conductivity. [ABSTRACT FROM AUTHOR]

The energetic state of water in the soil-plant system is a relevant theme in ecosystems affected by abiotic stress. Thus, the present study aimed to investigate the water potential in soil and in sorghum grown in Fluvisol irrigated with water of increasing electrical conductivity and different ionic compositions. Solutions were prepared with different ionic compositions (NaCl and a salt mix) and with six increasing levels of electrical conductivity (0, 2.5, 5.0, 7.5, 10, and 12.5 dS m−1), with a randomized block design and 4 repetitions. The leaf water potential and leaf osmotic potential were determined 60 days after sowing. The soil osmotic potential was measured by saturation paste and the matric potential was estimated by the soil water retention curve. The increase in electrical conductivity, regardless of the type of saline solution applied, causes interference in the energy status of the water in the soil, especially concerning the osmotic potential. The type of salt exerts an influence on the water potential in the soil. In contrast, the salt type does not influence the potentials of water in the plant. It is not recommended adopting the same values of water total potential for the soil determined in sorghum at night. [ABSTRACT FROM AUTHOR]

Triblock copolymers comprising chemically complementary poly(ethylene oxide)/polyacrylamide (TBC) and their partially hydrolyzed derivative (TBChydr) were investigated as possible ion-conducting membranes for Li-ion batteries (LBs), dye-sensitized solar cells (DSSCs) and fuel cells (PEFCs). Two TBC samples consisting PEO blocks of variable block length (MnPEO = 6·104 and 3.5·104 kDa) were synthesized and used for these purpose. It was noticed that ionic conductivity of TBC membranes increases with PEO block lengthening from 6.2·10−11 to 3.2·10−9 S⋅cm−1. The introduction of additional ionic groups -COOH in polyacrylamide block of TBC has a positive effect on the conductive characteristics of copolymer membranes. The ionic conductivity of TBC membranes filled with LiPF6 increases with increasing of salt content. [ABSTRACT FROM AUTHOR]

The films of poly (ethylene oxide) (PEO) and poly (vinylidene fluoride) (PVDF)-based blended polymer electrolyte films complexed with sodium perchlorate (NaClO4) salt were prepared using the solution casting method. The complexation of NaClO4 salt with the blend of polymers PEO and PVDF was confirmed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The melting temperatures were measured by differential scanning calorimetry (DSC). The surface morphology was examined by scanning electron microscopy (SEM). The prepared films were subjected to electrical impedance spectroscopy (EIS) to investigate ionic conductivity, dielectric and electrical modulus studies. It was observed that adding a small amount of PVDF to the PEO host polymer improves the interaction between the ions and the polymer and results in more ionic dissociation. Consequently, the number of active mobile carriers in the polymer matrix increases. The ionic conductivity studies have shown the maximum conductivity 2.84 × 10−6 S/cm at 303 K for the polymer blend 0.8PEO + 0.2PVDF complexed with 5 wt% NaClO4 and it is attributed to a decrease in crystallinity. Ionic transport numbers of various prepared samples were measured using Wagner's polarization technique. [ABSTRACT FROM AUTHOR]

This paper describes the results of solution casting technique derived PVP polymer electrolytes with different concentrations of Fe3+ ion as the dopant. Thermogravimetric curves of the pure and Fe3+ doped PVP polymer films show three distinct steps of weight loss. X-ray diffraction patterns indicate an enhanced amorphous nature of the polymer electrolyte with the increase in dopant concentration. SEM elucidates the surface morphology of the system. The optical band gaps of the films showed a decreasing trend with increasing dopant concentration. The FTIR spectra confirmed the complexation between the Fe3+ ions and the host polymer in terms of changes in intensity and certain bands position. The maximum ionic conductivity of 5.62 × 10−8 Scm−1 at 303 K has been observed for 5 mol% Fe3+ ions doped PVP sample. Hence, the observed properties of pure and Fe3+ ions doped PVP polymer electrolytes look very desirable and promising for battery applications. [ABSTRACT FROM AUTHOR]

In the present work, we have prepared a liquid crystal-carbon nanotube (LC-CNT) composite by dispersing a low concentration of carboxylic group (-COOH) functionalised multi-walled CNTs (MWCNTs) in a liquid-crystal 6CHBT and studied in detail the alterations in thermal and electrical parameters. Thermodynamic studies reveal that transition processes are becoming fast due to the dispersion of MWCNTs. The change in the behaviour of transitions is credited to the reduction in ionic impurities owing to the ion trapping characteristic of CNTs. The isotropic liquid to nematic transition temperature of the composite system is increasing for the exothermic cycle as compared to that of the pure sample. The average transition enthalpies and entropies for various transitions of the composite system are increasing as compared to those of the virgin sample. Longitudinal component of the permittivity and dielectric anisotropy of the composite system is slightly reduced as compared to those of the virgin sample. Relaxation frequencies of an observed relaxation mechanism corresponding to the rotation of molecules about their short axes of the composite system are enhanced as compared to the undispersed sample. Total ionic conductivity of the composite system is boosted as compared to those of the pure sample. [ABSTRACT FROM AUTHOR]

Series of oligomeric ionic liquid crystals (OILCs) based on various anions including bromide (Br−), tetrafluoroborate (BF4−), dodecylbenzenesulphonate (A-SO3−) and (+)-10-camphorsulphonate (D-SO3−) are synthesised by use of pyridine-containing monomers, terminal bromo-substituted alkanes and anion replacement reagents. The effect of anions on the chemical structure, liquid-crystalline behaviour, and ionic conductivity is investigated. The OILCs show various mesophases including smectic, hexagonal columnar and bicontinuous cubic phase due to the change in anions. These mesophase types are determined by two incompatible segments derived from ionic mesogens and flexible alkyl chains in the microstructure. For the OILCs based on A-SO3− and D-SO3− anions, a curvature of the interfaces between the layers arises due to the increased size of one segment, resulting in columnar and cubic mesophases. The ionic conductivity is investigated in the way that a lithium ion solution passing through the oriented OILC films at room temperature. For the OILC films with various anions, ionic conductivities of the measuring system increase a little in the order A-SO3− > D-SO3− > BF4−> Br−. The values based on A-SO3− anion films show nearly twofold increase compared with those based on Br- anions, which can be attributed to the effects of both ion migration and ionic channels in the microstructures. [ABSTRACT FROM AUTHOR]

The incorporation of aluminum anodes in metal-air galvanic cells is very interesting due to its intrinsic physico-chemical properties that include a high theoretical specific capacity (2.98 Ah g−1) compared to lithium (3.86 Ah g−1), low density, negative standard potential versus the standard hydrogen electrode (SHE), high abundance in the earth's crust, recyclability, and environmental friendliness. In this report, various hydrogels based on xanthan are described that were prepared at different pH values in order to produce solid electrolytes characterized by high ionic conductivity. These electrolytes have been characterized in aluminum-air galvanic cells using Pt/C based air cathodes. The performance of the cells was characterized by discharge tests performed at constant currents across the range from 3 to 6 mA/cm2. The ability of recharging the cells was evaluated by determining the electrolyte electrochemical window using cyclic voltammetry (CV) measurements. The ionic conductivity of the hydrogels was determined by electrochemical impedance spectroscopy (EIS). The results evidenced the superior performance of acidic hydrogels in terms of cell capacity and anodic efficiency, due to the capability of xanthan as self-corrosion inhibitor, but the rechargeability was hindered because of the current consuming hydrogen reduction. A larger electrochemical window was observed for neutral hydrogels, but with low cell voltage, and by alkaline electrolytes, but at the expense of the anodic efficiency. [ABSTRACT FROM AUTHOR]

A series of anion exchange membranes (CSPY-x-QMSNs) were synthesised based on the schiff base functionalised chitosan (CSPY) as polymer matrix, a given amount of quaternized mesoporous silica (QMSNs) as filler, glutaraldehyde (GA) as crosslinker and the iodomethane as quaternization reagent. The maximum conductivity (3.55 × 10−2 S cm−1) at 80°C, which is about six times that of CSPY-0-QMSNs (the content of QMSNs is 0 wt%), was obtained under the content of QMSNs is 20 wt% (CSPY-20-QMSNs). The accelerated ageing experiment was carried out in 3 mol L−1 KOH solution for 120 h at 80°C, whichrevealed that theconductivity of CSPY-20-QMSNs membranes retains approximately 89.1% of its initial conductivity. Methanol permeability of CSPY-x-QMSNs membranes was only 1.2–3.3% of the Nafion-117 membrane in 3 mol L−1 methanol at 60°C for 3 h. [ABSTRACT FROM AUTHOR]

The effect of single-walled carbon nanotubes (SWCNTs) on the dielectric, conductivity, and electro-optic properties of nematic liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) has been studied. It was shown that the additive of SWCNTs with concentration of 0.5% leads to an increase in the order parameter of 5CB. In this case, the clearing point is raised, the longitudinal component of the dielectric permittivity increases while the transverse component decreases. The incipient percolation effect promotes to the dominance of hopping electron conductivity over ionic conductivity, leading to an increase in specific conductivity. The elastic splay constant of 5CB is enhanced and, accordingly, the threshold voltage of the Freedericksz effect increases in this situation. An increase in distance between LC molecules leads to decreasing of viscosity. As a result, the flip-flop motion of molecules become easier and the switching times are also reduced. [ABSTRACT FROM AUTHOR]

Nanoscale metal oxides based binder-free electrodes have application prospects in the energy storage field. In this work, Fe2O3 nanosheets composited with carbon matrix were prepared via the electrochemical deposition on the dopamine treated stainless steel substrate, followed by annealing treatment. The electrode delivers discharge capacity of 1242 mAh·g−1 at 600 mA·g−1 current density after 100 cycles. Furthermore, the electrode exhibited outstanding rate capability and its reversible capacity reaches to 960 mAh·g−1 at 1800 mA·g−1 current density. The properties of full-cells comprising LiFePO4 cathode were also studied. The improved cycle performance could be attributed to high electronic, ionic conductivity and strong tolerance to volume change benefited from the unique nanostructure and amorphous carbon structure. This work may provide a facile and efficient method for the synthesis of high performance Fe2O3 anode materials. [ABSTRACT FROM AUTHOR]

We present a computational approach for identifying the important descriptors of the ionic conductivities of lithium solid electrolytes. Our approach discriminates the factors of both bulk and grain boundary conductivities, which have been rarely reported. The effects of the interrelated structural (e.g. grain size, phase), material (e.g. Li ratio), chemical (e.g. electronegativity, polarizability) and experimental (e.g. sintering temperature, synthesis method) properties on the bulk and grain boundary conductivities are investigated via machine learning. The data are trained using the bulk and grain boundary conductivities of Li solid conductors at room temperature. The important descriptors are elucidated by their feature importance and predictive performances, as determined by a nonlinear XGBoost algorithm: (i) the experimental descriptors of sintering conditions are significant for both bulk and grain boundary, (ii) the material descriptors of Li site occupancy and Li ratio are the prior descriptors for bulk, (iii) the density and unit cell volume are the prior structural descriptors while the polarizability and electronegativity are the prior chemical descriptors for grain boundary, (iv) the grain size provides physical insights such as the thermodynamic condition and should be considered for determining grain boundary conductance in solid polycrystalline ionic conductors. [ABSTRACT FROM AUTHOR]

Lithium (Li+) ion conducting nanocomposite polymer blend electrolytes (NCPBEs) based on poly(ethylene oxide) (PEO), poly(vinylidene fluoride hexafluoropropylene) (P(VdF-HFP)) as polymer hosts, lithium perchlorate (LiClO4) as an electrolyte and strontium titanate (SrTiO3) as a nanofiller have been prepared by both the conventional stirring and ultrasonic irradiation methods. Complex formation and hence the structural changes of the prepared samples have been confirmed by X-ray diffraction analysis. Conductivity studies have been carried out by means of AC impedance spectroscopy. In order to highlight the role of ultrasonic irradiation, conductivity values have been compared with the values obtained through conventional mechanical stirring method. It has been found that the system with 15 minutes of ultrasonic irradiation resulted in better homogenous dispersion of SrTiO3 in PEO/P(VDF-HFP)/LiClO4 matrix. Maximum ionic conductivity of 2.519 × 10−4 Scm−1 has been obtained for 6 wt% of SrTiO3 system which is a magnitude higher than the ionic conductivity value, 2.031 × 10−5 Scm−1 obtained for the original NCPBE prepared using conventional mechanical stirring at room temperature. Further, ionic conductivity value increases with the increase of temperature and it exhibit the Arrhenius relation. Higher degree of free ionic motion in the samples has been proven by the increase in intensity of photoluminescence spectra peaks. The dielectric properties of the prepared samples have also been studied using the complex dielectric permittivity spectra and complex electric modulus spectra. The morphology and hence the surface roughness of the samples have been depicted through AFM study. [ABSTRACT FROM AUTHOR]

Ceramic samples of the ternary 0.5Y0.1Zr0.9O2 − 0.5(0.6SrTiO3 − 0.4BiScO3) system consisting of the individual Y0.1Zr0.9O2 and 0.6SrTiO3 − 0.4BiScO3 subsystems were synthesized using solid-state processing techniques. Coexistence of the tetragonal P42/nmc phase characteristic of the 5Y0.1Zr0.9O2 subsystem and the cubic P m 3 ¯ m and tetragonal P4mm phases characteristic of the 0.6SrTiO3 − 0.4BiScO3 subsystem was found at room temperature via the XRD analysis. An examination of the dielectric properties showed anomalous changes within three temperature fields. The dielectric anomalies corresponding to the lowest temperature field (below room temperature) are associated with a diffuse ferroelectric phase transition. Mean temperature dielectric anomalies are corresponding to a dielectric relaxation process. The temperature position of these anomalies strongly depends on a measuring frequency and falls in the temperature 600 ÷ 900 K range. High temperature dielectric anomalies induced an ionic conductivity are observed above ∼900 K. [ABSTRACT FROM AUTHOR]

New polymer electrolytes have been prepared from room temperature ionic liquid (IL) and poly(vinylidene fluoride)-hexafluoropropylene copolymer [PVdF-HFP]. The variation of thermal and electrical properties with varying polymer to IL concentration was investigated. The electrolytes had high thermal stabilities. The IL-PVdF-HFP electrolytes were freestanding, flexible films with room temperature conductivities of the order of 10−3 S cm−1. Increase in conductivity was found with increasing IL and also with increasing temperature. Increase in conductivity can be attributed to the fact that with increasing IL amorphicity increases as evident from XRD result. Dielectric studies showed decrease in relaxation time with increasing IL concentration indicating increase in polymer segmental motion which result in increase in conductivity. [ABSTRACT FROM AUTHOR]

A novel Sb2S3/SnO2 bundle-like nanocomposite has been synthesized via a facile solution method followed by a hydrothermal process. When used as the anode material for sodium-ion battery (SIB), this material with unique hetero-nanostructure shows superior electrochemical performance to those of individual Sb2S3 and SnO2. The Sb2S3/SnO2 anode shows an initial reversible capacity of 711.4 mAh/g and remains at 81.9% of the initial performance after 100 cycles at a current density of 50 mA/g. The enhanced performance is ascribed to unique hetero nanostructure with synergetic effect between Sb2S3 and SnO2 in Sb2S3/SnO2 composite, which can enhance both the electronic and ionic conductivities of the anode and reduce the volume change during the charge and discharge processes. The high electrochemical performance indicates that the combination of Sb2S3 and SnO2 to form hetero nanocomposite is a promising strategy for fabricating high-performance SIB anodes. [ABSTRACT FROM AUTHOR]

Multi-stimuli- responsive mechanical strong stretchable hydrogel has grabbed extensive attention in recent years. Here, a novel stretchable conductive biocompatible near-infrared light(NIR)-/thermal-/pH-/ionic concentration- responsive carboxymethyl chitosan (CMCTs)/graphene oxide (GO)/poly(N-isopropylacrylamide)(PNIPAm) nanocomposite double network hydrogel was fabricated through a simple one-pot in situ free radical polymerization, which is initiated by ultraviolet (UV) light and using N-(3-dimethylaminopropyl)-N-ethylcarbodiimidehydrochloride (EDC) and N,N'-bis(acryloyl)cystamine (BAC) as cross-linkers respectively, instead of toxic organic molecules. When the concentration of CMCTs, GO, EDC and BAC is 22.50, 0.103, 7.50 and 0.467 mg/mL respectively, the obtained hydrogel sample owns the highest tensile strength of 1046 kPa at failure strain of 1286% and a corresponding compressive stress of 2.37 MPa at deformation of 90%. Besides, these hydrogels have an obvious pH-/thermal-/ionic concentration-responsive properties depending on the concentration of the above mentioned factors, and their good conductive property makes them as candidate material for healthcare biosensors. Finally, we attempt to design a novel thermal-/NIR-responsive double network structure bilayer hydrogel, which has the potential use as remote actuator in dangerous places in the future. [ABSTRACT FROM AUTHOR]

AgI can transform a face-centred cubic lattice structure under pressures in the range 0.4–11.3 GPa. These phases also exhibit high ionic conductivities, particularly at high temperatures. The full-potential linear muffin-tin-orbital (FP-LMTO) method is used to investigate the ion conduction mechanisms of AgI under high pressures, wherein the exchange correlation energies of electrons are calculated via both local density approximation and generalised gradient approximation and then compared. The total energy calculations exhibit saddle points along the migration pathways, where Frenkel defects should be stable. Our results suggest that Frenkel defects do not easily migrate from stable positions, particularly under high pressures. This implies that Frenkel defects dominate ionic conduction not only in AgCl and AgBr, but also in rocksalt-structured AgI. [ABSTRACT FROM AUTHOR]

Li6.25Al0.25La3Zr2O12 (LLZO) is one of the most promising solid-state electrolytes due to its electrochemical and chemical stability against metallic Li and high ionic conductivity at room temperature. Despite its favorable attributes, it has been shown that Li metal can penetrate LLZO above a critical current density (CCD). Currently, the mechanism by which this phenomenon occurs has not been completely elucidated. However, microstructural defects such as grain boundaries have been pointed out as one of the defects where Li metal preferentially propagates. Thus, microstructural characterization techniques that do not require extensive sample preparation are valuable to correlate processing conditions with resulting microstructure and properties. In this work, a thermal grooving process was optimized to minimize lithium loss allowing to visualize and study the microstructure of LLZO. The proposed technique does not require extensive sample preparation such as what is required for electron backscattering diffraction (EBSD). Variables such as temperature and atmosphere were tuned to optimize thermal grooving while maintaining phase purity (91.4 wt %). We believe this simple method to visualize grains and grain boundaries will help guide efforts to correlate processing conditions with electrolyte properties and ultimately move forward to enable solid-state battery technology. [ABSTRACT FROM AUTHOR]

Incorporation of magnesium oxide nano particles (MgONPs) in a nematic liquid crystal display material namely 4-pentyl-4'-cyanobiphenyl (5CB) have been analyzed by differential scanning calorimeter, polarizing light microscopy and dielectric spectroscopy. MgONPs have been dispersed in two different concentrations in pure 5CB viz. 0.2 and 0.6 wt%. It has been experimentally noticed that with the increase of MgONPs concentrations in 5CB, the nematic to isotropic transition temperatures decreases and dielectric anisotropy increases. Relaxation frequency of an observed relaxation mode corresponding to molecular rotation about the short axis is almost unchanged after dispersion of MgONPs. The ionic conductivity has increased by approximately one order of magnitude for 0.6 wt% MgONPs and decreased for 0.2 wt%. [ABSTRACT FROM AUTHOR]

Although all-solid-state batteries have good safety and high energy density, they still need to explore high performance solid-state electrolytes to achieve high ionic conductivity, wide electrochemical window and excellent mechanical properties. In this work, we designed a hybrid solid electrolyte to solve these problems via mixing PEO, ionic liquid EmimFSI (1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide), LLZO (Li6.5Mg0.05La3Zr1.6Ta0.4O12) and lithium salt, which aimed at suppression of PEO crystallization and employed to improve the mechanical and electrochemical stability. Accordingly, the LLZO@EmimFSI@PEO derived hybrid solid electrolyte provides an ionic conductivity of 1.0×10-4 S cm-1 at 40oC and electrochemical stability window above 5.0 V vs. Li/Li+. Furthermore, the symmetric cell of Li/hybrid solid electrolyte/Li exhibits flat voltage profiles and stable lithium plating/stripping process, a solid-state battery based on the hybrid solid electrolyte combined with high-energy lithium metal anode and NCM622 (LiNi0.6Co0.2Mn0.2O2) cathode was also demonstrated. [ABSTRACT FROM AUTHOR]

Thin NASICON-type Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte membrane is successfully fabricated through tape-casting. A high density of 3.28 g cm−3 of the membrane with a porosity of 4.5% has been achieved when it is sintered at 900°C for 11 h. The membrane shows a comparative ionic conductivity with that of the glass-ceramic pellets. The total ionic conductivity of the present membrane is 2.62 × 10–4 S cm−1 at room temperature, and it maintains a stable conductivity of 1.3 × 10–4 S cm−1 in a 0.5 M LiOH and 0.5 M Li3PO4 buffer solution, which can fully afford the requirements of the membrane used in lithium–air batteries. High-density thin LAGP membrane with comparative ionic conductivity has been successfully prepared by tape-casting, which can fully afford the essential requirements of using in Li–air battery. [ABSTRACT FROM AUTHOR]

LiFePO4 is a promising cathode material for lithium-ion batteries due to its excellent rate capability and superior safety. However, its relatively low energy density makes the research efforts towards another olivine structure material LiMnPO4, which exhibits higher energy density and operating voltage. Nevertheless, LiMnPO4 does not show the remarkable electrochemical performance attributing from the low electronic/ionic conductivity. To solve the problems, a facile solvothermal method is used to successfully synthetise the LiMn1-xFexPO4/C with different Fe/Mn ratio (LMFP/C) nanoparticle in this paper. The length of the obtained LiMn1-xFexPO4/C is less than 200 nm. Owing to the doping of iron and the nano-structure, the LiMn0.5Fe0.5PO4/C nanoparticle exhibits high discharge capacities of 153.6, 143.2 and 134.5 mAh g−1 at rates 0.1 C, 1 C and 5 C, respectively. Furthermore, the effects of pH on the morphology evolution and electrochemical performance have been also investigated in detail. [ABSTRACT FROM AUTHOR]

The influence of capped gold nanospheres (GNSs) on the direct current (DC) electric conductivity ( σ D C ) of a ferroelectric liquid crystal (FLC) confined in a cell with blocking electrodes was experimentally investigated. In framework of this work, several measurement techniques of σ D C , such as dielectric and conductivity spectroscopies, were utilised. However, it was demonstrated that only the capacitive technique allowed estimating values of σ D C of both pure FLC and FLC/GNSs nanodispersion confined in the cell with blocking electrodes. The experimental results confirm the assumption that the gold nanoparticles adsorb the impurities' ions in FLC which leads to the decrease in the conductivity of the FLC layer. [ABSTRACT FROM AUTHOR]

The chemical cross-linking of epoxy resin has been known as an imperative way to improve the mechanical strength and thermal stability of solid polymer electrolytes (SPEs). Herein, we prepare flexible epoxy-based SPEs with high ion conductivity for electrochemical devices via ring-opening polymerization. A diglycidyl ether of bisphenol-A (DGEBA) epoxy resin was selected as the mechanical supporting SPE matrix. The high flexibility of SPEs can be obtained by adding poly(ethylene glycol) diglycidyl ether (PEGDE) plasticizer to the epoxy resin. Furthermore, the incorporation of electrolyte mixture of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salts and 1-butyl-3 methylimidazolium bis(trifluorosulfonyl)imide (BMIM-TFSI) ionic liquids allows for boosting ionic conductivity of the epoxy-based SPEs. Consequently, the high room temperature ionic conductivity ∼2.4 × 10−3 S/cm was achieved in the SPE containing 30 wt% of the epoxy and 70 wt% of the electrolyte mixture. [ABSTRACT FROM AUTHOR]

Recently, research on solid polymer electrolytes (SPEs) for lithium-ion batteries (LIBs) has been actively carried out as an alternative to conventional liquid electrolytes that present safety issues such as flammability and explosion. However, the SPEs show relatively low ion conductivity, compared to the liquid electrolytes. In this study, a poly(vinylidene difluoride) (PVDF)-based SPE was prepared by introducing two different electrolytes; one is weak-binding lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt mixture with solvating plastic crystal succinonitrile (SN) and the other is lithium bis(fluorosulfonyl)imide (LiFSI) salts. Among the SPEs studied, the PVDF/LiFSI-containing SPE membrane exhibited the highest room temperature ion conductivity of 1 x 10−3 S/cm, characterized by electrochemical impedance spectroscopy (EIS). [ABSTRACT FROM AUTHOR]

The melting (Tm) and crystallization (Tc) temperature increased with increasing solvent phenyl propanol (PhP) concentration in the mixture of solvent propylene carbonate and phenyl propanol (PC/PhP). It is also a little enhances of Tm and Tc with adding ethylene carbonate (EC) to propylene carbonate (PC). The melting (Tm) and softening temperature (Tsoft) follows the following order of solvents PC

The influence of Ag7GeS5I nanoparticles on dielectric properties of planar-oriented 6CB liquid crystal was investigated at 293 K within the frequency range from 6 to 106 Hz. The concentration of nanoparticles varied between 0 to 0.1 wt.%. The obtained results were compared with the influence of the same concentrations of Сu7GeS5I nanoparticles. It was shown that the Сu7GeS5I nanoparticles influence the conductivity of the liquid crystal significantly less than the Ag7GeS5I nanoparticles. [ABSTRACT FROM AUTHOR]

Effects of cation substitutions on crystal structure parameters, microstructure, dielectric and ferroelectric properties of ceramic solid solutions (Na0.5Bi0.5)(Ti1-xMgx)O3 with x = 0 ÷ 0.1 were studied. Phase transitions near 400 K demonstrate a pronounced relaxor behavior typical for (Na0.5Bi0.5)TiO3 (NBT) based compositions conditioned by presence of polar nanoregions in nonpolar matrix. Changes in the perovskite structure parameters, microstructure, and functional properties of Mg2+ modified NBT ceramics confirmed the influence of the acceptor dopant amount on their properties. Increase in total conductivity at high temperatures and effects of dielectric relaxation were observed with increasing amount of magnesium cations indicating enhancement of ionic conductivity. [ABSTRACT FROM AUTHOR]

Effects of cation substitutions on crystal structure parameters, microstructure, dielectric and ferroelectric properties of ceramic solid solutions (Na0.5Bi0.5)(Ti1-xMgx)O3 with x = 0 ÷ 0.1 were studied. Phase transitions near 400 K demonstrate a pronounced relaxor behavior typical for (Na0.5Bi0.5)TiO3 (NBT) based compositions conditioned by presence of polar nanoregions in nonpolar matrix. Changes in the perovskite structure parameters, microstructure, and functional properties of Mg2+ modified NBT ceramics confirmed the influence of the acceptor dopant amount on their properties. Increase in total conductivity at high temperatures and effects of dielectric relaxation were observed with increasing amount of magnesium cations indicating enhancement of ionic conductivity. [ABSTRACT FROM AUTHOR]

Electrical conductivity σ was studied in single- and polycrystalline lithium heptagermanate Li2Ge7O15 doped with Al. In Li2Ge7O15:Al single crystal conductivity demonstrated strong anisotropy. As compared with pure crystal, doping significantly increased conductivity along the structural channels parallel to a and c axes. The doping effect was interpreted by supposing that Al3+ substituted for Ge4+ hosts. Li interstitials (ALi) were considered as the defects compensating charge imbalance introduced by the impurity. Heterovalent substitution Al3+(Ge4+) noticeably increased concentration of ALi which were mobile enough and contributed to conductivity. Influence of Al doping on σ was compared for Li2Ge7O15 single crystal and polycrystal. [ABSTRACT FROM AUTHOR]

New organic–inorganic nanocomposites based on PVA, SiO2 and SSA were prepared in a single step using a solution casting method, with the aim to improve the thermomechanical properties and ionic conductivity of PVA membranes. The structure, morphology, and properties of these membranes were characterized by Raman spectroscopy, small- and wide-angle X-ray scattering (SAXS/WAXS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), water uptake (Wu) measurements and ionic conductivity measurements. The SAXS/WAXS analysis showed that the silica deposited in the form of small nanoparticles (∼ 10 nm) in the PVA composites and it also revealed an appreciable crystallinity of pristine PVA membrane and PVA/SiO2 membranes (decreasing with increasing silica loading), and an amorphous structure of PVA/SSA and PVA/SSA/SiO2 membranes with high SSA loadings. The thermal and mechanical stability of the nanocomposite membranes increased with the increasing silica loading, and silica also decreased the water uptake of membranes. As expected, the ionic conductivity increased with increasing content of the SSA crosslinker, which is a donor of the hydrophilic sulfonic groups. Some of the PVA/SSA/SiO2 membranes had a good balance between stability in aqueous environment (water uptake), thermomechanical stability and ionic conductivity and could be potential candidates for proton exchange membranes (PEM) in fuel cells. [ABSTRACT FROM AUTHOR]

Electrospun PVA/SiO2 separator membranes were presented and their electrochemical performance was evaluated for use in Li-ion batteries. Polyvinyl alcohol (PVA) was used to prepare nanofiber based membranes due to advantages such as low cost, water solubility, and biodegradability. Sol gel technique was employed to introduce SiO2 in PVA nanofibers. It was found that PVA separator membranes had superior electrochemical properties with highly porous structure. Introducing SiO2 further improved porosity, liquid electrolyte uptake, as well as ionic conductivity, and reduced interfacial resistance. Furthermore, when PVA/SiO2 separator membranes were assembled into lithium/lithium iron phosphate cells, higher cycling and C-rate performance was observed compared to those using commercial microporous polyolefin membrane. [ABSTRACT FROM AUTHOR]

Solution combustion route was employed for synthesis of the parent, La2Mo2O9 and its derivatives with formula La2-xBixMo1.95V0.05O9-δ (0.200 ≤ x ≤ 0.075). Powder X-Ray diffraction, SEM, DSC and impedance spectroscopy techniques were used to characterize the synthesized compounds. The results of structural, thermal and temperature dependent conductivity confirm the room temperature stabilization of the cubic phase in all the doped compounds. All the doped compounds exhibit enhanced electrical conductivity with respect to the parent compound in intermediate temperature range where as compounds with x = 0.075 and x = 0.100 show higher electrical conductivity compared to the vanadium substituted compound, La2Mo1.95V0.05O9-δ, throughout the whole temperature range. In the cubic region of La2Mo2O9, conductivity is slightly enhanced compared to the parent compound for the composition x = 0.100. However, it is lower in the case of single vanadium doped compound [1]. The highest conductivity is obtained for the composition x = 0.100 at temperature 750°C and the value is 0.041 S.cm−1. [ABSTRACT FROM AUTHOR]