Investigation on the effect of nanosilica towards corn starch–lithium perchlorate-based polymer electrolytes

Biodegradable corn starch–lithium perchlorate (LiClO₄)-based solid polymer electrolytes with addition of nano-sized fumed silica (SiO₂) were prepared by solution casting technique. Ionic conductivity at ambient temperature was measured by AC impedance spectroscopy. Upon addition of nano-sized SiO₂, the ionic conductivity at room temperature is increased. The optimum ionic conductivity value obtained was 1.23?×?10^?4?S?cm^?1 at 4?wt% SiO₂. This may be attributed to the low crystallinity of the polymer electrolytes resulting from the dispersed nanosilica particles. Fourier–transform infrared spectroscopy studies confirmed the complexation between corn starch, lithium perchlorate, and silica. The thermal properties of the prepared samples were investigated with differential scanning calorimetry and thermogravimetric analysis. The surface morphology of the polymer electrolytes confirmed the agglomeration of particles after excess dispersion of inorganic filler. This was proven in the scanning electron microscopy studies.     

Transport Coefficients of Ag–SiO<Subscript>2</Subscript> Plasmas

Calculated values of viscosity, thermal and electrical conductivities of plasma formed in mixtures of silver (Ag) and silica (SiO₂) are presented. The calculations, which assume local thermodynamic equilibrium, are performed for three pressures (1, 10 and 30 atm) in the temperature range from 4,000 to 30,000 K. All the data for the potential interactions and the necessary formulations to obtain values of transport coefficients are given in details. For atmospheric pressure, five mixtures (100% Ag, 75% Ag and 25% SiO₂, 50% Ag and 50% SiO₂, 25% Ag and 75% SiO₂, 100% SiO₂) in weight percentage are studied. In order to analyse the pressure influence on the transport coefficients, three samples of Ag–SiO₂ mixtures (100% Ag, 50% Ag and 50% SiO₂, 100% SiO₂) in weight percentage are discussed for pressures of 1, 10 and 30 atm. In addition for the test case of oxygen plasma, we compare the computation code results with values obtained by other authors: discrepancies are found and explained.      

Deliquescence Relative Humidity Measurements Using an Electrical Conductivity Method

Several methods used in the published literature for determining the deliquescence relative humidity (DRH) of salts and the mutual deliquescence relative humidity (MDRH) of salt mixtures were reviewed. Experiments were conducted to evaluate an electrical conductivity method for determining the DRH of salts and the MDRH of salt mixtures. The electrical impedance of a conductivity cell containing Na₂SO₄, CaCl₂ and NaCl+NaNO₃+KNO₃ was measured as a function of relative humidity at temperatures up to 70 ^∘C. To provide a basis for interpreting the results of the impedance measurements, computer modeling of the specific electrical conductivity of single salts and salt mixtures at 25 ^∘C also was performed. The results of the study demonstrated that the electrical conductivity method provides a convenient and accurate method for determining the DRH of single salts and the MDRH of salt mixtures. The derived DRH and MDRH values were in good agreement with those determined using a hygrometer method. The conductivity method, however, is a more reliable technique than the hygrometer method for determining the MDRH of salt mixtures because the conductivity method is insensitive to slight deviations of mixture composition from the eutonic value.     

Synthesis and characterization of cancrinite-type zeolite, and its ionic conductivity study by AC impedance analysis

The synthesis of cancrinite in the system NaOH-SiO₂-Al₂O₃-NaHCO₃-H₂O was performed, according to methods described in the literature, in an autoclave under hydrothermal conditions at T = 473 K. The electrical properties of cancrinite-type zeolite pellets were investigated by complex impedance spectroscopy in the temperature range 465?C800°C. The effect of temperature on impedance parameters was studied using an impedance analyzer in a wide frequency range (1 Hz to 13 MHz). The real and imaginary parts of complex impedance trace semicircles in the complex plane are plotted. The bulk resistance of the material decreases with rise in temperature. This exhibits a typical negative temperature coefficient of resistance (NTCR) behavior of the material. The results of bulk electrical conductivity and its activation energy are presented. The modulus analysis suggests that the electrical transport processes in the material are very likely to be of electronic nature. Relaxation frequencies follow an Arrhenius behavior with activation energy values not comparable to those found for the electrical conductivity.     

Properties and Extraction for [Ni(NH3)6]2+ of ATPS-a Formed by Aqueous Cationic–Anionic Surfactant Mixtures

The properties and extraction for [Ni(NH₃)₆]²⁺ of anionic aqueous two-phase systems (ATPS-a) that formed in mixtures of cetyltrimethylammonium bromide (CTAB) and excess sodium dodecyl sulfate (SDS) aqueous solutions were investigated. The results showed that the properties and extraction effects were strongly affected by the surfactant concentration, the temperature of system, and the mole fraction of surfactants. The increase of temperature induces narrower phase region and larger phase volume ratio. In addition, [Ni(NH₃)₆]²⁺ was extracted into the surfactant-rich phase with higher distribution coefficient when the liquid crystal had the birefringent properties. Moreover, the distribution coefficient can be improved through reducing the concentration of surfactant from 0.15 to 0.05 mol · L^?1 or increasing mole fraction of CTAB from 21.9% to 23.1%. The results showed that ATPS of cationic–anionic surfactants was efficient for [Ni(NH₃)₆]²⁺ extraction with distribution coefficients of 13.5 when the total surfactant concentration was 0.05 mol · L^?1, mole fraction of CTAB was 21%, and temperature was 34°C.     

Intermediate temperature ionic conductivity of Sm1.92Ca0.08Ti2O7–δ pyrochlore

The results of concentration cell electromotive force methods (EMF) and electrochemical impedance spectroscopy measurements on the pyrochlore system Sm_1.92Ca_0.08Ti₂O_7–δ are presented. The data have been used to estimate total and partial conductivities and determine transport numbers for protons and oxide ions under various conditions. The EMF techniques employed include corrections for electrode polarisation resistance. The measurements were performed using wet and dry atmospheres in a wide \( {p_{{{{\rm{O}}_{{2}}}}}} \) range using mixtures of H₂, N₂, O₂, and H₂O in the temperature region where proton conductivity was expected (500–300 °C). The impedance measurements revealed the conductivity to be mainly ionic under all conditions, with the highest total conductivity measured being 0.045 S/m under wet oxygen at 500 °C. Both bulk and grain boundary conductivity was predominantly ionic, but electronic conductivity appeared to play a slightly larger part in the grain boundaries. EMF data confirmed the conductivity to be mainly ionic, with oxide ions being the major conducting species at 500 °C and protons becoming increasingly important below this temperature.

     

Intermediate temperature ionic conductivity of Sm1.92Ca0.08Ti2O7�C�� pyrochlore

The results of concentration cell electromotive force methods (EMF) and electrochemical impedance spectroscopy measurements on the pyrochlore system Sm_1.92Ca_0.08Ti₂O_7?C?? are presented. The data have been used to estimate total and partial conductivities and determine transport numbers for protons and oxide ions under various conditions. The EMF techniques employed include corrections for electrode polarisation resistance. The measurements were performed using wet and dry atmospheres in a wide $ {p_{{{{\rm{O}}_{{2}}}}}} $ range using mixtures of H₂, N₂, O₂, and H₂O in the temperature region where proton conductivity was expected (500?C300?°C). The impedance measurements revealed the conductivity to be mainly ionic under all conditions, with the highest total conductivity measured being 0.045?S/m under wet oxygen at 500?°C. Both bulk and grain boundary conductivity was predominantly ionic, but electronic conductivity appeared to play a slightly larger part in the grain boundaries. EMF data confirmed the conductivity to be mainly ionic, with oxide ions being the major conducting species at 500?°C and protons becoming increasingly important below this temperature.     

Hydrogen Gas Sensing of High Electrical Conducting-P2O5-SiO2 Glasses Prepared by Sol-Gel Process

High proton-conducting P₂O₅-SiO₂ glass was applied to the electrolyte of the hydrogen concentration cell for hydrogen gas sensing. 5P₂O₅·95SiO₂ glass was prepared using the sol-gel method and its electrical conductivity and electromotive force were measured at 50°C as a function of both the ambient humidity and hydrogen gas concentration. The electrical conductivities increased with increasing humidity and reached 10^–2 S/cm at 90% relative humidity. The electromotive force of the hydrogen concentration cell, where the glass was used as a membrane, showed good Nernstian response to hydrogen pressure in the high relative humidity region.     

A new Na+ glass-dispersed Na2CO3 composite for a solid state electrochemical CO2 gas sensor

The electrical conductivity of the 40Na₂O:50SiO₂:10B₂O₃ glass-dispersed Na₂CO₃ composite solid electrolyte system, prepared by liquid phase sintering, is systematically investigated using complex impedance spectroscopy. The unreacted glass glues the Na₂CO₃ grains together, which not only reduces the micropores but also improves the ionic conductivity and mechanical strength of the pellet. The conductivity enhancement in such a composite solid electrolyte system is discussed in the light of the increased concentration of charge carriers in a diffuse space charge layer formed at the crystalline-glass interface. A galvanic CO₂ gas sensor using an optimised composite electrolyte (50 wt% glass-dispersed Na₂CO₃) is found to be more stable against thermal cycles (heating and cooling) vis-à-vis the sensor based on a pure crystalline solid electrolyte. Received: 12 June 1998 / Accepted: 21 October 1998     

Elektrische Leitfähigkeiten geschmolzener Salzmischungen aus Erdalkalimetallbromiden und Alkalimetallbromiden

Electrical Conductivity of Molten Alkaline Earth Bromide - Alkali Bromide Salt Mixtures The temperature and concentration dependence of the specific electrical conductivity was measured for binary CaBr₂? MBr(M?Li, K, Rb, Cs) and KBr–(Sr, Ba)Br₂ mixtures. In the systems CaBr₂? (K, Rb, Cs)Br and SrBr₂–KBr minima were found on the isotherms of the specific and molar electrical conductivity at the concentration x ≈0,5.     

Electrical Properties Investigation in PA12/PANI Composites

Summary: Volume conducting PA-12 based composites powders were chemically prepared by in situ polymerization and aniline doping at room temperature. These kinds of polyamide / PANI composites were investigated regarding their electrical properties. Their ac and dc electrical properties measured in the frequency range of 10⁻²–10⁷ Hz are reported and the frequency dependence of electrical conductivity was investigated as a function of PANI concentration leading to the determination of the conductivity. The experimental conductivity was found to increase continuously with PANI content and explained by percolation theory with a relatively low percolation threshold of about 0.4 wt.%. The dielectric behavior of various PANI polymer composites has been characterized by the critical frequency ω_c (denoting the crossover from the dc plateau of the conductivity to its frequency dependent ac behaviour). Modelling the conductivity behavior versus volume fraction using Slupkowski approach has revealed that the considered parameters are not sufficient to describe the electrical conductivity behavior.     

Characterization of the Electrical Conductivity of Concentrated Suspensions of Silica in Aqueous Solutions of Sulfuric Acid

The electrical conductivity of stable concentrated suspensions of SiO₂ in aqueous solutions of sulfuric acid was studied as influenced by the concentration and size of SiO₂ particles.     

Electrical conductance,density and viscosity of the system lead(II) dodecanoate/dodecanoic acid

Data are presented for the densities, electrical conductances and viscosities of the molten system lead(II) dodecanoate/dodecanoic acid. Over the concentration range studied, molar volumes are linear functions of concentration at any selected temperature, although there are indications of deviations from ideal behaviour over the complete composition range from pure soap to pure acid. The molar volumes of the system lead(II) carboxylate/carboxylic acid for the even chain acids C₁₀ to C₁₈ are linear functions of chain length. As with other lead(II) dodecanoate systems, the Arrhenius plots for the conductance of the mixtures show curvature.Activation energies for conductance in the low temperature region show a steady decrease with increasing mole fraction of the acid. It is suggested that this arises largely from the increased mobility of the Pb²⁺ ion. The activation energies for viscous flow in the mixtures are similar to that of pure lead dodecanoate. Studies of the viscosities of the system lead(II) carboxylate/carboxylic acid as a function of the temperature for the even chain length acids C₁₀ to C₁₈ suggest a slight decrease in size of the unit of viscous flow when acid is present.     

Specific features of the synthesis and the physicochemical properties of nanocomposite polymer electrolytes based on poly(ethylene glycol) diacrylate with the introduction of SiO<Subscript>2</Subscript>

The specific features of the synthesis and the physicochemical properties of new nanocomposite polymer electrolytes (NPE) based on poly(ethylene glycol) diacrylate, a liquid electrolyte, and silicon dioxide were studied. The kinetics of polymerization of the system in question were studied by isothermal calorimetry and the optimal conditions for the hardening of the NPE were selected. The dependence of the conductivity of the electrolyte samples on the amount of SiO₂ nanopowder introduced, the presence of preliminary ultrasonic treatment of the nanocomposite mixture before the synthesis, and the storage duration of the samples was studied using the electrochemical impedance method. The maximum conductivity (4.3?10^–3 S cm^–1 at 20 °C) was observed for samples without preliminary treatment with the introduction of 6 wt.% of SiO₂ and for the samples after ultrasonic treatment with 8 wt.% of SiO₂. The electrolyte films with the optimal SiO₂ content of 4 wt.% maintained their properties for 24 months.     

Morphology,crystalline structure,and properties of poly(vinylidene fluoride)/silica hybrid composites

Poly(vinylidene fluoride)/silica (PVDF/SiO₂) hybrid composite films were prepared via sol–gel reactions from mixtures of PVDF and tetraethoxysilane in dimethylacetamide. Their morphology, crystalline structure, and thermal, mechanical, and electrical properties were examined. For morphology measurements, scanning electron microscopy and optical microscopy were applied. X‐ray diffraction and infrared analyses showed that the crystalline structure of PVDF was not changed much by the addition of SiO₂, indicating that there was no interaction between PVDF and SiO₂. With increasing SiO₂ content, the melting temperature rarely changed, the degree of crystallinity and the dielectric constant decreased, and the decomposition temperature slightly increased. A PVDF/SiO₂ hybrid composite film with 5 wt % SiO₂ exhibited balanced mechanical properties without a severe change in the crystalline structure of PVDF, whereas for the hybrid composites with higher SiO₂ contents (>10 wt %), the mechanical properties were reduced, and the spherulite texture of PVDF was significantly disrupted by the presence of SiO₂ particles. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 19–30, 2002     

Dependence of thermal diffusion factor of binary mixtures to the thermodynamic state by NEMD simulation

In this paper, we investigate the dependence of thermal diffusion factor and thermal conductivity to the temperature, density and mole fraction in Lennard–Jones binary mixtures of isotopes, noble gases and SF₆–noble gases by non-equilibrium molecular dynamics simulations.The results for the isotopic mixtures indicated that the density has a crucial effect on the dependence of thermal diffusion factor on the temperature. For isotope system at low density, thermal diffusion factor increased with temperature then remains constant at higher temperatures and the slope of thermal diffusion factor vs. temperature is positive while at higher density, thermal diffusion factor decreased with temperature and then fluctuate. For noble gas mixtures, thermal diffusion factor reduces with increasing of temperature and remain constant at high temperatures. For SF₆–Ar system, thermal diffusion factor has a negative slope and reduced with increasing of temperature, but remain nearly constant at high temperatures. For Xe–SF₆ thermal diffusion factor changed sign and the slope of thermal diffusion factor vs. temperature was negative. The results also show that thermal conductivity increases with temperature for all systems.The dependence of thermal diffusion factor to mole fraction of heavier component also investigated. The inverse of thermal diffusion factor versus mole fraction of heavier component is linear for isotope mixtures at thermodynamic conditions: (a) Low temperature, large mass ratio and all densities. (b) High temperature, large mass ratio and low densities. For Ne–Kr mixture, the inverse of thermal diffusion factor shows a linear dependence to the mole fraction of heavier component in moderate temperatures and all densities. For SF₆–Ar and Xe–SF₆ mixtures, the inverse of thermal diffusion factor has linear behaviour at moderate temperatures and low density and high temperature and low density, respectively.     

Fabrication of new polypyrrole/silicon nitride hybrid materials for potential applications in electrochemical sensors: Synthesis and characterization

In this research, an efficient fabrication process of conducting polypyrrole (PPy)/silicon nitride (Si₃N₄) hybrid materials were developed in order to be employed as transducers in electrochemical sensors used in various environmental and biomedical applications. The fabrication process was assisted by oxidative polymerization of pyrrole (Py) monomer on the surface of Si/SiO₂/Si₃N₄ substrate in presence of FeCl₃ as oxidant. To improve the adhesion of PPy layer to Si₃N₄ surface, a pyrrole-silane (SPy) was chemically bonded through silanization process onto the Si₃N₄ surface before deposition of PPy layer. After Py polymerization, Si/SiO₂/Si₃N₄-(SPy-PPy) substrate was formed. The influence of SPy concentration and temperature of silanization process on chemical composition and surface morphology of the prepared Si/SiO₂/Si₃N₄-(SPy-PPy) substrates was studied by FTIR and SEM. In addition, the electrical properties of the prepared substrates were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was found that the best silanization reaction conditions to get Si/SiO₂/Si₃N₄-(SPy-PPy) substrate with high PPy adhesion and good electrical conductivity were obtained by using SPy at low concentration (4.3 mM) at 90°C. These promising findings open the way for fabrication of new hybrid materials which can be used as transducers in miniaturized sensing devices for various environmental and biomedical applications.     

Structure, Microstructure, and Mixed Conduction of [(ZrO2)0.92(Y2O3)0.08]0.9(TiO2)0.1

[(ZrO₂)_0.92(Y₂O₃)_0.08]_0.9(TiO₂)_0.1 (titania-doped yttria stabilized circonia, 10TiYSZ) samples were prepared by solid state reaction from mixtures of 8 mol% yttria-doped ZrO₂ (YSZ) and TiO₂ and characterized in terms of structure, microstructure, and electrical properties. [(ZrO₂)_0.97(Y₂O₃)_0.03]_0.9(TiO₂)_0.1 (titania-doped tetragonal zirconia polycrystalline, 10TiTZP) was also prepared for comparison in some specific studies. Ionic transport properties were measured by impedance spectroscopy in air as a function of temperature. DC techniques including electromotive force (EMF) and Ion Blocking measurements (IB) were carried out in order to determine the electronic contribution to the total conductivity. The addition of titania to YSZ induces the tetragonal zirconia phase formation, thus [(ZrO₂)_0.92(Y₂O₃)_0.08]_0.9(TiO₂)_0.1 is a composite material and is constituted by two solid solutions, titania-doped yttria-stabilized zirconia (67.7 mole fraction) and titania-doped tetragonal zirconia (32.3 mole fraction). A decrease in bulk ionic conductivity, of one order of magnitude, when TiO₂ is added to YSZ is observed in the whole temperature range. Furthermore, in the bulk conductivity vs the reciprocal of the temperature plot, a bending (from 550°C to higher temperatures) toward higher activation energies was detected. The bending could indicate the existence mainly of Ti⁴⁺-Vö associated pairs with an association energy of 0.43±0.02 eV. It could mean that Ti-O bonds become stronger and shorter and could produce the formation of microdomains of a ZrTiO₄-like structure. The addition of titanium is effective in increasing the electronic conductivity under reducing conditions. Conductivity as a function of Po₂ and IB results cannot be related to the formation of small polarons during the reduction process. Furthermore, according to the calculations based on the small polaron theory, inconsistent values for the radius of a small polaron (r_p) are obtained in both 10TiYSZ and 10TiTZP. However, large polarons can explain the transport properties in these materials under reducing conditions in agreement with the experimental data.     

Ionic conductivity of hybrid films composed of polyacrylonitrile,ethylene carbonate,and LiClO4

The electrical conductivity of hybrid films consisting of polyacrylonitrile (PAN), ethylene carbonate (EC), and LiClO₄ was investigated. In these films, EC and LiClO₄ are found to be molecularly dispersed in PAN, forming solid solutions over a wide composition range. The ionic character of the electrical conductivity is demonstrated. The conductivity is not correlated with the content of LiClO₄ or of PAN, but primarily with the mole ratio [EC]/[LiClO₄] in the films. An increase in the [EC]/[LiClO₄] ratio enhances the conductivity. When the ratio is about 2, the conductivity attains 10^?4–10^?5 S cm^?1 at 25°C. This change in conductivity results from a change in carrier mobility. PAN makes the films solid without decreasing the carrier mobility. In the hybrid films, the carrier mobility and the macroscopic viscosity are not related by Walden's rule. The high conductivity is due to regions in the film characterized by a low microscopic viscosity. This is determined by the mole ratio [EC]/[LiClO₄] and largely controls the carrier mobility.     

Synthesis,Characterization and Oxide Ionic Conductivity of Binary β‐(Bi2O3)1‐x(Lu2O3)x System

In this research, the effects of doping Lu₂O₃ to α‐Bi₂O₃ in the range of 0.01 < x < 0.10 in a series of different mole fractions (1% < n < 10% mole ratios) was studied. Beside, heat treatment was performed by applying a cascade temperature rise in the range of 700‐800 °C for 72 hours and new phases were obtained in the (Bi₂O₃)_1‐x(Lu₂O₃)_x system. After heat treatment for 72 hours at 800 °C; mixtures, containing 2‐8% mole Lu₂O₃, formed a tetragonal phase. As a result of subjecting mixtures, containing 9% and 10% mole Lu₂O₃, to a quenching process at 825 °C, tetragonal phases were obtained. With the help of XRD, the crystal systems and lattice parameters of the solid solutions were obtained and their characterization was carried out. Thermal measurements were made by using a simultaneous DTA/TG system. The total conductivity (σ_T) in the β‐Bi₂O₃ doped with Lu₂O₃ was measured using the four‐probe DC method.