Conductivity studies of plasticized PEO–HPF6–fumed silica nanocomposite polymer electrolyte system

The effect of the addition of propylene carbonate (PC) on the ion transport behaviour of nanocomposite polymer electrolytes having composition of polyethylene oxide?Chexafluorophosphoric acid?Cfumed silica has been studied. The ionic conductivity of 6.89?×?10^?4 S cm^?1 at 298?K has been obtained for these electrolytes along with good mechanical and thermal properties. The variation of ¹H NMR linewidth with temperature shows line narrowing at the glass transition and melting temperature of the electrolytes which suggests the onset of long-range ion translational motion. The increase in ionic conductivity with the addition of PC is related to the transformation of these electrolytes to the amorphous phase which has been supported by X-ray diffraction results. The polymer electrolytes are thermally stable up to around 498?K and hence are suitable for various applications.     

Electrical properties of proton conducting solid biopolymer electrolytes based on starch–chitosan blend

Two systems (salted and plasticized) of starch–chitosan blend-based electrolytes incorporated with ammonium chloride (NH₄Cl) are prepared via solution cast technique. The incorporation of 25 wt% NH₄Cl has maximized the room temperature conductivity of the electrolyte to (6.47?±?1.30)?×?10^?7 S cm^?1. Conductivity is enhanced to (5.11?±?1.60)?×?10^?4 S cm^?1 on addition of 35 wt% glycerol. The temperature dependence of conductivity for all electrolytes is Arrhenian, and the value of activation energy (E _a ) decreases with increasing conductivity. Conductivity is found to be influenced by the number density (n) and mobility (μ) of ions. The complexation between the electrolytes components is proven by Fourier transform infrared analysis. The relaxation time (t _r ) for selected electrolytes is found to decrease with increasing conductivity and temperature. Conduction mechanism for the highest conducting electrolyte in salted and plasticized systems is determined by employing Jonscher’s universal power law.     

Spectroscopic studies on ion dynamics of PVP–NH4SCN polymer electrolytes

Proton-conducting polymer electrolyte comprising of poly(N-vinyl pyrrolidone) (PVP) and ammonium thiocyanate (NH₄SCN) are prepared by solvent casting method with different polymer–salt concentrations. The changes in the Raman spectra with increasing NH₄SCN concentration state that the free ion concentration is maximum for 20 mol% NH₄SCN concentrated system. At higher salt concentrations (25 mol%), the effective number of charge carriers decreases due to the formation of ion aggregates as confirmed by the Raman analysis. Solid-state NMR and MAS NMR studies are performed to obtain the information about the ionic structure, mobility of the charge carriers, and also to gain insight into the polymer–salt interactions in the polymer electrolytes. The results of ionic transference number show that the charge transport in these polymer electrolytes is mainly due to ions.     

Lithium ion-conducting polymer electrolytes based on PVA–PAN doped with lithium triflate

Ionics - Blend polymer electrolytes with optimized composition (92.5 PVA:7.5 PAN) doped with lithium triflate (LiCF3SO3) have been prepared in different concentrations by solution casting...     

Development of proton conducting biopolymer membrane based on agar–agar for fuel cell

A proton-conducting polymer electrolyte based on agar and ammonium nitrate (NH₄NO₃) has been prepared through solution casting technique. The prepared polymer electrolytes were characterized by impedance spectroscopy, X-ray diffraction, and Fourier transform infra-red spectroscopy. Impedance analysis shows that sample with 60 wt.% NH₄NO₃ has the highest ionic conductivity of 6.57 × 10⁻⁴ S cm⁻¹ at room temperature. As a function of temperature, the ionic conductivity exhibits an Arrhenius behaviour increasing from 6.57 × 10⁻⁴ S cm⁻¹ at room temperature to 1.09 × 10⁻³ S cm⁻¹ at 70 °C. Transport parameters of the samples were calculated using Wagner’s polarization method and thus shows that the increase in conductivity is due to the increase in the number of mobile ions. Fuel cell has been constructed with the highest proton conductivity polymer 40agar/60NH₄NO₃ and the open circuit voltage is found to be 558 mV.

     

Thermal and electrical studies on composite gel electrolyte system: PEG–PVA–(NH4CH2CO2)2

The present article reports the synthesis and characterisation of a highly conducting composite polymer gel electrolyte, namely polyethylene glycol–polyvinyl alcohol (PVA)–ammonium succinate system. Formation of an amorphous composite gel electrolyte has been evidenced in differential scanning calorimetry experiments. Thermogravimetric analysis of the composite gel electrolyte has shown better thermal stability of films containing 25 wt% PVA. Composite gel system containing 10 wt% PVA exhibits optimal ionic conductivity (4.0 × 10^?4 s cm^?1) and its variation with temperature follows Vogel, Tamman and Fulcher relationship. The magnitude of variation in ionic conductivity (with temperature) of these composite electrolytes and its Williams, Landel and Ferry fit reveals liquid-like charge transport. Composite electrolyte with 25 wt% PVA appears to be a suitable candidate for device applications on the basis of experimental findings.     

Solvent-free nanocomposite proton-conducting membranes composed of cesium salt of phosphotungstic acid doped PVDF–CTFE/PEO blend

In this research, novel nanocomposite membranes were prepared using polymer blend of polyethylene oxide (PEO) and polyvinylidene fluoride–chloro tetrafluoro ethylene (PVDF–CTFE) copolymer with cesium salt of phosphotungstic acid (Cs_2.5H_0.5PWO₄₀) as proton conductor. Nanocomposite membranes were prepared by solvent-free procedure. The DSC studies show a decrease in crystalinity of polymer matrix with increasing PEO to PVDF–CTFE proportional ratio and the filler. The TGA studies show that membranes are stable up to 180 °C. The TGA also indicates that addition of cesium salt of phosphotungstic acid increases the thermal stability of membranes. The SEMs exhibit that membranes are non-porous and the additive components are homogenously dispersed. Conductivity tests for membranes were carried out in the range of 25–100 °C in dry and hydrated states. Results show that by increasing the temperature, membranes conductivities are increased. In dry state, except at the temperature of 45 °C, membranes which have the highest crystalinity, have the highest conductivity. The alteration of the conductivity in the range of temperatures in dry condition may be attributed to segmental motion of polymer which resulted in proton hopping from one site to another or increasing free volume for proton motion. In fully hydrated state, dynamic equilibrium between different proton moieties determines the mode of proton conductivity which can be described by Grothuss mechanism. In the presence of water molecule, the free proton may be formed. The conductivity for the membrane in hydrated state with the blend ratio of PVDF:PEO = 95:5 w/w and 10% addition of cesium salt of phosphotungstic acid at the temperature of 90 °C is 1.05 × 10⁻⁴ S cm⁻¹.     

Mössbauer studies of acrylonitrile/alkyl methacrylate copolymers doped with ferric chloride

Acrylonitrile/methyl methacrylate (A/M), acrylonitrile/ethyl methacrylate (A/E) and acrylonitrile/n-butyl methacrylate (A/B) copolymers containing ferric chloride were prepared by free radical bulk polymerization. TGA studies show that the addition of ferric chloride increases the thermal stability of these copolymers. Mössbauer studies of the copolymers showed the presence of Fe³⁺ species only. Mössbauer spectra of the copolymer heated at 200°C, 350°C and 500°C did not show a reduction of the Fe³⁺ species, and α-Fe₂O₃ was the final product formed.     

Conductivity studies and ion transport mechanism in LiI–Li3PO4 solid electrolyte

Mixtures of LiI–Li₃PO₄ were sintered at low temperature. It was observed that the conductivity improved up to 10⁻³ S cm⁻¹ with the addition of LiI. Infrared technique (Fourier transform infrared spectroscopy [FTIR]) was employed to detect the presence of polyhedral structures. From the FTIR spectra of the binary samples with various weight percents of LiI, the PO₄ ³⁻ bands and the PO bending experienced small shifting which indicates that interaction has occurred. Alternating current conductivity versus frequency shows a linear variation suggesting that the behavior follows Jonsher power law. The conduction mechanism of LiI–Li₃PO₄ solid electrolyte follows the quantum mechanical tunneling model.     

Oriental behaviour of some homologues of 4-n-pentyl-phenylthio-4′-n-alkoxybenzoate doped with dichroic dye

The long-range orientational order of three members of 4-n-pentylphenylthio-4′-n-alkoxybenzoate series doped with a dichroic dye was studied by means of electronic absorption and fluorescence measurements. The order parameters <P₂> and <P₄> as well as the orientational distribution function were determined on the basis of absorption and emission spectra of linearly polarized light recorded as a function of temperature in the nematic, smectic A, and smectic C phases. An influence of the dye molecular structure on the orientational order of the dye/liquid crystal mixture was observed. Moreover, the dependence of the order parameter values on the length of the alkoxy chain in liquid crystal molecules was found. It was shown that the order parameter <P₄>, obtained from fluorescence measurements, can be helpful in recognizing the second-order or weakly first-order transitions between various liquid crystalline phases.     

Study of phase transition in a [CdHgI4 : 0.2AgI] mixed conducting composite system doped with KI and K2SO4

New composite superionic systems, [CdHgI₄?:?0.2AgI]?:?0.xKI and [CdHgI₄?:?0.2AgI]?:?0.xK₂SO₄ (x?=?0.2, 0.4, 0.6?mol. wt%), were prepared, using [CdHgI₄?:?0.2AgI] mixed composite system as the host. Electrical conductivity was measured to study the transition behavior at frequencies of 100?Hz, 120?Hz, 1?kHz, and 10?kHz in the temperature range from 150°C to 250°C using a GENRAD 1659 RLC Digibridge. A sharp increase in conductivity was observed during β?→?α phase transition. Upon increasing the dopant-to-host ratio, the conductivity of the superionic systems exhibited Arrhenius (thermally activated)-type behavior. Differential thermal analysis, differential scanning calorimetry, thermogravimetric analysis, and X-ray powder diffraction were performed to confirm the doping effect and transition in the host. The phase transition temperature increased with an increase in the dopant concentration. Activation energies in eV for pre- and post-transition phase behavior are reported.     

Preparation,structural, photoluminescence and magnetic studies of Cu doped ZnO nanoparticles co-doped with Ni by sol–gel method

Zn_0.96−xNi_0.04Cu_xO nanoparticles have been synthesized by varying different Cu concentrations between 0% and 4% using simple sol–gel method. X-ray diffraction studies confirmed the hexagonal structure of the prepared samples. The formation of secondary phases, CuO (111) and Zn (101) at higher Cu content is due un-reacted Cu²⁺ and Zn²⁺ ions present in the solution which reduces the interaction between precursor ions and surfaces of ZnO. Well agglomerated and rod-like structure noticed at Cu=4% greatly de-generate and enhanced the particle size. The nominal elemental composition of Zn, Cu, Ni and O was confirmed by energy dispersive X-ray analysis. Even though energy gap was increased (blue-shift) from Cu=0–2% by quantum size effect, the s–d and p–d exchange interactions between the band electrons of ZnO and localized d electrons of Cu and Ni led to decrease (red-shift) the energy gap at Cu=4%. Presence of Zn–Ni–Cu–O bond was confirmed by Fourier transform infrared analysis. Ultraviolet emission by band to band electronic transition and defect related blue emission were discussed by photoluminescence spectra. The observed optical properties concluded that the doping of Cu in the present system is useful to tune the emission wavelength and hence acting as the important candidates for the optoelectronic device applications. Ferromagnetic ordering of Cu=2% sample was enhanced by charge carrier concentration where as the antiferromagnetic interaction between neighboring Cu–Cu ions suppressed the ferromagnetism at higher doping concentrations of Cu.     

An NMR Study of Outer-Sphere Interactions of BF4 − Anions with Paramagnetic Ions

The significance and role of outer-sphere interactions for the chemistry of complex compounds and solutions have been discussed in the literature time and again.^1,2 The existence of the complexes per se in solutions is determined not only by the interactions of the central ion with the near-by ligands, but also with the particles of the outer or secondary coordination sphere. Now, while “intra-sphere” complexes may be both labile and inert with respect to their kinetic behavior in solutions, outer-sphere compounds are predominantly labile. Inasmuch as the majority of outer-sphere compounds cannot be isolated from solutions, NMR-spectroscopy is essentially one of the most convenient methods for their study. Naturally, such investigations are complicated by an exchange of particles constituting associate compositions, and this exchange may be sufficiently rapid to present interest in itself.     

Development of poly(glycerol suberate) polyester (PGS)–PVA blend polymer electrolytes with NH<Subscript>4</Subscript>SCN and its application

Besides commercially available synthetic polymers, the present work has been undertaken to explore the significance of poly(glycerol suberate) (PGS) polyester synthesised under lab scale in energy storage device. In this regard, a blend polymer electrolyte comprising of polyvinyl alcohol (PVA), poly(glycerol suberate) (PGS) polyester along with the various proportions of ammonium thiocyanate (NH₄SCN) was prepared adopting solution casting technique. The synthesised polyester PGS was characterised by Fourier transform infrared (FT-IR) spectroscopy, ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy. The prepared electrolyte film was subjected to FT-IR analysis to study the complexation that has occurred within the blend. Its amorphous nature was revealed from X-ray diffraction (XRD) studies. Influence of NH₄SCN on the glass transition temperature (T_g) was drawn from differential scanning calorimetry (DSC) technique. The dispersion of dopant within the polymer matrix was supported by scanning electron microscopy (SEM) followed by its elemental composition from energy dispersive spectroscopy (EDS). From the AC impedance technique, maximum conductivity of 3.01?×?10^?4 S cm^?1 was elicited for the optimised electrolyte (1 g PVA?+?0.75 g PGS?+?0.6 g NH₄SCN). Frequency-dependent dielectric and modulus spectra were analysed to study the mechanism of transportation. Transport parameters evaluated by Wagner’s polarisation method proved that the conductivity was predominantly due to cations. Proton conducting battery was configured with the highest conducting electrolytic film and its cell parameters are presented.     

Microwave Impedance of Thin-Film Superconductor–Normal Metal Hybrid Structures with a High Conductivity Ratio

Physics of the Solid State - The temperature dependence of the linear electrodynamic response of thin-film superconductor (MoN)–normal metal (Al) hybrid structures with a high conductivity...     

Recovery of electrical resistivity,short-range order formation and migration of defects in electron-irradiated Fe–4Cr alloy doped with carbon

Resistivity recovery (RR) data of Cr4 alloy doped with carbon (Cr4C) after irradiation with 5 MeV electrons are presented and compared with RR data of non-doped Cr4 alloy. Analysis of the defect- and short-range order-induced parts of RR has confirmed the proposed earlier scheme of the evolution of Frenkel pair defects on post-irradiation anneal in Cr4 and Cr9. Vacancies start free migration around 205–210?K; however, the related peak of stage III is invisible in conventional RR plots. Interstitials atoms (IAs) trapped in stage I at configurations of several Cr atoms start their long-range migration at 220?K. Migrating vacancies are captured by carbon atoms in Cr4C while IAs are not. Dissociation of vacancies from carbon atoms at 350?K gives rise to a decoration of carbon atoms with Cr atoms. Indications are seen that a release of vacancies captured by atoms of residual nitrogen takes place around 250–260?K.     

Structural and thermal studies of [PVA–LiAc] : TiO2 polymer nanocomposite system

Nanocomposite polymer electrolyte consisting of polyvinyl alcohol (PVA) and lithium acetate with TiO₂ filler has been synthesised by combination of solution cast technique and sol–gel process. The composite electrolyte films were characterised by different experimental techniques. The average particle size of composite electrolytes lies between 25 and 30?nm. System is essentially ionic with maximum conductivity of polymer electrolyte 90[80PVA–20LiAc]:10TiO₂ (～4.5?×?10^?6?S?cm^?1) at room temperature.     

Experimental equipment for studies of interaction of IR-radiation with liquid hydrides of groups IV–VI elements

The complex of special experimental apparatus for studies of interaction between IR-radiation and the thermally-stable volatile inorganic hydrides of groups IV–VI elements of the 2nd, 3rd and 4th periods in the liquid state and in the liquefied gas solutions is described. The main methods of solute concentration and integral absorption coefficients measurement are considered. The results of studies of IR-radiation absorption by volatile inorganic hydrides such as SiH₄, NH₃, PH₃, AsH₃, H₂S, and H₂Se in the liquid state and in the cryogenic solutions are presented. Using intensity, frequency and IR-absorption band contour data, the main mechanisms of intermolecular interactions in these liquids are discussed.     

Improved efficiency of dye-sensitized solar cells applied with nanostructured N–F doped TiO2 electrode

Dye-sensitized solar cells (DSSCs) were fabricated with N–F-doped TiO₂ electrodes. The XRD pattern of the N–F-doped TiO₂ is almost the same as that of pure TiO₂, showing that N and F doping has little influence on the formation of anatase titania. The influence of dopant N and F on band energetics and photoelectrochemical properties of nanostructured TiO₂ electrodes were investigated. Compared with pure TiO₂ electrodes, the E_fb of N–F-doped TiO₂ electrodes shifted a little in electrolytes containing LiClO₄. However the total trap densities were remarkably decreased as TiO₂ electrodes were doped with N and F. Finally the N–F-doped TiO₂ electrodes were sensitized with N3 and their photoelectrochemical properties were studied. Experimental results showed that the photoelectric conversion efficiency of N3 sensitized N–F-doped TiO₂ electrodes was 8.61% under irradiation of 100 mW cm^?2 white light, about 17.1% higher than that of a pure TiO₂ electrode.     

Sol–gel synthesized powder and pulsed laser deposited film of amorphous indium zinc oxides doped with Fe

Chemical co-precipitation method was used to synthesize nano-structured α-Fe₂O₃-CeO₂ composite by calcination of the goethite–cerium hydroxide precursor. It was observed that the precursor contained goethite matrix doped with cerium. Calcination of the precursor at 400°C showed the formation of nanosize hematite. Mössbauer spectra show the presence of a paramagnetic component in the precursor but not in the samples calcined at 400°C to 800°C temperatures. Our study shows that Ce precipitated as CeO₂ and stuck on the surface of hematite particles. The precipitation of Ce as CeO₂ is independent of the concentration of Ce in the Ce–Fe–O composite.