C. Sanjeeviraja

Electrical conductivity characterization of polyacrylonitrile-ammonium bromide polymer electrolyte system

A new proton-conducting polymer electrolyte based on polyacrylonitrile (PAN) doped with ammonium bromide (NH4Br) has been prepared using solution casting technique. The complexation of NH4Br with PAN polymer has been studied using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The differential scanning calorimetry (DSC) thermograms of PAN with NH4Br electrolyte membrane show the decrease in glass transition temperature (Tg). This reduction of Tg of membrane reveals the increase of segmental motion of polymer electrolyte. The ionic conductivity of the prepared polymer electrolyte has been found by ac impedance spectroscopic analysis. The maximum ionic conductivity (2.5u2009×u200910−3xa0Sxa0cm−1) has been obtained for 30xa0mol% NH4Br-doped PAN polymer electrolyte. The temperature-dependent conductivity of the polymer electrolyte follows an Arrhenius relationship. The dielectric spectra show low frequency dispersion. The relaxation time (τ) has been calculated from loss tangent spectra (tan δ). Ionic transference number measured has been found to be in the range of 0.92–0.99 for all the polymer electrolyte system. The result reveals that the conducting species are predominantly ions. Using the maximum ionic conducting polymer electrolyte, the primary proton-conducting battery with configuration Zn+ZnSo4·7H2O/70 PAN:30 NH4Br/PbO2 + V2O5 has been fabricated, and its discharge characteristics have been studied.

Preparation and characterization of PVA complexed with amino acid, proline

Polymers have been studied for drug delivery system. To use polymer, polyvinyl alcohol (PVA) for drug delivery, one has to understand the interaction between PVA and the drug to be used. The drug, amino acids are essentials for human health. An attempt is made to study the interaction between PVA and Proline, one of the amino acids. Polymer electrolyte based on PVA complexes with different concentrations of Proline (a type of amino acid) by solution casting method using water as a solvent has been prepared. The prepared films have been investigated by different techniques. The increase in amorphous nature of the polymer electrolyte has been confirmed by X-ray diffraction (XRD) analysis. From the XRD spectra, the average particle size is calculated using the Debye–Scherrer formula. DSC measurements show decrease in Tg with increasing proline concentration. The Fourier transform infrared (FTIR) analysis reveals the complex formation between PVA and Proline. The dielectric permittivity (ε*) and modulus (M*) have been calculated from the alternating current (ac) impedance spectroscopy in the frequency range 42xa0Hz–1xa0MHz. The maximum conductivity has been found to be 1.24u2009×u200910−5xa0Sxa0cm−1 at ambient temperature for 75Mwt% PVA:25Mwt% Proline membrane.

Influence of metals on the structural, vibrational, and electrical properties of lithium nickel phosphate

LiNi1 − xMxPO4 (M = Zn, Al and xu2009=u20090, 0.05, 0.10, 0.15, and 0.20) was synthesized by classical solid-state reaction method. The reaction temperature is determined by thermogravimetric analysis. X-ray diffraction patterns show that an impurity peak is absorbed for Al3+-doped samples but not in the case of Zn2+-doped samples. Laser Raman studies confirm that phase pure LiNiPO4 is formed and the dopant is entered into the host lattice. Impedance spectroscopy is used to study the ion dynamics of both doped and undoped systems. Higher DC conductivity value is observed for LiNi0.85Zn0.15PO4 and LiNi0.925Al0.05PO4 compared with pristine LiNiPO4. The temperature-dependent DC conductivity and the frequency-dependent dielectric loss maxima are found to obey the Arrhenius law of conduction. In the modulus analysis, the stretching exponent β is found to be temperature independent. The scaling behavior of the imaginary part of the electric modulus suggests that the relaxation mechanism is independent of temperatures. Electrochemical impedance spectroscopy (EIS) studies also show that electrical conductivity is increased upon Zn2+ and Al3+ doping.

Structural, Morphological, Vibrational and Electrical Studies on Zn Doped Nanocrystalline LiNiPO4

Olivine structured LiNi1-xZnxPO4 (x=0, 0.05, 0.10, 0.15, 0.20) have been prepared by a polyol method using 1, 2 propanediol as a polyol medium. The XRD results of pure and Zn doped LiNiPO4 sample authenticate the orthorhombic crystal structure with high crystalline nature. The crystallite size is calculated from the Debye Scherer formula and it is found in the range of 55-65nm and 49-55nm for undoped and doped samples respectively. The thermal properties of LiNi1-xZnxPO4 were investigated by thermo gravimetric analysis (TG) and differential thermal analysis. Laser Raman studies confirm that the dopant is entered in to the LiNiPO4 lattice. Morphology of the samples is analyzed through SEM analysis. The higher electrical conductivity is calculated for LiNi0.85Zn0.15PO4 sample compared with other concentrations of dopant and it is found to be 1.08×10-7 S cm-1 at ambient temperature. Dielectric and Modulus studies are also discussed through impedance spectroscopy.

Study of Bio – Degradable Polymer PCL with NH4 SCN

Abstract Membrane of PCL doped with NH 4 SCN of different concentration (0.1 – 0.6 mol. Wt. %) have been prepared by solution casting technique using DMF as solvent. XRD, FTIR and Ac Impedance studies have been undertaken for the above mentioned film. XRD pattern of pure PCL shows peak at (21 O , 24 O ). Above two peak decreases in intensity as the concentration of NH 4 SCN increases. Complex formation between PCL and NH 4 SCN has been confirmed by FTIR analysis. The ionic conductivity is 1.24x10 -05 S/cm for PCL 1g : NH4SCN 0.6 mol. Wt. % membrane. Dielectric and Modulus results have been discussed. 1. Introduction Research on bio degradable polymers has received increasing attention in recent years because of their wide application in environmentally friendly packaging biomedical materials but also in various industrial applications such as computer and mobile phone industry. The most popular biodegradable polymers are aliphatic polyester such as PCL, Polylactic acid, Poly (butylenes adipate teraph thalate), poly hydroxy butyrale. Among biodegradable Polymer PCL, a semicrystalline linear aliphatic polyester known for the compatibility and bio degradability which make it useful material resorbable surfaces, drug delivery systems, etc. PCL is one of more hydrophobic of the commercially available. It has a good mechanical property with low melting point and low Tg around -60

Proton Conducting Polymer Electrolyte Based on Pan

Various polymers such as PVA, PVAc, PVP and etc., doped with ammonium salts have been studied for proton conduction. But the study of proton conduction in polymer PAN is scarce. The proton conducting polymer electrolytes composed of polyacrylonitrile (PAN) with ammonium nitrate (NH4NO3) in different molar ratios, have been prepared by solution casting method, using DMF as solvent. The increase in amorphous nature of the polymer electrolytes has been confirmed by X-ray diffraction analysis (XRD). The complex formation between polymer and dissociated salt has been confirmed by Fourier transform infrared spectroscopy (FTIR). The ionic conductivity, dielectric permittivity (e*) and electric modulus (m*) have been calculated from the ac impedance spectroscopy in the frequency range 42HZ-5MHZ. The activation energy of doped PAN polymer electrolyte is calculated using Arrhenius plot. Based on the study of relaxation spectra, it is found that the relaxation time decreases with increase in temperature. INTRODUCTION In recent years, proton conducting polymer electrolytes have attracted considerable attention owing to their application in fuel cells, humidity & gas senors and electrochromic displays.1,2 The main advantages of polymer electrolytes are their good mechanical properties, the ease of fabrication of films of desirable sizes, and their ability to form good electrode – electrolyte contact. Solid polymer electrolytes (SPE), consisting of an ionic conductive polymer matrix and a supporting electrolyte salt, were firstly introduced by Fenton et al.3 The development of polymer system with high ionic conductivity is one of the main objectives in polymer research. A variety of polymers such as Poly (acrylonitrile) (PAN), Poly (vinyl chloride) (PVC) and Poly (methyl methacrylate) (PMMA) has been used as polymer matrices.4-5 Proton conducting polymer electrolytes can be obtained by doping the polymer either with alcohol, amine, amide or amide groups6 or with strong acids or ammonium salts. Ammonium salts have been reported as good donors of proton to the polymer matrix. Literature survey indicates that the synthesis and characterization of ammonium salts doped proton conducting polymer electrolytes based on Poly (acrylonitrile) (PAN) is rare. PAN is one of the most important fibers – forming polymers and has been widely used because of its high strength, abrasion resistance and good insect resistance.7 PAN is used to produce large variety of products including ultra filtration membranes, hollow fibers for reverse osmosis, fibers for textiles, oxidized frame retardant fibers like PANOX and carbon fiber. However the conductivity of PAN is < 10-14 S cm-1 and the static problem restricts its further applications. PAN is usually synthesized using free radical polymerization. Usually they are copolymers of acrylonitrile and methyl acrylate or acrylonitrile and methyl methacrylate. PAN has a melting point of about 3190C, and it also decomposes at this temperature. So PAN membrane is prepared by solution casting technique. In the present work, NH4NO3 doped PAN polymer electrolytes have been prepared and subjected to various characterizations such as XRD, FTIR and Ac impedance spectroscopy. EXPERIMENTAL DETAILS The polymer PAN (Aldrich) of average molecular weight 1, 50, 000 and the salt NH4NO3 were used as the raw materials in this study. Dimethyl formamide (DMF) was used as the solvent. The polymer electrolytes PAN doped with NH4NO3 in different compositions such as 100:0; 95:05; 90:10; 85:15; 80:20 and 75:25 were prepared by solution casting technique. The mixture of PAN and NH4NO3 was stirred continuously with a magnetic stirrer for several hours at temperature 600 C to obtain a homogenous solution. The solution was then poured into propylene petri dishes and allowed to evaporate in vacuum oven at 650C. After 48 hours, free standing transparent films were obtained. X-ray diffraction patterns of the prepared samples were recorded at room temperature on a Philips X’Pert PRO diffractometer using Cukα radiation. FTIR spectra were recorded for the polymer electrolyte films using a SHIMADZU IR Affinity -1 Spectrometer in the range of 400 4000 cm-1 at room temperature. Conductivity measurements were carried out by using a HIOKI 3532 LCZ meter in the frequency range of 42 Hz – 1MHz over the temperature range of 303 – 343 K. Possible interaction between PAN and NH4NO3. The possible interaction between PAN and NH4NO3 has been pictorially represented in the scheme 1 along with the structure. The proton from the salt interacts with the polar groups of the host polymer matrix.