K. Vijaya Kumar

Preparation and characterization of PAN–KI complexed gel polymer electrolytes for solid-state battery applications

The free standing and dimensionally stable gel polymer electrolyte films of polyacrylonitrile (PAN): potassium iodide (KI) of different compositions, using ethylene carbonate as a plasticizer and dimethyl formamide as solvent, are prepared by adopting ‘solution casting technique’ and these films are examined for their conductivities. The structural, miscibility and the chemical rapport between PAN and KI are investigated using X-ray diffraction, Fourier transform infrared spectroscopy and differential scanning calorimetry methods. The conductivity is enhanced with the increase in KI concentration and temperature. The maximum conductivity at 30°C is found to be 2.089 × 10−5 S cm−1 for PAN:KI (70:30) wt%, which is nine orders greater than that of pure PAN (< 10−14 S cm−1). The conductivity-temperature dependence of these polymer electrolyte films obeys Arrhenius behaviour with activation energy ranging from 0.358 to 0.478 eV. The conducting carriers of charge transport in these polymer electrolyte films are identified by Wagner’s polarization technique and it is found that the charge transport is predominantly due to ions. The better conducting sample is used to fabricate the battery with configuration K/PAN + KI/I2+ C + electrolyte and good discharge characteristics of battery are observed.

Physicochemical Studies on Nano Silver Particles Prepared by Green and Chemical Methods

AgNPs were synthesized by two different methods chemically using sodium citrate as reducing agent, plant mediated by achyranthes aspera as reducing agent. Chitosan (CS) biopolymer is used as a capping agent in order to enhance the stability and dispersibility as well as to remove aggregation. The appearance of surface Plasmon band in the ultraviolet-visible spectra (410-445 nm) is due to the formation of AgNPs in different sizes. Also the data was clarified that the CS molecules coordinate to the surface of nanoAg particles through their head-groups. FTIR spectra were recorded in a Perkin Elmer version 10.03.06, Spectro Photometer. The FTIR analysis suggests that the prepared chitosan silver nanocomposite film consists of an intermediate/or complex of tri-ammonium citrate, chitosan and metal ions. Finally Antibacterial activity of Ag-CS composites indicating that highest antibacterial activity was detected with green film than chemical film.

Nano-Pr2O3 Doped PVA

Varying concentrations of nano-Pr2O3 doped in “PVA + Sodium Citrate (90 : 10)” polyelectrolyte films are synthesized using solution cast technique and the films are characterized adopting FTIR, XRD, SEM, and DSC methods. The film with 3.0% of nano-Pr2O3 content is more homogenous and possesses more amorphous region that facilitate the deeper penetration of nanoparticles into the film causing more interactions between the functional groups of the polymeric film and nano-Pr2O3 particles and thereby turning the film more friendlily to the proton conductivity. The conductivity is maximum of 7 × 10−4 S/cm at room temperature for 3.0% nano-Pr2O3 film and at that composition, the activation energy and crystallinity are low. With increase in temperature, the conductivity is increasing and it is attributed to the hopping of interchain and intrachain ion movements and furthermore decrease in microscopic viscosity of the films. The major charge carriers are ions and not electrons. These films are incorporated successfully as polyelectrolytes in electrochemical cells which are evaluated for their discharge characteristics. It is found that the discharge time is maximum of 140 hrs with open circuit voltage of 1.78 V for film containing 3% of nano-Pr2O3 and this reflects its adoptability in the solid-state battery applications.

Preparation and Characterization of Nano-Dy2O3-Doped PVA + Na3C6H5O7 Polymer Electrolyte Films for Battery Applications

Composite polymer electrolyte films containing various concentrations of nano-Dy2O3 (1.0 to 4.0%) in PVA + sodium citrate (90 : 10) are synthesized adopting solution cast method and are characterized using FTIR, XRD, SEM, and DSC techniques. The investigations indicate that all components are homogenously dispersed. Films containing 3% of nano-Dy2O3 are more homogenous and less crystalline, and the same is supported by DSC studies indicating the friendly nature to ionic conductivity. Transference number studies reveal that the major charge carriers are ions. With the increase in % of nano-Dy2O3, the conductivity increases and reaches maximum in 3% film with a value of 1.06 × 10−4 S/cm (at 303 K). Further, the conductivity of the film increases with raise in temperature due to the hopping of interchain and intrachain ion movements and fall in microscopic viscosity at the matrix interface of the film. Electrochemical cells are fabricated using these films with the configuration “anode (Mg + MgSO4)/[PVA (90%) + Na3C6H5O7 (10%) + (1–4% nano-Dy2O3)]/cathode (I2 + C + electrolyte),” and various discharge characteristics are evaluated. With 3% nano-Dy2O3 film, the maximum discharge time of 118 hrs with open-circuit voltage of 2.68 V, power density of 0.91 W/kg, and energy density of 107.5 Wh/kg are observed. These findings reflect the successful adoption of the developed polymer electrolyte films in electrochemical cells.

Synthesis and characterization of chitosan based silver nano composite system for antibacterial applications

An attempt has been made in the present work to Synthesize a new bio polymer (Chitosan) based Solid silver colloid nano composite system by chemical facile method. In the present research article the silver colloid was produced by chemical reduction of silver salt (silver nitrate AgNO3) solution and sodium citrate was used as a reducer. Several experimental techniques such as infrared radiation (IR), XRD, UV-Visible and FT-IR measurements were employed to characterize this bio polymer nano composite system. The IR studies confirm the salvation of Ag(0) nano particles with chitosan. UV-VIS spectrometry indicated formation of nanoparticles. The surface Plasmon resonance peak in absorption spectra of silver colloidal solution showed absorption maximum at 433 nm. Whereas XRD and FTIR studies revealed that the complexation of the host bio polymer chitosan with dispersed silver nano particles. A preliminary characteristic which allows us to realize the size of formed silver nano particles was made on the basis of the measurements of UV-VIS absorption and FT-IR. These developed films shows enhanced optical properties desired for antibacterial and biomedical applications.