M. Parans Paranthaman

Mesoporous TiO2–B Microspheres with Superior Rate Performance for Lithium Ion Batteries

Advanced energy storage systems such as lithium ion batteries are important approaches to mitigate energy shortage and global climate warming issues that the world is currently facing. High power and high energy density are essential to batteries for applications in electric vehicles, stationary energy storage systems for solar and wind energy as well as smart grids. Because conventional lithium ion batteries are inadequate to meet these needs, advanced materials with high capacity and fast chargedischarge capability are critical for next generation lithium ion batteries. [ 1 ] Titanium dioxide (TiO 2 ) with various polymorphs (anatase, rutile, and TiO 2 –B (bronze)) have been widely investigated as lithium ion battery anode materials, due to their advantages in terms of cost, safety and rate capability. [ 2 ] In particular, the polymorph of TiO 2 –B shows a favorable channel structure for lithium mobility, which results in fast chargedischarge capability of a lithium cell. [ 3 ] It has been identifi ed that the lithium intercalation in TiO 2 –B features a pseudocapacitive process, rather than the solid-state diffusion process observed for anatase and rutile. [ 4 ] Theoretical studies have uncovered that this pseudocapacitive behavior originates from the unique sites and energetics of lithium absorption and diffusion in TiO 2 –B structure. [ 5 ] As a result, TiO 2 –B nanoparticles, [ 6 ] nanotubes, [ 7 ]

Studies on supercapacitor electrode material from activated lignin-derived mesoporous carbon.

We synthesized mesoporous carbon from pre-cross-linked lignin gel impregnated with a surfactant as the pore-forming agent and then activated the carbon through physical and chemical methods to obtain activated mesoporous carbon. The activated mesoporous carbons exhibited 1.5- to 6-fold increases in porosity with a maximum Brunauer-Emmett-Teller (BET) specific surface area of 1148 m(2)/g and a pore volume of 1.0 cm(3)/g. Both physical and chemical activation enhanced the mesoporosity along with significant microporosity. Plots of cyclic voltammetric data with the capacitor electrode made from these carbons showed an almost rectangular curve depicting the behavior of ideal double-layer capacitance. Although the pristine mesoporous carbon exhibited a range of surface-area-based capacitance similar to that of other known carbon-based supercapacitors, activation decreased the surface-area-based specific capacitance and enhanced the gravimetric specific capacitance of the mesoporous carbons. A vertical tail in the lower-frequency domain of the Nyquist plot provided additional evidence of good supercapacitor behavior for the activated mesoporous carbons. We have modeled the equivalent circuit of the Nyquist plot with the help of two constant phase elements (CPE). Our work demonstrated that biomass-derived mesoporous carbon materials continue to show potential for use in specific electrochemical applications.

Electrical properties of epoxy resin based nano-composites

We investigate the electrical properties of composite materials prepared as nano- and sub-micron-scale metal-oxide particles embedded in a commercial resin. The filler particles are barium titanate and calcium copper titanate. The physical and structural characteristics of the constituents and the fabricated composites are reported. Electrical characterization of the composite samples is performed using time- and frequency-domain dielectric spectroscopy techniques. The electrical breakdown strength of samples with nano- and sub-micron-sized particles have better electrical insulation properties than the unfilled resin.

Reverse micellar synthesis of cerium oxide nanoparticles

Cerium oxide, CeO2, nanoparticles were prepared using reverse micellar synthesis, using cerium nitrate as a starting material, sodium hydroxide as a precipitating agent, n-octane as the oil phase, cetyl trimethyl ammonium bromide (CTAB) as the surfactant, and 1-butanol as the co-surfactant. Using x-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM), the average size of the nanoparticles obtained was found to be around 3.7 nm, and the particles had a well defined polyhedral shape. The particles also showed strong UV absorption and room temperature photoluminescence. The photoluminescence peak was sensitive to the particle concentration and showed a blue-shift upon dilution.

Aligned ZnO Nanorod Arrays Grown Directly on Zinc Foils and Zinc Spheres by a Low-Temperature Oxidization Method

Vertically aligned, dense ZnO nanorod arrays were grown directly on zinc foils by a catalyst-free, low-temperature (450-500 degrees C) oxidization method. The zinc foils remain conductive even after the growth of ZnO nanorods on its surface. The success of this synthesis largely relies on the level of control over oxygen introduction. By replacing zinc foils with zinc microspheres, unique and sophisticated urchin-like ZnO nanorod assemblies can be readily obtained.

Enhancement of dielectric strength in nanocomposites

In this paper, we report the dielectric breakdown properties of a nanocomposite, a potential electrical insulation material for cryogenic high voltage applications. The material is composed of a high molecular weight polyvinyl alcohol and nanosized in situ synthesized titanate particles. The dielectric breakdown strengths of the filled material samples, measured in liquid nitrogen, indicate a significant increase in their strengths as compared to unfilled polyvinyl alcohol. We conclude that nanometre-sized particles can be adopted as a voltage stabilization additive.

Enhanced flux pinning by BaZrO3 and (Gd,Y)2O3 nanostructures in metal organic chemical vapor deposited GdYBCO high temperature superconductor tapes

We have formed BaZrO3 nanocolumns and (Gd,Y)2O3 nanoprecipitates in reel-to-reel metal organic chemical vapor deposition (MOCVD) processed (Gd,Y)Ba2Cu3O7−x coated conductors and increased the critical currents (Ic) of the conductors in applied magnetic fields to remarkable levels. A (Gd,Y)Ba2Cu3O7−x tape of 1 m in length with 6.5% Zr-additions and 30% composition rich in both Gd and Y showed Ic values of 813 A/cm width at (self-field, 77 K) and above 186 A/cm width at (1 T, 77 K). The strongly enhanced flux pinning over a wide range of magnetic field orientations can be attributed to the bidirectionally aligned defect structures of BaZrO3 and (Gd,Y)2O3 created by optimized MOCVD conditions.

Conductive surface modification of LiFePO4 with nitrogen-doped carbon layers for lithium-ion batteries

The surface of rod-like LiFePO4 modified with a conductive nitrogen-doped carbon layer has been prepared using hydrothermal processing followed by post-annealing in the presence of an ionic liquid. The conductive surface modified rod-like LiFePO4 exhibits good capacity retention and high rate capability as the nitrogen-doped carbon layer improves conductivity and prevents aggregation of the rods during cycling.

High performance Cr, N-codoped mesoporous TiO2 microspheres for lithium-ion batteries

Cr, N-codoped TiO2 mesoporous microspheres have been successfully synthesized by a facile hydrothermal reaction followed by annealing under an ammonia atmosphere. Through introduction of Cr, the nitrogen doping level was increased from 2.81 at.% for N-doped TiO2 to 5.68 at.% for Cr, N-codoped TiO2, which improves the electrical conductivity of TiO2. When used as an anode for lithium-ion rechargeable batteries, the Cr, N-codoping TiO2 microspheres led to an enhanced performance of 159.6 mA h g−1 at 5 C with a drop of less than 1% after 300 cycles.

Orienting oxygen vacancies for fast catalytic reaction.

A strategy to enhance the catalytic activity at the surface of an oxide thin film is unveiled through epitaxial orientation control of the surface oxygen vacancy concentration. By tuning the direction of the oxygen vacancy channels (OVCs) in the brownmillerite SrCoO2.5 , a 100-fold improvement in the oxygen reduction kinetics is realized in an epitaxial thin film that has the OVCs open to the surface.