Oxide-based bifunctional oxygen electrode for rechargeable metal/air batteries

Statistical methods for optimizing the morphology of oxide-based, bifunctional oxygen electrodes for use in rechargeable metal/air batteries are examined with regard to binder composition, compaction time, and compaction load. Results show that LaNiO3 with PTFE binder in a nickel mesh envelope provides a satisfactory electrode.

Low-temperature polymer precursor-based synthesis of nanocrystalline particles of lanthanum calcium manganese oxide (La0.67Ca0.33MnO3) with enhanced ferromagnetic transition temperature

We report a simple modified polymeric precursor route for the synthesis of highly crystalline and homogenous nanoparticles of lanthanum calcium manganese oxide (LCMO). The LCMO phase formation was studied by thermal analysis, x-ray powder diffraction, and infrared spectroscopy at different stages of heating. These nanocrystallites (average particle size of 30 nm) possess ferromagnetic-paramagnetic transition temperature (T-c) of 300 K, nearly 50 K higher than that of a single crystal. The Rietveld analysis of the powder x-ray diffraction data of the nanopowders reveals significant lattice contraction and reduction in unit cell anisotropy-these structural changes are correlated to the enhancement in T-c.

External Bias Dependent Direct To Indirect Band Gap Transition in Graphene Nanoribbon

In this work, using self-consistent tight-binding calculations. for the first time, we show that a direct to indirect band gap transition is possible in an armchair graphene nanoribbon by the application of an external bias along the width of the ribbon, opening up the possibility of new device applications. With the help of the Dirac equation, we qualitatively explain this band gap transition using the asymmetry in the spatial distribution of the perturbation potential produced inside the nanoribbon by the external bias. This is followed by the verification of the band gap trends with a numerical technique using Magnus expansion of matrix exponentials. Finally, we show that the carrier effective masses possess tunable sharp characters in the vicinity of the band gap transition points.

Microwave irradiation-assisted method for the deposition of adherent oxide films on semiconducting and dielectric substrates

We report a method for the deposition of thin films and thick coatings of metal oxides through the liquid medium, involving the micro waveirradiation of a solution of a metal-organic complex in a suitable dielectric solvent. The process is a combination of sol-gel and dip-coating methods, wherein coatings can be obtained on nonconducting and semiconducting substrates, within a few minutes. Thin films of nanostructured ZnO (wurtzite) have been obtained on Si(100), glass and polymer substrates, the nanostructure determined by process parameters The coatings are strongly adherent and uniform over 15 mm x 15 mm, the growth rate similar to 0.25 mu m/min Coatings of nanocrystalline Fe2O3 and Ga2O3 have also been obtained The method is scalable to larger substrates, and is promising as a low temperature technique for coating dielectric substrates, including flexible polymers. (C) 2010 Elsevier B.V. All rights reserved.

Electron microscopic investigation of high-temperature oxide superconductors

Electron microscopic investigations have been carried out on superconducting YBa2Cu3 O7−δ, NdBa2Cu3 O7−δ and related oxides. All these orthorhombic oxides exhibit twin domains. Based on high resolution electron microscopy, it is shown that there is no significant change in the structure across the twins. Oxides of the La2−x Sr x (Ba x )CuO4 system do not show twins, but exhibit other types of defects. Twins appear to be characteristic of only the orthorhombic 123 structures.

2,4-Lutidine-1-oxide complexes of lanthanide perchlorates

2,4-Lutidine-1-oxide (2,4-LutO) complexes of lanthanide perchlorates of the formulae Ln2(2,4-LutO)13(ClO4)6 (Ln = Pr and Nd) and Ln2(2,4-LutO)15 (ClO4)6 (Ln = La, Tb, Dy, Ho and Yb) have been prepared and characterised by chemical analysis, IR, NMR, conductance and electronic spectral data. Proton NMR data along with the IR data show that the ligand coordinates to the metal ion through the oxygen. Conductance data of the complexes in acetone and nitrobenzene indicate that the perchlorate is not coordinated to the metal ion.

Growth of titanium oxide overlayers by thermal oxidation of titanium

This paper describes a theoretical model for the growth of titanium oxide by thermal oxidation of titanium. It is shown that this model can explain the formation of layers of different oxides of titanium and the changes in these layers with variations in the conditions of oxidation. Some experimental X-ray diffraction results which support the model are also given.

High contrast laser writing in insitu textured germanium films via a novel chemical oxide formation

A high contrast laser writing technique based on laser induced efficient chemical oxidation in insitu textured Ge films is demonstrated. Free running Nd-YAG laser pulses are used for irradiating the films. The irradiation effects have been characterised using optical microscopy, electron spectroscopy and microdensitometry. The mechanism for the observed contrast has been identified as due to formation of GeO2 phase upon laser irradiation using X-ray initiated Auger spectroscopy (XAES) and X-ray photoelectron spectroscopy (XPS). The contrast in the present films is found to be nearly five times more than that known due to GeO phase formation in similar films.

Delamination and solvothermal decomposition of layered zinc hydroxysalt: Formation of bimodal zinc oxide nanostructures

Dodecylsulphate-intercalated zinc hydroxysalt, Zn-5(OH)(8)(DS)(2)center dot mH(2)O delaminates to give monolayer colloidal dispersions in alcohols such as 1-butanol and ethylene glycol. The extent of delamination and the stability of the colloidal dispersion are comparable to those of layered double hydroxides. The solvothermal decomposition of the colloidal dispersion of the hydroxysalt in ethylene glycol yields a bimodal ZnO having a nanotubular structure decorated with nanosheets. (C) 2010 Elsevier Masson SAS. All rights reserved.

Impedance‐frequency characteristics of metal‐oxide‐semiconductor structures on polycrystalline silicon

This paper reports the variations in impedance with frequency of metal‐oxide‐semiconductor (MOS) structures on polycrystalline silicon. The origin of these impedance‐frequency characteristics are qualitatively explained. These characteristics indicate that the MOS structure on polycrystalline silicon can be exploited to realize voltage controlled filters.

Investigations on Bi2CuO4: a quasi-one-dimensional oxide system

The potential of Bi2CuO4 as the first oxide system to show a linear-chain magnetic behaviour is examined. Electron diffraction studies do not resolve the previously reported ambiguity regarding its space group. The magnetic susceptibility data at high temperatures are best fitted to a uniform antiferromagnetic spin-1/2 Heisenberg chain. At low temperatures, however, neither the uniform nor the alternating Heisenberg antiferromagnetic model fits the data. Magnetic susceptibility data over the entire temperature range can be fitted if one assumes dimeric units with a nearly degenerate second singlet state close to the ground state, these states being separated from an excited triplet state by an energy gap. A simple heuristic model of a dimer that gives such an energy level spectrum is examined.

Investigation of the effect of nonlocal scale on ultrasonic wave dispersion characteristics of a monolayer graphene

In this article, an ultrasonic wave propagation in graphene sheet is studied using nonlocal elasticity theory incorporating small scale effects. The graphene sheet is modeled as an isotropic plate of one-atom thick. For this model, the nonlocal governing differential equations of motion are derived from the minimization of the total potential energy of the entire system. An ultrasonic type of wave propagation model is also derived for the graphene sheet. The nonlocal scale parameter introduces certain band gap region in in-plane and flexural wave modes where no wave propagation occurs. This is manifested in the wavenumber plots as the region where the wavenumber tends to infinite or wave speed tends to zero. The frequency at which this phenomenon occurs is called the escape frequency. The explicit expressions for cutoff frequencies and escape frequencies are derived. The escape frequencies are mainly introduced because of the nonlocal elasticity. Obviously these frequencies are function of nonlocal scaling parameter. It has also been obtained that these frequencies are independent of y-directional wavenumber. It means that for any type of nanostructure, the escape frequencies are purely a function of nonlocal scaling parameter only. It is also independent of the geometry of the structure. It has been found that the cutoff frequencies are function of nonlocal scaling parameter (e(0)a) and the y-directional wavenumber (k(y)). For a given nanostructure, nonlocal small scale coefficient can be obtained by matching the results from molecular dynamics (MD) simulations and the nonlocal elasticity calculations. At that value of the nonlocal scale coefficient, the waves will propagate in the nanostructure at that cut-off frequency. In the present paper, different values of e(o)a are used. One can get the exact e(0)a for a given graphene sheet by matching the MD simulation results of graphene with the results presented in this paper. (C) 2010 Elsevier B.V. All rights reserved.

XPS evidence for molecular charge-transfer doping of graphene

By employing X-ray photoelectron spectroscopy (XPS), we have been able to establish the occurrence of charge-transfer doping in few-layer graphene covered with electron acceptor (TCNE) and donor (TTF) molecules. We have performed quantitative estimates of the extent of charge transfer in these complexes and elucidated the origin of unusual shifts of their Raman G-bands and explained the differences in the dependence of conductivity on n- and p-doping. The study unravels the cause of the apparent difference between the charge-transfer doping and electrochemical doping. (C) 2010 Elsevier B.V. All rights reserved.