Influence Of Citrate/nitrate Ratio On The Preparation Of Li 0.5la0.5tio3 Nanopowder By Combustion Method

Preparation of nano-crystalline Li0.5La0.5TiO 3 perovskite material using citrate-nitrate redox reaction by the combustion technique is reported. The role of the ammonium nitrate concentration used to co-precipitate the Li0.5La0.5Ti-citrate precursor is revealed by ATD/TG, XRD, SEM-EDX and HRTEM techniques. Thermo-gravimetric analysis data show how the intensity of the exothermic peak associated with the citrate-nitrate redox reaction decreases until disappearance as the citrate/nitrate molar ratio increases. The XRD study indicates that a single-phase cubic Li0.5La0.5TiO3 phase is formed at 350 C when the citrate/nitrate ratio varies between 0.13 and 0.17. The formed Li0.5La0.5TiO3 powders show an average particle size of 15-20 nm. Electrochemical impedance spectroscopy technique reveals a relative high ionic conductivity inside the grain for the nanometric Li0.5La0.5TiO3 material, with values of around 10-4 S/cm at room temperature. © 2013 Elsevier Ltd and Techna Group S.r.l. 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Preparation and study as positive electrode of Li0.33La0.56TiO3-PANI nanocomposite

A new electrode material based on the Li0.33La0.56TiO3-polyaniline nanocomposite is reported. This material is prepared by in situ polymerisation of aniline in the presence of Li0.33La0.56TiO3 nanoparticles. The nanocomposite and its precursors are characterised by X-ray diffraction, thermogravimetry, Fourier transform infrared, TEM, SEM, electrical conductivities and electrochemical measurements. The structural and electrochemistry study reveals the existence of relatively strong interactions between the conducting polymer and the oxide particles to assure good synergy in the transport process. The dc and ac electrical conductivities and diffusion coefficient measurements at room temperature indicate that the conductivity values are several orders of magnitude higher in the composite than in the oxide alone. This behaviour determines better reversibility for Li insertion in charge-discharge cycles compared to the pristine oxide and polymer when it is used as electrode of lithium batteries.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Preparation and characterization of LiNi0.8Co0.2O2/PANI microcomposite electrode materials under assisted ultrasonic irradiation

A preparation method for a new electrode material based on the LiNi0.8Co0.2O2/polyaniline (PANI) composite is reported. This material is prepared by in situ polymerization of aniline in the presence of LiNi0.8Co0.2O2 assisted by ultrasonic irradiation. The materials are characterized by XRD, TG-DTA, FTIR, XPS, SEM-EDX, AFM, nitrogen adsorption (BET surface area) and electrical conductivity measurements. PANI in the emeraldine salt form interacts with metal-oxide particles to assure good connectivity. The dc electrical conductivity measurements at room temperature indicate that conductivity values are one order of magnitude higher in the composite than in the oxide alone. This behavior determines better reversibility for Li-insertion in charge-discharge cycles compared to the pristine mixed oxide when used as electrode of lithium batteries. (c) 2005 Elsevier B.V. All rights reserved

Sugarcane molasses as a pseudocapacitive material for supercapacitors

Oxygen-rich carbons were obtained from sugarcane molasses by two methods: direct carbonisation on one hand, and hydrothermal carbonisation and subsequent pyrolysis on the other hand. As no activation treatments were applied, the porous texture was poorly developed and mainly composed of ultramicropores with restricted access to electrolyte ions. Despite this, the directly carbonised molasses exhibited specific capacitances up to 153 F g(-1) at 0.5 mV s(-1) in 1 M H2SO4 electrolyte when tested as electrodes in a three-electrode system. Given the low specific surface areas of the carbons, the capacitance values were mainly assigned to their pseudocapacitance contributions. The latter were more adequately estimated by considering the NLDFT surface area (SNLDFT) than the BET area (ABET) due to the narrow porosity of the materials. Maximum values of pseudocapacitance contribution of 35.2% were attained for the carbon with a SNLDFT of 178 m(2) g(-1), which were explained by the high concentrations of surface oxygen groups, such as quinones and carbonyls

Thermoelectric Transport Properties of CuFeInTe3

In this paper we report on the preparation of CuFeInTe3 and its thermoelectric properties. Optical diffuse reflectance and Raman scattering spectroscopies, as well as X-ray powder diffraction were also carried out. Unprecedented for CuFeInTe3, a direct and an indirect band gap were found from its absorption spectrum. From Hall effect measurements at 300 K the carrier concentration (n), electrical conductivity (σ) and mobility (μ) were determined. In order to investigate whether this material is suitable for thermoelectric applications, the Seebeck coefficient (S), the thermal conductivity (κ) and σ as a function of temperature were measured. The measurements of Hall and Seebeck coefficients showed that alloying CuInTe2 with Fe2+ produces a change from the original p-type to n-type conductivity and causes a decrease in the κ value, while leaving σ unchanged. Relatively large S values were found for CuFeInTe3, with respect to CuInTe2, which were explained on the basis of a probable electron effective mass increase due to Fe2+ incorporation. It was also found, that thermal and electrical conductivities decrease with increasing temperature in the range between 300 and 450 K, while the figure of merit (zT) reaches values of 0.075 and 0.126 at 300 and 450 K respectively. Thus, the zT of CuFeInTe3increases with temperature, reaching values larger than those reported for CuInTe2

Thermoelectric transport properties of CuFeInTe3

© 2015 Elsevier B.V. In this paper we report on the preparation of CuFeInTe3 and its thermoelectric properties. Optical diffuse reflectance and Raman scattering spectroscopies, as well as X-ray powder diffraction were also carried out. Unprecedented for CuFeInTe3, a direct and an indirect band gap were found from its absorption spectrum. From Hall effect measurements at 300 K the carrier concentration (n), electrical conductivity (σ) and mobility (μ) were determined. In order to investigate whether this material is suitable for thermoelectric applications, the Seebeck coefficient (S), the thermal conductivity (κ) and σ as a function of temperature were measured. The measurements of Hall and Seebeck coefficients showed that alloying CuInTe2 with Fe2+ produces a change from the original p-type to n-type conductivity and causes a decrease in the κ value, while leaving σ unchanged. Relatively large S values were found for CuFeInTe3, with respect to CuInTe2, which were explained on the basis of a probable electron effective mass increase due to Fe2+ incorporation. It was also found, that thermal and electrical conductivities decrease with increasing temperature in the range between 300 and 450 K, while the figure of merit (zT) reaches values of 0.075 and 0.126 at 300 and 450 K respectively. Thus, the zT of CuFeInTe3 increases with temperature, reaching values larger than those reported for CuInTe2

A Metal–Organic Framework-Based Material for Electrochemical Sensing of Carbon Dioxide

The free primary hydroxyl groups in the metal-organic framework of CDMOF-2, an extended cubic structure containing units of six Î-cyclodextrin tori linked together in cube-like fashion by rubidium ions, has been shown to react with gaseous CO2 to form alkyl carbonate functions. The dynamic covalent carbon-oxygen bond, associated with this chemisorption process, releases CO2 at low activation energies. As a result of this dynamic covalent chemistry going on inside a metal-organic framework, CO2 can be detected selectively in the atmosphere by electrochemical impedance spectroscopy. The as-synthesized CDMOF-2 which exhibits high proton conductivity in pore-filling methanolic media, displays a ∼550-fold decrease in its ionic conductivity on binding CO2. This fundamental property has been exploited to create a sensor capable of measuring CO2 concentrations quantitatively even in the presence of ambient oxygen. © 2014 American Chemical Society.1