			Home About us Contact

Cobalt Oxide (cobalt + oxide)

Distribution by Scientific Domains

Polymers and Materials Science	60%
Chemistry	40%

Selected Abstracts

A New Superconducting Phase of Sodium Cobalt Oxide,

ADVANCED MATERIALS, Issue 21 2004
K. Takada
A new superconducting sodium cobalt oxide (see Figure, left) has been synthesized through soft-chemical modification using ,-NaCoO2 as a parent compound, in place of the ,-Na0.7CoO2 used to make the first cobalt oxide superconductor (see Figure, right). A three-layer periodicity of the CoO2 stacking sequence exists in the present material, in contrast to a two-layer one in the previous. The new oxide has a superconducting transition at 4.6,K. [source]

Thermoelectric Performance of Epitaxial Thin Films of Layered Cobalt Oxides Grown by Reactive Solid-Phase Epitaxy with Topotactic Ion-Exchange Methods

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2007
Kenji Sugiura
This article reviews high-quality epitaxial film growth of layered cobalt oxides by reactive solid-phase epitaxy (R-SPE) with topotactic ion-exchange methods. Epitaxial film of Na0.8CoO2 was grown on a (0001)-oriented ,-Al2O3 substrate by R-SPE using CoO film as the starting material. The Na0.8CoO2 epitaxial films were converted into high-quality epitaxial films of Sr0.32Na0.21CoO2 and [Ca2CoO3]xCoO2 by topotactic ion-exchange methods. The Sr0.32Na0.21CoO2 film exhibited better stability against moisture than that of the Na0.8CoO2 film, while it retained the good thermoelectric properties of Na0.8CoO2. The [Ca2CoO3]xCoO2 film exhibited a high electrical conductivity of 2.95 × 102 S/cm and a large Seebeck coefficient of +125 ,V/K at 300 K. [source]

Sintering Temperature Dependence of Thermoelectric Performance and Crystal Phase of Calcium Cobalt Oxides

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010
Masahiro Tahashi
Polycrystalline samples were synthesized by a conventional solid-state reaction. As starting materials, Co3O4 and Ca(OH)2 were mixed in a molar ratio of Ca:Co=3:4 and sintered at 1073,1373 K. The compound phases and thermoelectric properties of the resulting products were dependent on the sintering temperature. X-ray diffraction analysis showed that the Ca3Co4O9 compound was stable up to 1193 K and that Ca3Co2O6 was formed at 1273 K. At 1373 K, the sample decomposed into cobalt oxide and calcium oxide. A maximum power factor of about 100 ,W/(K2·m) at 873 K was obtained for the Ca3Co4O9 phase sintered at 1193 K. [source]

Fabrication of a Sensitive Cholesterol Biosensor Based on Cobalt-oxide Nanostructures Electrodeposited onto Glassy Carbon Electrode

ELECTROANALYSIS, Issue 24 2009
Abdollah Salimi
Abstract Electrodeposited cobalt oxide (CoOx) nanomaterials are not only used for immobilization of cholesterol oxidase (ChOx) but also as electron transfer mediator for oxidation of H2O2 generated in the enzymatic reaction. Voltammetry and flow injection analysis (FIA) were used for determination of cholesterol. FIA determination of cholesterol with biosensors yielded a calibration curve with the following characteristics: linear range up to 50,,M, sensitivity of 43.5,nA ,M,1 cm,2 and detection limit of 4.2,,M. The apparent Michaelis-Menten constant and the response time of the biosensor are 0.49,mM and 15,s, respectively. This biosensor also exhibits good stability, reproducibility and long life time. [source]

A New Superconducting Phase of Sodium Cobalt Oxide,

Sintering Temperature Dependence of Thermoelectric Performance and Crystal Phase of Calcium Cobalt Oxides

Disordered misfit [Ca2CoO3][CoO2]1.62 structure revisited via a new intrinsic modulation

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2008
Hervé Muguerra
The structure of the thermoelectric lamellar misfit cobalt oxide [Ca2CoO3][CoO2]1.62 was refined again using single-crystal X-ray diffraction data. A new commensurate intrinsic modulation was observed involving a modulation vector orthogonal to the misfit direction (,,0,,,). The five-dimensional superspace group is C2/m(1,0)(,0,)gm and the structure was solved using a commensurate approximation. A new model is given involving an occupation modulation of the split sites of the [CoO] layer. This [CoO] layer can be described by triple chains running along b. The residual disorder along b can then be explained by the assumption of a local ordering with two types of clusters: CoO2 and Co5O4. A powder neutron diffraction experiment confirmed the ordering evidenced by the single-crystal X-ray diffraction study, but was not sufficient by itself to deal with this double modulated scheme. The new intrinsic modulation is destroyed by partial metal substitutions in the [CoO] layer. The structural modifications of this layer directly influence the physical properties which are related to the electronic structure of the [CoO2] layers. [source]

The Mechanism of Water Oxidation: From Electrolysis via Homogeneous to Biological Catalysis

CHEMCATCHEM, Issue 7 2010
Holger Dau Prof.
Abstract Striving for new solar fuels, the water oxidation reaction currently is considered to be a bottleneck, hampering progress in the development of applicable technologies for the conversion of light into storable fuels. This review compares and unifies viewpoints on water oxidation from various fields of catalysis research. The first part deals with the thermodynamic efficiency and mechanisms of electrochemical water splitting by metal oxides on electrode surfaces, explaining the recent concept of the potential-determining step. Subsequently, novel cobalt oxide-based catalysts for heterogeneous (electro)catalysis are discussed. These may share structural and functional properties with surface oxides, multinuclear molecular catalysts and the catalytic manganese,calcium complex of photosynthetic water oxidation. Recent developments in homogeneous water-oxidation catalysis are outlined with a focus on the discovery of mononuclear ruthenium (and non-ruthenium) complexes that efficiently mediate O2 evolution from water. Water oxidation in photosynthesis is the subject of a concise presentation of structure and function of the natural paragon,the manganese,calcium complex in photosystem,II,for which ideas concerning redox-potential leveling, proton removal, and OO bond formation mechanisms are discussed. The last part highlights common themes and unifying concepts. [source]

Cobalt Hydroxide Nanosheets and Their Thermal Decomposition to Cobalt Oxide Nanorings

CHEMISTRY - AN ASIAN JOURNAL, Issue 4 2008
Xiaohe Liu Dr.
Abstract We demonstrate herein that single-crystalline ,-cobalt hydroxide (,-Co(OH)2) nanosheets can be successfully synthesized in large quantities by a facile hydrothermal synthetic method with aqueous cobalt nitrate as the cobalt source and triethylamine as both an alkaline and a complexing reagent. This synthetic method has good prospects for the future large-scale production of single-crystalline ,-Co(OH)2 nanosheets owing to its high yield, low cost, and simple reaction apparatus. Single-crystalline porous nanosheets and nanorings of cobalt oxide (Co3O4) were obtained by a thermal-decomposition method with single-crystalline ,-Co(OH)2 nanosheets as the precursor. A probable mechanism of formation of ,-Co(OH)2 nanosheets, porous Co3O4 nanosheets, and Co3O4 nanorings was proposed on the basis of the experimental results. [source]