Understanding the key parameters for the rational design of layered oxide materials by composite sol-gel procedures

Previous works have well demonstrated that particle size of the filler used in layered oxide formulation is the first important parameter and must be decreased below 5 μm (Agrafiotis, 1999-2000 [10]). But once the particle size is set what are the next formulation parameters to highlight as critical? How do we improve cohesion and adhesion of the coatings? To highlight the key parameters driving the quality of coating, a model layered oxide material was prepared inside a pan granulator. The model composite sol gel formulation is based on boehmite nanoparticles (binder) and amonomodal two micrometer grain size gamma alumina (filler) which is applied onto alpha alumina beads substrate. The influences of the wetting method and relative amount of filler and binderwere investigated. Extensive characterization and imaging of the layered materials (SEM, Cryo-SEM, EPMA, Washburn test, mechanical tests, Hg-porosimetry) were used in order to follow the microstructure evolution of coating during and at the end of drying. Several crack propagation schemes were observed and explained qualitatively. Overall quality of coating is mainly related to the sol-gel transition of the binder. It defines if prior to shaping, the binder primer will be able to improve the coating adhesion and it defines also the nature and extent of damages that the coating undergoes during drying. The mechanical properties of layered oxide materials obtained using composite sol-gel formulation are definitely correlated with the binder gel shrinkage during drying

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

Attenuation of water coning using dual completion technology

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Synthesis and Characterization of Co3O4 nanocubes with exposed {001} Facets as a Water Oxidation Catalyst

Internationa

Synthesis and Characterization of Co3O4 nanocubes with exposed {001} Facets as a Water Oxidation Catalyst

Internationa

New approach to preparation of nitrogen doped titania for visble range phtotocatalytic hydrogen production

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In situ/operando techniques for characterization of supported metal single-atom catalysts

This chapter presents the advances concerning in situ and operando characterization studies of supported single-atom catalysts (SAC), covering general information on the techniques which are currently used, and reviewing the range of recently published results that explore the understanding of both synthesis and structure-properties relationship. X-ray Absorption Spectroscopy is widely used since it is element specific and is able to study oxidation state, and bonding of metal atoms to ligands. Several IR studies are also present in the literature studying the bands associated with absorption of CO and the recent development of ambient pressure X-ray Photoelectron spectroscopy is promoting an increasing use of the technique. Electron microscopy techniques are used to probe supported SAC on an atomic scale, whether by imaging of structure, or by spectroscopic chemical analysis. The challenge of applying these techniques when the sample is not in a vacuum means that only a limited number of studies are available. Many of the recent studies show the advantages of combining more than one of these techniques

Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta3N5 Photocatalyst

SSCI-VIDE+ECI2D+SOC:ILLInternational audienceIn a photocatalytic suspension system with a powder semiconductor, the interface between the photocatalyst semiconductor and catalyst should be constructed to minimize resistance for charge transfer of excited carriers. This study demonstrates an in-depth understanding of pretreatment effects on the photo catalytic O-2 evolution reaction (OER) activity of visible-light-responsive Ta3N5 decorated with CoOx nanoparticles. The CoOx/Ta3N5 sample was synthesized by impregnation followed by sequential heat treatments under NH3 flow and air flow at various temperatures. Various characterization techniques, including X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), scanning transmission electron microscopy (STEM), and X-ray photoelectron spectroscopy (XPS), were used to clarify the state and role of cobalt. No improvement in photocatalytic activity for OER over the bare Ta3N5 was observed for the as-impregnated CoOx/Ta3N5, likely because of insufficient contact between CoOx and Ta3N5. When the sample was treated in NH3 at high temperature, a substantial improvement in the photocatalytic activity was observed. After NH3 treatment at 700 degrees C, the Co-0-CoOx core-shell agglomerated cobalt structure was identified by XAS and STEM. No metallic cobalt species was evident after the photocatalytic OER, indicating that the metallic cobalt itself is not essential for the reaction. Accordingly, mild oxidation (200 degrees C) of the NH3-treated CoOx/Ta3N5 sample enhanced photocatalytic OER activity. Oxidation at higher temperatures drastically eliminated the photocatalytic activity, most likely because of unfavorable Ta3N5 oxidation. These results suggest that the intimate contact between cobalt species and Ta3N5 facilitated at high temperature is beneficial to enhancing hole transport and that the cobalt oxide provides electrocatalytic sites for OER