Search results for "TRANSMISSION ELECTRON"
showing 10 items of 426 documents
Novel TiO2-WO3 self-ordered nanotubes used as photoanodes: Influence of Na2WO4 and H2O2 concentration during electrodeposition
2021
[EN] Hybrid TiO2-WO3 nanostructures has been synthesized by electrochemical anodization under controlled hydrodynamic conditions followed by electrodeposition in the presence of different contents of Na2WO4 (5, 15 and 25 mM) and H2O2 (20, 30 and 40 mM). The influence of the electrolyte used for electrodeposition on the morphology, crystalline structure and photoelectrochemical response for water splitting has been evaluated through Field Emission Electronic Microscopy, High-Resolution Transmission Electron Microscopy, Confocal Raman Spectroscopy, Grazing Incidence X Ray Diffraction, X-Ray Photoelectron Spectroscopy, Atomic Force microscopy and photocurrent versus potential measurements. Add…
Microstructure and magnetic properties of colloidal cobalt nano-clusters
2010
The magnetic response of nanometer sized Co nanoparticles (NP) prepared using reverse micelle solutions are presented. The use of complementary structural and morphological probes (like transmission electron microscopy, high resolution electron microscopy, X-ray absorption spectroscopy) allowed to relate the magnetic properties to the size, morphology, composition and atomic structure of the nanoparticles. All data agree on the presence of a coreshell structure of NPs made of a metallic Co core surrounded by a thin Co-oxide layer. The coreshell microstructure of NPs affects its magnetic response mainly raising the anisotropy constant. (C) 2010 Elsevier B.V. All rights reserved.
Synthesis and characterization of nanometric powders of UO2+x, (Th,U)O2+x and (La,U)O2+x
2009
This paper describes a new way of preparing nanometric powders of uranium oxide, to fit the needs of studies on UO{sub 2} oxidation, through the electrochemical reduction of U(VI) into U(IV). These powders can also be doped with radionuclides if necessary. The precipitation of oxides occurs in reducing and anoxic conditions. This original method makes it possible to synthesize nanometric UO{sub 2} powders with a calibrated size, as well as the Th- and La-doped UO{sub 2} powders with a predefined composition. The powder characterization by the X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron Microscopy shows the formation of spherical crystallites of UO{sub 2+x},…
Synthesis of yttrium aluminum garnet nanoparticles in confined environment III: Cerium doping effect
2018
Abstract Cerium yttrium aluminum garnet (Ce:YAG, CexY3-xAl5O12) nanoparticles doped with different cerium amount were obtained by calcining the precursors synthesized via co-precipitation in w/o microemulsion for 1 h at 900 °C. The structural and morphological properties were investigated by using X-ray Diffraction (XRD), Infrared Spectroscopy (IR) and Transmission Electron Microscopy (TEM) coupled with Energy Dispersive X-ray Spectroscopy (EDS) in order to investigate the effect of doping level on formation and microstructure of obtained nanoparticles. It was found that the composition of the final products strongly depends on the concentration of cerium. The formation of single YAG phase …
Mechanism of crystallization of Co-cordierites from stoichiometric powdered glasses
2002
Abstract The influence of cobalt, as a divalent cation, on the crystallization behaviour of the cordierite based glasses was studied. Powdered glass specimens of stoichiometric composition 2MO 2Al 2 O 3 5SiO 2 (M=Co and/or Mg) were obtained and thermally treated at several temperatures and times, and the sequence of crystallization and their microstructural evolution were analysed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Results on the crystallization sequence showed that the steps in the crystallization path are independent of the nature of the divalent cation. The first crystalline phase detected displayed the μ-cordierite structure, i.e. a solid…
Interfacial disorder of graphene grown at high temperatures on 4H-SiC(000-1)
2016
This paper presents an investigation of the morphological and structural properties of graphene (Gr) grown on SiC(000-1) by thermal treatments at high temperatures (from 1850 to 1950 °C) in Ar at atmospheric pressure. Atomic force microscopy and micro-Raman spectroscopy showed that the grown Gr films are laterally inhomogeneous in the number of layers, and that regions with different stacking-type (coupled or decoupled Gr films) can coexist in the same sample. Scanning transmission electron microscopy and electron energy loss spectroscopy shoed that a nm-thick C-Si-O amorphous layer is present at the interface between Gr and SiC. Basing on these structural results, the mechanisms of Gr grow…
Influence of the high energy ball milling on structure and reactivity of the Ni+Al powder mixture
2013
Abstract Investigation of the micro- and atomic structures for the planetary ball-milled Ni + Al mixtures has revealed existence of intermediate nano-crystalline and amorphous phases, which are not detectable by XRD analysis, but can be observed by means of HRTEM. Annealing of the milled mixtures at moderate temperature, 205–280 °C, transforms the nano-phases into crystal state and makes them XRD-detectable. These nano-scale structures may serve as nucleus for the intermetallic phases produced via reaction between Ni and Al and, therefore, decrease the activation energy of this reaction and diminish the temperature of the reaction initiation. Apparently, the active nano-phases are formed du…
THz nanocrystal acoustic vibrations from ZrO2 3D supercrystals
2013
International audience; We report sharp low-frequency Raman spectral features of supercrystals synthesized via the "benzyl alcohol route" and consisting of either yttrium-stabilized or pure zirconia (ZrO2) nanocrystals. In situ formed benzoate species control the nanocrystal growth and act as organic glue leading to the assembly of the nanocrystals in highly ordered 3D supercrystals. We attribute some Raman peaks to THz acoustic vibrations of individual nanocrystals which are only weakly coupled due to the strong acoustic mismatch between the capping ligands and the nanocrystals. Peak positions are consistent with nanocrystal sizes estimated from transmission electron microscopy and X-ray p…
Mesosynthesis of ZnO-SiO(2) porous nanocomposites with low-defect ZnO nanometric domains.
2011
Silica-based ZnO-MCM-41 mesoporous nanocomposites with high Zn content (5≤Si/Zn≤50) have been synthesized by a one-pot surfactant-assisted procedure from aqueous solution using a cationic surfactant (CTMABr = cetyltrimethylammonium bromide) as structure-directing agent, and starting from molecular atrane complexes as inorganic hydrolytic precursors. This preparative technique allows optimization of the dispersion of the ZnO nanodomains in the silica walls. The mesoporous nature of the final materials is confirmed by x-ray diffraction (XRD), transmission electron microscopy (TEM) and N(2) adsorption-desorption isotherms. The ZnO-MCM-41 materials show unimodal pore size distributions without …
Enhanced thermoelectric properties of lightly Nb doped SrTiO3 thin films
2021
Novel thermoelectric materials developed for operation at room temperature must have similar or better performance along with being as ecofriendly as those commercially used, e.g., BiTe, in terms of their toxicity and cost. In this work, we present an in-depth study of the thermoelectric properties of epitaxial Nb-doped strontium titanate (SrTiNbO) thin films as a function of (i) doping concentration, (ii) film thickness and (iii) substrate type. The excellent crystal quality was confirmed by high resolution transmission electron microscopy and X-ray diffraction analysis. The thermoelectric properties were measured by the three-omega method (thermal conductivity) and van der Pauw method (el…