Search results for "TRANSMISSION ELECTRON"

Growth of metal/oxide periodic multilayer : relation between structure and electrical behaviour in systems based on titanium and tungsten

2014

Periodic multilayers have found many applications in the fields of optics, mechanics or electronics. However, few studies focus on the electrical responses of the metal/oxide periodic structures versus temperature. The interest of this work was focused on the characterization of the multilayers and their electrical properties versus temperature. In TiO/Ti/TiO/TiO2 and WO/W/WO/WO3 systems produced by the reactive gas pulsing process, sample structures were established by transmission electron microscopy for sublayers thicknesses between 1.3 and 50.8 nm. Then, this study highlights a modification of conventional electrical behavior versus temperature. An empirical relationship was established…

Surface Defects as a Tool to Solubilize and Functionalize WS 2 Nanotubes

2017

Layered transition metal dichalcogenides contain a number of crystal defects which significantly change their properties may be beneficial or detrimental for a specific application. We have prepared defect-rich multiwalled WS2 nanotubes by reductive sulfidization of W18O49 nanowires that were obtained solvothermally from tungsten chloride in different alcohols. The synthesis of the W18O49 nanowires was monitored and their morphological characteristics (e. g. length, rigidity and aspect ratio) are described in detail. The effect of morphology of the nanowires on the synthesis of WS2 nanotubes was investigated in order to obtain WS2 nanotubes that are highly solvent dispersible. Dispersions o…

Immunoelectron microscopy labeling for the identification of oligodendrocytes and their precursor cells

2021

Los oligodendrocitos son las células mielinizantes del sistema nervioso central. Además de la mielinización, proporcionan apoyo metabólico y trófico a las neuronas. Estas células se originan a partir de células progenitoras de oligodendrocitos (OPC) que están ampliamente distribuidas en la sustancia blanca y gris. Los oligodendrocitos y las OPC se ven gravemente afectados en diferentes patologías del cerebro humano. Estas enfermedades son causadas por patologías con diferentes mecanismos, como mutaciones genéticas, infecciones, mutaciones que dan lugar a neoplasias, autoinmunidad y lesiones traumáticas. La mayoría de estas disfunciones resultan en desmielinización. De entre las múltiples té…

A new efficient, highly dispersed, Pd nanoparticulate silica supported catalyst synthesized from an organometallic precursor. Study of the homogeneou…

2018

[EN] A new Pd(0) catalyst supported on silica UVM-7 has been synthesized from the organometallic [Pd-2(mu-(C6H4) Pp(2))(2)(CH3CN)(4)](BF4)(2) precursor, characterized by the high dispersion, activity, and small size of the palladium nanoclusters fixed on the silica surface. The catalyst was tested for the Suzuki-Miyaura (SM) reaction of different 4-substitutedphenyl halides with phenylboronic acid. The kinetic study concurs with most of the catalytic action was carried out by Pd species originated by the partial solubilization of Pd immobilized on mesoporous silica. The Schmidt's analysis of differential selectivity (SADS) in several competitive SM reactions, together the STEM-HAADF and HRT…

Metallic nanoparticle enrichment at low temperature, shallow CO2 seeps in Southern Italy

2012

We report on metal enrichment along a natural pH gradient owing to increased CO2 degassing at cold, shallow seeps of Vulcano Island in the Mediterranean Sea, off Sicily. We assessed composition of unfiltered and filtered seawater (<100 nm) along acidic zones ranging between ambient and pH 5, and showed that most seep derived elements are present as nanoclusters which then aggregate into larger colloids while mixing with ambient seawater along a pH gradient. Size and elemental composition of such naturally occurring nanoparticles assessed by modern characterisation methods were in good agreement with the results from conventional analytical methods. We provide analytical evidence for the pre…

With Phosphinophosphonic Acids to Nanostructured, Water-Soluble, and Catalytically Active Rhodium Clusters

2007

Mechanical characterization of TiO2 nanofibers produced by different electrospinning techniques

2015

Abstract In this work TiO2 nanofibers produced by needle and needleless electrospinning processes from the same precursor were characterized and compared using Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and in situ SEM nanomechanical testing. Phase composition, morphology, Young's modulus and bending strength values were found. Weibull statistics was used to evaluate and compare uniformity of mechanical properties of nanofibers produced by two different methods. It is shown that both methods yield nanofibers with very similar properties.

Flash synthesis of zirconia nanoparticles by microwave forced hydrolysis

2001

Forced hydrolysis preparation of zirconia sols and powders by microwave heating of zirconium tetrachloride solutions at temperatures equal to 180 °C leads in a few minutes to monodispersed nanoscale zirconia particles. Synthesis was performed in a microwave reactor called the RAMO system. This microwave reactor was designed by the authors. This flash-synthesis process combines the advantages of forced hydrolysis (homogeneous precipitation) and microwave heating (very fast heating rates). The sols and powders were characterized by x-ray diffraction,photon correlation spectroscopy (PCS), small-angle x-ray scattering, and transmission electron microscopy. Sols are colloidally stable, which mea…

Facile synthesis and characterization of monocrystalline cubic ZrO2 nanoparticles

2007

Abstract Crystalline ZrO2 nanoparticles were prepared from zirconium isopropoxide by slow hydrolysis and subsequent hydrothermal treatment of solutions containing various amounts of sodium hydroxide at 180 °C. Whereas moderately basic solutions lead to the formation of nanoparticles of monoclinic ZrO2 with plate-like morphology, and nanoparticles of the cubic ZrO2 high-temperature polymorph with diameters of approx. 5 nm were obtained from strongly basic solutions. The morphology, structure and properties of as-synthesized nanoparticles were characterized using HRTEM, XRD, Raman spectroscopy, UV–vis, PL spectroscopy and BET measurements. The formation of both, the monoclinic and the cubic p…

ChemInform Abstract: Facile Synthesis and Characterization of Monocrystalline Cubic ZrO2Nanoparticles.

2008

Abstract Crystalline ZrO2 nanoparticles were prepared from zirconium isopropoxide by slow hydrolysis and subsequent hydrothermal treatment of solutions containing various amounts of sodium hydroxide at 180 °C. Whereas moderately basic solutions lead to the formation of nanoparticles of monoclinic ZrO2 with plate-like morphology, and nanoparticles of the cubic ZrO2 high-temperature polymorph with diameters of approx. 5 nm were obtained from strongly basic solutions. The morphology, structure and properties of as-synthesized nanoparticles were characterized using HRTEM, XRD, Raman spectroscopy, UV–vis, PL spectroscopy and BET measurements. The formation of both, the monoclinic and the cubic p…