Search results for "scanning electron"
showing 10 items of 667 documents
Pyroxene-based glass-ceramics as glazes for floor tiles
2005
Abstract Crystallization of a glass with composition in the diopside primary crystallization field in the MgO–CaO–Al 2 O 3 –SiO 2 quaternary system was investigated. Also the action of some additives, nucleants and fluxes, in the pyroxene development was examined. Glasses were prepared by conventional melting of a mixture of raw materials and cooled by pouring in water. Pellets of glass powder specimens were thermally treated at several temperatures up to 1200 °C. The crystallization path was followed by X-ray diffraction powder (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). The results proved that, in addition to the effect of B 2 O 3 and TiO 2 in…
Templated growth of smart coatings: Hybrid chemical vapour deposition of vanadyl acetylacetonate with tetraoctyl ammonium bromide
2009
Hybrid aerosol assisted and atmospheric pressure chemical vapour deposition methodology has been utilised to produce thin films of vanadium dioxide from vanadyl acetylacetonate. Tetraoctyl ammonium bromide (TOAB) was used in the aerosol precursor solution. The films were analysed by X-ray diffraction, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy. Their optical and thermochromic behaviour was also determined. It was found that the use of TOAB had a templating effect that led to a halving in the particle size and that this consequently led to a significant decrease in the thermochromic transition temperature of the films to 34 8C.
Influence of fluorine on the synthesis of anatase TiO2for photocatalytic partial oxidation: Are exposed facets the main actors?
2018
Anatase TiO2 samples were synthesized in the presence of different amounts of HF acid with the aim of understanding the effect of the presence of fluorine on the photocatalytic activity. It is well known that the presence of fluoride ions influences the photocatalytic performance by adsorption on the surface of TiO2 and that they are capping agents in the control of specific exposed facets. The samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, nitrogen adsorption–desorption measurements, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis spectrophotometry, and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity was eva…
Photoactivity of Nanostructured TiO2 Catalysts in Aqueous System and their Surface Acid-Base, Bulk and Textural Properties
2007
This work reports on the characterisation and determintion of the photocatalytic activity of some TiO2 catalysts prepared using TiCl4 as precursor. The samples, consisting of suspensions, dispersions or powders of nanonstructured anatase or rutile phases, were obtained in very mild conditions, i.e., by boiling the solution obtained after hydrolysis of TiCl4 at atmospheric pressure: it is worth noting that no calcination was necessary to obtain photoactive phases. The samples were characterised by X-ray diffraction (XRD), determination of the BET specific surface area (SSA), scanning electron microscopy (SEM) observations and diffuse reflectance spectroscopy (DRS). FT-IR spectroscopy was use…
Preparation and characterization of Al2O3 supported TiO2 catalysts employed for 4-nitrophenol photodegradation in aqueous medium
1998
Abstract In this paper the preparation and some bulk and surface characterizations of set of Al2O3 supported TiO2 photocatalysts are reported. The powders were home prepared by a wet impregnation method using titanium (IV) isopropylate. The impregnation was followed by thermal treatments and this procedure was repeated several times in order to obtain samples with different amounts of TiO2. The solids were characterized by X-ray diffraction, specific surface area determination, scanning electron microscopy coupled with an electron microprobe used in an energy-dispersive mode and diffuse reflectance spectroscopy. Moreover, all of them were tested as photocatalysts by using different kinds of…
One-Dimensional TiO2-B Crystals Synthesised by Hydrothermal Process and Their Antibacterial Behaviour on Escherichia coli
2016
We have successfully synthesised one-dimensional single crystals of monoclinic phase titanium dioxide nanostructures (TiO2-B), prepared by a hydrothermal process. Morphological characterization was carried out by atomic force and scanning and transmission electron microscopy techniques. In order to study the crystalline structure, samples were calcined at 500°C in an air-filled chamber. X-ray diffraction results indicated that as-prepared samples presented diffraction patterns of hydrate hydrogen titanate and those calcined at 500°C exhibited the TiO2-B and anatase phases, confirmed by Raman spectroscopy. Scanning electron microscopy results showed that the one-dimensional nanostructures ha…
Preparation of Photocatalytic Nanostructured TiO<sub>2</sub> Thin Films
2008
Photoactive films consisting of pure anatase, brookite or rutile were deposited on glass slides by a dip coating process from water dispersions or solutions obtained by using TiCl4 as the precursor. The films were characterized by X-ray diffraction, scanning electron microscopy and atomic force microscopy. The photocatalytic activity of the various samples was evaluated by using the photooxidation of 2-propanol in gas solid regime as probe reaction. Brookite and anatase films showed a good photoactivity degrading the substrate and the propanone produced during the reaction.
Mesocrystalline Cr and Sb-codoped anatase visible-light-driven photocatalyst
2018
Abstract We report on the synthesis, characterization and visible-light-driven photocatalytic activity of mesocrystalline Cr- and Sb-codoped anatase nanoparticles. Discrete and morphologically well-defined assemblies of anatase nanoparticles sized below 100 nm × 50 nm were prepared by hydrothermal aging of aqueous solutions containing titanium alkoxide, chromium acetylacetonate, antimony acetate and triethanolamine (TEOA) as stabilizer. The as-prepared and TEOA-free doped nanoparticles showed similar crystallographic parameters and spectroscopic features. The incorporation of Cr and Sb dopant cations into the anatase nanoparticles was evaluated by Rietveld refinement of X-ray diffraction pa…
Photoelectrochemical characterization of anatase-rutile mixed TiO2 nanosponges
2016
This work studies the influence of using hydrodynamic conditions during anodization on the morphology and electrochemical properties of anatase/rutile mixed TiO2 nanotubes (Reynolds number, Re = 0) and nanosponges (Re > 0). To this purpose different techniques were used, such as: microscopy techniques (Field-Emission Scanning Electron Microscope, FE-SEM, and Confocal Laser-Raman Spectroscopy), Electrochemical Impedance Spectroscopy (EIS), Mott Schottky (MS) analysis and photoelectrochemical water splitting tests. This investigation demonstrates that the morphology of TiO2 nanostructures may be greatly affected due to the hydrodynamic conditions and it can be adjusted in order to increase th…
Thermal effects on the growth by metal organic chemical vapour deposition of TiO2 thin films on (100) GaAs substrates
2002
Abstract TiO 2 thin films were deposited on (100) GaAs substrates by LP-MOCVD with deposition temperatures ( T d ) ranking from 450 to 750 °C. The structure of these layers was studied by X-ray diffraction (XRD) and Raman spectroscopy. The growth of the TiO 2 anatase phase was observed for T d T d >600 °C. Finally, X-ray photoelectron spectrometry (XPS) and secondary ion mass spectroscopy (SIMS) experiments showed the presence of small quantities of Ga and As through the whole film thickness, slightly increasing at the surface of the layers. This result was related to the SEM observations and explained by considering the growth conditions.