Search results for "Thermal Treatment"
showing 10 items of 146 documents
Alkaline treatment as a means to boost the activity of TiO(2)in selective photocatalytic processes
2020
In this work, the activity enhancement of TiO(2)photocatalysts by alkaline treatment has been investigated. Commercial (BDH, U.K., anatase phase) TiO(2)samples, treated in alkaline solutions of NaOH at different concentrations and temperatures, were tested for the photocatalytic partial oxidation of 3-pyridinemethanol in water under UVA irradiation to form vitamin B-3. Photocatalyst characterization has been carried out by XRD, BET, TEM, TGA, photoluminescence, FTIR, Raman, DRS, EPR and photocurrent measurements. The alkaline-treated samples showed an increased activity of up to 7 times (by considering first order rate constant values) compared to untreated BDH and the superior performance …
A comparative study of the photocatalytic activities of iron-titanium (IV) oxide photocatalysts prepared by various methods; spray pyrolysis, impregn…
1995
Abstract A series of iron/titanium oxide photocatalysts of varying Fe 3+ content have beenprepared by a number of different methods and subjected to controlled thermal treatment. Specimens have been characterised in terms of their crystalline structure and morphology, and indicate solid solutions containing both the anatase and rutile phases of TiO 2 , together with the formation of pseudo-brookite in some specimens. Intrinsic photo-activity measurements have been performed using a standard liquid-phase photocatalytic reaction. Results indicate that the photocatalytic activity of the specimens differs according to the method of preparation, and that all solids containing iron (III) species …
Polyacrylonitrile block copolymers for the preparation of a thin carbon coating around TiO2 nanorods for advanced lithium-ion batteries.
2013
Herein, a new method for the realization of a thin and homogenous carbonaceous particle coating, made by carbonizing RAFT polymerization derived block copolymers anchored on anatase TiO2 nanorods, is presented. These block copolymers consist of a short anchor block (based on dopamine) and a long, easily graphitizable block of polyacrylonitrile. The grafting of such block copolymers to TiO2 nanorods creates a polymer shell, which can be visualized by atomic force microscopy (AFM). Thermal treatment at 700 °C converts the polyacrylonitrile block to partially graphitic structures (as determined by Raman spectroscopy), establishing a thin carbon coating (as determined by transmission electron m…
Nanostructured Solids from Freeze-Dried Precursors: Multigram Scale Synthesis of TiO2 -Based Powders
2012
Nanocrystalline TiO2 and Ti1−xVxO2 (x = 0.01) powders have been prepared by thermal decomposition, in air, of amorphous precursors resulting from the freeze-drying of appropriate solutions. In addition, TiO2−xNy (anatase and rutile) and TiOxNy (rock-salt) have been prepared by thermal treatment in ammonia of a crystalline precursor (TiO2 obtained at 673 K). TEM and SEM images, as well as the analysis of the X-ray diffraction (XRD) patterns, show the nanoparticulated character of those solids obtained at low temperatures, with typical particle sizes in the 10–20 nm range when prepared at 673 K. The UV–Vis results indicate both the insertion of V in the anatase lattice and the feasibility of …
Sol-gel derived anatase TiO2: morphology and photoactivity
1994
Abstract High-surface area TiO 2 (anatase) was prepared by the sol-gel method and characterized by various instrumental and analytical methods, including X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, porosimetry, specific surface area measurements, scanning electron microscopy, and titration of surface hydroxyl groups. The specimen was tested for photodegradation of phenol and nitrophenols carried out in aqueous suspension at pH = 3; photoactivity was compared with that of commercially available anatase TiO 2 . Results are discussed in terms of porosity, surface area, and availability and population of surface OH groups, consequent upon the particular method used for…
Annealing of radiation induced oxygen deficient point defects in amorphous silicon dioxide: evidence for a distribution of the reaction activation en…
2011
The selective annealing of point defects with different activation energies is studied, by performing sequences of thermal treatments on gamma irradiated silica samples in the temperature range 300-450 °C. Our experiments show that the dependence on time of the concentration of two irradiation induced point defects in silica, named ODC(II) (standing for oxygen deficient centre II) and the E(γ)(') centre, at a given temperature depends on the thermal history of the sample for both of the centres studied; moreover in the long time limit this concentration reaches an asymptotic value that depends on the treatment temperature alone. These results suggest the existence of a distribution of the a…
Influence of Physical Treatments on the Potato Starch Granules Micro- and Ultrastructure
2012
In this research, potato starch was subjected to ph ysical treatments in order to analyse the changes at the micro- and ultrastructural levels an d finally to identify the optimal conditions for disintegrating the starch granules. For the analysi s, 10% aqueous solutions of potato starch were treated with a) microwaves; b) heat and c) heat com bined with ultrasounds. For each treatment type, the duration was 5 minutes, excepting the microwave treatment, where the time was 1 and 5 minutes; heat power varied from 180W to 900W at the tests with microwave, temperature varied between 65 o C and 100 o C in the thermal experiments and at the thermal ana lysis combined with ultrasounds temperature …
GROWTH AND PHOTOELECTROCHEMICAL BEHAVIOUR OF ELECTRODEPOSITED ZnO THIN FILMS FOR SOLAR CELLS
2012
Thin zinc oxide films were deposited potentiostatically from zinc nitrate aqueous solutions on ITO substrates. The influence of experimental parameters (temperature, electrolyte concentration, deposition potential) on structure and morphology of films was investigated. Deposited films were generally polycrystalline in structure, even if growth according to preferential planes occurs in certain conditions. The effect of thermal treatments in air at 150 and 350 °C was also studied. In some cases, Cl species were incorporated into deposit by adding zinc chloride to the electrolyte. A photoelectrochemical investigation, performed in neutral solution before and after thermal treatment, gives mor…
Influence of annealing atmosphere on photoelectrochemical response of TiO2 nanotubes anodized under controlled hydrodynamic conditions
2021
[EN] The influence of three annealing atmospheres (air, nitrogen and argon) and the use of controlled hydrodynamic conditions (from 0 to 5000 rpm) on morphological, structural, chemical and photoelectrochemical properties of TiO2 nanotubes have been evaluated. For this purpose, different characterization techniques have been used: Field Emission Scanning Electron Microscopy, Raman Confocal Laser Spectroscopy, X-Ray Diffraction, X-Ray Photoelectron Spectroscopy, Incident Photon-to-electron Conversion Efficiency measurements, ultraviolet-visible absorption spectra, Mott-Schottky analysis and photoelectrochemical water splitting tests. According to the results, it can be concluded that both hy…
Photoluminescence Study of ZnSe Single Crystals Obtained by Solid Phase Recrystallization under Different Pressure Conditions. Effects of Thermal Tre…
2002
ZnSe single crystals, obtained by the Solid Phase Recrystallization (SPR) method under three different pressure conditions, 10 and 5 atm of Se, and 2 atm of argon, have been investigated by means of photoluminescence (PL) and optical microscopy. Special attention has been paid to the surface state of the samples. Samples recrystallized under 10 atm of Se present the best rate between the PL response for the excitonic zone and the deep level one that shows a clean PL emission without significant peaks and/or bands. The presence of slip bands has been detected and analysed by means of optical microscopy and photoluminescence. In order to study the changes introduced by post growth thermal tre…