Search

A protective SiO2 coating was prepared by sol-gel method on stainless steel plates, using precursor solutions having 2 different concentrations: low (0.5M) and high (2M) concentration. The dip coating-drying cycles have been repeated three times, after that the coatings were thermally treated at 300°C or 500°C in air. Scanning electron microscopy (SEM), AFM and X-ray diffraction analyses have been applied. The corrosion resistances of SiO2 coated steels were examined in NaCl medium for 346 hours. Many microcracks and craters in the samples, prepared from solution of high concentration appear after corrosion attack. The coatings obtained from solution of low concentrations reveals almost unchanged surface structure without visible cracks and pits. The evaluated corrosion rate of this coating is lower than those of uncoated steel.

Silver- or nickel-loaded activated carbon (AC) catalysts were prepared by impregnation, and subsequent physicochemical pyrolysis and activation by continuous blowing of exhausted gas through the sample and addition of water vapor to the feed. The X-ray diffraction pattern of the catalyst samples included peaks characteristic of metallic Ago and Nio phase. The silver metal particles sized between 20 nm and 250 nm were homogeneously dispersed on the activated carbon surface. The metal loading of the Ni/AC sample did not lead to any agglomeration of the particles suggesting a stronger metal-support interaction and hence a higher degree of dispersion. The activity of the catalyst samples was tested in the heterogeneous catalytic reaction of ozone decomposition at ambient temperature. The Ag/AC and Ni/AC samples exhibited high activity providing almost complete ozone disintegration. The conversion degree was close to 97 % throughout the whole three-hour testing period. [ABSTRACT FROM AUTHOR]

An original patented procedure was applied to obtain activated ZnO powder and then it was doped with 1.5 mass % La to improve the photocatalytic performance. The effect of a nitric acid treatment (index a. t.) of the La/ZnO investigated by comparing with the non-treated La/ZnO samples, manifests a higher photocatalytic efficiency of the former in the oxidative degradation of the model textile wastewater pollutant azo dye Reactive Black 5. The acidically treated La/ZnO powders have been obtained by impregnation in 0.1 M HNO3 acidic solution, followed by thermal treatment at 100°C, 350°C and 500°C. The materials have been characterized by the XRD, XPS and single point BET methods. The XRD analysis shows the presence of three crystallographic phases: wurtzite, Zn(NO3) (OH). H2O and 4ZnO(OH)2.Zn(NO J2.H2O. The XPS data give evidence of N-atoms in ZnO after the acidic treatment. The best photocatalytic performance is shown by the La/ZnO a.t. dried at 100°C due to its highest nitrogen content. [ABSTRACT FROM AUTHOR]

For the first time a combination of microwaves and/or the conventional treatment method was used to dry and heat multilayered sol-gel ZnO/TiO/glass structures. Compact or porous TiO films were deposited as a bottom layer, covered with a ZnO film. The structures were characterized by X-ray Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDX) and Scanning Electron Microscopy (SEM). Only peaks of wurtzite ZnO crystalline phase were registered on the X-Ray diffractograms. The microwave irradiation leads to a formation of poorly crystallized multilayers with very small crystallites and enhanced surface roughness. This results in a better photocatalytic activity of these structures than the structures of the samples treated conventionally. It was established that the morphology of the bottom titania layer affects the reaction of photocatalytic degradation of Malachite Green dye (MG). The structures with the compact bottom TiO films showed higher activities than those on porous TiO films. This study offers an energy saving method of producing ZnO/TiO/glass multilayered structures of various morphologies and pronounced photocatalytic properties. The method does not involve any calcination step, normally applied to achieve a good degree of crystallization. This makes the method suitable for protecting substrates of low thermal stability. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Four photocatalyst samples, prepared from beech sawdust, were synthesized by an original method, combining pyrolysis and impregnation - two of them: TiO + activated carbon and other two - only activated carbon. The pyrolysis process has been carried out at two different temperatures - 680°C and 830°C. The prepared samples were characterized by a series of methods - XRD, BET, SEM and DTA/TG. The most important result was achieving visible light photocatalytic activity with an azo dye pollutant for both materials. The TiO/AC-680°C sample demonstrated higher activity under visible light illumination than the TiO/AC-830°C sample. The visible light activity was attributed to the active carbon component in the composite materials, which was evidenced by the photocatalytic tests with bare carbon (without any TiO) manifesting visible light activity. The AC-680°C carbon was superior to the AC-830°C under visible illumination probably due to its higher specific surface area and porous texture. UV-light testing of the photocatalytic activity revealed that the TiO/AC-680°C sample was higher than that of the TiO/AC-830°C under polychromatic UV-A illumination (320-400 nm with a maximum at l = 365 nm). The TiO/AC-680°C sample was also more efficient with the monochromatic UV-C illumination (l = 254 nm). Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The lithiated transition metal oxide LiVMoO6 has been synthesized by a novel melt quenching method that presents some advantages as compared to the classical solid-state reaction and soft-combustion synthesis. These are: the short preparation time and the possibility to control the grain size of LiVMoO6 powders. The local structure of LiVMoO6 samples prepared in different ways was characterized by IR spectral analysis. The oxidation state of Li, V, and Mo was determined by X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: Spray pyrolysis procedure for preparation of nanostructured TiO2 films with higher photocatalytic effectiveness and longer exploitation life is presented in this study. Thin films of active nanocrystalline TiO2 were obtained from titanium isopropoxide, stabilized with acetyl acetone and characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The activity of sprayed nanostructured TiO2 is tested for photocatalytic degradation of Reactive Black 5 dye with concentrations up to 80ppm. Interesting result of the work is the reduction of toxicity after photocatalytic treatment of RB5 with TiO2, which was confirmed by the lower percentage of mortality of Artemia salina. It was proved that the film thickness, conditions of post deposition treatment and the type of the substrate affected significantly the photocatalytic reaction. Taking into account that the parameters are interdependent, it is necessary to optimize the preparation conditions in order to synthesize photocatalytic active films. [Copyright &y& Elsevier]

The surface interaction of LiNi0.8Co0.2O2 with Mg(CH3COO)2 has been studied by XRD diffraction, SEM, X-ray photoelectron spectroscopy, EPR of Ni3+ ions and temperature programmed reduction. It has been shown that the interaction of LiNi0.8Co0.2O2 with Mg(CH3COO)2 at 600 °C yields a Mg-coating on the particle surface, the particle bulk being free from Mg-dopants. The structure and morphology of the Mg-coating depends on the Mg-loading. At low Mg-loading (up to 2 mol%) the surface interaction results in the formation of a thin layer of a “x MgO·(1−x) LiNi0.8Co0.2O2” solid solution with x⩽0.2 on the few top surface layers, which encapsulates the LiNi0.8Co0.2O2 particle. With increasing the Mg-loading, deposits of about 10 nm from a MgO-like phase also appear on the particle surface. The electrochemical performance of these composite materials is evaluated in constant current experiments. The Mg-treated oxides display a decreased initial capacity but an improved capacity retention upon cycling. Based on ex-situ XRD, EPR of Ni3+ and IR spectroscopy of cycled compositions, the electrochemical properties of Mg-treated oxides are discussed taking into account the composition and structure of the Mg-coating. [Copyright &y& Elsevier]