Lightweight Spam Filtering Methods

Validerat; 20140619 (global_studentproject_submitter)</p

DOPING SILVER TO ACTIVATED ZNO TO PROMOTE THE PHOTOCATALYTIC EFFICIENCY FOR AZO DYE DEGRADATION

Various silver doped ZnO activated powders were prepared through an original method of activation. The samples were characterized using XRD analysis, single point BET method, scanning electron microscopy (SEM). The photocatalytic properties of the samples were tested in the reaction of Reactive Black 5 azo dye (model waste water contaminant) oxidative discoloration in a semi-batch reactor. The silver doped samples have higher degree of cristallinity in comparison to the undoped sample and superior photocatalytic performance under UV-A light illumination. Another factor promoting the photocatalytic properties is the increase of the dopant content decreasing the ZnO particle mean size and increasing the specific surface area of the doped samples. The role of silver nanoparticles is to serve as traps for the photoexcited electrons thus preventing recombination and increasing the lifetime of the positively charged holes, acting as oxidation active sites

Preparation of sol-gel SiO2 coatings on steel and their corrosion resistance

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

Preparation of sol-gel SiO

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

EFFECT OF LA DOPANT ON THE PHOTOCATALYTIC EFFICIENCY OF ACTIVATED ZNO NANOPOWDERS

Activated ZnO powder was obtained by an original patented procedure and doped with 0.5, 1 and 1.5 wt % La to improve the photocatalytic performance. The crystalline structure, surface morphology and specific surface area were investigated by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and single point Brunauer-Emmett-Teller (BET) method. The XRD analysis of the oxide samples illustrates the formation of wurtzite ZnO. Increasing of La concentration results in higher degree crystallinity of the doped ZnO samples. The doped and non-doped ZnO crystallite sizes are in the range of 54÷57nm. Doping with La leads to increase of specific surface area compared to non-doped ZnO. The course of the photocatalytic reaction was followed spectrophotometrically based on the maximum absorbance wavelength of the model pollutant Reactive Black 5 (RB5). The samples doped with 1.5 wt % La exhibited the highest efficiency for the photocatalytic degradation of RB5 under UV illumination due to the higher degree of crystallinity, formation of solid solution and higher specific surface area

CORROSION BEHAVIOR OF LOW-CARBON STEEL COATED WITH DIFFERENT TYPE OF TIO2/ZRO2 LAYERS

Two type of multilayer structures based on ZrO2 coatings deposited on TiO2 were applied on low carbon steel and their structure, composition and anticorrosion properties were evaluated in 5%NaCl salt medium. The phase composition, morphology and the elemental distribution of the coatings were investigated using X-ray diffraction analysis, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and energy dispersive X-ray analysis (EDX). The corrosion performance of the coatings was evaluated by potentiodynamic polarization measurements (PD). The zirconia/titania mixed oxide coating exhibited an enhanced corrosion resistance than those of the low carbon steel as indicаted by the reduced current density, probably due to the presence of amorphous structure on the layers and dense surface without visible cracks and pits (barrier effect)

Modified Approach Using Mentha arvensis in the Synthesis of ZnO Nanoparticles&mdash;Textural, Structural, and Photocatalytic Properties

Zinc oxide arouses considerable interest since it has many applications&mdash;in microelectronics, environmental decontaminations, biomedicine, photocatalysis, corrosion, etc. The present investigation describes the green synthesis of nanosized ZnO particles using a low-cost, ecologically friendly approach compared to the classical methods, which are aimed at limiting their harmful effects on the environment. In this study, ZnO nanoparticles were prepared using an extract of Mentha arvensis (MA) leaves as a stabilizing/reducing agent, followed by hydrothermal treatment at 180 &deg;C. The resulting powder samples were characterized by X-ray diffraction (XRD) phase analysis, infrared spectroscopy (IRS), scanning electron microscopy (SEM), and electron paramagnetic resonance (EPR). The specific surface area and pore size distribution were measured by the Brunauer&ndash;Emmett&ndash;Taylor (BET) method. Electronic paramagnetic resonance spectra were recorded at room temperature and at 123 K by a JEOL JES-FA 100 EPR spectrometer. The intensity of the bands within the range of 400&ndash;1700 cm&minus;1 for biosynthesized ZnO (BS-Zn) powders decreased with the increase in the Mentha arvensis extract concentration. Upon increasing the plant extract concentration, the relative proportion of mesopores in the BS-Zn samples also increased. It was established that the photocatalytic performance of the biosynthesized powders was dependent on the MA concentration in the precursor solution. According to EPR and PL analyses, it was proved that there was a presence of singly ionized oxygen vacancies (V0+) and zinc interstitials (Zni). The use of the plant extract led to changes in the morphology, phase composition, and structure of the ZnO particles, which were responsible for the increased photocatalytic rate of discoloration of Malachite Green dye