M. Shipochka - Academia.edu (original) (raw)

Papers by M. Shipochka

Photocatalytically active ZnO nanosized films were deposited by polymer modified spray pyrolysis ... more Photocatalytically active ZnO nanosized films were deposited by polymer modified spray pyrolysis method. The influence of the polymers and the type of zinc precursor on the chemical composition, surface morphologies and the photocatalytic properties towards Malachite Green dye degradation were investigated. The amount of oxygen in the lattice (OL) and oxygen total (OT) as well as the atomic ratio of Zn/OT were evaluated by means of X-ray Photoelectron Spectroscopy (XPS). The ZnO films are non-stoichiometric. The addition of polymers to both zinc salt solutions does not change significantly the oxygen concentration in the films. After photocatalytic test the ratio OL/OT decreases, showing that the amount of adsorbed hydroxyl groups is increased. The films obtained from zinc acetate possess higher photocatalytic activity than those, obtained from zinc nitrate. The highest efficiency is achieved with the films obtained from zinc acetate with ethylcellulose addition.

Journal of Physics: Conference Series

Materials Chemistry and Physics

Journal of Alloys and Compounds

Copper-doped ZnO nanoparticles have been prepared by the precipitation method. The dopant content... more Copper-doped ZnO nanoparticles have been prepared by the precipitation method. The dopant contents in the samples were 0.24, 0.35 and 1.07 at.%. A set of techniques including XRD, XPS, TG - DTA, EPR and BET analysis has been applied to characterize Cu-doped ZnO samples. The results showed that the crystallite sizes of ZnO and Cu-doped ZnO nanoparticles were within the range of 45 ÷ 49 nm. The dopant exists in the form of isolated Cu2+ ions. According to the XPS analysis the copper ions are located mainly on the surface of the ZnO particles. The photocatalytic activity has been tested in the reaction of Reactive Black 5 discoloration under UV irradiation. Among all the investigated samples pure ZnO samples showed the best photocatalytic properties.

Thin photocatalytically active TiO2 fi lms are successfully deposited on glass and alumina foil s... more Thin photocatalytically active TiO2 fi lms are successfully deposited on glass and alumina foil substrates by spray pyrolysis method. The films are characterized by means of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), Thermal Analyses (TG-DTA). The XRD spectra of TiO2 thin fi lms, treated at 400◦C showed formation of nanosize anatase phase. The fi lms were studied with respect to the photo-initiated bleaching of azo dye Reactive Black 5 (RB5) under UV illumination. The influence of the substrate, treatment conditions and pH of the dye solution on the decoloration were investigated. It was found that the films, deposited on alumina foil revealed a better photocatalytic activity than those on glass substrates, due to the furrowed surface of the alumina substrate. The highest rate of decoloration was obtained at low pH value of the dye solution for fi lms treated at 400◦C.

A clinoptilolite zeolite was coated with copper via ion exchange and spray pyrolysis methods. Cu-... more A clinoptilolite zeolite was coated with copper via ion exchange and spray pyrolysis methods. Cu-clinoptilolites were tested as catalysts for decomposition of gas phase ozone. Catalytic activity up to 90% ozone conversion was observed for samples loaded via spray pyrolysis and at the same time the catalysts remained active over time. Ion exchanged form Cu-clinoptilolite shows smaller activity 15% ozone conversion. D.C. arc-AES, XRD, SEM and XPS analysis were carried on for chemical characterization of the samples.

Photocatalytically active TiO2 films were successfully prepared by sol gel method. The solutions ... more Photocatalytically active TiO2 films were successfully prepared by sol gel method. The solutions and suspensions, which consist of titanium alkoxide solution, enriched with Degussa P25 powder were spin coated on glass substrates. The phase composition and crystallite size of the films were characterized by means of X-ray diffraction (XRD). The morphology and chemical composition were studied by Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). The XRD spectra of TiO2 thin films аnnealed at 400◦C showed formation of nanosize anatase phase. The decolorization of Reactive Black 5 dye, used in the textile industry was investigated at different pH range. The pH of the dye solution and titanium precursor have effect on their photocatalytic properties. The films, obtained form suspensions, obtained by microwave-assisted drying and conventional treatment have a rate of the RB5 degradation compatible with those of conventionally treated TiO2 films.

Ozone: Science & Engineering, 2014

ABSTRACT Samples of Bulgarian perlite mineral deposit (natural alumino-silicate glass) in the Rho... more ABSTRACT Samples of Bulgarian perlite mineral deposit (natural alumino-silicate glass) in the Rhodope mountain were coated with Ag particles via a spray pyrolysis method. This method allows uniform distribution of the silver particles on the outer shell surfaces. SEM, XPS, FT-IR, and XRD methods were applied for characterization of the samples. The XRD investigations of the pristine samples revealed the formation of metallic silver and a small quantity of Ag2O3 phase. The presence of silver was also confirmed by XPS analysis. It was established that Ag/perlite composite prepared by spray pyrolysis is a promising catalyst for ozone decomposition. The high catalytic activity is preserved during the complete course of the catalytic reaction. After the catalytic activity test some structural and phase changes in the samples were observed. The XRD patterns of the ozonated samples proved the presence of metallic silver, AgO and Ag2O3 phases. The FT-IR analyses revealed that some bands, assigned to Si-O-Si stretching modes, were shifted to lower frequencies after the ozone decomposition test. In general, the spray pyrolysis method turned out to be a very suitable technique for preparation of highly active silver-coated perlite catalyst for efficient ozone removal.

Materials Science and Engineering: B, 2012

ABSTRACT Nanocrystalline porous ZnO films are deposited onto alumina foil substrates by polyvinyl... more ABSTRACT Nanocrystalline porous ZnO films are deposited onto alumina foil substrates by polyvinyl alcohol (PVA) modified spray pyrolysis. Water and ethanol–water mixture were used for preparation of the sols. The effect of polyvinyl alcohol on the morphological and photocatalytical properties of ZnO films was studied. It was found that the polyvinyl alcohol plays important role in formation of porous films structure with ganglia like morphology. Relatively compact granular morphology was observed for the ZnO samples, grown without organic surfactant. The X-ray diffraction patterns revealed the formation of phase-pure ZnO thin films. The FTIR spectra and DTA-TG analyses of the precursor mixtures: Zn(CH3COOH)2·2H2O and Zn(NO3)2·6H20 with PVA revealed that ZnO is formed before the final decomposition of the polymer at 350 °C.It was observed that both: the acetate precursor and the organic surfactant could enhance significantly the photocatalytic properties of the ZnO films. The films obtained from sols, containing PVA showed better photocatalytic decolorization of Malachite Green dye, than the films, deposited from unmodified sols.

Materials Chemistry and Physics, 2010

ABSTRACT Nanocrystalline porous ZnO films are deposited onto alumina foil substrates by polymer-m... more ABSTRACT Nanocrystalline porous ZnO films are deposited onto alumina foil substrates by polymer-modified spray pyrolysis of zinc nitrate and zinc acetate solutions. The dependence of the concentration of added ethylcellulose and the type of zinc precursor on both the photocatalytic properties and films morphologies is investigated. It is established that the addition of ethylcellulose as a modifier in the spray solution leads to the formation of a porous structure with crystallites sizes about 15nm, when zinc acetate is used as precursor. These films show better photocatalytic activity for degradation of Malachite Green (MG) dye than the films obtained from zinc nitrate modified solution. The zinc nitrate films exhibit weaker activity for degradation of MG regardless of their smaller crystallite size (8–12nm). This can be explained with their lower porosity than that of polymer-modified zinc acetate films. It is established that 450°C is the limit temperature of treatment for the preparation of ZnO films with good photocatalytic activities. This photocatalytic activity in films shows a drop in the comparison to the films treated at lower temperature, due to decreasing of the pore number and deterioration of the surface morphology.

Journal of Physics Conference Series

TiO2 layers for gas sensing applications were obtained by Liquid Phase Deposition (LPD). The laye... more TiO2 layers for gas sensing applications were obtained by Liquid Phase Deposition (LPD). The layers were deposited on gold-coated piezoelectric quartz crystals. The surface structure, morphology and chemical properties were analysed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). SEM showed that the layers were porous and composed of uniform crystalline grains. XPS indicated them to be non-stoichiometric.

Journal of Physics: Conference Series, 2012

Thin nano-sized TiO 2 films were deposited on aluminum foil substrates by the spray pyrolysis met... more Thin nano-sized TiO 2 films were deposited on aluminum foil substrates by the spray pyrolysis method, using Ti(i-OPr) 4 (TIP) and TiCl 4 (TC) as precursors. The films were characterized by means of X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). According to the XRD patterns the as-deposited films appear to be amorphous. The thermal treatment at 400 o C leads to the formation of anatase nano-crystallites. The XPS analyses showed that the Ti2p broad photoelectron peak of as-deposited TC films indicated a mixture of Ti 3+ and Ti 4+ oxidation states. After treatment at 400 o C the Ti2p peak displays only Ti 4+ oxidation state for both TIP and TC films. The number of hydroxyl groups on the surface is decreased after the thermal treatment. The photocatalytic activity of the films was studied towards degradation of azo dye Reactive Black 5 (RB5) as model wastewater pollutant under visible light illumination. It was found out that the films obtained from TC were more active than those obtained from TIP films. The thermally treated samples are better photocatalysts than those non-treated, because they posses anatase crystalline phase and stoichiometric TiO 2 . The TOC measurements showed minimal concentration of total organic carbon in the dye solution after 180 min of visible light irradiation.

Bulletin of Materials Science

Thin nanocrystalline TiO2–SnO2 films (0–50 mol% SnO2) were prepared on quartz and stainless steel... more Thin nanocrystalline TiO2–SnO2 films (0–50 mol% SnO2) were prepared on quartz and stainless steel substrates by sol–gel coating method. The obtained films were investigated by XRD, Raman spectroscopy and XPS. The size of the nanocrystallites was determined by XRD–LB measurements. We ascertained that the increase of treatment temperature and concentration of SnO2 in the films favour the crystallization of rutile phase. The substrate type influences more substantially the phase composition of the TiO2–SnO2 films. It was established that a penetration of elements took place fromthe substrate into the films. TiO2 films deposited on quartz substrate include a Si which stabilizes anatase phase up to 600 ◦C. The films which are deposited on stainless steel substrate and treated at 700 ◦C show the presence of significant quantity of rutile phase. This phenomenon could be explained by the combined effect of Sn dopant as well as Fe and Cr, which also are penetrated in the films from the steel...

Journal of Physics: Conference Series, 2014

Nanosized TiO2 films were deposited by spray pyrolysis and thermally treated at 400 o C. Then the... more Nanosized TiO2 films were deposited by spray pyrolysis and thermally treated at 400 o C. Then the films were dipped in 1M aqueous solution of HCl. The activated samples were divided into two parts -one part was dried (A) and another was annealed (AT) in air. The photocatalytic degradation of Reactive Black (RB5) textile dye under visible light was tested. The following instrumental methods: X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were applied for the phase and surface characterization of obtained samples. According to Raman and XRD analyses all films are anatase. The XRD showed that activated films are better crystallized than non activated TiO2 film. The presence of chlorine at 200.3 eV was registered for acid activated samples by X-Ray photoelectron spectroscopy. The acidic activated films exhibited higher rate of dye photodegradation than that of the reference TiO2 sample. The photocatalytic efficiency decreases in the order A > AT> non activated TiO2 films. The degradation rate constant for acid activated films is two times higher than those of the reference film. The hydroxyl content in TiO2 acidic activated films is greater than that of the non-activated films, which results in significant increase in the photocatalytic activity. In addition, the presence of chlorine may also lead to enhancement in efficiency.

Materials Science in Semiconductor Processing, 2014

The crystallographic phase, surface features and photocatalytic properties in the reaction of dec... more The crystallographic phase, surface features and photocatalytic properties in the reaction of decolorization of Malachite Green dye over TiO 2 (0-100 mol%) doped ZnO films have been investigated. The films have been prepared by polymer modified spray pyrolysis. The crystallization degree and the size of the crystallites comprising the films have been found to be influenced by the TiO 2 content in the spraying solution. The undoped ZnO film has little porosity. The titania dopant causes formation of hexagonal nanorods on the ZnO surface. The increase in TiO 2 content results in enhancement of both size and crystallization degree of the nanorods. When the TiO 2 content is increased (i) the Zn2p, O1s and Ti2p peaks are shifted to lower binding energies, (ii) the atomic ratio of O L /Zn is decreased and (iii) the amount of adsorbed hydroxyl (OH À ) species is increased. All the TiO 2 doped ZnO films manifested higher photocatalytic activity than that of the undoped ZnO and TiO 2 samples. The films obtained from solutions with 50 mol% TiO 2 showed the fastest decoloration of the dye.

The process of laser ablation of an aluminum surface with copper bromide laser (511 nm) was inves... more The process of laser ablation of an aluminum surface with copper bromide laser (511 nm) was investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), with the laser fluence varying from 5.3 to 11.1 J/cm 2 and the laser beam scanning velocity from 20 to 100 mm/s. The experiments were done in two kinds of ambient atmosphere: air and argon. SEM analysis showed the porous structure of the laser treated surface and formation of micro-and nano-sized particles. The dimensions of the agglomerates formed were smaller in argon atmosphere. Upon irradiation in Ar atmosphere the aluminum nanoparticles were formed in a metal state and their surface was oxidized after exposure to O 2 in air. However, two mechanisms are possible in air, the first one being the same as under Ar and the second occurring direct in the plasma. The binding energies of the Al 2p (74.0 eV) and O 1s (531.4 eV) peaks and the O/Al ratio give information on the oxidation of the surface and presence of aluminum in Al 2 O 3 and AlOOH. The oxide layer was porous, which was evidenced by SEM.

Journal of Alloys and Compounds, 2010

Thin nanocrystalline TiO 2 -SnO 2 films (0-50 mol% SnO 2 ) are coated on quartz and stainless ste... more Thin nanocrystalline TiO 2 -SnO 2 films (0-50 mol% SnO 2 ) are coated on quartz and stainless steel substrates by spray pyrolysis method. The synthesized films are investigated by XRD, Raman spectroscopy and XPS.

Bulletin of Materials Science, 2012

Thin nanocrystalline TiO 2 -SnO 2 films (0-50 mol% SnO 2 ) were prepared on quartz and stainless ... more Thin nanocrystalline TiO 2 -SnO 2 films (0-50 mol% SnO 2 ) were prepared on quartz and stainless steel substrates by sol-gel coating method. The obtained films were investigated by XRD, Raman spectroscopy and XPS. The size of the nanocrystallites was determined by XRD-LB measurements. We ascertained that the increase of treatment temperature and concentration of SnO 2 in the films favour the crystallization of rutile phase. The substrate type influences more substantially the phase composition of the TiO 2 -SnO 2 films. It was established that a penetration of elements took place from the substrate into the films. TiO 2 films deposited on quartz substrate include a Si which stabilizes anatase phase up to 600 • C. The films which are deposited on stainless steel substrate and treated at 700 • C show the presence of significant quantity of rutile phase. This phenomenon could be explained by the combined effect of Sn dopant as well as Fe and Cr, which also are penetrated in the films from the steel substrate. The titania films doped up to 10 mol% SnO 2 on stainless steel possess only 12-17 nm anatase crystallites, whereas the TiO 2 -(10-50 mol%) SnO 2 films contain very fine grain rutile phase (4 nm).

The use of lasers in materials processing is an increasingly attractive choice for high technolog... more The use of lasers in materials processing is an increasingly attractive choice for high technology manufacturing. Factors influencing the laser ablation process include laser beam parameters, such as wavelength, energy or fluence and pulse length, the material properties of the target, such as melting temperature, thermal diffusion rate, optical reflectivity, and the ambient gas. We investigated the influence of laser treatment on titanium wafers with CuBr laser (λ=511nm) by scanning laser beam with distance between paths 20μ. The laser fluence varied from 4.7 J cm -2 to 13.5 J cm -2 and the laser beam scanning velocity from 25mm/s to 100mm/s with duration of 30 ns. The experiments were done in two kinds of ambient atmosphere: air and argon. The morphology of the irradiated surface was studied by scanning electron microscopy (SEM). SEM study showed that the laser irradiation caused a change in the surface morphology due to the processes of melting and subsequent resolidification as well as particle deposition from the vapor plume. The chemical state and composition of the irradiated titanium surface were determined using the Ti2p and O1s binding energy values and O/Ti intensity ratio. The XPS results indicated that on the irradiated titanium surface is formed oxide layer with stoichiometry close to TiO II. It was found that the ambient atmosphere is responsible for the change in the microstructure and chemical state of the titanium target.