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

Papers by M. Shipochka

Study of diamond – Like carbon coatings for biomedical applications produced by electron-beam physical vapor deposition

PROCEEDINGS OF THE 11TH INTERNATIONAL ADVANCES IN APPLIED PHYSICS AND MATERIALS SCIENCE CONGRESS & EXHIBITION

Coatings

This study aimed to present the differences in the corrosion properties and protective ability of... more This study aimed to present the differences in the corrosion properties and protective ability of two bi-layer systems obtained on low-carbon steel in a model corrosive medium of 5% NaCl solution. These newly developed systems consist of Zn-Co (3 wt.%) or Zn-Ni (10 wt.%) alloy coatings as under-layers and a very thin TiO2 sol-gel film as a top-layer. Scanning electron microscopy (SEM) is used for characterization of the surface morphology of the samples indicating that some quantitative differences appear as a result of the different composition of both zinc alloys. Surface topography is investigated by means of atomic force microscopy (AFM), and the hydrophobic properties are studied by contact angle (CA) measurements. These investigations demonstrate that both sample types possess grain nanometric surface morphology and that the contact angle decreases very slightly. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are used for characterization of the chemical co...

High intensity orange-red emission of chemically deposited Sm3+-doped ZrO2 thin films - Beneficial effects of host and dopant

Journal of Materials Research and Technology

Preparation of supported copper catalyst by spray pyrolysis of copper acetate on HEU zeolite

Comptes Rendus De L Academie Bulgare Des Sciences, 2012

Enhanced effect of combination of new hybrid TiO2 phase and phosphorus dopant on the physicochemical properties and UV/Visible light photocatalytic activity

Materials Characterization, 2021

Abstract The presence of triple phase TiO2 new mixture (Magneli of higher order homologous series... more Abstract The presence of triple phase TiO2 new mixture (Magneli of higher order homologous series, brookite and anatase) containing P dopant ensures positive changes in the structure, in the phase composition and in the chemical composition. These changes explained the reasons for the enhanced UV/Vis photocatalytic efficiency towards oxidative degradation of ethylene and acetylsalycylic acid. The samples were characterized by a set of methods: Raman spectroscopy, Scanning Electron Microscopy (SEM), Diffuse-Reflectance Spectroscopy (DRS), Differential Thermal Analysis (DTA-TG), X-ray Photolelectron Spectroscopy (XPS), Transmission Electron Microscopy and High-Resolution Transmission Electron Microscopy (TEM/HRTEM), Electron Paramagnetic resonance (EPR) and X-ray Diffraction (XRD) analyses. The combination of the optimal set of values of Ti3+, oxygen radicals and vacancies, Ti-O-P bonds, narrower band gap is responsible for the higher quantum yield due to the increased number of charge carriers, while the unique phase mixture prevents the recombination of charge carriers. These factors guarantee enhanced rate of the photocatalytic reaction, and extended response to the visible light region.

Nanosized Zn2SnO4 powders synthesized by coprecipitation and consecutive hydrothermal treatment i... more Nanosized Zn2SnO4 powders synthesized by coprecipitation and consecutive hydrothermal treatment in two different alkaline media V. Blaskov*, I Stambolova, L. Dimitrov, M. Shipochka, D. Stoyanova, A. Eliyas 1) Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev, bl. 11, Sofia 1113, Bulgaria 2) Institute of Mineralogy and Crystallography “Acad. Ivan Kostov”, Bulgarian Academy of Sciences, Acad. G. Bonchev, bl. 107, Sofia 1113, Bulgaria 3Institute of Catalysis, Bulgarian Academy of Sciences, Acad. G. Bonchev, bl. 11, Sofia 1113, Bulgaria

Silver loaded zeolite was obtained by the spray pyrolysis method. The material was characterized ... more Silver loaded zeolite was obtained by the spray pyrolysis method. The material was characterized by DC arc atomic emission spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), IR spectroscopy and scanning electron microscopy (SEM). The concentration of Ag in the final samples, calculated from the XPS spectra, corresponds to that in the precursor solution. The SEM photographs reveal both separate silver particles and agglomerates located on the zeolite surface and inside the channels.

Photocatalytic Performance of Phosphorus Doped Titanium Dioxide Nanomaterials for Degradation of Reactive Black 5 Azo Dye

1 Institute of Catalysis, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bldg. 11, 1113 Sof... more 1 Institute of Catalysis, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bldg. 11, 1113 Sofia, Bulgaria 2 Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bldg. 11, 1113 Sofia, Bulgaria 3 Acad. I. Kostov Institute of Mineralogy and Crystallography, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bldg. 107, 1113 Sofia, Bulgaria 4 Institute of Electrochemistry and Energy Systems, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bldg. 10, 1113 Sofia, Bulgaria

Zirconium dioxide-titanium dioxide coatings were obtained by sol-gel method on stainless steel pl... more Zirconium dioxide-titanium dioxide coatings were obtained by sol-gel method on stainless steel plates. The samples were treated at three Zirconium dioxide-titanium dioxide coatings were obtained by sol-gel method on stainless steel plates. The samples were treated at three temperatures 300, 400 and 500oC. The morphology and chemical surface composition were examined by Scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), while the phase composition was examined by X-ray diffraction analyses (XRD). The corrosion resistance was evaluated by weight loss measurements in NaCl medium. The coatings are possess relatively smooth surface with some microcracks. After corrosion test the coatings treated at 500oC, keep their surface structure without visible signs of corrosion and thecorrosion tests revealed zero mass loss. The good protective properties of these coatings could be attributed to (i) amorphous structure, leading to deterior...

Coatings, 2021

Enhanced corrosion efficiency of low-carbon steel was achieved by newly developed hybrid multilay... more Enhanced corrosion efficiency of low-carbon steel was achieved by newly developed hybrid multilayers, composed of low-carbon steel coated with an electrodeposited zinc sublayer (1 µm), a chitosan (CS) middle layer and ZrO2 coating by the sol–gel method (top-layer). The middle chitosan layer was obtained by dipping galvanized steel substrate in 3% tartatic acid water solution of medium molecular-weight chitosan, composed of β-(1–4)-linked D-glucosamine and N-acetyl-D-glucosamine with a deacetylation degree of about 75–85% (CS). The substrates were dipped into CS solution and withdrawn at a rate of 30 mm/min. One part of the samples with the CS layer was dried at room temperature for 2 weeks, and another part at 100 °C for 1 h, respectively. After CS deposition treatment, the substrates were dipped into an isopropanol sol of zirconium butoxide with small quantity of polyethylene glycol (PEG400). The dipping-drying cycles of the ZrO2 coatings were repeated three times. After the third ...

Proceedings of 2nd International Online-Conference on Nanomaterials, 2020

Improved corrosion protection of low carbon steel was achieved by barrier non-toxic sol gel multi... more Improved corrosion protection of low carbon steel was achieved by barrier non-toxic sol gel multilayered structures, composed by ZrO2 top coating and TiO2 underlayers. Zirconium precursor solution was maintained constant, whereas, the TiO2 solution composition was modified with two different types of polymers, which were added separately to the starting titanium solution. The phase composition, morphology and corrosion protective properties were analyzed by X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Hydrophobicity properties were evaluated by the measuring of the contact angle with Ramé-Hart automated goniometer. Potentiodynamic polarization technique was used to determine the corrosion resistance and protective ability of the coatings in a 5% NaCl solution. Both polymeric modifications as compared to the non-modified titania layer demonstrated positive effect on the corrosion properties of the structures at conditions of external polarization. Due to amorphous structure of zirconia layer with relatively dense, hydrophobic surface of all of the samples extend the service life of low carbon steel in model corrosion medium. The feasibility of the sol gel deposition method makes possible to prepare oxide coatings with appropriate surface properties, which ensures high corrosion resistance.

Synthesis, characterization and activity of Pd/CaWO4 catalyst in the complete oxidation of C1–C6 alkanes and toluene

Reaction Kinetics, Mechanisms and Catalysis, 2021

CaWO4 nanoparticles were successfully obtained by direct mechanochemical synthesis. In the search... more CaWO4 nanoparticles were successfully obtained by direct mechanochemical synthesis. In the search of new and advanced catalysts, the CaWO4 has been modified by Pd and characterized by various techniques such as: N2-physisorption, XRD, IR, TEM, XPS, TPR and TPD. The results from the instrumental methods confirmed that CaWO4 can be formed at room temperature in the course of 5 h milling time period. The XPS and TEM analysis reveal that the palladium is homogeneously dispersed and it is present on the surface of the Pd/CaWO4 in three oxidation states: Pd0, Pd2+ and Pd4+.The properties of the obtained material were investigated by the reactions of complete catalytic oxidation of different alkanes and toluene. The characterization data after test for 96 h showed no significant difference in average particle sizes of Pd-crystallites and the phase composition, which can be considered as an evidence for the significant stability of the obtained material. Therefore the Pd/CaWO4 can be considered as perspective material for use as an active phase in preparation of environmental catalysts.

Phase Composition and Structure of TiO2 Powders: Effect of Phosphorus Dopant

Journal of Alloys and Compounds, 2019

The present work provides new insight into the long-term cycling stability of biomass-derived act... more The present work provides new insight into the long-term cycling stability of biomass-derived activated carbons as electrodes in symmetric supercapacitors on the basis of ex-situ and post-mortem spectroscopic and microscopic analyses. The physicochemical characterization of activated carbons is carried out by DTA/TG, XPS spectroscopy, SEM, AFM and BET analyses. The surface functional groups and pore size distribution are determined by Böhm titration method and Barett-Joyner-Halenda analysis, respectively. The supercapacitor performance of the composite electrodes is tested by charge/discharge galvanostatic experiments. To go inside into surface and bulk electrode changes during electrode cycling, the post-mortem XPS, SEM/EDS and AFM experiments are undertaken. It is found that activated carbon having higher content of acidic groups and narrow pore size distribution displays an impressive cycling stability in alkaline electrolyte solution. The observed changes in electrode morphology during cycling are discussed on the basis of electrode-electrolyte interaction.

Chemical Engineering Journal, 2019

New and complex results on catalytic activity, thermal stability, effect of H 2 O and SO 2 on the... more New and complex results on catalytic activity, thermal stability, effect of H 2 O and SO 2 on the Pd/La 2 O 3 -CeO 2 -Al 2 O 3 model system in methane combustion have been obtained. The catalyst characterization has been made by N 2 -physisorption, XRD, SEM/EDX, HRTEM, XPS, TPD, TPR and FTIR methods. The observed high activity is related to the stabilization of highly dispersed Pd 4+ species, strongly interacting with the support. As it was expected, La 2 O 3 prevented the sintering of the gamma-alumina carrier, in addition it probably contributed to avoid further agglomeration of the palladium species by the formation of La 2 PdO 4 mixed phase. It is supposed that the most probable reason for the observed decrease in activity in the presence of water vapor of thermally aged sample is the increase in PdO/Pdratio above its optimum. The presence of both H 2 O and SO 2 in the gas leads to formation of surface Al 2 (SO 4 ) 3 , thus indicating a limited possibility to regenerate completely the catalyst. The reaction pathway over Pd/La 2 O 3 -CeO 2 -Al 2 O 3 catalysts proceeds most probably through Mars-van Krevelen mechanism upon adsorption of water molecules on both oxidized and reduced sites and slow desorption of reaction products. For practical evaluation of the

Ultraviolet laser treatment of titanium surface

Journal of Physics: Conference Series, 2016

Interaction of a third harmonic of DPSS laser, wavelength 355 nm and pulse duration of 30 ns with... more Interaction of a third harmonic of DPSS laser, wavelength 355 nm and pulse duration of 30 ns with titanium wafers was studied. It was investigated the structure of laser ablated titanium surface, depending on the laser beam scanning speed, and laser pulse frequency. The titanium surface modification was studied by scanning electron microscopy (SEM) and XPS (X- ray Photoelectron Spectroscopy). Nanosecond irradiation with ultraviolet light of Ti plate led to the formation of high porous granular structures consisting of agglomerated micro- and submicro- particles.

Materials Science and Engineering: B, 2006

Influence of titanium precursor on the photocatalytic properties of TiO 2 sprayed films under visible light

Journal of Physics: Conference Series, 2012

ABSTRACT Thin nano-sized TiO2 films were deposited on aluminum foil substrates by the spray pyrol... more ABSTRACT Thin nano-sized TiO2 films were deposited on aluminum foil substrates by the spray pyrolysis method, using Ti(i-OPr)4 (TIP) and TiCl4 (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°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 Ti3+ and Ti4+ oxidation states. After treatment at 400°C the Ti2p peak displays only Ti4+ 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 TiO2. The TOC measurements showed minimal concentration of total organic carbon in the dye solution after 180 min of visible light irradiation.

CuBr laser treatment of titanium wafers

ABSTRACT The use of lasers in materials processing is an increasingly attractive choice for high ... more ABSTRACT 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 (lambda=511nm) by scanning laser beam with distance between paths 20mu. 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 TiO2. It was found that the ambient atmosphere is responsible for the change in the microstructure and chemical state of the titanium target.