Catalytic reactivity and surface chemical effects induced by the presence of water in the molecular system polyaniline(EB)–Pd–H2O were investigated. The polyaniline(EB) doped with palladium reveals its high activity and selectivity in the... more
Catalytic reactivity and surface chemical effects induced by the presence of water in the molecular system polyaniline(EB)–Pd–H2O were investigated. The polyaniline(EB) doped with palladium reveals its high activity and selectivity in the semihydrogenation: hexyne → hexenes (→ hexane). However, to demonstrate these effects, the specimen has to be submitted to a special treatment to lose most of its water. The
Research Interests:
Research Interests:
Research Interests: Materials Engineering, Civil Engineering, Materials Science, Electron Microscopy, Biomaterials, and 15 moreMedicine, Corrosion, Multidisciplinary, Phosphorus, Biocompatibility, Humans, Ion Implantation, Calcium Phosphate, Microstructures, Chemical Composition, Biocompatible Materials, Cell Survival, Electrochemical method, Bone and Bones, and Corrosion Resistance
The paper compares the effects of various surface modifications, ion implantation, alkaline treatment and anodic oxidation, upon the corrosion resistance and bioactivity of titanium. The chemical composition of the surface layers thus... more
The paper compares the effects of various surface modifications, ion implantation, alkaline treatment and anodic oxidation, upon the corrosion resistance and bioactivity of titanium. The chemical composition of the surface layers thus produced was determined by XPS, SIMS and EDS coupled with SEM. The structure of the layers was examined by TEM, and their phase composition by XRD. The corrosion resistance was determined by electrochemical methods after the samples were exposed to the test conditions for 13 h. The bioactivity of titanium was evaluated in a simulated body fluid at a temperature of 37 degrees C after various exposure time.
Research Interests: Engineering, Materials Science, Secondary Ion Mass Spectrometry, Scanning Electron Microscopy, Titanium, and 15 moreMedicine, Biological Sciences, Surface modification, Ion Implantation, CHEMICAL SCIENCES, Surface treatment, Surface Properties, Analytical and Bioanalytical Chemistry, Chemical Composition, Electrodes, Simulated Body Fluid, Hydrogen-Ion Concentration, Electrochemical method, Corrosion Resistance, and Anodic Oxidation
Double metal cyanide (DMC) catalysts are commonly applied at industrial ring-opening polymerization of the epoxides, being the initial stage of the polyurethanes manufacturing route. This group of catalysts is frequently used in industry,... more
Double metal cyanide (DMC) catalysts are commonly applied at industrial ring-opening polymerization of the epoxides, being the initial stage of the polyurethanes manufacturing route. This group of catalysts is frequently used in industry, but the knowledge on the molecular nature of their high activity and selectivity is limited to some phenomenological hypotheses based on overall chemical premises. To shine some light on the relation between structural and chemical properties of DMC catalysts and their activity, the complementary X-ray powder diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy and X-ray absorption spectroscopy studies were performed. The comprehensive characterization of DMC catalyst synthesized from ZnCl2 and potassium hexacyanocobaltate(III) solution, in presence of the organic ligand (tBuOH), confirmed that a significant part of the catalyst material reveals the features of the non-crystalline structure. Extended X-ray absorption fine structure (EXAFS) analysis established that only Zn atoms are the active metallic centers in the DMC catalyst. The coordination around Zn was changed from octahedral in reference material to tetrahedral in catalysts, and Cl atoms were detected near some of the Zn atoms, but no significant amount of oxygen atoms was detected, which agrees with XPS chemical analysis. The performed experimental studies give direct experimental evidence for the model deduced by Zhang et al., and for the calculation performed by Wojdel et al. Moreover, the generally accepted formula Zn3[Co(CN)6]2•xZnCl2•ytBuOH•zH2O describing this catalyst is not valid, because none of the compounds were detected by XRD or EXAFS techniques. Regarding the relation between structural and chemical activity of catalyst, we conclude that for the chemical activity of DMC catalyst not only is the content of Cl very important, but also the fraction of non-crystalline phase, the formation of which is stimulated by ligand. The non-crystalline fraction of catalyst may offer the easier access to the active center with Cl. Copyright © 2015 John Wiley & Sons, Ltd.
Research Interests:
This paper is concerned with the corrosion resistance and biocompatibility of titanium after surface modification by the ion implantation of calcium or phosphorus or calcium + phosphorus. Calcium and phosphorus ions were implanted in a... more
This paper is concerned with the corrosion resistance and biocompatibility of titanium after surface modification by the ion implantation of calcium or phosphorus or calcium + phosphorus. Calcium and phosphorus ions were implanted in a dose of 10(17) ions/cm(2). The ion beam energy was 25 keV. The microstructure of the implanted layers was examined by TEM. The chemical composition of the surface layers was determined by XPS and SIMS. The corrosion resistance was examined by electrochemical methods in a simulated body fluid (SBF) at a temperature of 37 degrees C. The biocompatibility was evaluated in vitro. As shown by TEM results, the surface layers formed during calcium, phosphorus and calcium + phosphorus implantation were amorphous. The results of the electrochemical examinations (Stern's method) indicate that the calcium, phosphorus and calcium + phosphorus implantation into the surface of titanium increases its corrosion resistance in stationary conditions after short- and ...
Research Interests:
Research Interests:
Research Interests: Materials Engineering, Biomedical Engineering, Mass Spectrometry, Secondary Ion Mass Spectrometry, Scanning Electron Microscopy, and 15 moreAtomic Force Microscopy, Corrosion, Cell line, Humans, Optical microscopy, Ion Implantation, Microstructures, Chemical Composition, Osteoblasts, Biocompatible Materials, Simulated Body Fluid, Body Fluids, Electrochemical method, Ions, and Corrosion Resistance
Research Interests:
Research Interests:
Research Interests: Condensed Matter Physics, Electromagnetic Radiation, Surface modification, Ultraviolet, Surface Morphology, and 11 moreSurface Structure, Spectrum, Scanning Electron Microscope, Microstructures, Soft X Ray, Penetration Depth, Polyethylene terephthalate, X Ray Photoelectron Spectroscopy, Extreme Ultraviolet, Chemical Modification, and Chemical Structure
The reduction of NO by CO was studied on gold catalysts supported on ceria-alumina, prepared by mechanochemical activation. The samples were characterized by means of XRD, TPR, XPS and Raman spectroscopy. The influence of water in the... more
The reduction of NO by CO was studied on gold catalysts supported on ceria-alumina, prepared by mechanochemical activation. The samples were characterized by means of XRD, TPR, XPS and Raman spectroscopy. The influence of water in the feed on the catalytic activity was evaluated as well. It was established that the addition of hydrogen and water improves NO reduction activity
Research Interests:
ABSTRACT Two series of Fe-doped (5, 10 and 20 wt% Fe2O3) ceria oxides were synthesized by mechanochemical mixing (MM) and impregnation (IM) methods. The Au catalysts (3 wt%) supported on these mixed oxides were tested in WGSR and PROX.... more
ABSTRACT Two series of Fe-doped (5, 10 and 20 wt% Fe2O3) ceria oxides were synthesized by mechanochemical mixing (MM) and impregnation (IM) methods. The Au catalysts (3 wt%) supported on these mixed oxides were tested in WGSR and PROX. Gold catalysts on supports prepared by IM exhibited WGS activity lower than that of gold on undoped ceria. Significantly better WGS performance was demonstrated over gold catalysts on supports synthesized by MM. The observed differences in the catalytic behavior were explained by the crucial role of the gold dispersion depending on the preparation method. The highest WGS activity of Au5FeCeMM catalyst was attributed to the cooperative catalytic work of Fe-modified ceria and magnetite with the highest extent of non-stoichiometricity. In contrast to WGSR, the catalytic behavior in PROX over gold catalysts on supports prepared by both methods did not differ significantly. Fe likely acted as a ceria modifier because no changes in Fe-phases and Fe valence state were observed upon reaction. The nanosized hematite particles covering the ceria grains in the case of the IM method could diminish the ceria basicity explaining the observed good and stable PROX performance over Au10FeCeIM catalyst in the presence of CO2 and water.
Research Interests:
This work presents the results of investigation of the properties of OT-4-0 titanium alloy surface layers subjected to carbon implantation. Polished samples were implanted with carbon doses of 5×1015, 1×1016, 1×1017, and 2×1017C+cm−2 at... more
This work presents the results of investigation of the properties of OT-4-0 titanium alloy surface layers subjected to carbon implantation. Polished samples were implanted with carbon doses of 5×1015, 1×1016, 1×1017, and 2×1017C+cm−2 at an energy of 100keV. The corrosion resistance was examined by the Stern and potentiodynamic methods in 0.9% NaCl solution at a temperature of 37°C. The composition
Research Interests:
Research Interests:
We report an efficient synthesis of Ag–In–S and Ag–In–Zn–S nanocrystals with strong photoluminescence (QY = 59%) in the visible to near-infrared range.
Research Interests:
Research Interests:
The effect of... more
The effect of "two-point" interactions of Zn(II) and Co(II) metalloporphyrins, bearing 15-crown-5 ether peripheral substituents, on their assembling in Langmuir and Langmuir-Blodgett (LB) films was investigated. That is, simultaneously, the central metal ion of the porphyrin was axially ligated by a nitrogen-containing ligand in the emerged part of the Langmuir film on one hand, and a suitably selected cation pertaining in the subphase solution was supramolecularly complexed by the crown ether moiety in the submerged part of the film on the other. The compression and polarity properties of the Langmuir films of the derivatized free-base 5,10,15-triphenyl-20-(benzo-15-crown-5)porphyrin, H2(TPMCP), and the corresponding cobalt(II) and zinc(II) metalloporphyrins, denoted as Co(TPMCP) and Zn(TPCMP), respectively, as well as inclusion complexes of the metalloporphyrins with selected cations were investigated. For the axial ligation of Zn(II) and Co(II), pyrazine (pyz) and 4,4'-bipyridnine (bpy) aromatic as well as piperazine (ppz) and 1,4-diazabicyclo[2.2.2]octane (DABCO) cyclic heteroaliphatic ligands were selected. The films were formed on the water subphase solution in the absence and presence of LiCl, NaCl, or NH4Cl. The Langmuir films were built of monolayer J-type aggregates of tilted porphyrin macrocycles. The porphyrins formed rather labile complexes with the cations in the subphase. Nevertheless, the XPS analysis revealed that these cations were LB transferred together with the porphyrins onto solid substrates. In the Co(TPMCP) Langmuir films formed on the water subphases, Co(II) was complexed by aromatic but not cyclic heteroaliphatic ligands, while, in these films formed on the NaCl subphase solutions, the metalloporphyrin was also complexed by DABCO. In Langmuir films spread on alkaline subphase solutions, both aromatic and heteroaliphatic ligands formed complexes with Co(TPMCP) of different stoichiometries. The X-ray reflectivity and GIXD measurements performed on selected LB films revealed some structure-building effects of the axial ligation.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
ABSTRACT This paper is concerned with the surface modification of titanium by the PEO method (plasma electrolytic oxidation) in the solutions which contain Ca P Si and Na The chemical composition of the thus formed surface layers was... more
ABSTRACT This paper is concerned with the surface modification of titanium by the PEO method (plasma electrolytic oxidation) in the solutions which contain Ca P Si and Na The chemical composition of the thus formed surface layers was examined by XPS and EDS The morphology of the surface was observed by SEM The phase composition was determined by X-ray diffraction (XRD) The adhesive strength of the oxide layers was evaluated by the scratch-test The corrosion resistance was determined in a simulated body fluid (SBF) at a temperature of 37 C by electrochemical methods for various exposure times The oxide layers obtained were porous and enriched with Ca P Si and Na and their properties depended on the electrolyte solution and the parameters of the oxidation process The results of the electrochemical examinations show that the surface modification by PEO does not worsen the corrosion resistance of titanium after a 13 h exposure in SBF The electrochemical impedance spectroscopy (EIS) results indicate that the surface layers have a complex structure and that their electric properties undergo changes during long term exposures in SBF (C) 2010 Elsevier B V All rights reserved
Research Interests: Materials Engineering, Condensed Matter Physics, Titanium, Surface Coatings, Electrochemical Impedance Spectroscopy, and 9 moreSurface modification, Surface and Coatings Technology, X ray diffraction, Electrical Properties, Chemical Composition, Complex Structure, Simulated Body Fluid, Electrochemical method, and Corrosion Resistance
ABSTRACT