Serguei Belochapkine - Academia.edu (original) (raw)

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Papers by Serguei Belochapkine

Journal of Applied Physics, 2013

ABSTRACT Here, we present an implementation of the moving Preisach model to describe the magnetic... more ABSTRACT Here, we present an implementation of the moving Preisach model to describe the magnetic behaviour of Sm-Co films. We use two independent Preisach distributions to separate the magnetization into reversible and irreversible components. The numerical simulation works very well for a system where two magnetic phases are weakly or negligibility coupled. We tested our implementation on nanocrystalline Sm-Co films prepared by sputtering and having composition around Sm25Co75. We found that the Sm25Co75 film has a soft and hard phase and quantified their contributions to the total magnetization. Using the moving Preisach model, we characterized the properties of the hard phase, which has a coercivity of 1.26 T and contribution of 74% to the total magnetization. The soft magnetic phase contributes 26% to the total magnetization and has a coercivity of 0.056 T.

Materials and Corrosion, Apr 1, 2009

This paper describes a transmission electron microscopy (TEM) investigation of copper coupons exp... more This paper describes a transmission electron microscopy (TEM) investigation of copper coupons exposed to a corrosive mixed flowing gas environment (MFG). A focused ion beam (FIB) liftout technique was used to extract electron transparent specimens for TEM investigation. A duplex corrosion film comprising cuprite (Cu 2 O) and chalcocite (Cu 2 S) developed on the copper substrate.

Materials at High Temperatures, 2012

Abstract: The effect of room-temperature (∼ 20 C) air-oxidation on void formation in sputter-depo... more Abstract: The effect of room-temperature (∼ 20 C) air-oxidation on void formation in sputter-deposited thin films of aluminum and its alloys was investigated using a transmission electron microscope. It was found that after air-oxidation, only lithium-bearing aluminum alloy films exhibited a high (∼ 4× 10 16 cm-3) density of small (∼ 2 nm) voids, whereas pure aluminum or lithium-free aluminum alloy films did not contain any voids. In lithium-bearing aluminum alloy films, both aluminum and lithium atoms migrate to the surfaces to ...

Materials and Corrosion, 2009

Langmuir, 2012

The high surface areas of nanostructured electrodes can provide for significantly enhanced surfac... more The high surface areas of nanostructured electrodes can provide for significantly enhanced surface loadings of electroactive materials. The fabrication and characterization of nanoporous gold (np-Au) substrates as electrodes for bioelectrochemical applications is described. Robust np-Au electrodes were prepared by sputtering a goldÀsilver alloy onto a glass support and subsequent dealloying of the silver component. Alloy layers were prepared with either a uniform or nonuniform distribution of silver and, post dealloying, showed clear differences in morphology on characterization with scanning electron microscopy. Redox reactions under kinetic control, in particular measurement of the charge required to strip a gold oxide layer, provided the most accurate measurements of the total electrochemically addressable electrode surface area, A real . Values of A real up to 28 times that of the geometric electrode surface area, A geo , were obtained. For diffusion-controlled reactions, overlapping diffusion zones between adjacent nanopores established limiting semi-infinite linear diffusion fields where the maximum current density was dependent on A geo . The importance of measuring the surface area available for the immobilization was determined using the redox protein, cyt c. The area accessible to modification by a biological macromolecule, A macro , such as cyt c was reduced by up to 40% compared to A real , demonstrating that the confines of some nanopores were inaccessible to large macromolecules due to steric hindrances. Preliminary studies on the preparation of np-Au electrodes modified with osmium redox polymer hydrogels and Myrothecium verrucaria bilirubin oxidase (MvBOD) as a biocathode were performed; current densities of 500 μA cm À2 were obtained in unstirred solutions.

Functional Materials Letters, 2012

ABSTRACT

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2009

Platinum nanoparticles of less than 5 nm size have been synthesized by the reduction of H 2 PtCl ... more Platinum nanoparticles of less than 5 nm size have been synthesized by the reduction of H 2 PtCl 6 using sodium borohydride in water-in-oil (w/o) microemulsions of water/TritonX-100/cyclohexene/1-hexanol at 25 ± 2 • C. Size and shape of the particles are determined through HRTEM images.

Catalysis Today, 2005

A coating technique based on the deposition–precipitation of aluminium hydroxide from supersatura... more A coating technique based on the deposition–precipitation of aluminium hydroxide from supersaturated aluminate solutions was applied to the preparation of catalyst supports for application in a glass microreactor. The porous alumina layer obtained after calcination of the deposited hydroxide was characterised by BET, SEM and XRD techniques. Pt/Al2O3 catalysts were prepared using the deposited porous alumina as support. The microreactor

Catalysis Today, 2003

A modified robotic workstation has been developed which is able to reproduce a conventional catal... more A modified robotic workstation has been developed which is able to reproduce a conventional catalyst preparation method used routinely in our laboratory, thereby increasing significantly the number of catalysts that can be prepared at once. This paper describes some of the features of this modified system and outlines some of the difficulties encountered in transferring from manual to automatic operation. Some catalytic test results are given for the selective oxidation of propane over a catalyst consisting of Mo-V-Nb-W oxides supported on alumina which illustrate good reproducibility of data for samples prepared with the robotic system and a close similarity with data obtained with equivalent manually prepared materials.

Meeting Abstracts, Sep 28, 2007

This paper describes a Transmission Electron Microscopy (TEM) investigation on the surface of cop... more This paper describes a Transmission Electron Microscopy (TEM) investigation on the surface of copper coupons exposed to a Class III Mixed Flowing Gas environment (MFG) following the guidelines given by Battelle and IEC for environmental testing1-6. A Focused ion beam (FIB) lift-out technique utilising a 30 kV Ga+ ion beam was used to extract electron transparent specimens with nanometer scale precision. Using this procedure, the thin corrosion film in the samples (exposed at different time intervals) were studied. The nature ...

Applied Catalysis B: Environmental, 2012

Nanostructured ceria-alumina mixed oxides containing different concentrations of ceria (10 and 30... more Nanostructured ceria-alumina mixed oxides containing different concentrations of ceria (10 and 30 wt.%) were prepared by the sol-gel method using organo-metallic precursors of alumina and ceria. The size of alumina and ceria particles in the prepared Ce-Al-O mixed oxides was smaller than that of pure alumina or ceria. The gold catalysts (3 wt.% Au) supported on ceria-alumina mixed oxides by deposition-precipitation (DP) using HAuCl 4 and urea were characterized by several techniques: TEM, XPS and UV-vis spectroscopy, and temperature programmed reduction/oxidation (TPR/TPO). The catalytic activity of prepared Au/CeO 2 -Al 2 O 3 catalysts in CO oxidation was higher than that of Au/Al 2 O 3 and Au/CeO 2 catalysts. Nanostructured ceria incorporated into an alumina matrix has been found quite effective for gold species activation in CO oxidation. In fact, transient analysis of CO oxidation provided an estimate of the relative content of (Au-ceria vacancy) active sites in catalysts. Obtained values are in good agreement with the order of activity for tested samples and gold dispersion according to EXAFS data.

Journal of Catalysis, 2012

Aerobic selective oxidation of the naturally occurring lignan hydroxymatairesinol (HMR) to anothe... more Aerobic selective oxidation of the naturally occurring lignan hydroxymatairesinol (HMR) to another lignan oxomatairesinol (oxoMAT) was carried out at 70°C and atmospheric pressure over different gold and gold-palladium catalysts. Several groups of gold catalysts were prepared: Au ion-exchanged on Y-zeolites promoted by Cu, Ni, Fe; Au and Au-Pd supported via deposition-precipitation with urea -DPU on metal oxides (magnesia, alumina, ceria, zirconia, and lanthanum oxide); and Au on alumina, and alumina-ceria-zirconia mixed oxides prepared by the sol-gel method. The catalysts were characterized by ICP-AES, TEM, XPS and UV-Vis techniques. Acidity of supports was studied by an FTIR method using pyridine as a probe molecule. No catalytic activity was detected in case of gold catalysts based on zeolites. Au and Au-Pd catalysts supported on metal oxides showed different activity and selectivity in the HMR transformation depending on the support acidity/basicity and the active phase. The highest activity was reached over Au supported on alumina with big transport pores displaying 100% selectivity to oxoMAT.