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Gavrilovic A.,CEST Center Of Electrochemical Surface Technology | Rafailovic L.D.,CEST Center Of Electrochemical Surface Technology | Artner W.,CEST Center Of Electrochemical Surface Technology | Wosik J.,CEST Center Of Electrochemical Surface Technology | Whitehead A.H.,CEST Center Of Electrochemical Surface Technology
Corrosion Science | Year: 2011

The potentiodynamic polarization curves in 0.5M NaCl solution before and after crystallization of Fe73.5Cu1Nb3Si15.5B7 alloy have been studied in relation to the microstructure and alloy composition. It was shown that the corrosion resistance of the alloy strongly depending on these two factors. The observed decrease in corrosion resistance of the alloy after the heat treatment up to 480°C in comparison to the corrosion resistance of the alloy in the as prepared state is attributed to the increased inhomogeneity of the alloy that coincides with the first appearance of Fe3Si phase. Further heating (up to 600°C) resulted in an increase in the number of Fe3Si nanocrystallites and the appearance of a FeCu4 phase. After annealing at 600°C the lowest corrosion rate, 0.004mma-1, was observed. Annealing of the samples at higher temperatures (>600°C) induced formation of six crystalline phases which proved detrimental to the corrosion resistance of the Fe73.5Cu1Nb3Si15.5B7 alloy. Solid corrosion products were identified on the surface of the samples after anodic polarization. © 2011 Elsevier Ltd.


Walkner S.,CEST Center Of Electrochemical Surface Technology | Hassel A.W.,CEST Center Of Electrochemical Surface Technology | Hassel A.W.,Johannes Kepler University
Electrochimica Acta | Year: 2014

Two different zinc coatings of composition ZnMg2Al2 (Zn + 2 wt.% Mg + 2 wt.% Al) and ZnAl53 (Zn + 53 wt.% Al) were investigated in aqueous solution at pH 12.0 with a novel setup, the so-called impedance titrator. This device is able to perform electrochemical measurements including, but not limited to, impedance spectroscopy in dependency of different pH-values. The setup allows holding the pH-value with a precision of at least 0.05 by dosing the required amount of titrating agent to the system. If the alkaline pH region is investigated, hydroxide ions are consumed in the course of passive layer formation. The amount of consumed hydroxide allows to quantitatively follow the formation of the hydroxide film and its thickness. Cross section SEM shows an excellent agreement of 13 μm after 7 h for ZnMg2Al2. At a constant pH value, the hydroxide concentration is constant and film formation is well defined and kinetically characterised. The consumption of hydroxide by the ZnAl53 coating is higher resulting from the solubility of the Al as aluminate under alkaline conditions. The composition of the precipitates contains less than 3 wt.% of Al. The observed processes and the formation of corrosion products are recorded and differences in the behaviour of the two coatings are discussed. © 2014 Elsevier Ltd. All rights reserved.


Wiesinger R.,Austrian Academy of Fine Arts | Martina I.,Austrian Academy of Fine Arts | Kleber C.,Austrian Academy of Fine Arts | Kleber C.,CEST Center Of Electrochemical Surface Technology | And 2 more authors.
Corrosion Science | Year: 2013

The interaction of highly pure polycrystalline silver samples with ozone (500ppb) was investigated under certain relative humidity (RH) content (0%, 50% and 90%) in synthetic air. All experiments were performed at room temperature (22°C) and atmospheric pressure. Highly surface sensitive methods were used to investigate chemical, morphological and structural changes and composition of the corrosion products formed at different RH and reaction times. Silver is oxidized by ozone forming Ag2O/AgO(AgIAgIIIO2) surface species. The oxide formation and corrosion rate is dependent on the RH content in the atmosphere, showing that silver is most susceptible to ozone oxidation at 50% RH. © 2013 Elsevier Ltd.


Nedelkovski V.,AIT Austrian Institute of Technology | Schwaighofer A.,AIT Austrian Institute of Technology | Wraight C.A.,Urbana University | Nowak C.,AIT Austrian Institute of Technology | And 2 more authors.
Journal of Physical Chemistry C | Year: 2013

Surface-enhanced IR absorption spectroscopy (SEIRAS) in the ATR configuration has been performed on reaction centers (RCs) from R. sphaeroides. Surface-enhancement is achieved by a thin, structured gold film present on the surface of an ATR crystal. Purified RCs are immobilized as a monolayer on top of the gold film via a poly his-tag engineered to the C-terminal end of the M subunit. Subsequently, the RCs are reconstituted into a lipid bilayer by in situ dialysis. Light-minus-dark absorbance spectra were recorded under continuous illumination using the spectrum in the dark as the reference. A number of strong bands have been observed indicating the excitation of the special pair as well as alterations of quinone/quinol species. Spectra were recorded at different time intervals with and without liposoluble Q10 coreconstituted into the lipid phase. A steady (photostationary) state was approached slowly and bands were found to increase or decrease reversibly on illumination and relaxation. Tentative assignments were made for some bands, based on previous FTIR measurements. The long time scale of these processes was tentatively explained in terms of interprotein reactions of RC molecules. © 2013 American Chemical Society.


Babushkina O.B.,CEST Center Of Electrochemical Surface Technology | Ekres S.,CEST Center Of Electrochemical Surface Technology
Electrochimica Acta | Year: 2010

FTIR spectroscopy was used to identify the oxochloride species of tantalum(V) in ionic liquids and to confirm the correlations between their presence in electrolytes and the changes in the route of electrochemical reduction of tantalum(V). Electrochemical behaviour of the mixtures (x)1-butyl-1-methyl-pyrrolidinium chloride-(1 - x)TaCl5 at x = 0.80, 0.65, and 0.40 was investigated over the temperature range 90-160 °C with respect to the electrochemical deposition of tantalum and was discussed in terms of spectroscopic data. The mechanism of electrochemical reduction of tantalum(V) in the basic and acidic electrolytes depends strongly on the structure and composition of the electro active species of tantalum(V) defined by the molar composition of ionic liquids and on the competition between tantalum(V) chloride and oxochloride species. In the basic mixture at x = 0.80, with octahedral [TaCl6]- ions as the electrochemically active species only the first reduction step Ta5+ → Ta 4+ at -0.31 V was observed. The competitive reduction of tantalum(V) oxochloride species occurs at more anodic potential (-0.01 V) than the reduction of the chloride complexes and can restrict the further reduction of tantalum(IV). In the basic ionic liquid at x = 0.65, the cyclic voltammograms exhibit reduction peaks at -0.31 V and -0.51 V attributed to the diffusion controlled process as [TaCl6]- + e- → [TaCl6]2- and [TaCl6]2- + e - → [TaCl6]3-. The further irreversible reduction of tantalum(III) to metallic state may occur at -2.1 V. In the acidic ionic liquids, at x = 0.40 the electrochemical reduction of two species occurs, TaCl6- and Ta2Cl11- and it is limited by two electron transfer for both of them at -0.3 V and -1.5 V, respectively. © 2010 Elsevier Ltd. All rights reserved.


Montealegre Melendez I.,ARC Seibersdorf Research | Neubauer E.,ARC Seibersdorf Research | Angerer P.,CEST Center Of Electrochemical Surface Technology | Danninger H.,Vienna University of Technology | Torralba J.M.,Charles III University of Madrid
Composites Science and Technology | Year: 2011

The goal of this work is the evaluation of nanoscaled reinforcements; in particular nanodiamonds (NDs) and carbon nanotubes (CNTs) on properties of titanium matrix composites (TiMMCs). By using nano sized materials as reinforcement in TiMMCs, superior mechanical and physical properties can be expected. Additionally, titanium powder metallurgy (P/M) offers the possibility of changing the reinforcement content in the matrix within a very wide range. In this work, TiMMCs have been produced from titanium powder (Grade 4). The manufacturing of the composites was done by hot pressing, followed by the characterisation of the TiMMCs. The Archimedes density, hardness and oxygen content of the specimens in addition to the mechanical properties were compared and reported in this work. Moreover, XRD analysis and SEM observations revealed in situ formed titanium carbide (TiC) phase after hot pressing in TiMMCs reinforced with NDs and CNTs, at 900 °C and 1100 °C respectively. The strengthening effect of NDs was more significant since its distribution was more homogeneous in the matrix. © 2011 Elsevier Ltd.


Reiner-Rozman C.,CEST Center Of Electrochemical Surface Technology | Larisika M.,AIT Austrian Institute of Technology | Nowak C.,AIT Austrian Institute of Technology | Nowak C.,CEST Center Of Electrochemical Surface Technology | Knoll W.,AIT Austrian Institute of Technology
Biosensors and Bioelectronics | Year: 2015

We present an experimental and theoretical characterization for reduced Graphene-Oxide (rGO) based FETs used for biosensing applications. The presented approach shows a complete result analysis and theoretically predictable electrical properties. The formulation was tested for the analysis of the device performance in the liquid gate mode of operation with variation of the ionic strength and pH-values of the electrolytes in contact with the FET. The dependence on the Debye length was confirmed experimentally and theoretically, utilizing the Debye length as a working parameter and thus defining the limits of applicability for the presented rGO-FETs. Furthermore, the FETs were tested for the sensing of biomolecules (bovine serum albumin (BSA) as reference) binding to gate-immobilized anti-BSA antibodies and analyzed using the Langmuir binding theory for the description of the equilibrium surface coverage as a function of the bulk (analyte) concentration. The obtained binding coefficients for BSA are found to be same as in results from literature, hence confirming the applicability of the devices. The FETs used in the experiments were fabricated using wet-chemically synthesized graphene, displaying high electron and hole mobility (μ) and provide the strong sensitivity also for low potential changes (by change of pH, ion concentration, or molecule adsorption). The binding coefficient for BSA-anti-BSA interaction shows a behavior corresponding to the Langmuir adsorption theory with a Limit of Detection (LOD) in the picomolar concentration range. The presented approach shows high reproducibility and sensitivity and a good agreement of the experimental results with the calculated data. © 2015 Elsevier B.V.


Babushkina O.B.,CEST Center Of Electrochemical Surface Technology | Lomako E.O.,CEST Center Of Electrochemical Surface Technology | Freyland W.,Karlsruhe Institute of Technology
Electrochimica Acta | Year: 2012

The electrochemical behaviour of basic and acidic ionic liquids (x)1-butyl-1-methyl-pyrrolidinium chloride-(1 - x)NbCl 5 at x = 0.80, 0.60, and 0.40 was investigated over the temperature range 90-160 °C in respect to the electrochemical deposition of niobium. This is discussed in connection with in situ Raman spectroscopic data. The mechanism of electrochemical reduction of niobium (V) depends strongly on the structure and composition of the electrochemical active species of niobium (V) defined by the molar composition of the ionic liquids. In basic mixtures at x = 0.80, the self-reduction of Nb(V) → Nb(IV) was confirmed by Raman spectroscopy and [NbCl 6] 2- (75%) and [NbCl 6] - (25%) octahedral complexes are the electrochemical active species at 140 °C. At x = 0.60, the dominant species are NbCl 6 - octahedra. In acidic ionic liquids at x = 0.40, the electrochemical reduction of two species occurs, NbCl 6 - and Nb 2Cl 11 -, and it is limited by one electron transfer for NbCl 6 - at -0.45 V and by two electrons transfer for Nb 2Cl 11 - at -1.12 V and -1.27 V, respectively. In basic melts the electrodeposition of metallic niobium is presumably possible at potentials negative of - 2.1 V versus Pt-quasi reference at a temperature of 140 °C. © 2011 Elsevier Ltd.


Neubauer E.,RHP Technology GmbH and Co. KG | Neubauer E.,AIT Austrian Institute of Technology | Kitzmantel M.,RHP Technology GmbH and Co. KG | Kitzmantel M.,AIT Austrian Institute of Technology | And 2 more authors.
Composites Science and Technology | Year: 2010

With a continuous improvement of the production techniques for carbon nanofibers and carbon nanotubes along with an improvement of the available qualities of the materials, these reinforcements have been introduced into polymers, ceramics and metals. While in the field of polymers first success stories have been published on carbon nanofiller reinforcements, up to now metals containing these types of nanofillers are still a topic of intensive research. Basically a similar situation were found in those days, when micron sized carbon fibers came on the market. Today many applications of carbon fiber reinforced composites are existing, while metals reinforced with conventional carbon fibers are still only found in niche applications.Several reasons can be identified, why the introduction of carbon based nanofillers (nanofibers/nanotubes) into metallic matrices is a difficult task. Nevertheless it is worthwhile to carry out systematic studies in this field due to the excellent and promising thermal, electrical, mechanical or tribological properties of the nanofillers.This paper gives an overview and summarises the activities related to carbon nanotubes and nanofibers used as a reinforcement in metallic matrix materials. The main challenges and the potential with respect to material properties will be discussed. © Elsevier Ltd.


Zikin A.,Ac2t Research Gmbh | Zikin A.,Tallinn University of Technology | Antonov M.,Tallinn University of Technology | Hussainova I.,Tallinn University of Technology | And 2 more authors.
Tribology International | Year: 2013

The aim of the current study was to investigate erosive and impact/abrasive wear behaviour of TiC-NiMo and Cr3C2-Ni reinforced NiCrBSi hardfacings at temperatures up to 700 C. Coatings were produced using plasma transferred arc cladding process. It was shown that the high temperature wear behaviour of TiC-NiMo and Cr3C2-Ni NiCrBSi hardfacings is influenced by oxidation. The formation of mechanical mixed layers and oxide films was observed for both investigated coatings. TiC-NiMo and Cr3C2-Ni reinforced hardfacings show high wear resistance at all testing temperatures for both impact/abrasion and erosion conditions. © 2012 Elsevier Ltd.

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