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Milosev I.,Jozef Stefan Institute | Zerjav G.,Jozef Stefan Institute | Calderon Moreno J.M.,Institute of Physical Chemistry Ilie Murgulescu | Popa M.,Institute of Physical Chemistry Ilie Murgulescu
Electrochimica Acta | Year: 2013

The properties of a novel, quaternary Ti-20Nb-10Zr-5Ta alloy were investigated in relation to its use in biomedical applications. Its microstructure was revealed by X-ray diffraction, and composition by energy dispersive X-ray measurements. Electrochemical oxidation in three simulated physiological solutions, 0.9% NaCl, Hanks' physiological solution and minimum essential medium, was studied and compared to the behaviour of its individual metal components. Its electrochemical behaviour is similar to those of tantalum and niobium and is superior to those of titanium and, especially, zirconium. The superior corrosion protectiveness in physiological solution was ascribed to the formation of a complex oxide layer. The composition of the latter was studied as a function of formation potential, using X-ray photoelectron spectroscopy. The layer is comprised predominantly of titanium oxide but also contains oxides of alloying elements. The incorporation of alloying oxides in the passive layer is probably the basis for the exceptional protectiveness of this alloy under simulated physiological conditions. These characteristics form the basis of a great potential for the use of Ti-20Nb-10Zr-5Ta alloy in biomedical applications. © 2013 Elsevier Ltd. All rights reserved.

Brun N.,Max Planck Institute of Colloids and Interfaces | Brun N.,Kyoto University | Wohlgemuth S.A.,Max Planck Institute of Colloids and Interfaces | Osiceanu P.,Institute of Physical Chemistry Ilie Murgulescu | Titirici M.M.,Queen Mary, University of London
Green Chemistry | Year: 2013

A new sustainable approach based on the hydrothermal carbonization of biomass-derivatives is reported for the synthesis of nitrogen-doped carbon-based aerogels. The catalyst-free hydrothermal treatment of both carbohydrate-based derivatives, i.e. glucose, d-glucosamine and/or N-acetyl-d-glucosamine, and phenolic compounds, i.e. phloroglucinol and/or cyanuric acid, led to highly porous monolithic gels. After pyrolysis under an inert atmosphere, conductive N-doped carbon aerogels were obtained, displaying nitrogen-doping levels of 3-5 wt% and BET surface areas of up to 450 m2 g-1. These original materials showed the first promising results as electrocatalysts for the oxygen reduction reaction and are expected to be used in a wide variety of fields, including for advanced energy conversion and storage devices. © 2013 The Royal Society of Chemistry.

Lupu S.,Polytechnic University of Bucharest | Totir N.,Institute of Physical Chemistry Ilie Murgulescu
Collection of Czechoslovak Chemical Communications | Year: 2010

The electrochemical preparation, characterization and analytical applications of a hybrid material consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) conducting polymer and Prussian Blue (PB; iron(III) hexacyanoferrate(II)) are presented. The hybrid material was prepared by a two-steps method. In a first step, the organic conducting polymer coating was deposited onto platinum electrode surface from an aqueous solution containing the monomer and ferricyanide ions. In the second step, the resulted modified electrode Pt|PEDOTFeCN was immersed in an aqueous solution containing Fe 3+ ions and the electrode potential was cycled between 0.6 and -0.4 V. The in situ formation of PB inside the PEDOT matrix has been demonstrated using cyclic voltammetry and electrochemical quartz crystal microbalance. The hybrid material maintains the electrochemical features of each component, i.e. organic and inorganic components. The inorganic component showed electrochemical activity only for the Prussian blue/Everitt's salt redox system. The hybrid material displayed electrocatalytic activity towards dopamine oxidation in the presence of a large excess of ascorbic acid. © 2010 Institute of Organic Chemistry and Biochemistry.

Almatrouk H.S.,Kuwait Institute for Scientific Research | Chihaia V.,Institute of Physical Chemistry Ilie Murgulescu
International Journal of Hydrogen Energy | Year: 2015

We present the results of our DFT-based investigations on the effects of the substitution of magnesium with cobalt and nickel in the magnesium hydride on the bulk properties and on the hydrogen adsorption and desorption on the MgH2(001) surface. We present the energetic aspects of these interactions. Our calculations point to the merit of the cobalt and nickel dopants in the magnesium hydride destabilization, which facilitates the hydrogen release. Copyright © 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Vasilescu C.,Institute of Physical Chemistry Ilie Murgulescu | Drob S.I.,Institute of Physical Chemistry Ilie Murgulescu | Neacsu E.I.,Institute of Physical Chemistry Ilie Murgulescu | Mirza Rosca J.C.,University of Las Palmas de Gran Canaria
Corrosion Science | Year: 2012

A new quaternary Ti-20Nb-10Zr-5Ta alloy with β-near microstructure was obtained. Its native passive film composition and its modification and corrosion resistance after 2000 immersion hours in simulated biofluids were studied. The native film on the alloy surface contains TiO 2, Nb 2O 5, ZrO 2, Ta 2O 5 protective oxides as was demonstrated by XPS. After 2000h, XPS revealed the presence of same oxides and calcium, phosphorous ions deposited from physiological solutions as hydroxyapatite. In Ringer and Ringer-Brown solutions, the new alloy presented low corrosion rates. Impedance data exhibited a passive film with two layers: an inner, barrier layer and an outer, porous layer. © 2012 Elsevier Ltd.

Ionita G.,Institute of Physical Chemistry Ilie Murgulescu | Chechik V.,University of York
Chemical Communications | Year: 2010

Formation of organogels from covalently linked polyethylene glycols and cyclodextrins and their encapsulation/release properties were monitored with EPR spectroscopy using spin labels and spin probes; changes in molecular tumbling rates provided information on spin probe/label location inside the gel network, and molecular properties of the gel. © 2010 The Royal Society of Chemistry.

Escolastico S.,Polytechnic University of Valencia | Somacescu S.,Institute of Physical Chemistry Ilie Murgulescu | Serra J.M.,Polytechnic University of Valencia
Chemistry of Materials | Year: 2014

Nd5.5WO11.25-δ is a mixed proton-electron conducting oxide, which shows an important mixed conductivity and stability in moist CO2 environments. However, the H2 fluxes obtained with this material are not high enough in order to apply them as H2 separation membranes in industrial applications. Re6+ cation presents similar ionic radii than W6+ and Re6+ can be reduced to different oxidation states under the operating conditions typical for hydrogen membrane separation. This fact leads to the improvement of the electronic conductivity and produce the generation of oxygen vacancies with the subsequent increase in the ionic conductivity. This work presents the synthesis as nanosized powders as well as the structural and electrochemical characterization of mixed conducting materials based on the system Nd5.5W 1-xRexO11.25-δ where x = 0, 0.1, 0.5 and 1. The evolution of the crystalline structure and the shrinkage behavior are studied as a function of the sintering temperature. Total conductivity in reducing and oxidizing environments is studied systematically for samples sintered at 1350 C. The H/D isotopic effect and the hydration influence are also analyzed by means of DC-electrochemical measurements. H2 permeation is carried out for the selected compound, Nd5.5W0.5Re 0.5O11.25-δ, in the range of 700-1000 C, obtaining a peak H2 flux value of 0.08 mL·min-1·cm -2. The reduction of the Re cation in this compound under reducing conditions is investigated by TPR and XPS. Finally, the stability of this material under CO2-rich gas stream was evaluated by measuring H 2 permeation using a CO2 containing atmosphere as sweep gas. © 2013 American Chemical Society.

Teodorescu M.,Institute of Physical Chemistry Ilie Murgulescu | Dragoescu D.,Institute of Physical Chemistry Ilie Murgulescu | Gheorghe D.,Institute of Physical Chemistry Ilie Murgulescu
Journal of Chemical Thermodynamics | Year: 2013

Isothermal (vapor + liquid) equilibrium data are reported for the binary mixtures containing (nitromethane or nitroethane + 1,4-dichlorobutane) at three temperatures, (343.15, 353.15, 363.15) K. The measurements were performed by means of an ebulliometer which allows sampling from both phases in equilibrium. The experimental data were correlated using the Redlich-Kister, Wilson, NRTL and UNIQUAC excess Gibbs energy models by means of maximum likelihood method, taking into account the vapour phase imperfection in terms of the second virial coefficients. Both systems are zeotropic and show positive deviations from ideal behaviour. The experimental VLE data are analysed in terms of the Modified UNIFAC (Do) model. © 2012 Elsevier Ltd. All rights reserved.

Popa M.,Institute of Physical Chemistry Ilie Murgulescu | Moreno J.M.C.,Institute of Physical Chemistry Ilie Murgulescu
Journal of Alloys and Compounds | Year: 2011

Reactive lanthanum orthoferrite nanoparticles were obtained by a polymeric precursor route. Nanoparticle growth and crystallization from amorphous precursor, as well as the formation of a grain boundary network in polycrystalline aggregates at different calcination temperatures were studied by conventional and high-resolution electron microscopy; electron and X-ray diffraction analysis; Raman; IR; and UV-vis spectroscopy. Microstructure measurements were compared to X-ray diffraction and chemical analysis results. Electron diffraction, combined with electron microscopy results were used to determine the content of amorphous phase. The coherent crystalline domain size and the particle size have been monitored by XRD and electron microscopy in order to determine the evolution of both crystal size and the onset temperature for crystallites formation. The results demonstrate that at 550 °C we obtain pure single-phase nanocrystalline LaFeO 3, sized ∼40 nm, without the presence of amorphous phase. The magnetization curves in the 5-350 K range indicate weak ferromagnetism of the LaFeO 3 powders. © 2011 Elsevier B.V. All rights reserved.

Spataru T.,Institute of Physical Chemistry Ilie Murgulescu | Spataru N.,Institute of Physical Chemistry Ilie Murgulescu
Journal of Hazardous Materials | Year: 2010

A composite obtained by depositing platinum nanoparticles in a polytyramine (PTy) matrix, electrochemically formed on graphite substrate, was used as electrode material for the investigation of phenol oxidation by use of anodic voltammetry. The results show that, in acidic media, the measurement of the oxidation peak current can be used as the basis for a simple, rapid method for the determination of phenol within a concentration range of 0.3-10. mM. A much better resistance to fouling during phenol detection (compared both with smooth platinum and with Pt nanoparticles on bare graphite substrate) is the main advantage of the Pt-PTy composite. These results are also noteworthy because they provide a basis for additional experiments devoted to obtaining new composite materials with improved performances for phenol anodic oxidation. © 2010 Elsevier B.V.

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