National Institute Of Materials Physics - Romania

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5714 articles found

2361. The bioactivity mechanism of magnetron sputtered bioglass thin films

Authors: Berbecaru, C; Stan, GE; Pina, S; Tulyaganov, DU; Ferreira, JMF

Published: OCT 1 2012, APPLIED SURFACE SCIENCE, 258, 9848, DOI: 10.1016/j.apsusc.2012.06.039

Smooth and adherent bioactive coatings with similar to 0.5 mu m thickness were deposited onto Si substrates by the radiofrequency-magnetron sputtering method at 150 degrees C under 0.4 Pa of Ar atmosphere using a bioglass powder as target with a composition in the SiO2-CaO-MgO-P2O5-CaF2-B2O3-Na2O system. The bioactivity of the as-prepared bioglass samples was assessed by immersion in simulated body fluid for different periods of time up to 30 days. Grazing incidence X-ray diffraction, Fourier transform infra-red spectrometry and energy dispersive spectroscopy revealed that important structural and compositional changes took place upon immersing the samples in SBF. Whilst the excellent biomineralisation capability of the BG thin films was demonstrated by the in vitro induction of extensive and homogenous crystalline hydroxyapatite in-growths on their surfaces, a series of bioactivity process kinetics peculiarities (derogations from the classical model) were emphasised and thoroughly discussed. (C) 2012 Elsevier B. V. All rights reserved.

2362. Analysis of the phase lapse problem in closed interferometers

Authors: Tolea, M; Moldoveanu, V; Dinu, IV; Tanatar, B

Published: OCT 1 2012, PHYSICS LETTERS A, 376, 3234, DOI: 10.1016/j.physleta.2012.07.007

We investigate the connection between the asymmetry of the Fano resonances in a mesoscopic interferometer with an embedded quantum dot and the pi lapses in the phase of the "bare" dot transmittance. Consecutive Fano resonances with the same (opposite) sign of the Fano parameter imply the presence (absence) of a phase lapse with pi between the corresponding resonances of the dot. Our results suggest that the famous "phase lapse" problem, first reported by Schuster et al. [R. Schuster, E. Buks, M. Heiblum, D. Mahalu, V. Umansky, H. Shtrikman, Nature 385 (1997) 417], can therefore be experimentally addressed in closed interferometers. It is also proposed that the Fano effect can be used to extract the phase distributions of the eigenfunctions for a mesoscopic 20 shape, via the parity of the resonances. In the presence of electron-electron interaction, one can calculate the phases of the T-matrix elements. The numerical results lead to the same conclusions as for the non-interacting case. (C) 2012 Elsevier B.V. All rights reserved.

2363. Structural, Optical, and Dielectric Properties of Bi1.5-xZn0.92-yNb1.5O6.92-delta Thin Films Grown by PLD on R-plane Sapphire and LaAlO3 Substrates

Authors: Le Febvrier, A; Galca, AC; Corredores, Y; Deputier, S; Bouquet, V; Demange, V; Castel, X; Sauleau, R; Lefort, R; Zhang, LY; Tanne, G; Pintilie, L; Guilloux-Viry, M

Published: OCT 2012, ACS APPLIED MATERIALS & INTERFACES, 4, 5233, DOI: 10.1021/am301152r

Bi1.5-xZn0.92-yNb1.5O6.92-delta thin films have the potential to be implemented in microwave devices. This work aims to establish the effect of the substrate and of the grain size on the optical and dielectric properties. Bi1.5-xZn0.92-yNb1.5O6.92-delta thin films were grown at 700 degrees C via pulsed-laser deposition on R-plane sapphire and (100)(pc) LaAlO3 substrates at various oxygen pressures (30, 50, and 70 Pa). The structure, morphology, dielectric and optical properties were investigated. Despite bismuth and zinc deficiencies, with respect to the Bi1.5Zn0.92Nb1.5O6.92 stoichiometry, the films show the expected cubic pyrochlore structure with a (100) epitaxial-like growth. Different morphologies and related optical and dielectric properties were achieved, depending on the substrate and the oxygen pressure. In contrast to thin films grown on (100)(pc) LaAlO3, the films deposited on R-plane sapphire are characterized by a graded refractive index along the layer thickness. The refractive index (n) at 630 nm and the relative permittivity (epsilon(t)) measured at 10 GHz increase with the grain size: on sapphire, n varies from 2.29 to 2.39 and epsilon(r) varies from 85 to 135, when the grain size increases from 37 nm to 77 nm. On the basis of this trend, visible ellipsometry can be used to probe the characteristics in the microwave range quickly, nondestructively, and at a low cost.

2364. Neutron field parameter measurements on the JET tokamak by means of super-heated fluid detectors

Authors: Gherendi, M; Zoita, VL; Craciunescu, T; Johnson, MG; Pantea, A; Baltog, I; Edlington, T; Hellesen, C; Kiptily, V; Conroy, S; Murari, A; Popovichev, S

Published: OCT 2012, REVIEW OF SCIENTIFIC INSTRUMENTS, 83, DOI: 10.1063/1.4739410

The neutron field parameters (fluence and energy distribution) at a specific location outside the JET Torus Hall have been measured by means of super-heated fluid detectors (or "bubble detectors") in combination with an independent, time-of-flight, technique. The bubble detector assemblies were placed at the end of a vertical line of sight at about 16 m from the tokamak mid plane. Spatial distributions of the neutron fluence along the radial and toroidal directions have been obtained using two-dimensional arrays of bubble detectors. Using a set of three bubble detector spectrometers the neutron energy distribution was determined over a broad energy range, from about 10 keV to above 10 MeV, with an energy resolution of about 30% at 2.5 MeV. The very broad energy response allowed for the identification of energy features far from the main fusion component (around 2.45 MeV for deuterium discharges). [http://dx.doi.org/10.1063/1.4739410]

2365. Antioxidant effects induced in biological macromolecular systems by high density photons through localized excitations

Authors: Comorosan, S; Polosan, S; Popescu, I; Paslaru, L; Nastase, A; Mitrica, R; Ionescu, E

Published: OCT 2012, BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, 1817, S130, DOI: 10.1016/j.bbabio.2012.06.345

2366. Stanford R. Ovshinsky Prize for Excellence in Amorphous Chalcogenides

Authors: Popescu, M

Published: OCT 2012, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 249, 1836, DOI: 10.1002/pssb.201200348

The short history of the Ovshinsky Prize conferred for Excellence in Amorphous Chalcogenides is presented.

2367. Epitaxial ferromagnetic samarium and samarium silicide synthesized on Si(001)

Authors: Costescu, RM; Gheorghe, NG; Husanu, MA; Lungu, GA; Macovei, D; Pintilie, I; Popescu, DG; Teodorescu, CM

Published: OCT 2012, JOURNAL OF MATERIALS SCIENCE, 47, DOI: 10.1007/s10853-012-6672-z

Samarium is deposited on Si(001) at various temperatures (room temperature to 400 A degrees C), and the surface structure, interface reactivity, electron configuration, and magnetic properties are investigated by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), and magneto-optical Kerr effect (MOKE), respectively. It is found that metal Sm is present on samples prepared at room temperature with an interface layer containing mostly Sm2+ and a lower amount of Sm3+. When samples are prepared at high temperature, much less Sm-0 is found with an increasing amount of Sm2+. Freshly prepared Sm-0 and SmSi2 layers react strongly with oxygen from the residual gas, promoting formation of Sm2O3 at the expense of both metal Sm and SmSi2. Room temperature ferromagnetism is observed for all prepared layers with a decrease of the saturation magnetisation when samples are prepared at high temperature. It is found that ferromagnetism implies mostly Sm3+ and Sm metal. In addition to these findings, this work proposes a new assignment of the Sm 3d chemically shifted components. Also, a noticeable variation of the XPS Sm 3d spin-orbit splitting is found as a function of the Sm ionization state.

2368. Thermal behaviour of some new complexes with decaaza bismacrocyclic ligand as potential antimicrobial species

Authors: Bucur, C; Badea, M; Larisa, C; Marinescu, D; Grecu, MN; Stanica, N; Chifiriuc, MC; Olar, R

Published: OCT 2012, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 110, 241, DOI: 10.1007/s10973-012-2199-4

Novel complexes of type M2L(CH3COO)(4)center dot nH(2)O (M:Ni, n = 4; M:Cu, n = 2 and M:Zn, n = 0; L: ligand resulted in 1,2-phenylenediamine, 3,6-diazaoctane-1,8-diamine and formaldehyde template condensation) were synthesised and characterised. The features of complexes have been assigned from microanalytical, IR, UV-Vis, H-1 NMR, EPR as well as magnetic data at room temperature. Processes as water elimination as well as oxidative degradation of both organic components (bismacrocycle and acetate) were observed. The final product of decomposition was metal (II) oxide as powder X-ray diffraction indicates.

2369. Structural, optical, and electric properties of BNT-BT0.08 thin films processed by sol-gel technique

Authors: Cernea, M; Trupina, L; Dragoi, C; Galca, AC; Trinca, L

Published: OCT 2012, JOURNAL OF MATERIALS SCIENCE, 47, 6971, DOI: 10.1007/s10853-012-6646-1

Thin films with the composition [(Bi0.5Na0.5)TiO3](0.92)-[BaTiO3](0.08) (hereafter BNT-BT0.08) were deposited on Pt-Si by spin-coating from a stable sol precursor. The BNT-BT0.08 film, crystallized on the Bi0.5Na0.5TiO3 rhombohedral lattice, was obtained after annealing the film-gel at 700 A degrees C. The films have a smooth surface (Rms = 2.76 nm) and grains with ferroelectric domains. The film showed a bandgap of 3.25 eV and a refractive index of 2.20 at a wavelength of 630 nm. The dielectric characteristics of BNT-BT0.08 thin films were measured at room temperature and 10 kHz the dielectric constant (epsilon (r)) was 243 and the loss tangent (tan delta) was 0.38. The remnant polarization (P (r)) was 0.87 mu C/cm(2) and the coercive field (E (c)) was 220 kV/cm at 10 kHz and room temperature. The current density was approximately 2.7 x 10(-5) A/cm(2) at low electric fields (100 kV/cm). BNT-BT0.08 thin films shown piezoelectric properties (d (33eff) = 100 pm/V) comparable to those of PZT thin films.

2370. Superparamagnetic magnetite-divinylbenzene-maleic anhydride copolymer nanocomposites obtained by dispersion polymerization

Authors: Donescu, D; Raditoiu, V; Spataru, CI; Somoghi, R; Ghiurea, M; Radovici, C; Fierascu, RC; Schinteie, G; Leca, A; Kuncser, V

Published: OCT 2012, EUROPEAN POLYMER JOURNAL, 48, 1716, DOI: 10.1016/j.eurpolymj.2012.07.012

Magnetite alternating copolymers divinylbenzene-maleic anhydride (DVB-MA) composites were prepared by dispersion polymerization. Because magnetite is used as a complex with oleic acid (Fe(3)O(4)OLA), the final hybrids show good dispersion of inorganic nanofillers in the polymer matrix. The obtained composites were analyzed by infrared absorption spectrometry, diffuse reflectance in visible light, thermogravimetry, X-ray fluorescence, X-ray diffraction, dynamic light scattering, scanning electron microscopy and vibrating sample magnetometry. The obtained results indicate the successful preparation of magnetite nanoparticles with an average size of about 23 nm dispersed in micrometer size copolymer spherical particles, which relative content can be controlled via the processing parameters. A relationship between the relative content of magnetite nanoparticles and the size of the polymer particles, with direct influence on the diffuse reflectance in the visible domain, was observed. A superparamagnetic behavior was evidenced at room temperature with a blocking temperature lower than as expected from the bulk anisotropy constant and the average size of the magnetite nanoparticles. Both the unexpected low blocking temperature and the observed low specific magnetizations were explained by a defected and poor crystalline structure of the magnetite nanoparticles, giving rise to spin disorder and diminished crystalline anisotropy constant. (C) 2012 Elsevier Ltd. All rights reserved.