National Institute Of Materials Physics - Romania

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860 articles found

621. Growth and structural characterization of Y0.6Lu0.4Ca4O(BO3)(3) new nonlinear crystal

Authors: Gheorghe, L; Achim, A; Voicu, F; Ghica, C

Published: AUG 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 1683, DOI:

The nonlinear optical (NLO) crystal Y0.6Lu0.4Ca4O(BO3)(3) (starting composition) of good quality has been grown from the melt by the Czochralski pulling method. X-ray diffraction experiments show that the structure of grown crystal belongs to the monoclinic system with space group Cm and its unit cell parameters have been measured to be a = 0.80711(2)nm, b = 1.60132(1)nm, c = 0.35230(8)nm and beta = 101.166(1)degrees. The crystal possesses a wide transmission range from UV to IR, which is advantageous for applications as new NLO material for frequency doubling of solid state lasers operating in the near infrared range.

622. COLUMN STUDY OF CADMIUM ADSORPTION ONTO POLYACRYLONITRILE/HYDROXYAPATITE COMPOSITE BEAD

Authors: Wang, X; Min, BG; Lyoo, WS; Chihaia, V; Gartner, M; Stoica, TF; Bae, JY; Suh, SH

Published: AUG 2010, REVUE ROUMAINE DE CHIMIE, 55, 447, DOI:

Macroporous polyacrylonitrile/hydroxyapatite (PAN/HAp) composite bead was studied for cadmium removal in a fixed-bed column. The morphology of PAN/HAp composite bead was measured. The adsorption performance of PAN/HAp composite bead in the column was examined by varying bed height and HAp amount in PAN bead. The maximum adsorption capacity and the exhaustion time were determined from the breakthrough curves. Experimental data was described using the Adams-Bohart model. Bed height did not exert large influence on the maximum adsorption capacity and the exhaustion time. The kinetic rate constant and the adsorption capacity of the bed were found to be affected by the total HAp amount.

623. ADSORPTION COMPLEXES OF COLLAGENOUS POLYPEPTIDE-IONIC SURFACTANT IN AQUEOUS MEDIUM 2. THE INFLUENCE OF ADSORPTION COMPLEXES OF POLYPEPTIDE-IONIC SURFACTANT ON THERMAL STABILITY OF COLLAGEN TYPE I

Authors: Micutz, M; Staicu, T; Sulea, D; Leca, M; Ghica, C

Published: AUG 2010, REVUE ROUMAINE DE CHIMIE, 55, 510, DOI:

In the first part of this study it has shown that the interaction between collagenous polypeptides (collagen type I with native structure of triple helix and collagen hydrolyzates with no significant secondary structure) and ionic surfactants (sodium dodecyl sulfate and hexadecyl trimethylammonium bromide) involves the formation of micelle-like clusters of ionic surfactant adsorbed onto polypeptide backbone (polypeptide-surfactant complexes) at surfactant concentrations much lower than its cmc. The present investigation is focused on the influence of polypeptide-ionic surfactant complexation on thermal denaturation of the collagen type I extracted from calfskin and young horse tendons. On the basis of capillary viscometry, a good correlation between denaturation temperatures and activation energies of viscous flow for the dilute aqueous collagen-ionic surfactant solutions at pH 2.5 and 8.0 has been found. Beginning from that, it has established that the presence of ionic surfactant reduces thermal stability of the two collagens, with a more pronounced effect in the case of sodium dodecyl sulfate. Accordingly, it has been proposed a thermal denaturation mechanism of the collagen triple helix in the presence of ionic surfactants.

624. Synthesis and structural characteristics of nitrogen doped TiO2 aerogels

Authors: Popa, M; Macovei, D; Indrea, E; Mercioniu, I; Popescu, IC; Danciu, V

Published: JUL 2010, MICROPOROUS AND MESOPOROUS MATERIALS, 132, 86, DOI: 10.1016/j.micromeso.2009.12.024

Nitrogen doped TiO2 aerogels were obtained by sol gel process followed by supercritical drying with liquid CO2. Urea and NH3 (25% aqueous solution) were used as nitrogen sources. The as-prepared aerogels were submitted to thermal treatments performed under different experimental conditions (temperature and heating time). Increasing the temperature from 450 degrees C to 550 degrees C a decrease about 32% and 15.4% of the particle size and surface OH groups' concentration, respectively and an increase about 21.4% of the incorporated nitrogen in TiO2 lattice were observed. The immersion of the TiO2 aerogels in NH3 solution induced a decreasing by 48.86% and by 80% of the S-BET and the aerogel porosity, respectively. The photocatalytic activity of the obtained N-doped TiO2 was found to depend mainly on the nitrogen incorporation in the TiO2 lattice. (C) 2009 Elsevier Inc. All rights reserved.

625. Doped aluminium based spinels synthesized by a soft chemistry method

Authors: Mindru, I; Marinescu, G; Gingasu, D; Patron, L; Diamandescu, L; Ghica, C; Mironov, B

Published: JUN 15 2010, MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS, 170, 106, DOI: 10.1016/j.mseb.2010.02.036

Structural and optical properties of (Co0.01Zn0.99)Al2O4 and Zn(Al(1.99)Ln(0.01))O-4 (where Ln(III)=Eu(III), Tb(III)) spinels obtained by a variant of the complexation method-tartarate route were studied. The tartarate precursors have been characterized by IR, UV-vis and luminescence spectroscopy. The doped aluminium based spinets have been investigated by X-ray diffraction (XRD), transsmision electron microscopy (TEM), infrared spectroscopy (IR), ultraviolet visible spectroscopy (UV-vis) and luminescence spectroscopy. Pure spinel nanometer powders were obtained. Under excitation at 380 nm the nanoparticles exhibits strong luminescence corresponding to D-5(0) -> F-7(2) transition of Eu3+ ions and respectively, to D-5(4) -> 7 F-j (j = 3, 4, 5, 6) transition of Tb3+ ions. No blue emission from the D-5(3) state were observed. (C) 2010 Elsevier B.V. All rights reserved.

626. Removal of Reactive Black 5 azo dye from aqueous solutions by catalytic oxidation using CuO/Al2O3 and NiO/Al2O3

Authors: Bradu, C; Frunza, L; Mihalche, N; Avramescu, SM; Neata, M; Udrea, I

Published: JUN 7 2010, APPLIED CATALYSIS B-ENVIRONMENTAL, 96, 556, DOI: 10.1016/j.apcatb.2010.03.019

CuO/Al2O3 and NiO/Al2O3 catalysts prepared by incipient wetness impregnation were used for the oxidation of Reactive Black 5 (RB5) in aqueous solution. Removal of the dye was assessed by High Performance Liquid Chromatography (HPLC) and Total Organic Carbon (TOC) measurements and the generation of the hydroxyl radicals in the process was evaluated by chemiluminescence measurements. To put in evidence the interaction RB5 - catalyst and the surface species formed onto catalysts during the oxidation, Diffuse Reflectance Infrared Fourier Transform (DRIFT) analysis was performed. A different behavior of the two catalytic systems was revealed by the comparative analysis of the data obtained from the adsorption and oxidation tests. Only CuO/Al2O3 was effective in the RB5 degradation, NiO/Al2O3 acted as a simple adsorbent. In the presence of CuO/Al2O3, at H2O2 concentration of 40 mM the azo dye was totally eliminated from both solution and catalyst surface after 4 h, with a mineralization degree higher than 90%. However, a strong inhibition of the catalytic oxidation of RB5 was observed in the presence of phosphate ions. In the conditions of hydrogen peroxide excess, the rate equation in the case of copper catalyst was simply expressed by a pseudo-first order equation and the model was found to fit well the data. The amount of copper leached from catalyst during the oxidation process was only 1.0-1.6% per cycle leading to the conclusion that the decrease of the dye mineralization with the number of cycles has to be explained mostly by the surface covering with the reaction products, at least to a certain extent. (C) 2010 Elsevier B.V. All rights reserved.

627. RHENIUM-188 LABELLED ALBUMIN MICROSPHERES FOR THERAPY OF LIVER TUMORS

Authors: Borza, VN; Neacsu, E; Mustaciosu, C; Luca, A; Barna, C; Popescu, N; Mercioniu, I; Albert, P; Hurduc, A; Moldovan, L; Savi, GP; Savi, I; Matei, L

Published: MAY 15 2010, JOURNAL OF LABELLED COMPOUNDS & RADIOPHARMACEUTICALS, 53, 471, DOI:

628. Specificity of defects induced in silicon by RF-plasma hydrogenation

Authors: Ghica, C; Nistor, LC; Stefan, M; Ghica, D; Mironov, B; Vizireanu, S; Moldovan, A; Dinescu, M

Published: MAR 2010, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 98, 785, DOI: 10.1007/s00339-009-5527-1

Silicon wafers have been submitted to hydrogen RF-plasma treatment in various experimental conditions. Hydrogen RF-plasma treatment induced two kinds of effects on Si wafers, depending on the treatment conditions: surface corrugation and formation of structural defects below the free surface. Atomic force microscopy (AFM) investigations showed that the surface roughness significantly increased with the treatment duration, leading to the formation of pyramidal humps on the surface. The structural defects resulting after the plasma treatments were investigated by conventional and high-resolution transmission electron microscopy (CTEM and HRTEM) techniques. The specificity of the induced extended defects due to hydrogen decoration was emphasized. Three types of extended defects were identified and characterized: planar defects in the {111} and {100} planes and nanometric voids. Point defects related to the hydrogenation process were investigated by electron paramagnetic resonance (EPR) in correlation with the electron microscopy results.

629. Study of the Kramers rare earth ions ground multiplet with a large orbital contribution by multifrequency EPR spectroscopy: Ce3+ in PbWO4 scintillator

Authors: Popescu, FF; Bercu, V; Barascu, JN; Martinelli, M; Massa, CA; Pardi, LA; Stefan, M; Nistor, SV; Nikl, M

Published: MAR 2010, OPTICAL MATERIALS, 32, 575, DOI: 10.1016/j.optmat.2009.11.015

A multifrequency Electron Paramagnetic Resonance (EPR) investigation of Ce3+ impurities in PbWO4 single-crystals at the conventional microwave frequency (CMF) (X-band: 9.43 GHz) and at the high frequencies/fields (HF) 95, 190 and 285 GHz was carried out. The resulting spectra are well described at all frequencies by an axial spin-Hamiltonian corresponding to an effective spin one-half system in a tetragonal site symmetry. The diagonal values of the effective g matrix of the lowest doublet of the ground multiplet, g(parallel to) and g_, are frequency dependent at high fields. For the magnetic field perpendicular to the tetragonal axis, the g_-parameter exhibits also a small azimuthal angular dependence, which is frequency dependent, corresponding to the tetragonal S-4 symmetry. These HF effects are associated with the mixing by the large Zeeman interaction of some of the upper-lying doublets of the ground multiplet into the lowest-lying doublet states. The CMF and multifrequency HF-EPR analysis gives a good description of the magnetic properties and allows an estimation of the crystal field splitting of the ground multiplet of Ce3+ ions with tetragonal symmetry S-4 in the PbWO4 scintillator. (c) 2009 Elsevier BM. All rights reserved.

630. Structure and properties of silver doped SnSe2 and Ge2Sb2Te5 thin films prepared by pulsed laser deposition

Authors: Popescu, M; Velea, A; Sava, F; Lorinczi, A; Tomescu, A; Simion, C; Matei, E; Socol, G; Mihailescu, IN; Andonie, A; Stamatin, I

Published: MAR 2010, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 207, 520, DOI: 10.1002/pssa.200982900

Amorphous thin films of SnSe2 and Ge2Sb2Te5 doped by different amount of silver (0.1, 0.2, 0.5 and 1 Ag atoms per formula unit) have been prepared by pulsed laser deposition (PLD) starting from solid polycrystalline targets. The films were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The good gas sensing properties for CO, as well as the sensitivity for CH4 and NO of the Ag; doped SnSe2 films have been demonstrated in the composition SnSe2Ag0.2. The structural effect of silver introduced in Ge2Sb2Te5 matrix has been investigated. The freshly deposited thin films doped by various amount of Ag develop three phases: an amorphous one, and two crystalline phases consisting of a major fcc cubic phase of AgSbTe2 and a minor cubic phase of composition Ag2Te. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim