National Institute Of Materials Physics - Romania

Publications

860 articles found

611. Structural and electrical properties of ceramic composite 10Y(2)O(3):CeO2+(10%)(150ppm)Y2O3:alpha-Al2O3

Authors: Ionascu, AM; Mercioniu, I; Notingher, PV; Popescu-Pogrion, N

Published: 2011, 2011 7TH INTERNATIONAL SYMPOSIUM ON ADVANCED TOPICS IN ELECTRICAL ENGINEERING (ATEE), DOI:

The attractive properties of Yttria doped ceria, particularly the structural and material properties, have led to vast research efforts to investigate and develop such materials. One of the main applications of this ceramic is in the solid oxides fuel cells for intermediate temperatures IT-SOFC. The aim of this paper is the preparation and characterization of Y doped Ceria - low Y doped alpha-Al2O3, a new composite for IT-SOFC. (10 mol %) Y : CeO2 and (150 ppm) Y : alpha - Al2O3 - composite were obtained by sol-gel or mechanical route for 10YSC, mechanical route for 150 Y : alpha - Al2O3. Grain shapes, grain size distributions and the mean grain value were determined by SEM, EDX and statistical investigations.

612. SYNTHESIS AND PRELIMINARY CHARACTERIZATION OF ERBIUM LITHIUM NIOBIUM GALLIUM GARNET

Authors: Toma, O; Gheorghe, L; Vlaicu, AM

Published: 2011, ROMANIAN JOURNAL OF PHYSICS, 56, 934, DOI:

The synthesis of a new garnet, Er3Li0.275Nb0.275Ga4.45O12 (ErLNGG), by solid-state reaction, is reported. A comparison of the fluorescence spectra of Er3+ in ErLNGG and in Er-doped (5 at. %) Calcium Lithium Niobium Gallium Garnet (CLNGG) suggests an ordering of the partially disordered CLNGG when Ca2+ ions are completely substituted by Er3+ ions.

613. Experimental configuration for the simultaneous study of magnetization reversal and giant magnetoresitance effects in exchange coupled spin valve structures

Authors: Schinteie, G; Kuncser, C; Kuncser, A; Iofciu, F; Jepu, I; Antohe, S

Published: SEP-OCT 2011, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 13, 1094, DOI:

A designed experimental configuration for the simultaneous study of magnetization reversal and giant magnetoresistance effects in layered systems is reported. The suitability of the device, designed mainly for didactical purposes, to prove giant magneto-resistance effects is exemplified in case of exchange coupled spin valve structures. The multilayer structures were prepared by theromo-ionic vacuum arc methods and initially characterized by X-ray diffractometry and energy dispersive Xray spectroscopy. According to the performed experiments, it has been clearly proven the presence of magnetoresistance maxima ever ranges of applied fields inducing antiparallel magnetizations of the two ferromagnetic layers interfacing a thin conductive layer.

614. Skin Layer Defects in Si by Optimized Treatment in Hydrogen RF Plasma

Authors: Ghica, C; Nistor, LC; Vizireanu, S; Dinescu, G; Moldovan, A; Dinescu, M

Published: DEC 20 2010, PLASMA PROCESSES AND POLYMERS, 7, 991, DOI: 10.1002/ppap.201000066

The first step of the smartcut (TM) process consists in inducing structural defects below the free surface of a silicon wafer, usually by implantation of light elements, such as hydrogen or helium. An alternative way to induce subsurface defects is by plasma treatment. In this work, we present a morphological and structural study on silicon wafers submitted to hydrogen plasma treatment, using two plasma-processing geometries. The parameters of the plasma treatment have been varied in order to limit the surface roughness and to confine the induced defects in a narrow region (50 nm) below the wafer surface. The morphological and structural investigations have been performed by AFM and TEM.

615. Study of magnetic nanovectors by Wet-STEM, a new ESEM mode in transmission

Authors: Maraloiu, VA; Hamoudeh, M; Fessi, H; Blanchin, MG

Published: DEC 15 2010, JOURNAL OF COLLOID AND INTERFACE SCIENCE, 352, 392, DOI: 10.1016/j.jcis.2010.08.066

Many nanovectors used for therapy (drug targeting radiation therapy) or diagnostic such as Magnetic Resonance Imaging (MRI) have a composite structure consisting of an organic core or organic coverage encapsulating magnetic nanoparticles and they are commonly dispersed in liquid suspensions for intravenous injection Here is presented the application of a new Environmental Scanning Electron Microscopy (ESEM) mode in transmission so called Wet-STEM for transmission imaging of droplets of such suspensions This is illustrated by Wet-STEM images from PLLA/Re nanospheres (about 100-300 nm in diameter) loaded with magnetite nanoparticles (about 10 nm in diameter) and from iron oxide core (about 5 nm in size) MRI contrast agents both examples in aqueous suspensions It is shown that the Wet STEM mode allows both the collective behavior of such nanovectors in suspension to be characterized and the inner composite structure of individual vectors to be revealed Such experimental results are discussed by comparison with Monte Carlo computer simulations of the distribution of the electrons scattered through the samples in rather large solid angles (between 20 degrees and 47 degrees) corresponding to the detection conditions (C) 2010 Elsevier Inc All rights reserved

616. CO sensing mechanism with WO3 based gas sensors

Authors: Hubner, M; Simion, CE; Haensch, A; Barsan, N; Weimar, U

Published: NOV 26 2010, SENSORS AND ACTUATORS B-CHEMICAL, 151, 106, DOI: 10.1016/j.snb.2010.09.040

The interaction between CO and WO3 based gas sensors was investigated in operando conditions by using resistance, catalytic conversion and DRIFTS measurements. The experimental results are showing that the sensing involves the reduction of the metal oxide, which is the opposite of the case of SnO2, the other extremely relevant material for semiconducting oxides based gas sensors. (C) 2010 Elsevier B.V. All rights reserved.

617. Investigations of the neodymium doped quartz glasses obtained by the hybrid sot-gel method

Authors: Niciu, H; Vasiliu, C; Manea, A; Radu, D; Secu, M; Onose, C; Ghervase, L; Niciu, D; Feraru, ID; Grigorescu, CEA

Published: OCT 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1623, DOI:

Undoped and neodymium doped quartz glasses were obtained by the hybrid sol-gel method. The vitrification was performed in He atmosphere. The Nd(3+) characteristic absorption bands in the UV and VIS were put into evidence. Investigations in the NIR range revealed a small amount (86 ppm) of OH(-) in the vitreous matrix. FTIR and Raman spectra exhibit the SiO(2) glass characteristic vibrations and also the characteristic vibrations of Si-OH and Si-Cl bonds. The photoluminescence peaks at 640, 920 and 1080 nm belonging to the Nd(3+) doped quartz glass were evidenced.

618. Multifrequency ESR Characterization of Paramagnetic Point Defects in Semiconducting Cubic BN Crystals

Authors: Nistor, SV; Stefan, M; Ghica, D; Goovaerts, E

Published: OCT 2010, APPLIED MAGNETIC RESONANCE, 39, 101, DOI: 10.1007/s00723-010-0136-x

Low-frequency (X-band) electron spin resonance (ESR) investigations on commercially available large-grained cubic boron nitride (cBN) superabrasive powders of various coloration, combined with high-frequency (W-band) ESR measurements on oriented submillimeter-size single crystallites selected from the same powder samples, resulted in a clear identification of several types of paramagnetic point defects. The resulting spin Hamiltonian parameters describing the ESR spectra observed in the 3-293 K temperature range and the photosensitivity of the paramagnetic defects observed in amber-colored cBN samples are reported. It is shown that the nature of the paramagnetic centers depends on the color of the investigated samples and that, in many cases, uncontrolled impurities seem to be involved in their structure.

619. Localization of Mn2+ Ions in Mesoporous ZnS

Authors: Nistor, SV; Stefan, M; Nistor, LC; Mateescu, CD; Birjega, R

Published: SEP 2010, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 10, 6205, DOI: 10.1166/jnn.2010.2599

Nanocrystalline cubic ZnS doped with 0.2% mol manganese, exhibiting a stable mesoporous structure, was synthesized at room temperature by a non toxic surfactant-assisted liquid liquid reaction. The X-ray diffraction measurements demonstrate the formation of a sponge-like mesoporous material built from cubic ZnS nanocrystals of 1.8 nm average sizes, with a tight distribution of pores of 1.8 nm mean diameter. The transmission electron microscopy images confirm the formation of the mesoporous structure with walls of 3.1 nm mean thickness built from cubic ZnS nanocrystallites of 2.1 nm average size. The resulting tight distribution of crystallites and pores yields a well resolved Electron Paramagnetic Resonance spectrum, with the narrowest reported component lines attributed to three types of isolated Mn2+ centers, called Mn2+ (I), Mn2+ (II) and Mn2+ (III). From the analysis of the spin Hamiltonian parameters it is shown that in the Mn2+ (I) centers the paramagnetic ion is situated at substitutional Zn sites in the ZnS nanocrystals, being also subjected to a small axial distortion. The relative concentration changes under thermal treatment experiments strongly suggest that in both Mn2+ (II) and Mn2+ (III) centers the Mn2+ ion is localized on the surface of the ZnS nanocrystallites, being bond to an oxygen ion in the first case and to an additional water molecule in the second case.

620. Blue CoAl2O4 spinel via complexation method

Authors: Mindru, I; Marinescu, G; Gingasu, D; Patron, L; Ghica, C; Giurginca, M

Published: AUG 1 2010, MATERIALS CHEMISTRY AND PHYSICS, 122, 497, DOI: 10.1016/j.matchemphys.2010.03.032

Cobalt-aluminate spinel, CoAl2O4, has been synthesized by two synthesis variants of the complexation method: tartarate and gluconate routes. The complex precursors have been characterized by IR, UV-vis spectroscopy and thermal analysis. The cobalt-aluminate spinet has been investigated by XRD, IR, UV-vis and luminescence spectroscopy and TEM. The results indicated that in both cases the single-phase nanocrystalline CoAl2O4 spinet was formed. The average crystallite size from TEM images was in the range 50-60 nm. The emission spectra of CoAl2O4 in the visible region confirmed the presence of tetrahedral coordinated Co2+ ion. (C) 2010 Elsevier B.V. All rights reserved.