National Institute Of Materials Physics - Romania

Publications

5714 articles found

2691. Exotic Vortex Matter: Pancake Vortex Molecules and Fractional-Flux Molecules in Some Exotic and/or Two-Component Superconductors

Authors: Crisan, A; Tanaka, Y; Iyo, A

Published: JAN 2011, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 24, 6, DOI: 10.1007/s10948-010-0892-8

The discovery of superconductivity in MgB2 and, more recently, in iron pnictides, revived the interest in two-component and other exotic superconductors, including in the field of vortex matter, as was shown recently by the discovery of "type 1.5" superconductivity. However, even some "older" exotic cuprates grown by high-pressure techniques showed interesting anomalies related to the interplay between Josephson and magnetic coupling and/or two-gap superconductivity. Here, we will present two such examples of exotic vortex matter: magnetically-coupled pancake-vortex molecules in super-multilayered cuprates, and vortex molecules composed of fractional flux quanta glued by an interband phase difference soliton, and will discuss the major differences between MgB2 and such multilayer cuprates in terms of the relative strength of the interband interaction and, respectively, in terms of the coherence and penetration lengths.

2692. Nano Techniques for Enhancing Critical Current in Superconducting YBCO Films

Authors: Mikheenko, P; Dang, VS; Kechik, MMA; Wang, Y; Sarkar, A; Tanner, JL; Abell, JS; Crisan, A

Published: JAN 2011, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 24, 1064, DOI: 10.1007/s10948-010-0861-2

A range of nano techniques is explored in order to increase the critical current in pulsed laser deposited (PLD) superconducting YBa2Cu3O (x) (YBCO) thin films. The structural measurements are linked with magnetic and transport measurements of the films. The effectiveness of PLD techniques is analyzed from the point of view of the dimensionality of nanostructures formed prior to and during the film growth. It is shown that a combination of two-dimensional substrate decoration with nanoparticles before the film deposition and one-dimensional growth of external phase nanorods during the deposition offers a high critical current in magnetic field both along the c-axis and in the ab-plane of YBCO.

2693. Structural and chemical properties of cerium-magnetoplumbite in cerium based IT-SOFC compounds

Authors: Vlaicu, AM; Mercioniu, I; Vasile, BS; Negrila, CC; Logofatu, C; Cretu, NC; Nita, P; Popescu-Pogrion, N

Published: JAN 2011, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 5, 145, DOI:

Yttria doped ceria reinforced with yttria doped alumina compound for IT-SOFC applications has been prepared by sol-gel method and sintered at 1300 degrees C, 1400 degrees C, 1500 degrees C. XRD, and SEM show the presence of a needle-like cerium-magnetoplumbite (CeAl11O17) phase in the compound; the oxygen deficient phase grows from the alumina phase by using ceria from the surrounding matrix and releasing oxygen ions As the sintering temperature is increased, the alumina phase is gradually transformed into CeAl11O17. Compared to the yttria doped ceria without reinforcement, the obtained compounds with ceria-magnetoplumbite show only a slight decrease of the Young elasticity modulus. However, the samples become brittle after backing in oxygen atmosphere (1000 degrees C, and 1500 degrees C).

2694. Short-term repeatability of a rad-hard EPI diode applied in electron processing dosimetry

Authors: dos Santos, TC; Goncalves, JAC; Pintilie, I; Bueno, CC

Published: 2011, 2011 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE (NSS/MIC), 236, DOI:

The rad-hard EPI diode was characterized envisaging its application in on-line 1.5 MeV electron beam dosimetry in radiation processing. As expected from a current sensitivity loss (13.5%) to the accumulated dose up to 750 kGy, the EPI diode exhibited good short-term repeatability (CV = 1.9%) which is better than that required for CTA dosimeters, routinely applied in radiation processing. The dose-response curve of the EPI diode was fitted by a second order polynomial function for doses up to 775 kGy. In addition, some preliminary studies on the radiation damage effects induced in this diode using a Capacitance Deep Level Transient Fourier Spectroscopy system are presented. The results showed that up to almost 1.5 MGy only 3 defects (VO, V-2 and CiOi) can influence the carrier lifetime and current generated. Further radiation damage studies are under way.

2695. METHODOLOGY FOR STUDY THE LUBRICANTS BEHAVIOR

Authors: Irina, R; Valentin, RA; Tom, S; Diana, B; Nicoleta, PP; Florin, P

Published: 2011, PROCEEDINGS OF THE 5TH INTERNATIONAL CONFERENCE ON MANUFACTURING SCIENCE AND EDUCATION (MSE 2011), VOL I, 82, DOI:

The paper presents the experimental methods for determining lubricants wear degree and their durability, which led to the development of a global methodology for the lubricant behavior study. It is achieved a complex, service life, monitoring tool, based on four modules, input and output targets and the logical interconnections between elements.

2696. PRODUCTION AND CHARACTERIZATION OF CdTe WIRE ARRAYS FOR HYBRID INORGANIC/ORGANIC PHOTOVOLTAIC CELLS

Authors: Florica, C; Arghir, I; Ion, L; Enculescu, I; Antohe, VA; Radu, A; Radu, M; Chisulescu, G; Dina, N; Antohe, S

Published: JAN-MAR 2011, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 6, 27, DOI:

A new approach for obtaining hybrid inorganic/organic photovoltaic structures, based on CdTe nanowires and organic dye films is reported. The wire arrays of CdTe (10(6) wires/cm(2)) were electrochemically grown using a template method. Ion track polycarbonate foils (30 micrometer thick) were used as templates and the growth conditions for obtaining good quality and stoichiometric CdTe nanowires were identified. After dissolving the polycarbonate template, a CdTe thin film (300 nm) has been deposited by thermal vacuum evaporation onto the wire array before the deposition of ZnPc film as organic absorber. Finally a ZnO thin film was deposited by Electron Pulsed Deposition on ZnPc, working as TCO top electrode. The structural, morphological, electrical and optical properties of each component layer are investigated. Typical parameters of the prepared photovoltaic structures are determined. The external quantum efficiency of the Au/wire array CdTe/CdTe(300 nm)/ZnPc/ZnO structures was significantly increased, with respect to that of Au/wire arrays CdTe/ZnPc/ZnO structures.

2697. EFFECT OF TEMPERATURE ON THE MAGNETIC PROPERTIES OF CERAMIC MAGNETIC MATERIALS USED FOR TEMPERATURE TRANSDUCERS

Authors: Miclea, C; Amarande, L; Cioangher, M; Trupina, L; Miclea, CT; Plavitu, C; Spanulescu, I; Mihailescu, M

Published: 2011, 2011 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2011), 34TH EDITION, VOLS 1 AND 2, 272, DOI:

Three ceramic magnetic compositions within the CuZnTi ferrite system, having the Curie temperatures centered around 60 degrees C, 80 degrees C and 100 degrees C, respectively were investigated in order to determine the time-temperature stability of their main magnetic properties. Rates of changes of 33, 66 and 100 ppm/h of the maximum slopes of permeability were found for the samples aged at 60 degrees C, 80 degrees C and 100 degrees C, respectively. The samples aged at temperatures higher than 200 degrees C show a rather sudden decrease of the maximum slope of permeability, but no shift of the Curie temperature and the working point, corresponding to the temperature where the slope has the maximum value. The results are discussed in terms of the migration processes of the cations, especially Cu2+, from metastable positions on which they were frozen during the rapid cooling of the samples from the sintering temperature, to the more stable ones, namely the octahedral sites into the spinel lattice.

2698. ELECTRICAL FIELD INDUCED PROPERTIES OF NEMATIC LIQUID CRYSTAL/COPOLYMER PARTICLES COMPOSITE

Authors: Manaila-Maximean, D; Rosu, C; Danila, O; Donescu, D; Ghiurea, M; Cotorobai, F

Published: 2011, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN-SERIES A-APPLIED MATHEMATICS AND PHYSICS, 73, 200, DOI:

Particles of the type divinylbenzene - maleic anhydride alternated copolymers have been synthesized. Their dimensions were determined by electron microscopy and are in the range 1-2 mu m. These particles were mixed by stirring and ultrasound with nematic liquid crystals ZLI 1221(Merck), in a concentration of 5% wt. (polymer/LC) and filled in conventional sandwich cells formed by ITO covered glass. Current-voltage characteristics and switching tunes have been studied.

2699. DIRECT OPTICAL ABSORPTION MEASUREMENTS IN GASEOUS MEDIA BY THE CAVITY RING-DOWN SPECTROSCOPY TECHNIQUE FOR THE DEVELOPMENT OF A LOSSMETER

Authors: Cotirlan-Simioniuc, C; Logofatu, C; Lazarescu, MF

Published: 2011, ROMANIAN REPORTS IN PHYSICS, 63, 1082, DOI:

2700. SENSOR OF NITROGEN DIOXIDE BASED ON SINGLE WALL CARBON NANOTUBES AND MANGANESE-PORPHYRIN

Authors: Popescu, M; Simandan, ID; Sava, F; Velea, A; Fagadar-Cosma, E

Published: JUL-SEP 2011, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 6, 1256, DOI:

New sensors based on single wall carbon nanotubes (SWCNTs) and porphyrins have been tested for sensitivity to NO(2) gas. SWCNTs embedded in barium stearate multilayers were deposited with the help of Langmuir-Blodgett technique. It was demonstrated a sensitive effect of the sensor for NO(2) gas. The coverage of the sensor with metalloporphyrin (Mn) leads to strong enhancing of the sensitive effect to NO(2), besides, the selectivity was preserved both around room temperature and at larger operating temperature (up to 200 degrees C). No sensitivity to CO and CH(4) was evidenced. The NO(2) sensitivity strongly increased at 100 degrees C but at high operation temperatures (150-200 degrees C) a different behaviour is observed, probably due to the structural change of porphyrin or porphyrin-SWCNT interaction. The reversibility of the sensor resistivity is reasonably good at the optimum operating temperature (100 degrees C).