National Institute Of Materials Physics - Romania

Publications

5974 articles found

1351. Addition of carbon fibers into B4C infiltrated with molten silicon

Authors: Solodkyi, I; Bezdorozhev, O; Vterkovskiy, M; Bogomol, I; Bolbut, V; Kruger, M; Badica, P; Loboda, P

Published: JAN 2019, CERAMICS INTERNATIONAL, 45, 174, DOI: 10.1016/j.ceramint.2018.09.148

Boron carbide added with 0-20 wt% carbon fibers was subject to Si infiltration. Samples mainly consist of B13C2, beta-SiC and unreacted Si. Some amount of SiB6 and alpha-SiC was also detected, while formation of B-12(B,C,Si)(3) phase was suppressed due to short infiltration time. The carbon fibers react with Si and result in formation of a composite core-shell fiber with SiC-shell and C-core. Theoretical estimations suggest that these composite fibers have a strong influence on the enhancement of the bending strength. Although apparently in good agreement with experimental data showing an increase of bending strength up to 510 +/- 27 MPa in the sample with 10 wt% carbon fiber, the implications of phase changes with the carbon fiber amount has to be carefully considered. At higher amounts of carbon fibers, bending strength decreases.

1352. Composite BNT-BT0.08/CoFe2O4 with core-shell nanostructure for piezoelectric and ferromagnetic applications

Authors: Cernea, M; Vasile, BS; Ciuchi, IV; Surdu, VA; Bartha, C; Iuga, A; Galizia, P; Galassi, C

Published: JAN 2019, MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS, 240, 15, DOI: 10.1016/j.mseb.2019.01.001

In this work, we report on the synthesis and characterization of BNT-BT0.08/CoFe2O4 biphasic composite with core-shell structure. This artificial core (BNT-BT0.08/shell (CoFe2O4) heterostructure was prepared by sol-gel method and the resulting composite was characterized in term of microstructure, dielectric, piezoelectric and magnetic properties. BNT-BT0.08/CoFe2O4 sintered ceramic shows high permittivity (epsilon' >= 30) and high dielectric losses (tan delta >= 10) in the low frequency range (nu <= 10(4) Hz), remnant polarization (Pr) of similar to 7.7 mu C/cm(2) and, remanent magnetization (Mr) of 24 emu/g at 5 K and of 14 emu/g, at room temperature. The present study reveals that the ferroelectric, piezoelectric and magnetic properties of this new architectured composite depend on the amount of each component and, can be tailored by adjusting their synthesis conditions. BNT-BT0.08/CoFe2O4 core-shell material investigated in this work provides a novel way to exploit new applications for the multifunctional composite, such as piezoelectric sensor, magnetoelectronic sensors and data storage devices.

1353. Extrinsic absorption in spark plasma sintered Zr0.8Sn0.2TiO4 ceramics investigated by terahertz time-domain spectroscopy

Authors: Nedelcu, L; Burdusel, M; Grigoroscuta, MA; Geambasu, CD; Banciu, MG; Badica, P

Published: 2019, 2019 44TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES (IRMMW-THZ), DOI:

Solid-state reaction synthesized Zr0.8Sn0.2TiO3 powders have been compacted by spark plasma sintering. In order to reduce the oxygen vacancies, the sintered samples were annealed ex-situ in air. Single-phase ceramics with different amount of oxygen vacancies and, consequently, different extrinsic absorption were investigated by terahertz time-domain spectroscopy. The results showed that the terahertz spectroscopy could be a suitable technique for tailoring the absorption properties of the spark plasma sintered materials.

1354. Passively mode-locked self-frequency doubling Yb:LGSB laser

Authors: Porebski, M; Kowalczyk, M; Gheorghe, L; Greculeasa, M; Broasca, A; Voicu, F; Sotor, J

Published: 2019, 2019 CONFERENCE ON LASERS AND ELECTRO-OPTICS EUROPE & EUROPEAN QUANTUM ELECTRONICS CONFERENCE (CLEO/EUROPE-EQEC), DOI:

1355. Isospin dynamics and nuclear dipolar degree of freedom

Authors: Papa, M; Barcenau, I; Acosta, L; Cardella, G; Gnoffo, B; Lanzalone, J; Lombardo, I; Maiolino, C; Pagano, A; Pagano, EV; Pirrone, S; Politi, G; Porto, F; Russotto, P; Trifiro, A; Trimarchi, M; Verde, G; Vigilante, M

Published: MAR-JUN 2019, NUOVO CIMENTO C-COLLOQUIA AND COMMUNICATIONS IN PHYSICS, 42, DOI: 10.1393/ncc/i2019-19103-1

The strong connection between the dipolar signal as obtained from the measured velocities and charge of all fragments produced in a heavy collision and the dynamics of the isospin equilibration processes is illustrated. Effects due to both statistical and dynamical mechanisms are shortly discussed. Experimental data related to semi-peripheral collisions induced on the Ca-48 + Al-27 at 40 MeV/nucleon system are also shown and compared with CoMD-III calculations.

1356. TAILORING SP2/SP3 RATIO IN DIAMOND-LIKE CARBON FILMS VIA DEPOSITION PARAMETERS IN A HIGH VOLTAGE ANODIC VACUUM PLASMA

Authors: Badulescu, M; Anghel, A; Surdu-Bob, CC; Logofatu, C; Luculescu, C

Published: 2019, ROMANIAN REPORTS IN PHYSICS, 71, DOI:

Tailoring sp(2)/sp(3) ratio in diamond-like carbon thin films offers new surface engineering solutions for the continuously increasing devices requirements in various fields. We report here the control of sp(2)/sp(3) carbon content using the high voltage anodic plasma in vacuum. Correlation of data obtained by visible Raman Spectroscopy and XPS spectra of our DLC films with deposition parameters showed an increase in sp(3) bonding of about 10% when decreasing the discharge voltage from 600 V to 200 V or increasing the anode-substrate distance from 15 cm to 36 cm.

1357. Comparison between dielectric and pyroelectric properties of PZFNT and BST type ceramics

Authors: Stancu, V; Amarande, L; Botea, M; Iuga, A; Leonat, LN; Tomulescu, AG; Cioangher, M; Balescu, LM; Pintilie, L

Published: 2019, PROCESSING AND APPLICATION OF CERAMICS, 13, 276, DOI: 10.2298/PAC1903269S

Ba0.75Sr0.25TiO3 (BST) and PbZr0.68Fe0.14Nb0.14Ti0.04O3 (PZFNT) ceramic pellets were obtained by ceramic technology and their structural, ferroelectric and pyroelectric properties were investigated. The relative density of BST and PZFNT is about 93% and 90%, respectively, with an average grain size of 102 mu m and 6.45 mu m. Both materials have similar room temperature dielectric constants (similar to 2000), but PZFNT shows higher remnant polarization (similar to 15 mu C/cm(2)) and better pyroelectric properties (similar to 1.69 . 10(-4) C/m(2)K), which recommend it for pyroelectric detectors, infrared radiation- and laser pulse energy-meters.

1358. PHOTO-ELECTRICAL PROPERTIES OF THIN FILMS WITH GE NANOPARTICLES EMBEDDED IN TIO2 MATRIX

Authors: Stavarache, I; Maraloiu, VA

Published: 2019, ROMANIAN REPORTS IN PHYSICS, 71, DOI:

We present photo-electrical properties of thin films formed of Ge nanoparticles in TiO2 correlated with structure and morphology. The films co-deposited on Si using magnetron sputtering were annealed in conventional oven at 550 degrees C. We performed structure investigations by X-ray diffraction, transmission electron microscopy and measured current-voltage characteristics in dark and under illumination at different temperatures. We show that the films are formed of cubic Ge nanoparticles in nanostructured anatase TiO2 matrix. Also, (TiGe)O-2 with rutile structure was observed. The films have high photosensitivity under white light as the ratio between photo- and dark currents (-1 V) is of similar to 10(2).

1359. High performance NIR photosensitive films of Ge nanoparticles in Si3N4

Authors: Stavarache, I; Prepelita, P; Lalau, I; Cojocaru, O; Teodorescu, VS; Ciurea, ML

Published: 2019, 2019 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2019), 42ND EDITION, 228, DOI:

Films of amorphous Ge nanoparticles in Si3N4 on heated Si and quartz substrates at 300 degrees C were obtained by co-sputtering Ge, and Si3N4. The films structure and photo-electrical behaviour were studied through transmission electron microscopy and, current voltage and spectral photo-current investigations, respectively. The spectral photo-current were correlated with results obtained from transmission electron microscopy. Under illumination the current present a high increase with about one order of magnitude compared with the dark one. The photo-current spectra show a widening in near infrared to 0.97eV. Internal quantum efficiency values for -1V and 0V were determined.

1360. Controlling SWIR photosensitivity limit by composition engineering: from Ge to GeSi nanocrystals embedded in TiO2

Authors: Dascalescu, I; Cojocaru, O; Lalau, I; Palade, C; Slav, A; Lepadatu, AM; Lazanu, S; Stoica, T; Ciurea, ML

Published: 2019, 2019 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2019), 42ND EDITION, 40, DOI:

The VIS-SWIR photosensing properties of Ge and GeSi NCs embedded in TiO2 films are investigated. For this, we deposit GeTiO2 and GeSiTiO2 films, respectively by magnetron sputtering and then we perform rapid thermal annealing (RTA) for Ge NCs and GeSi NCs formation, respectively. Raman studies and spectral photocurrent measurements were carried out. Ge NCs formation is evidenced in the Raman spectrum of GeTiO2 film annealed at 550 degrees C. The photocurrent spectra measured on the Ge NCs-TiO2 film present four peaks separated by deconvolution. The broad peaks at similar to 700, 890, 1010 nm are due to photo-effects in the Ge NCs-TiO2 film. More than that, the photocurrent increases exponentially with the increase of bias voltage. The cut-off wavelength is similar to 1240 nm. We achieve the extension of the photosensitivity limit to similar to 1310 nm in GeSi NCs-TiO2 films (800 degrees C RTA).