National Institute Of Materials Physics - Romania

Publications

5714 articles found

1831. Scaling and passively Q-switch operation of a Nd:YAG laser pumped laterally through a YAG prism

Authors: Dascalu, T; Salamu, G; Sandu, O; Dinca, M; Pavel, N

Published: APR 2015, OPTICS AND LASER TECHNOLOGY, 67, 168, DOI: 10.1016/j.optlastec.2014.10.017

We report on scaling of a laser configuration in which a YAG prism is used to couple the pump beam from a fiber-coupled diode laser directly into a Nd:YAG medium. Several resonator geometries have been investigated. In free generation regime laser pulses at 1.06 mu m with energy of 22.1 mJ for the pump energy of 44.6 mJ were obtained from a 10.0 mm long, 1.0-at% Nd:YAG single crystal that had the high-reflectivity mirror coated directly on one of the laser crystal surface. The slope efficiency was 0.51. A similar uncoated Nd:YAG crystal placed in a plane-plane resonator delivered laser pulses with 17.8 mJ energy under the pump with 45.4 mJ energy, at 0.40 slope efficiency. Further, a passively Q-switched Nd:YAG/Cr4+:YAG composite ceramic laser pumped through a YAG prism has been built. Using a Cr4+:YAG saturable absorber of 0.85 initial transmission the device delivered laser pulses with 0.29 mJ energy and 11 ns duration. The output performances are compared to those obtained in a classical end-pumping scheme. (C) 2014 Elsevier Ltd. All rights reserved.

1832. Advanced ceramics in the SnO2-ZnO binary system

Authors: Mihaiu, S; Toader, A; Atkinson, I; Mocioiu, OC; Hornoiu, C; Teodorescu, VS; Zaharescu, M

Published: APR 2015, CERAMICS INTERNATIONAL, 41, 4945, DOI: 10.1016/j.ceramint.2014.12.056

In the present work, we report a systematic study of the phase formation and sintering ability of different oxide compositions in the SnO2-ZnO binary system using solid state reactions. For some selected compositions mechanically activated powders were also investigated. Structural and morphological characterizations of the samples were performed by X-ray diffraction (XRD), FT-IR Spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Only the formation of Zn2SnO4 binary compound was revealed in the experimental conditions. Based on the structural results the subsolidus equilibrium phase diagram was established. The sintering ability of the studied samples was also determined, establishing the compositions domains of obtaining dense or porous ceramics. The investigation by impedance spectroscopy in the 300-600 K temperature range shows that all studied samples exhibit n-type semiconductor behavior with low values of the activation energy (0.18-0.34 eV). (C) 2014 Elsevier Ltd and Teclma Group S.r.l. All rights reserved.

1833. Ceramics and amorphous thin films based on gallium sulphide doped by rare-earth sulphides

Authors: Popescu, M; Sava, F; Lorinczi, A; Velea, A; Simandan, ID; Badica, P; Burdusel, M; Galca, AC; Matei, E; Preda, N; Secu, M; Socol, G; Jipa, F; Zamfirescu, M; Balan, A

Published: APR 2015, SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 30, DOI: 10.1088/0268-1242/30/4/044001

Bulk ceramics of Ga2S3 and rare-earth sulfides (EuS, Gd2S3, Er2S3) as well as combinations thereof have been prepared by spark plasma sintering (SPS). The disk-shaped ceramics were used as targets for pulsed laser deposition (PLD) experiments to obtain amorphous thin films. The properties of these new bulks and amorphous thin films have been investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), optical transmission spectroscopy, and atomic force microscopy (AFM). In order to test the photoexpansion effect in Gd2S3 and the possibility to create planar arrays of microlenses, the film was irradiated with femtosecond laser pulses at different powers. For low laser power pulses (up to 100mW power per pulse) a photoexpansion effect was observed, which leads to formation of hillocks with a height of 40-50 nm. EuS doped Gd2S3 thin film shows luminescence properties, which recommend them for optoelectronic applications.

1834. Microstructure and properties of epitaxial Sr2FeMoO6 films containing SrMoO4 precipitates

Authors: Deniz, H; Preziosi, D; Alexe, M; Hesse, D; Eisenschmidt, C; Schmidt, G; Pintilie, L

Published: APR 2015, JOURNAL OF MATERIALS SCIENCE, 50, 3138, DOI: 10.1007/s10853-015-8874-7

Thin films of Sr2FeMoO6 (SFMO) were grown by pulsed laser deposition in non-optimized argon ambient pressures. The films were found to contain a high number of precipitates of foreign phases. The nature and microstructure of these phases were investigated in detail by high-resolution scanning transmission electron microscopy (STEM) and X-ray diffractometry (XRD). We found out that the dominant foreign phase embedded in the SFMO film matrix was SrMoO4 (SMO). Through STEM and XRD analysis, we determined that the SMO phase grows epitaxially with respect to the surrounding SFMO matrix and has a fairly good crystallinity. Although the SFMO films include many foreign precipitates, they still exhibit good conducting properties and moderate magnetization values. Tuning the growth of the SMO phase on top of SFMO films to obtain a natural tunnel barrier might pave the way for future applications of SFMO in spintronic devices.

1835. Dry reforming of methane on ceria prepared by modified precipitation route

Authors: Rotaru, CG; Postole, G; Florea, M; Matei-Rutkovska, F; Parvulescu, VI; Gelin, P

Published: MAR 25 2015, , DOI: 10.1016/j.apcata.2015.01.024

1836. Effect of counterion on the mesomorphic behavior and optical properties of columnar pyridinium ionic liquid crystals derived from 4-hydroxypyridine

Authors: Pana, A; Badea, FL; Ilis, M; Staicu, T; Micutz, M; Pasuk, I; Circu, V

Published: MAR 5 2015, JOURNAL OF MOLECULAR STRUCTURE, 1083, 251, DOI: 10.1016/j.molstruc.2014.11.059

A series of 3,4,5-tridodecyloxybenzyl pyridinium salts derived from 4-hydroxypyridine has been designed and prepared. The liquid crystalline properties of these compounds were investigated by polarized optical microscopy, differential scanning calorimetry and powder X-ray diffraction while their thermal stability was studied by thermogravimetric analysis. The N-3,4,5-tridodecyloxybenzyl-4-pyridone intermediate shows a monotropic columnar hexagonal mesophase ranging from 56 degrees C down to room temperature while the corresponding bromide dodecyl O-alkylated pyridinium salt shows one enantiotropic columnar mesophase and one additional monotropic columnar phase at lower temperatures. Replacing bromide ion (Br-) with other counterions (NO3-, BF4- and PF6-) resulted in mesophase suppression. These luminescent pyridinium salts show weak emission in dichloromethane solutions at room temperature and a pronounced red-shifted emission in solid state. Photoluminescent properties of the pyridinium salts do not depend significantly on the nature of counterion employed. (C) 2014 Elsevier B.V. All rights reserved.

1837. Thin films of amorphous Ga2S3 and rare-earth sulphides

Authors: Popescu, M; Lorinczi, A; Sava, F; Velea, A; Simandan, ID; Badica, P; Burdusel, M; Galca, AC; Socol, G; Jipa, F; Zamfirescu, M

Published: MAR 1 2015, MATERIALS LETTERS, 142, 231, DOI: 10.1016/j.matlet.2014.12.028

The aim of this research is to prepare amorphous thin films of undoped gallium sulphide and doped with rare-earth sulphides, of rare-earth sulphides and to investigate their physical properties. We have prepared thin amorphous films of Ga2S3, EuS, Er2S3, Gd2S3, and Ga2S3 doped with rare-earth sulphides (Ga2S3:EuS, Ga2S3:Er2S3, Ga2S3:Gd2S3) by Pulsed laser Deposition (PLD). The corresponding targets for preparation of amorphous thin films were obtained by Spark Plasma Sintering (SPS) from commercially available powders of binary sulphides. The structural results for the undoped and doped Ga2S3 thin films indicate a packing of disordered layers similar to that of amorphous As2S3. Femtosecond laser irradiation of the Ga2S3 thin films shows a photoexpansion effect at low laser power (85-100 mW) and an ablation effect at higher laser power (above 105 mW). The threshold between low power and high power pulses is situated at higher value for Ga2S3 (100 mW) in comparison with the case of As2S3 thin films (20 mW). (C) 2014 Elsevier B.V. All rights reserved.

1838. Biomimetic nanocrystalline apatite coatings synthesized by Matrix Assisted Pulsed Laser Evaporation for medical applications (vol 181, pg 56, 2014)

Authors: Visan, A; Grossin, D; Stefan, N; Duta, L; Miroiu, FM; Stan, GE; Sopronyi, M; Luculescu, C; Freche, M; Marsan, O; Charvillat, C; Ciuca, S; Mihailescu, IN

Published: MAR 2015, MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS, 193, 206, DOI: 10.1016/j.mseb.2014.10.011

1839. Applicability of the Stoner-Wohlfarth Model for Ni-Fe Graded Thin Films

Authors: Kuncser, A; Schinteie, G; Ghica, C; Antohe, S; Kuncser, V

Published: MAR 2015, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 28, 969, DOI: 10.1007/s10948-014-2684-z

Fe-Ni graded films have been prepared by co-sputtering permalloy and Fe targets at different time-power sequences. Morpho-structural and magnetic investigations have been performed by transmission electron microscopy, Xray reflectometry, conversion electron Mossbauer spectroscopy and magneto-optic Kerr effect vector magnetometry, proving the thickness dependence of the properties. A magnetization reversal involving the displacement of Bloch-type walls is characteristic for a 115 nm thick Fe-Ni graded film whereas an in-plane coherent rotation of the spins, according to a Stoner-Wohlfarth mechanism was evidence for a 23 nm thick Fe-Ni graded film.

1840. Fabrication of magnetite-based core-shell coated nanoparticles with antibacterial properties

Authors: Grumezescu, AM; Cristescu, R; Chifiriuc, MC; Dorcioman, G; Socol, G; Mihailescu, IN; Mihaiescu, DE; Ficai, A; Vasile, OR; Enculescu, M; Chrisey, DB

Published: MAR 2015, BIOFABRICATION, 7, DOI: 10.1088/1758-5090/7/1/015014

We report the fabrication of biofunctionalized magnetite core/sodium lauryl sulfate shell/antibiotic adsorption-shell nanoparticles assembled thin coatings by matrix assisted pulsed laser evaporation for antibacterial drug-targeted delivery. Magnetite nanoparticles have been synthesized and subsequently characterized by transmission electron microscopy and x-ray diffraction. The obtained thin coatings have been investigated by FTIR and scanning electron microscope, and tested by in vitro biological assays, for their influence on in vitro bacterial biofilm development and cytotoxicity on human epidermoid carcinoma (HEp2) cells.