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Bucharest, Romania

Pavel E.,Storex Technologies | Jinga S.I.,Polytechnic University of Bucharest | Vasile B.S.,Polytechnic University of Bucharest | Dinescu A.,National Institute for RandD in Microtechnologies | And 2 more authors.
Optics and Laser Technology | Year: 2015

We report novel results for 3D recording of an optical disk with ultra-high density. Multilayer 5 nm nanomarks were experimentally obtained by using fluorescent photosensitive glass-ceramics and an optical head with λ=650 nm and NA=0.60. The distance between adjacent 5 nm nanomarks has been reduced to 10 nm. Ultra-high density optical data is recorded by focusing laser beam of a CW laser diode operating at low power (Pmax=10 mW). © 2015 Elsevier Ltd. All rights reserved. Source


Baicea C.,Polytechnic University of Bucharest | Dorca O.,Polytechnic University of Bucharest | Cuciureanu A.,Polytechnic University of Bucharest | Trusca R.,METAV RandD | Trisca-Rusu C.,National Institute for Research and Development in Microtechnologies
Proceedings of the International Semiconductor Conference, CAS | Year: 2011

This paper presents the synthesis and characterization of a composite polysulfone-polyaniline membrane for electrochemical applications. The polysulfone membrane was obtained by the phase inversion process and polyaniline, obtained from the polymerization of p-phenylenediamine in the presence of hydroquinone, was filtered through this membrane. The material was characterized by thermal analysis, Scanning Electron Microscopy and FT-IR spectroscopy. © 2011 IEEE. Source


Dumitrache F.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Morjan I.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Fleaca C.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Birjega R.,Romanian National Institute for Lasers, Plasma and Radiation Physics | And 3 more authors.
Applied Surface Science | Year: 2011

Iron/iron carbide core and carbon shell nanoparticles with improved magnetic properties were successfully synthesized by laser pyrolysis. As iron and carbon precursors, iron pentacarbonyl and pure or argon-diluted acetylene/ethylene mixtures, respectively, were used. The aim of the present optimization is the improvement of the magnetic properties of the nanomaterials by the increase of the iron percent in powders simultaneously to the maintaining of the protective character of the carbon coverage of nanoparticles. The chemical content and the crystalline structure were monitored by EDX, XRD and TEM techniques. In the first study, the content of acetylene as carbon source was diminished from 75% to 0%. Consequently the percent iron increased from 10 at.% to 28 at.% while oxygen remained relatively constant (around 5 at.%). In the second step, only diluted ethylene was used (maximum 87.5 vol.% Ar). In this case, an increase of iron to 46 at.% is observed. An optimum 50% carbon source dilution was found. Above this value, the carbon content increases and below it, superficial oxidation increases through the diminishing of the carbon shell. The magnetic properties and the Fe phase composition of the Fe-C samples were analyzed by temperature dependent Mössbauer spectroscopy. © 2010 Elsevier B.V. All rights reserved. Source


Alexandrescu R.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Morjan I.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Dumitrache F.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Birjega R.,Romanian National Institute for Lasers, Plasma and Radiation Physics | And 8 more authors.
Applied Surface Science | Year: 2012

Intermetallic Fe-Sn and nanocrystalline metallic Sn nanoparticles have been successfully synthesized from organic precursors using the laser pyrolysis technique with ethylene as sensitizer. Nano-structured Sn (single phase) was prepared by the pyrolysis of Sn(CH 3) 4 (TMT) vapors. Controlled Fe/Sn atomic ratios, ranging from 0.69 to 1.64 were obtained for the prepared Fe-Sn nanopowders by the control of Fe(CO) 5 and TMT flows, respectively. XRD studies evidence three main phases: the tetragonal metallic Sn phase and the intermetallic FeSn 2 phase and, to a much lesser extent, the cubic ternary carbide Fe 3SnC. Complex core-shell structural characteristics were found by HRTEM analysis. More complete information about the Fe phase distributions in the new intermetallic Fe-Sn nanomaterial is provided by temperature dependent 57Fe Mössbauer spectroscopy. © 2012 Elsevier B.V. Source


Fleaca C.T.,National Institute for Laser, Plasma and Radiation Physics | Dumitrache F.,National Institute for Laser, Plasma and Radiation Physics | Morjan I.,National Institute for Laser, Plasma and Radiation Physics | Alexandrescu R.,National Institute for Laser, Plasma and Radiation Physics | And 4 more authors.
Applied Surface Science | Year: 2013

We report the synthesis of novel nanocomposites based on Fe@C nanoparticles obtained from Fe(CO)5 and C2H4/H2 by laser pyrolysis technique using a three nozzles injector. The αFe-FexCy@C particles (below 24 nm diameter) were first functionalized with hydrophilic groups using Na carboxymethylcellulose. Oxidic precursors (Si(OC2H5)4 or Ti(OC 2H5)4) dissolved in ethanol were mixed with ethanolic suspensions of hydrophilized Fe@C nanoparticles using strong ultrasonication, then with water (at different pH values) and finally the Fe-containing composites were recovered by magnetic separation. The SiO 2 and TiO2-coated powders were characterized by XRD, FT-IR and TEM techniques and their magnetic hysteresis curves were recorded at different temperatures. Both composites contain submicron aggregates of Fe@C nanoparticles embedded in/surrounded by a disordered porous oxidic matrix/shell. Near superparamagnetic behavior and room temperature and 26 A m2/kg (for Fe@C/SiO2) or 57 A m2/kg (for Fe@C/TiO2) saturation magnetization values were recorded and a blocking temperature around 500 K was extrapolated. © 2013 Elsevier B.V. Source

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