Entity

Time filter

Source Type

Bucharest, Romania

Ciuprina F.,Polytechnic University of Bucharest | Plesa I.,Polytechnic University of Bucharest | Notingher P.V.,Polytechnic University of Bucharest | Rain P.,Joseph Fourier University | And 2 more authors.
Proceedings of the 2010 IEEE International Conference on Solid Dielectrics, ICSD 2010 | Year: 2010

The dielectric behaviour of nano-SiO2 filled low density polyethylene is investigated over a frequency range of 10 mHz - 10 MHz and for different temperatures from 250 K to 350 K. It is shown that the presence of nanoparticles change significantly the dielectric behaviour of the polymer system. The frequency variations of the permittivity and of the tan delta emphasize a α-relaxation process, for each of the nanocomposite samples. The relaxation is more important and occurs at higher frequencies with the increase of the filler content. The increase of the temperature leads to a shift of the relaxation frequency to higher values. Results from chemiluminescence measurements and from X-ray diffraction analysis are discussed in connection with the dielectric behaviour. ©2010 IEEE. Source


Prepelita P.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Medianu R.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Sbarcea B.,ICPE CA | Garoi F.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Filipescu M.,Romanian National Institute for Lasers, Plasma and Radiation Physics
Applied Surface Science | Year: 2010

ZnO thin films with thikness d = 100 nm were deposited onto different substrates such as glass, kapton, and silicon by radio frequency magnetron sputtering. The structural analyses of the films indicate they are polycrystalline and have a wurtzite (hexagonal) structure. The ZnO layer deposited on kapton substrate shows a stronger orientation of the crystallites with (0 0 2) plane parallel to the substrate surface, as compared with the other two samples of ZnO deposited on glass and silicon, respectively. All three layers have nanometer-scale values for roughness, namely 1.7 nm for ZnO/glass, 2.4 nm for ZnO/silicon, and 6.8 nm for ZnO/kapton. The higher value for the ZnO layer deposited on kapton substrate makes this sample suitable for solar cells applications. Transmission spectra of these thin films are strongly influenced by deposition conditions. With our deposition conditions the transparent conducting ZnO layer has a good transmission (78-88%) in VIS and NIR domains. The values of the energy gap calculated from the absorption spectra are 3.23 eV for ZnO sample deposited onto glass substrate and 3.30 eV for the ZnO sample deposited onto kapton polymer foil substrate. The influence of deposition arrangement and oxidation conditions on the structural, morphological, and optical properties of the ZnO films is discussed in the present paper. © 2009 Elsevier B.V. All rights reserved. Source


Badea D.M.,INCDMTM | Tanasescu F.T.,CER | Marin A.,UPB | Stefanescu G.,CER | And 4 more authors.
Romanian Review Precision Mechanics, Optics and Mechatronics | Year: 2015

There is a general consensus that transfer of technology is the engine of the company, the results of public research institutes and universities have quickly applied, as further expanding its Technology Transfer acting not only formal technology transfer (sale of licenses and patents), but also transfer information technology through direct transmission of knowledge, common organization of activities between people from academia and industry, although this model has elements that are found on all models, and contain specific elements economy of a country and its culture technique. TT Among the programs that respond both theoretical elements and others with practical experience resulting from certain companies were retained significant elements of the study models: Fraunhofer, Vinnova, the American universities, as well as some proposals for significant items which may be taken into consideration in the development of TT concept in Romania. A number of elements that can be drawn from this analysis and useful for policy-making technology transfer in Romania will be mentioned in the paper. © 2015, Editura Cefin. All rights reserved. Source


Carp O.,Institute of Physical Chemistry Ilie Murgulescu | Patron L.,Institute of Physical Chemistry Ilie Murgulescu | Culita D.C.,Institute of Physical Chemistry Ilie Murgulescu | Budrugeac P.,ICPE CA | And 2 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2010

The thermal stability of two kinds of dextran-coated magnetite (dextran with molecular weight of 40,000 (Dex40) and 70,000 (Dex70)), obtained by dextran adsorption onto the magnetite surface is investigated in comparison with free dextran in air and argon atmosphere. The thermal behavior of the two free dextran types and corresponding coated magnetites is similar, but atmosphere dependent. The magnetite catalyzes the thermal decomposition of dextran, the adsorbed dextran displaying lower initial decomposition temperatures comparative with the free one in both working atmospheres. The dextran adsorbed onto the magnetite surface decomposes in air through a strong sharp exothermic process up to ~450 °C while in argon atmosphere two endothermic stages are identified, one in the temperature range 160-450 °C and the other at 530-800 °C. © 2009 Akadémiai Kiadó, Budapest, Hungary. Source


Prepelita P.,National Institute for Laser, Plasma and Radiation Physics | Craciun V.,National Institute for Laser, Plasma and Radiation Physics | Sbarcea G.,ICPE CA | Garoi F.,National Institute for Laser, Plasma and Radiation Physics
Applied Surface Science | Year: 2014

Transparent thin films of SnO2, ZnO:Al, and ITO were deposited onto glass substrate by vacuum thermal evaporation technique, from 0.5 cm diameter grains (i.e. ITO, ZnO:Al (3%) and SnO2) with 99.99% purity. To improve the quality (i.e. stoichiometry and morphology) of these thin films, they were annealed at 400 °C in air for 2 h. Following this annealing, the samples become suitable to be used as contact electrodes for solar cells. The investigations were performed on samples having a polycrystalline structure, as revealed by X-ray diffraction analysis after annealing process. Moreover, these thin films had a strong orientation with the following planes parallel to the substrate: (1 0 1) for SnO2, (0 0 2) for ZnO:Al and (2 2 2) for ITO film respectively. Atomic force microscopy (AFM) investigations of the ZnO:Al (Rrms = 2.8 nm) and ITO samples (Rrms = 11 nm) show they are homogeneous and a slightly higher roughness (Rrms = 51 nm) for the SnO2 thin film surface. The size and shape of the grains were also observed and investigated by scanning electron microscopy (SEM). All SnO2, ZnO:Al and ITO transparent thin films are uniform and dense.The values obtained for electrical resistivity, transmission and energy bandgap as well as conductivity and transparency properties of these thin films, make them suitable to be used as transparent contact electrodes for solar cells. © 2014 Elsevier B.V. All rights reserved. Source

Discover hidden collaborations