National Institute Of Materials Physics - Romania

Publications

5975 articles found

3691. Film-substrate lattice-engineering of HTS thin films

Authors: Endo, K; Badica, P

Published: 2008, INTERNATIONAL SYMPOSIUM ON LATTICE EFFECTS IN CUPRATE HIGH TEMPERATURE SUPERCONDUCTORS (LEHTSC2007), 108, DOI: 10.1088/1742-6596/108/1/012045

Materials may show anisotropic properties on different crystal directions and this is also the case of High Temperature Superconductors (HTS). To take advantage of the materials anisotropy one concept of interest is "orientation engineering" in thin films. This can be realized through the control of the film-substrate lattice relationship. Some examples in this regard are presented in this work and through comparative analysis we try to evaluate the viability of this approach and of he entcountered problems. It is expected that in the future this approach will generate new nano composite materials with new properties and effects leading to development of new devices with new or improved functionality.

3692. Growth control of perovskite-related oxide thin films

Authors: Endo, K; Badica, P

Published: 2008, ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES, 64, C559, DOI: 10.1107/S0108767308082056

3693. Synthesis and Electro-Optical Studies on Composite Material: Functionalized Copolymer Particles/Nematic Liquid Crystal

Authors: Manaila-Maximean, D; Rosu, C; Donescu, D; Frunza, S

Published: 2008, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 495, 520, DOI: 10.1080/15421400802432477

We have synthesized new functionalized copolymers of the type divinyl benzene maleic anhydride (DVB-MA) in order to ensure a better compatibility with the penthyl-phenol group of the liquid crystal. These particles have been mixed by stirring and ultrasound with nematic liquid crystals ZLI 1221 (Merck), concentration 5% b.w. (copolymer/LC). We applied cycles of temperature and electric field, corresponding to the TSDC method. We measured the depolarization currents and simultaneously the optical transmission as a function of the electric field and temperature. We obtained information regarding the conduction mechanism, the distribution of the activation energy and the influence of the polarizing voltage oil the optical transmission.

3694. Scanning electron microscopy and resistive transition of in-situ grown YBCO films by pulsed laser deposition

Authors: Branescu, M; Ward, I; Huh, J; Matsushita, Y; Zeltzer, G

Published: 2008, INTERFACIAL NANOSTRUCTURES IN CERAMICS: A MULTISCALE APPROACH, 94, DOI: 10.1088/1742-6596/94/1/012007

In this paper we summarize the deposition parameters, the crystalline structure and the critical temperature of the in-situ grown YBa2Cu3O7-delta(YBCO) films obtained by pulsed laser deposition (PLD) using our kinetic cool-down regime, described in previous papers. We analyze the resistive transition curves and the corresponding scanning electron microscopy (SEM) pictures of the best in-situ grown YBCO films, in order to better characterize the films and refine the deposition process. SEM pictures reveal the typical surface morphology of both in-situ grown and post-deposition, oxygen atmosphere annealed YBCO films. A significant smoother surface of the in-situ grown films is obtained.

3695. Transport and magnetic properties of CrO2-polymer magnetic composites

Authors: Sandu, V; Popa, S; Plapcianu, C; Sandu, E; Hurduc, N; Nor, I

Published: 2008, MULTI-FUNCTIONAL MATERIALS AND STRUCTURES, PTS 1 AND 2, 47-50, +, DOI: 10.4028/www.scientific.net/AMR.47-50.326

We report the transport and magnetic properties of sintered CrO2-polymer composites. In order to improve the elastic properties of the CrO2-based composites, we investigated two types of styrene-based copolymers: poly(methyl methacrylate)-styrene (9/1 and 5/5) and linear polysiloxane-g-styrene as well as poly(methyl methacrylate)-butadiene 9/1. The electric transport and magnetoresistance are consistent with the spin tunneling model at low temperatures but the contribution of spin independent channels becomes important at high temperature and high fields. All composites display ferromagnetism at room temperature with saturation at low fields and a slightly temperature-dependent coercive field for the samples grafted either with butadiene or with styrene except for CrO2-polysiloxane-g-styrene composite where it exponentially decreases with increasing temperature.

3696. Correlation between ionization and displacement damage in silicon detectors for energies of interest in astroparticle and particle physics applications

Authors: Lazanu, I; Lazanu, S

Published: 2008, ROMANIAN REPORTS IN PHYSICS, 60, 387, DOI:

The use of semiconductors as detectors for particle and astroparticle physics imposes the understanding of the processes produced in material, their effects on the electronic properties, in their microscopic structure and at the device level. Calculations of LET and NIEL for different ions including hypothetical exotic particles put into evidence the peculiarities of these interactions.

3697. MICROWAVE FILTERS WITH MULTIPLE CROSS-COUPLINGS AND MAXIMUM NUMBER OF CONTROLLED ATTENUATION POLES

Authors: Lojewski, G; Militaru, N; Banciu, MG

Published: 2008, CAS: 2008 INTERNATIONAL SEMICONDUCTOR CONFERENCE, PROCEEDINGS, +, DOI: 10.1109/SMICND.2008.4703373

In this paper a novel configuration of microwave planar filters, with multiple cross-couplings and with a number of poles of attenuation NZ equal to the order N of the filter, is investigated The position of the poles on the frequency axis can be controlled, allowing the design of band-pass filters with improved selectivity with respect to the adjacent channels. The new configurations were designed and verified by em-field simulation. The responses of the designed filters are in good agreement with the specification, confirming the possibilities of designing microwave band-pass filters of a relatively low order with moderate losses and with improved performances.

3698. Mechanical Treatments at Room Temperature of Nb3Sn Practical Wires: pre-torsion for wires with a different architecture

Authors: Badica, P; Oguro, H; Awaji, S; Nishijima, G; Watanabe, K

Published: 2008, 8TH EUROPEAN CONFERENCE ON APPLIED SUPERCONDUCTIVITY (EUCAS'07), 97, DOI: 10.1088/1742-6596/97/1/012036

Room temperature mechanical treatment consisting of multiple torsion loadings (named pre-torsion) was applied to Nb3Sn composite wires with different architecture to reduce thermal residual compressive strain experienced by the superconducting Nb3Sn filaments. Due to this effect all investigated wires have shown enhancement of the critical current density, I-c up to 56% at 15T and 4.2K. Enhancement of I-c was larger for the reinforced wires than for the wires without reinforcement suggesting that reinforcement is useful in strain relaxation during pre-torsion. The best results were obtained when the position of the reinforcement was located in the outer region of the wire. Pre-torsion is similar or more efficient than cycles of bending loadings (named pre-bending). For pre-torsion important parameter is rotation angle per length of the wire and optimum conditions for short wires are valid for long wires. Uniformity of Ic along the length of a 99cm wire after pre-torsion was within +/-2.1A.

3699. INVESTIGATION ON MICROWAVE SIGNAL PROPAGATION THROUGH SOME LEFT-HANDED STRUCTURES

Authors: Banciu, MG; Ioachim, A; Militaru, N; Lojewski, G

Published: 2008, CAS: 2008 INTERNATIONAL SEMICONDUCTOR CONFERENCE, PROCEEDINGS, +, DOI: 10.1109/SMICND.2008.4703340

Some aspects of microwave propagation through left-handed materials are investigated in this paper. The strong distortion of a Gaussian TEM pulse through a material with negative refraction index is studied in the time domain. Moreover, a method of extracting the constitutive parameters of a material by using the scattering parameters of a sample two-port is developed This method is then applied to some left-handed microstrip structures.

3700. High temperature thermoluminescence of Mn2+-doped MgF2 phosphor for personal dosimetry

Authors: Secu, M; Secu, CE; Jipa, S; Zaharescu, T; Cutrubinis, M

Published: FEB-JUN 2008, RADIATION MEASUREMENTS, 43, 386, DOI: 10.1016/j.radmeas.2007.11.047

Thermoluminescence (TL) curve recorded after gamma-irradiation at room temperature of Mn2+-doped MgF2 phosphor shows TL peaks at 91, 147, 200, 235 and 295 degrees C. The 147 degrees C peak was tentatively attributed to the F centres recombination with hole centres trapped in the neighbourhood of the Mn2+ impurity. This peak shows a good stability (low fading) and has been used to characterise the TL phosphor dosimetric properties. TL dose dependence has shown a good linearity in the range from 0.2 to 10 mGy, which makes it suitable for personal and medical dosimetry. The TL curves recorded after gamma rays or particles irradiation are similar, which suggests the possibility to use the phosphor also for particle detection. (C) 2007 Elsevier Ltd. All rights reserved.