National Institute Of Materials Physics - Romania

Publications

5781 articles found

2571. DROP IMAGES WITH REFLECTION SPOTS: IMPROVED PROCESSING FOR DETERMINATION OF WETTING CONTACT ANGLES

Authors: Cotorobai, VF

Published: 2012, ROMANIAN REPORTS IN PHYSICS, 64, 481, DOI:

Improvements in automatic processing of movie frames taken on commercial Drop Shape Analysis systems are presented, regarding the use of particular edge detection algorithms that account for optical peculiarities of the drop image formed on digital video camera sensors. These improvements can lead to better measurements of contact angles for drop images that present spots of reflected light close to edge and in the case of very low contact angles.

2572. TRANSPORT MECHANISMS IN SiO2 FILMS WITH EMBEDDED GERMANIUM NANOPARTICLES

Authors: Palade, C; Lepadatu, AM; Stavarache, I; Maraloiu, AV; Teodorescu, VS; Ciurea, ML

Published: 2012, 2012 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1 AND 2, 2, 94, DOI:

This paper reports on the conduction mechanisms in amorphous SiO2 films with embedded Ge nanoparticles. For this, measurements of current-temperature and current-voltage were employed and correlated with the microstructure results obtained from transmission electron microscopy (TEM). TEM images reveal that our films contain big Ge nanoparticles with low density and small Ge nanoparticles with high density, the last ones being the only responsible for the electrical transport. Two transport mechanisms were found at low and high temperature respectively, namely hopping on localized states in a band near Fermi level and charge excitation to the extended states at mobility edge.

2573. First principles study and variable range hopping conductivity in disordered Al/Ti/Mn-doped ZnO

Authors: Plugaru, R; Sandu, T; Plugaru, N

Published: 2012, RESULTS IN PHYSICS, 2, 197, DOI: 10.1016/j.rinp.2012.10.004

Based on first principles electronic structure calculations using the Coherent Potential Approximation (CPA) in the Blackman-Esterling-Berk (BEB) multiscattering formalism and the variable range hopping (VRH) model proposed by Mott, we evaluate the low temperature dc conductivity and its temperature dependence for n-doped wurtzite-type M:ZnO, with M = Al, Ti, Mn, at concentrations of 2, 5 and 10 at.% respectively. We theoretically determine the phenomenologic quantities in the expression of the hopping conductivity, as well as the temperature range in which the VRH model is applicable to the investigated compounds. We show that self-consistent CPA-BEB and LSDA+U calculations yield reasonable band gaps, dopant state localization and also spin magnetic moments for the Ti and Mn systems. These results are discussed in comparison with reported data obtained by supercell LSDA+U calculations for similar systems. The results in this study point to 2-5 at.% Ti and approximately 2 at.% Al codoping in wurtzite-type ZnO as an interesting option to obtain a material with an increased low temperature dc conductivity and ferromagnetic background. (C) 2012 Elsevier B.V. Open access under CC BY-NC-ND license.

2574. Surface Analysis of Inhibitor Film Formed by 4-Amino-N-(1,3-thiazol-2-yl) Benzene Sulfonamide on Carbon Steel Surface in Acidic Media

Authors: Samide, A; Tutunaru, B; Negrila, C; Prunaru, I

Published: 2012, SPECTROSCOPY LETTERS, 45, 64, DOI: 10.1080/00387010.2011.598599

Inhibitive properties of the antibacterial sulfa drug sulfathiazole-IUPAC name being 4-amino-N-(1,3-thiazol-2-yl) benzene sulfonamide-on the corrosion of carbon steel in 1.0M HCl solution were investigated using weight loss measurements, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Sulfathiazole is a good adsorption inhibitor, and the inhibition efficiency increases with increasing concentration. Adsorption is spontaneous and is best described by Temkin isotherm. XPS analysis showed, at this stage, that the main product of corrosion is a nonstoichiometric Fe3+ oxide/oxyhydroxide consisting of a mixture of Fe2O3, alpha, and gamma-FeO(OH) and/or Fe(OH)(3), where alpha, gamma-FeO(OH) is the main phase.

2575. HIGH-DENSITY GREEN PHOTONS EFFECTS ON NaCl SOLUTIONS DETECTED BY RED BLOOD CELLS MEMBRANES

Authors: Mitrica, R; Popescu, I; Paslaru, L; Badila, D; Polosan, S; Cristache, L; Ionescu, E; Tataru, C; Comorosan, S

Published: JAN-MAR 2012, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 7, 235, DOI:

This paper presents a new technique for investigating the modifications induced by high-density green light [GL] on water in NaCl solutions. Solutions of 0,45 g% and 0,9 g%, irradiated with green light (lambda = 527 nm, intensity 3.10(5) Lx) were used. As a receptor for measuring the irradiation effect we used red blood cell (RBC) permeability in hypotonic media, the so-called osmotic shock. After RBC lysis in hypotonic medium, the released hemoglobin was spectrophotometrically determined at lambda = 550 nm. The values of the osmotic shock for the samples obtained with GL-irradiated NaCl solutions were significantly lower than the values obtained with non-irradiated controls. This may indicate that the penetration of water inside the membranes canaliculi is hindered. This new type of result was complemented by chronoamperometry and impedance spectroscopy determinations. The current density of the irradiated solution decreases from the value of 29.5 mu A.cm(-2) in the control to 17.74 mu A.cm(-2) in the irradiated sample with a corresponding decrease of ionic mobility. The impedance value of the GL irradiated NaCl solutions were significantly lower than the control values, thus correlating well with the data recorded by chronoamperometry. All these data may indicate large water cluster formation through GL irradiation which are beyond the cellular aquaporine channels capacity. A similar process is identified by using red light, as well as blue light, though with a much smaller output.

2576. Magnetic Interfaces at the Nanoscale: From Fundamentals to Technological Applications

Authors: Angelakeris, M; Crisan, O; Martinez-Boubeta, C

Published: 2012, JOURNAL OF NANOMATERIALS, 2012, DOI: 10.1155/2012/619485

2577. NONLINEAR OPTICAL PROCESSES MANIFESTING AS ANDERSON LOCALIZATION OF LIGHT IN MESOSCOPIC MATERIALS

Authors: Baltog, I; Baibarac, M; Mihut, L; Smaranda, I; Lefrant, S

Published: APR-JUN 2012, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 13, 117, DOI:

Abnormal anti-Stokes Raman emission (AASRE) is defined by an anti-Stokes/Stokes intensity ratio much greater than expected on the basis of the equilibrium population of excited vibration states provided by the Boltzmann law. AASRE can be observed both in materials with intrinsic nonlinear optical properties as LiNbO3 or materials in which the nonlinear optical properties are induced by resonant optical excitation, as carbon nanotubes. Using a surface enhanced Raman scattering (SERS) device, consisting from single wall carbon nanotubes deposited on a rough Au or Ag support and LiNbO3 in form of powder, we demonstrate that under continuous single beam excitation they present AASRE whose properties are similar to a single beam pumped Coherent Anti-Stokes Raman Scattering. AASRE is usually accompanied by a coherent backscattering, it can be considered as Anderson localization of light that results from a wave-mixing mechanism of the incident laser light with a Stokes shifted Raman light produced by a spontaneous Raman light scattering process. The transport of the light inside of sample, giving rise to AASRE and coherent backscattering, is done by an elastic light scattering mechanism.

2578. The critical current density of SiC-doped MgB2 as determined from the Campbell penetration depth using the tunnel-diode resonator technique

Authors: Guo, ZC; Suo, HL; Liu, ZY; Sandu, V; Aldica, G; Badica, P

Published: NOV-DEC 2012, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 6, 979, DOI:

The tunnel-diode resonator (TDR) technique for accurate measurements of the magnetic penetration depth is used to measure the London and Campbell penetration depths of polycrystalline SiC doped (10wt.%) MgB2. The Campbell length was used to investigate the field and temperature dependence of the critical current density. The as determined critical current density provides values as high as 6x10(6) A/cm(2) at 4.2K, 1T, which is higher than values estimated by Bean method.

2579. Ba(Zn1/3Ta2/3)O-3 perovskite ceramics doped with Nb5+, Ce4+ or Yb3+

Authors: Busuioc, C; Jinga, SI; Stoleriu, S; Nedelcu, L; Andronescu, E

Published: MAR-APR 2012, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 14, 244, DOI:

Ba(Zn1/3Ta2/3)O-3 (BZT) perovskite material has stimulated a large interest due to its excellent dielectric properties in microwave frequency range, enabling the miniaturization of communications devices. In this work, BZT ceramics were prepared by the conventional solid-state reaction method, being doped with Nb5+, Ce4+ or Yb3+. BZT resonators were compositional, structural, morphological and electrical characterized. The influence of the dopants and sintering temperature on the microwave dielectric properties of BZT samples was investigated. The resonator doped with 0.5 mol% Nb2O5 and sintered at 1600 degrees C / 2 h exhibits the best dielectric behaviour: e(r) similar to 25.9 and Qxf similar to 159 THz.

2580. Energy loss and transient phenomena induced by exotic particles in materials for detectors

Authors: Lazanu, S; Lazanu, I

Published: 2012, XXVII INTERNATIONAL CONFERENCE ON PHOTONIC, ELECTRONIC AND ATOMIC COLLISIONS (ICPEAC 2011), PTS 1-15, 388, DOI: 10.1088/1742-6596/388/7/072015

In the present contribution, the peculiarities of the electronic and nuclear energy loss of some "exotic" particles, as well as the transient phenomena produced in materials during their stopping are investigated, for their potential use in detectors. In some cases (e. g. strangelets or fullerene ions), these phenomena are produced directly by the incoming particles, and also by their secondary products, while in others (e. g. weakly interacting massive particles) only by the recoils resulting from their elastic scattering on the nuclei of the target. The analysis is made in the frame of a thermal spike model, as time and space dependencies of the electronic and atomic temperatures in the neighbourhood of the interaction point or of the trajectory of the particle.