National Institute Of Materials Physics - Romania

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5781 articles found

3231. MOSSBAUER BACKSCATTERING MEASUREMENTS ON EU-151

Authors: Bibicu, I; Cretu, C

Published: 2009, ROMANIAN JOURNAL OF PHYSICS, 54, 519, DOI:

The possibility to make surface measurements in the nano or micro range by Mossbauer spectroscopy using (151)Eu Mossbauer isotope is demonstrated. Measurements were made with a new flow detector in a backscattering geometry. With this detector it is possible to detect conversion electrons or low energy X-rays. An Eu(2)O(3) sample has been used. These measurements have been performed for the first time in Romania.

3232. ASPECTS OF TEMPERATURE DEPENDENCE ON Au-Ti/GaAs(SI) SCHOTTKY BARRIER

Authors: Negrila, CC; Ungureanu, F; Ghita, RV

Published: 2009, CAS: 2009 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, PROCEEDINGS, 458, DOI:

Fabrication of Au-Ti Schottky structure on GaAs semi-insulating wafer was related to an ultra-high vacuum deposition condition and low vacuum annealing in low vacuum and temperature range T=320-360 degrees C. There are presented representative I-V characteristics in dark and in different light (power levels). The spectral response has a maximum in Delta lambda = (850-950) nm corresponding to a band-to-band transition. The complex dependence of optical generated non-equilibrium carriers is related to the equivalent state density at the conduction band edge (in T(3/2) factor) and in exponential distribution factor exp (-(E-F)/kT).

3233. Preparation and Characterization of Polar Aniline Functionalized Copolymers Thin Films for Optical Non-Linear Applications

Authors: Stanculescu, A; Rasoga, O; Preda, N; Socol, M; Stanculescu, F; Ionita, I; Albu, AM; Socol, G

Published: 2009, FERROELECTRICS, 389, 173, DOI: 10.1080/00150190902993291

This paper presents a study of two monomeric structures containing functional groups with different electronegativities [NH/NH-NH and NO2] and two different polymeric structures prepared by the copolymerisation of maleic anhydride and methylmethacrylate/maleic anhydride and vinyl benzyl chloride, and subsequent functionalization with 2,4 dinitroaniline. Thin films have been prepared by Matrix Assisted Pulsed Laser Evaporation (MAPLE) and UV-VIS, FTIR, Raman and Photoluminescence Spectroscopy have been used to comparatively investigate the properties of the synthesised compounds. We have evidenced the second harmonic emission (SHG), process sustained by the asymmetry of the chemical structure, which is correlated with the crystallization in non-centrosymmeric structures.

3234. CATALYTIC AND ELECTRICAL PROPERTIES OF IRON OXIDE IN DEEP PROPANE OXIDATION

Authors: Munteanu, C; Ionescu, NI; Feder, M; Diamandescu, L; Caldararu, M

Published: NOV-DEC 2009, REVUE ROUMAINE DE CHIMIE, 54, +, DOI:

The catalytic activity of hematite (alpha-Fe(2)o(3)) was studied in deep propane oxidation. Propane conversion to CO(2) was more than 90% at 400 degrees C in excess of oxygen. The AC electrical conductivity measurements performed in situ showed that at low temperature the surface conductivity is influenced by the presence of moisture in the feed which is adsorbed on the surface. Based on the conductivity data obtained in absence of oxygen coupled with information provided by Mossbauer spectroscopy, the results are discussed in terms of the redox-type mechanism.

3235. Cobalt doped ZnO prepared by electrochemistry: chemistry, morphology, and magnetism

Authors: Enculescu, I; Matei, E; Vasilache, V; Teodorescu, CM

Published: 2009, NANOTECH CONFERENCE & EXPO 2009, VOL 3, TECHNICAL PROCEEDINGS: NANOTECHNOLOGY 2009: BIOFUELS, RENEWABLE ENERGY, COATINGS FLUIDICS AND COMPACT MODELING, +, DOI:

ZnO:Co thin Films are prepared by electrochemical deposition at different overpotentials and investigated by scanning electron microscopy, X-ray photoelectron spectroscopy and Kerr magnetometry (MOKE). Increse of structural disorder and crystallite re-orientation are observed for cobalt doped samples (especially for those obtained at - 750 and at - 800 mV overpotentials). MOKE magnetometry revealed room temperature ferromagnetic behaviour only for ZnO:Co deposited at - 850 mV. These are the samples with the less cobalt content and lowest structural perturbation of the ZnO matrix by cobalt.

3236. Modelling of dissolution kinetics of thin amorphous chalcogenide films

Authors: Popescu, M; Sava, F; Lorinczi, A; Velea, A; Vlcek, M; Jain, H

Published: 2009, PHILOSOPHICAL MAGAZINE LETTERS, 89, 376, DOI: 10.1080/09500830902960117

A theoretical relationship for the dissolution kinetics of thin chalcogenide films is proposed. The influence of light irradiation on the film dissolution is taken into account. The theoretical curves are in good agreement with the experimental dissolution results obtained for As2S3 thin amorphous films.

3237. ABSORPTION AND LUMINESCENCE PROPERTIES OF C-70 AGGREGATES IN SOLVENT MIXTURES

Authors: Husanu, AM; Baltog, I; Baibarac, M; Preda, N; Mihut, L; Velula, T; Bucur, C

Published: 2009, ROMANIAN JOURNAL OF PHYSICS, 54, 538, DOI:

We report the formation of stable C-70 aggregate forms in o-dichlorobenzene/N-methyl-2-pyrrolidinone (DCB/NMP) and o-dichlorobenzene/acetonitrile (DCB/ACN) mixtures and their characterization by UV-VIS absorption spectroscopy and photoluminescence. As NMP acts on C-70 both as a solvent and reactant due to the unpaired electrons of the amidic nitrogen atom, molecular complexes (C-70/NMP) that aggregate slowly are formed by the binding of the NMP molecule to the fullerene cage. This interaction is seen in the UV-VIS absorption spectra of C-70 in DCB/NMP solvent mixtures by a gradual modification of the absorption spectra when increasing the NMP concentration. On the other hand, DCB and ACN combined form it typical solvent/non-solvent mixture favoring an intense aggregation of fullerenes. This yields to the C-70 clusters formations, having different size, similar to a precipitation process. Their characteristic is an abrupt variation in the absorbance appearing when the ACN is used in a greater extent. This different behavior of C-70 aggregation in DCB/NMP and DCB/ACN mixtures is also seen in their luminescence spectra recorded at different excitation wavelengths. While the PL spectra of C-70 solvated in DCB/NMP solution keeps almost the same modified shape irrespective the NMP concentration, the luminescence spectra Of C-70 in DCB/ACN mixture partially regains the powder C-70 PL signature as the ACN concentration is increased.

3238. Dielectric Properties of Paraelectric Ba1-xSrxTiO3 Ceramics

Authors: Nedelcu, L; Toacsan, MI; Banciu, MG; Ioachim, A

Published: 2009, FERROELECTRICS, 391, 41, DOI: 10.1080/00150190903001086

Ba1-xSrxTiO3 solid solutions with x = 0.4, 0.5, 0.6 and 0.75 were prepared by solid state reaction at 1260 degrees C. The complex dielectric constant dispersion was investigated in the frequency range 1Hz divided by 10 MHz for temperatures between -100 degrees C and 100 degrees C. Microwave measurements, performed at room temperature, show amonotonically decrease of the permittivity from about 3000 to 300 with the increase of the strontium content. Moreover, the variation of the dielectric loss from 0.8% to less than 0.2% with the increase with x was observed. The results indicate that the paraelectric Ba1-xSrxTiO3 materials are suitable for microwave applications.

3239. THE INTERCALATION OF PbI2 WITH 2,2 '-BIPYRIDINE EVIDENCED BY PHOTOLUMINESCENCE. FT-IR AND RAMAN SPECTROSCOPY

Authors: Preda, N; Mihut, L; Baibarac, M; Baltog, I; Husanu, M; Bucur, C; Velula, T

Published: 2009, ROMANIAN JOURNAL OF PHYSICS, 54, 675, DOI:

Hybrid material based on PbI2 intercalated with 2,2'-bypiridine (BIPY) was investigated by correlated studies of photoluminescence. infrared absorption and Raman spectroscopy. The PbI2(BIPY) intercalated compound has been synthesized by the chemical reaction of K1 and Pb(NO3)(2) in aqueous BIPY solution The optical studies reveal different properties for the hybrid material in comparison with those of pure PbI2 and BIPY. In the photoluminescence spectrum of the intercalated compound. recorded at liquid nitrogen temperature a new intense hand emission with maximum at 2 07 eV is observed. The excitation spectrum reveals it broad hand featured by several maxima at 2.77, 3.34 and 3 70 eV. New absorption bands at about 1589, 1489, 1435, 1312, 1009 cm(-1) are observed in the IR spectrum of PbI2(BIPY). The Raman spectrum of intercalated compound discloses new lines at 67, 83, 127 cm(-1) and the shift of two Raman lines from 994 cm(-1) to 1010 cm(-1) and from 1045 cm(-1) to 1060 cm(-1). A charge transfer process, leading to the formation of lead-BIPY coordination complexes. is considered its responsible for the strong host-guest interaction revealed by almost all experimental data

3240. THE SIMULATION IN THE REAL CONDITIONS OF ANTIBACTERIAL ACTIVITY OF TiO2 (Fe) FILMS WITH OPTIMIZED MORPHOLOGY

Authors: Gartner, M; Anastasescu, C; Zaharescu, M; Enache, M; Dumitru, L; Stoica, T; Stoica, TF; Trapalis, C

Published: 2009, NANOSTRUCTURED MATERIALS AND NANOTECHNOLOGY II, 29, +, DOI:

The aim of this study was to provide and characterize nanostructured TiO2 films for application in the depollution of the contaminated water against Escherichia coli (E. coli). The nanometric size of particles and the porosity of the films have been correlated with the technological parameters of the deposition process. For this aim three-layer TiO2 films were deposited by sol-gel and dip-coating method on SiO2/glass substrate. Iron (1 and 7%) and polyethylene glycol (PEG(600)) (0.014-0.110 M) were added to the coating solutions to study their effect on the porosity of the samples and respectively on the amorphous to anatase phase transition, as well as on the antibacterial activity. The samples were characterized using different complementary methods such as X-ray Diffraction (XRD), Spectroscopic Ellipsometry (SE), Atomic Force Microscopy (AFM), dynamics (growth and adherence) of E. coli development versus nanofilm composition (where the amount of bacterial inoculums used was closer to those Found in wasted waters). The obtained films have shown low toughness (values bellow 0.74 nm) and the particle size in nanometric range. The direct optical band gap values increases with the Fe content tip to 2.64 eV (470 nm), leading to an active photocatalyst tinder visible light (in our case under natural illumination condition). The inhibitory effect towards the E. Coli is Correlated with PEG and Fe concentration and was found to he the strongest for the sample containing 0.069 M PEG.