National Institute Of Materials Physics - Romania

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5781 articles found

3241. The effect of textural properties of the gamma-Al2O3:Ni catalyst template on the nanostructured carbon grown by PECVD

Authors: Birjega, R; Vizireanu, SI; Dinescu, G; Nistor, LC; Ganea, R

Published: JUL-AUG 2009, SUPERLATTICES AND MICROSTRUCTURES, 46, 301, DOI: 10.1016/j.spmi.2008.10.032

Nanostructured carbon was grown by a plasma enhanced chemical vapour deposition (PECVD) technique, under similar conditions, on two mesoporous gamma-Al2O3:Ni catalyst templates, compacted into pellets. The two catalysts differ by the mean pore size of the gamma-alumina which was 7.5 nm and 3.7 nm and by the Ni particle dimensions of similar to 4 nm and similar to 2 nm, respectively. The paper proves, by X-ray diffraction (XRD) and transmission electron microscopy (TEM), the close dependence of the resulting morphology and dimensions of the deposited carbon nanostructures, on both pore and Ni particles sizes of the gamma-Al2O3:Ni catalyst templates. (C) 2008 Elsevier Ltd. All rights reserved.

3242. STRUCTURAL AND OPTICAL PROPERTIES OF SOL-GEL DERIVED HYDROXYAPATITE FILMS IN DIFFERENT STAGES OF CRYSTALLIZATION AND DENSIFICATION PROCESSES

Authors: Tionica, S; Gartner, M; Ianculescu, A; Anastasescu, M; Slav, A; Pasuk, I; Stoica, T; Zaharescu, M

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

Hydroxyapatite (HAp) films, widely used as a biocompatible material for hard tissues repairing. are studied in this paper for a better control and understanding of the crystallization and densification of sol-gel deposited layers. Calcium nitrate and triethyl phosphite diluted in alcohols were used as calcium and phosphorus precursors. HAp coatings were obtained by spinning method, followed by drying and annealing in the range 130-750 degrees C. Specific temperatures of the chemical reactions of HAp formation have been revealed by thermogravimetric analysis (TG-DTA). Structural. chemical and optical characterizations of the films were performed by Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Analysis (EDX) facilities, X-ray diffraction (XRD). Fourier Transform Infrared Spectroscopy (FTIR) and Spectral Ellipsometry (SE). The film crystallinity increases with file annealing temperature above 550 degrees C. XRD lines of HAp crystallographic planes become narrow at 750 degrees. and correspond to a single crystallographic phase. The Film morphology depends not only on annealing history but also on the synthesis parameters. Thus. layers with large grains of well sinterized HAp nano-crystals can be obtained. Using EDX measurements, the Ca/P ratio was found close to the stoichiometric value in the well sinterized HAp grain regions and slightly increased 1.82 for boundary regions between grains. The density of pores usually observed in sol-gel derived films was estimated for different samples using modeling of SE data.

3243. The Influence of the Electrode Type on the Electric-Ferroelectric Properties of Sandwich PbZr0.2Ti0.8O3-BiFeO3-PbZr0.2Ti0.8O3 Structure

Authors: Pintilie, L; Dragoi, C; Stancu, V; Pintilie, I

Published: 2009, FERROELECTRICS, 391, 66, DOI: 10.1080/00150190903001235

PbZr0.2Ti0.8O3-BiFeO3-PbZr0.2Ti0.8O3 (PZT-BFO-PZT) structure was prepared by sol-gel method on Pt/Si wafers. Three metals were tested as top electrod: Au, Cu, and Pt. A double hysteresis loop was observed in all cases, suggesting an antiferroelectric-like behavior. The values for remnant polarization and coercive field are about 3 mu C/cm(2) and 115 kV/cm, respectively. The saturation polarization is about 22 mu C/cm(2). Capacitance and leakage current show significant dependence on the top metal electrode. The results were explained considering the presence of a Schottky-type contact at the PZT-metal interface.

3244. Mossbauer backscattering measurements on Sn

Authors: Bibicu, I; Nicolescu, G; Cretu, C

Published: 2009, ADVANCED TOPICS IN OPTOELECTRONICS, MICROELECTRONICS, AND NANOTECHNOLOGIES IV, 7297, DOI: 10.1117/12.823676

3245. Novel Microwave Planar Bandpass Filter Structures With Strongly Asymmetric Characteristics

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

Published: 2009, 2009 MEDITERRANEAN MICROWAVE SYMPOSIUM, +, DOI:

In this paper the problem of designing simple low-cost planar microwave bandpass filters with strongly asymmetric characteristics, filters that can very efficiently attenuate one of the two adjacent channels, is investigated. In case of a fourth-order filter, the usual quadruplet structure leads to two transmission zeros located one on each side of the passband, but higher attenuation can be obtained for one of the two adjacent channels by designing filters with two transmission zeros in the same (upper or lower) stopband. The new topology investigated in this paper offers the possibility of designing such quadruplets with two transmission zeroes situated both on the same side of the passband, in prescribed and controlled positions. Filters with this novel structure can provide very high attenuation not only at a single frequency, but in a larger adjacent frequency band.

3246. STRUCTURAL MODELLING OF NANO-CARBONS AND NANO-CHALCOGENIDES

Authors: Sava, F; Popescu, M

Published: JAN-APR 2009, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 10, 25, DOI:

The structure of nano-carbon objects (ball-like, nanotubes, defected graphenes) has been modeled by a Monte-Carlo computer procedure. The structure of nano-chalcogenides objects based on two-dimensional network of arsenic sulphide has been modeled. The results were compared to the experimental data whenever possible. The structural modelling was proved as a powerful method for predicting new nano-structural elements in various low-dimensional materials.

3247. BEAM SHAPING WITH ANISOTROPIC PERIODIC STRUCTURES

Authors: Rasoga, O; Dragoman, D

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

We show that an anisotropic periodic structure can shape an incident optical beam with a large angular divergence. This is a new application of photonic crystals, which does not require any additional energy source, such as an electric field

3248. Interface States in 4H-and 6H-SiC MOS Capacitors: a Comparative Study between Conductance Spectroscopy and Thermal Dielectric Relaxation Current Technique

Authors: Lovlie, LS; Pintilie, I; Kumar, SCP; Grossner, U; Svensson, BG; Beljakowa, S; Reshanov, SA; Krieger, M; Pensl, G

Published: 2009, SILICON CARBIDE AND RELATED MATERIALS 2008, 615-617, 500, DOI: 10.4028/www.scientific.net/MSF.615-617.497

The purpose of this work is to compare the density of shallow interface states (D-it) at the interface of SiO2/SiC MOS capacitors as deducted by the conductance spectroscopy (CS) and thermally dielectric relaxation current (TDRC) techniques. Both capacitors of 4H- and 6H-SiC (n-type) arc investigated, and both ordinary dry oxidation and,in improved industrial procedure have been employed. The two techniques are found to give rather good agreement for interface states located >= 0.3 eV below the conduction band edge (E-c) while for more shallow states vastly different distributions of D-it are obtained. Different reasons for these contradictory results are discussed, such as strong temperature and energy dependence of the capture cross section of the shallow interface States.

3249. STUDIES ON MULTIFUNCTIONAL TEXTILE MATERIALS. IMAGE BASED ANALYSIS AND CLASSIC SPECTROSCOPY

Authors: Beica, T; Frunza, L; Nistor, LC; Zgura, I; Dorogan, A; Carpus, E

Published: 2009, ROMANIAN JOURNAL OF PHYSICS, 54, 400, DOI:

Measurements by optical microscopy and spectroscopy were performed on different textile materials (yarn, woven, knitted materials) in order to get their characterization. Thus, using non-specialized classical equipment, the value of the yarn diameter can be estimated. The yarn behavior during the stretching can be directly observed. The observation of the water imbibition by following the shape and stability of a water droplet placed onto the textile material was also developed; in this way the wetting kinetics of different textile materials was obtained. In addition, the spectral properties of woven materials allowed for the study of the modifications induced by different treatments of the woven materials.

3250. Characteristics of Vacuum Deposited Sucrose Thin Films

Authors: Ungureanu, F; Predoi, D; Ghita, RV; Vatasescu-Balcan, RA; Costache, M

Published: 2009, INTERFACE CONTROLLED ORGANIC THIN FILMS, 129, 71, DOI: 10.1007/978-3-540-95930-4_11

Thin films of sucrose (C12H22O11) were deposited on thin cut glass substrates by thermal evaporation technique (p similar to 10-5 torr). The surface morphology was putted into evidence by FT-IR and SEM analysis. The experimental results confirm a uniform deposition of an adherent sucrose layer. The biological tests (e.g., cell morphology and cell viability evaluated by measuring mitochondrial dehydrogenise activity with MTT assay) confirm the properties of sucrose thin films as bioactive material. The human fetal osteoblast system grown on thin sucrose film was used for the determination of cell proliferation, cell viability and cell morphology studies.