National Institute Of Materials Physics - Romania

Publications

5781 articles found

2201. Size Effects in Nanostructures Basics and Applications Preface

Authors: Kuncser, V; Miu, L

Published: 2014, SIZE EFFECTS IN NANOSTRUCTURES: BASICS AND APPLICATIONS, 205, VII, DOI:

2202. THERMAL EFFECTS PRODUCED AT CRYOGENIC TEMPERATURES IN MATERIALS USED AS BOLOMETRIC DETECTORS FOR DARK MATTER

Authors: Lazanu, I; Lazanu, S

Published: 2014, ROMANIAN REPORTS IN PHYSICS, 66, 972, DOI:

In the modern cryogenic technique the heat deposited as phonons, the ionization and/or light from scintillation signals could be used for detection. Also, the formation of defects in the lattice structure of material is possible. In the case when the ionization signal is used for detection, a bias voltage must be applied and thus the generalised Luke-Neganov effect must be considered with contributions from the energy stored in the semiconductor lattice as stable defects in the form of Frenkel pairs. In the process of interaction between the projectile particle and the target, the transient phenomena by which the energy is transferred producing ionization, heat and defects was investigated in the frame of a thermal spike model. A detailed discussion of the associated difficulties of this analysis is done and the results put in evidence the interplay between the primary energies deposited in the electronic and lattice subsystems. This process affects the effective number of defects and the energy stored, which is taken into consideration in the balance of energy conservation in Luke Neganov effect

2203. MOSSBAUER SPECTROSCOPY STUDY ON YVO4:Eu LUMINESCENT MATERIAL

Authors: Bibicu, I; Constantinescu, S; Diamandescu, L; Voiculescu, AM; Cotoi, E

Published: 2014, ROMANIAN REPORTS IN PHYSICS, 66, 1017, DOI:

The information about the local neighborhood of Eu Mossbauer isotope locating in yttrium vanadate nanoparticles was obtained by the room temperature measurements, in transmission and electron backscattering geometry. The Eu has the valence state 3+ and two different quadrupole elementary patterns can be distinguished up to around T-0 = 700 degrees C. At higher temperatures, the Mossbauer spectra consist in a single quadrupole pattern. Electron-backscattering spectra revealed a tendency to change T-0 and a higher distortion of the Eu neighborhood.

2204. Polyester fabrics coated with SiOx nanoparticles by vacuum deposition at small angle. Structural characterization and wetting properties

Authors: Frunza, L; Zgura, I; Enculescu, M; Frunza, S; Ganea, CP; Rasoga, O; Cotorobai, F; Dorogan, A

Published: JAN-FEB 2014, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 16, 181, DOI:

Vacuum deposition at small angle was successfully applied in deposition of SiOx particles onto polyester textile materials; this deposition is here presented in comparison with that upon other materials made from poly(lactic acid), polyamide or hemp. Structural and spectroscopic characterization of deposited samples has been performed and compared with that of the raw materials. The deposited particles are amorphous. Contact angle measurement by the sessile drop method, was used to study the wettability behavior of the investigated composite systems. The hierarchical roughness structure generates hydrophylic properties onto polyester fabrics and the other functionalized samples after deposition. The deposition technique was proven to be highly reproducible, easy scalable and cheap, allowing a wide range of applications.

2205. UV SENSING EFFECT IN LANGMUIR-BLODGETT COMPLEX FILMS CONTAINING A NOVEL SYNTHESIZED Fe(III) PORPHYRIN

Authors: Baschir, L; Fagadar-Cosma, E; Creanga, I; Palade, A; Lascu, A; Birdeanu, M; Savastru, D; Savu, V; Antohe, S; Velea, A; Fagadar-Cosma, G; Popescu, M; Simandan, ID

Published: APR-JUN 2014, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 9, 857, DOI:

A novel structure of metalloporphyrin, namely: 5,10,15,20-tetrakis(3,4-dimethoxyphenyl)-porphyrin Fe(III) chloride, was successfully synthesized. UV sensitive structure based on barium stearate functionalized with the novel synthesized porphyrin and carbon nanotubes was obtained. A five monolayers structure was deposited from solution by Langmuir - Blodgett technique onto a ceramic substrate with interdigital platinum electrodes. The complex film shows sensitivity to UV radiation due to the fact that an electron is excited from a Fe d orbital into a porphyrin antibonding pi orbital and is moved onto the ligand that is attached, facilitating the charge separation, while the presence of SWCNT activates the transport of the charge carriers.

2206. Influence of 2,2 '-bipyridine on oxidative dissolution of iron monosulfide

Authors: Chirita, P; Badica, CE; Constantin, CA; Birsa, LM; Matei, E; Baibarac, M

Published: OCT-NOV 2014, SURFACE AND INTERFACE ANALYSIS, 46, 846, DOI: 10.1002/sia.5459

The 2,2'-bipyridine effects on iron monosulfide (FeS) oxidative dissolution rates have been examined by potentiodynamic polarization and electrochemical impedance spectroscopy. The adsorption of 2,2'-bipyridine to synthetic FeS was investigated by batch adsorption experiments, SEM, energy-dispersive X-ray analysis and Raman spectroscopy. The experiments were performed in air-saturated solutions at pH 5, 25 degrees C and an ionic strength of I = 0.004 M NaCl. Correlation between oxidative dissolution rates and 2,2'-bipyridine adsorption suggests that FeS oxidative dissolution is the result of two antagonistic processes: (i) the inhibiting adsorption of 2,2'-bipyridine on mineral surface and (ii) the promoting effect of 2,2'-bipyridine on the iron dissolution from FeS surface. Copyright (C) 2014 John Wiley & Sons, Ltd.

2207. Generation of Porous Alumina Layers in a Polydimethylsiloxane/Hydrogen Peroxide Medium on Aluminum Substrate in Corona Discharges

Authors: Groza, A; Surmeian, A; Diplasu, C; Luculescu, C; Negrila, C; Ganciu, M

Published: 2014, JOURNAL OF NANOMATERIALS, 2014, DOI: 10.1155/2014/578720

The porous alumina (Al2O3) layer obtained at the interface between polydimethylsiloxane/hydrogen peroxide medium and aluminum substrate under charged and neutral species injection produced in negative corona discharges in air at atmospheric pressure is analyzed by different methods in this paper. The scanning electron microscopy investigations showed the uniform distribution of the pores formed in the alumina layer and their columnar structures. Both energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) measurements indicate that during the anodization process of the aluminum in the polydimethylsiloxane/hydrogen peroxide medium in corona discharge the incorporation of silicon in the structure of the alumina layer is possible.

2208. Tetraethyl Orthosilicate Coated Hydroxyapatite Powders for Lead Ions Removal from Aqueous Solutions

Authors: Ghita, RV; Iconaru, SL; Popa, CL; Costescu, A; Le Coustumer, P; Motelica-Heino, M; Ciobanu, CS

Published: 2014, JOURNAL OF NANOMATERIALS, 2014, DOI: 10.1155/2014/176426

The goal of this study was to synthetize and characterize a porous material based on tetraethyl orthosilicate (TEOS) coated hydroxyapatite (HApTh) after removal experiments of Pb2+ ions from aqueous solutions. In order to study the morphology and composition, the samples obtained after removal experiments of Pb2+ ions from aqueous solution with the initial Pb2+ ion concentrations of the aqueous solutions were 0.1g.L-1 (HApTh-50) and 0.9g.L-1 (HApTh-450) have been investigated by scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometer (EDS), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). Removal experiments of Pb2+ ions were carried out in aqueous solutions with controlled concentration of Pb2+. After the removal experiment of Pb2+ ions from solutions, porous hydroxyapatite nanoparticles were transformed into HApTh-50 and HApTh-450 due to the adsorption of Pb2+ ions followed by a cation exchange reaction. The obtained results show that the porous HApTh nanopowders could be used for Pb2+ ions removal from aqueous solutions.

2209. Oxide Thin Films and Nano-heterostructures for Microelectronics (MOS Structures, Ferroelectric Materials and Multiferroic Heterostructures)

Authors: Pintilie, I; Pintilie, L; Filip, LD; Nistor, LC; Ghica, C

Published: 2014, SIZE EFFECTS IN NANOSTRUCTURES: BASICS AND APPLICATIONS, 205, 108, DOI: 10.1007/978-3-662-44479-5_4

Oxide materials are becoming of increasing interest due to their large variety of physical properties such as dielectric, magnetism, superconductivity, conductivity, ferroelectricity, multiferroism, etc. In addition, interfacing oxides with other materials is conferring new or better device functionalities. The main physical properties of oxides interfaces and their impact on the electrical properties of interest for microelectronic applications are presented. Further on, this subchapter is also devoted to the investigation and understanding of interface effects observed in heterostructures containing linear (SiO2) and non-linear (ferroelectrics) dielectrics in combination with wide-band gap semiconductor materials (e.g. ZnO and SiC) with special emphasis on size effects, interface quality and the opportunity to control the emergent phenomena in Metal-Oxide-Semiconductor (MOS) and Metal-Ferroelectric-Semiconductor (MFS) materials systems.

2210. Liquid crystals based on silver carbene complexes derived from dimeric bis(imidazolium) bromide salts

Authors: Pana, A; Ilis, M; Micutz, M; Dumitrascu, F; Pasuk, I; Circu, V

Published: 2014, RSC ADVANCES, 4, 59497, DOI: 10.1039/c4ra11023d

A series of bis(imidazolium) salts with different mesogenic groups (cyanobiphenyl or cholesteryl) and their silver carbene complexes with Br- anion has been designed and prepared. The liquid crystalline behaviour of these ionic liquids and their corresponding silver-carbene complexes was investigated by polarised optical microscopy (POM), differential scanning calorimetry (DSC) and powder X-ray diffraction while their thermal stability was studied by thermogravimetric analysis (TGA). The silver complexes are thermally stable on a broad temperature range with accessible transition temperatures close to ambient temperature. The compounds with cholesteryl groups show higher transition temperatures than the compounds possessing cyanobiphenyl mesogenic groups, but their thermal stability is limited by a slight decomposition before reaching the isotropic state. Interestingly, the bis(imidazolium) salt with two cyanobiphenyl groups at each side shows an enantiotropic nematic phase on a short range, being one of the few examples of ILC displaying nematic phase.