National Institute Of Materials Physics - Romania

Publications

5714 articles found

1661. Dielectric characterization of BaxSr1-xFe12O19 (x=0.05-0.35) ceramics

Authors: Cernea, M; Negrea, RF; Ciuchi, IV; Baldisserri, C; Trusca, R; Galassi, C

Published: JAN 2016, CERAMICS INTERNATIONAL, 42, 1056, DOI: 10.1016/j.ceramint.2015.09.029

BaxSr1-xFe12O19 (x=0.05, 0.15, 0.25, 0.35) ferrites were prepared by both the sol gel and conventional solid state reaction techniques. The structural characteristics and dielectric properties of these ferrites were investigated and compared. BaxSr1-xFe12O19 ceramics obtained by the sol gel method show homogeneous morphology and single crystalline phase while those prepared by solid state reaction route exhibit less homogeneous morphology, being accompanied by a secondary crystalline phase (BaFe2O4). The size of the grains varies in the range 200-300 nm for x=0.05-0.35 when the powders are prepared by sol gel method and, 600-700 nm for the powders prepared by solid state reaction. For the same value of x, the BaxSr1-xFe12O19 ferrites obtained via sol-gel display higher permittivity and lower dielectric losses compared to those prepared by solid state reaction route. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

1662. Crystallization and luminescence properties of a new Eu3+-doped LaOCl nano-glass-ceramic

Authors: Secu, M; Secu, CE; Bartha, C

Published: JAN 2016, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 36, 207, DOI: 10.1016/j.jeurceramsoc.2015.09.001

Glassy nanocomposites containing Eu3+-doped LaOCl nanocrystals of about tens of nm size embedded in a silica matrix have been prepared by using sol-gel route followed by controlled crystallization of the xerogel. Crystallization behavior of LaOCl nanocristalline phase was discussed on the basis of thermal analysis, X-ray diffraction and photoluminescence measurements. LaOCl nanocrystalline phase precipitation is the result of lanthanum chloride hydrolytic and oxidative reactions. As the annealing temperature increases nanocrystallites size grows up to tens of nm; Eu3+-ions are gradually incorporated during the nanocrystals growth. Structural changes were studied using the Eu3+ as probe ion and the luminescence properties were analysed by using Judd-Ofelt theory. (C) 2015 Elsevier Ltd. All rights reserved.

1663. Oral keratinocyte stem cells behavior on diamond like carbon films

Authors: Calenic, B; Greabu, M; Caruntu, C; Nicolescu, MI; Moraru, L; Surdu-Bob, CC; Badulescu, M; Anghel, A; Logofatu, C; Boda, D

Published: SEP-OCT 2016, ROMANIAN BIOTECHNOLOGICAL LETTERS, 21, 11922, DOI:

Diamond like carbon (DLC) is an amorphous carbon material suitable for use in a variety of in vivo biomedical applications, which may constitute a step forward in biotechnology of dental or orthopedic implants. Previous in vitro studies focusing on DLC films demonstrate that cellular behavior on DLC is cell type specific. The aim of the present study was to evaluate the interaction between DLC substrates and keratinocyte stem cells isolated from oral epithelia. Oral keratinocyte stem cells were isolated using a magnetic technique. Various DLC films were synthesized using Thermoionic Vacuum Arc plasma (TVA) by adjusting the distance between substrate and anode. We assessed important cell characteristics such as proliferation rate, colony forming efficiency of oral keratinocyte stem cells placed on various DLC films. Our results demonstrate that DLC substrates are biocompatible with the analyzed cell type, and do not affect cell size or colony forming efficiency, in specific conditions being able to stimulate their proliferative potential. The data demonstrates for the first time that oral keratinocyte stem cells are biocompatible with DLC films. Moreover the proliferative potential of cells may be enhanced by adjusting the deposition parameters of DLC films.

1664. PRELIMINARY STRUCTURAL ULTRASONIC CHARACTERIZATION OF HYDROXYAPATITE

Authors: Popa, CL; Antohe, S; Safciuc, F; El Kettani, MEC; Leduc, D; Antohe, F; Predoi, MV

Published: JUL-SEP 2016, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 11, 1006, DOI:

Synthetic hydroxyapatite (HAp) is one of the most commonly used material for a large variety of biomedical applications. This paper presents structural, morphological and preliminary ultrasonic characterizations of the HAp nanopowder synthesized by an adapted co-precipitation method. To this end, the structural and morphological properties were evaluated by Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS). Biological investigation were also performed in order to evidence the influence of HAp tablets on the development and growth of endothelial cells. The ultrasonic measurements obtained for the HAp dispersion allowed us to calculate the ultrasonic velocity and the attenuation. The study of ultrasonic waves propagation through dispersions could be used as future standard quality test, thus improving the quality of biomedical devices based on hydroxyapatite.

1665. Local Ordering at the Interface of the TiO2-WO3 Bi-Layers

Authors: Macovei, D; Dascaleanu, V; Teodorescu, CM; Luca, D

Published: 2016, NANOSTRUCTURES AND THIN FILMS FOR MULTIFUNCTIONAL APPLICATIONS: TECHNOLOGY, PROPERTIES AND DEVICES, 331, DOI: 10.1007/978-3-319-30198-3_10

Reducing the recombination rate of photo-generated electron-hole pairs in the surface of pristine TiO2 materials can be done, among others, via local spatial charge separation in the photocatalytically active surface region. A local electric field acting for this purpose can be ensured, for instance, in hetero-junction regions formed at the interface between a TiO2 film and a WO3 ultra-thin layer. The option for the WO3-TiO2 semiconductor pair is related to the suitable fit of their band structures. To model the interface, a more in-depth knowledge of local atomic environment is required. Here, we discuss the local atomic ordering and the related effects in the interface region of TiO2/WO3 and WO3/TiO2 structures grown on Si (100) substrates. Materials characterization was done by using XRD, XPS and XAS techniques. We demonstrate that tungsten atoms enter as W6+ or W4+ cations into the rutile-type TiO2 lattice, by substituting the Ti4+ cations. While W6+-Ti4+ substitution leaves the surrounding rutile matrix unchanged, the W4+-Ti4+ substitution induces a local rutile-to-anatase transition. The current results are relevant in designing new applications structures with enhanced photocatalytic performances.

1666. Enamel Based Composite Layers Deposited on Titanium Substrate with Antifungal Activity

Authors: Iconaru, SL; Prodan, AM; Turculet, CS; Beuran, M; Ghita, RV; Costescu, A; Groza, A; Chifiriuc, MC; Chapon, P; Gaiaschi, S; Hristu, R; Stanciu, GA; Trusca, R; Ganciu, M; Raita, SM; Vineticu, N; Ciobanu, CS

Published: 2016, JOURNAL OF SPECTROSCOPY, 2016, DOI: 10.1155/2016/4361051

The goal of this paper was to investigate the antifungal activity of Enamel layers deposited on titanium substrate (Ti-Enamel) and Enamel layers deposited on titanium substrate previously coated with a vinyl polydimethylsiloxane layer (Ti-PDMS-Enamel). The physicochemical properties were also investigated. The Candida albicans biofilm development on the obtained layers was examined after 24 h, 48 h, and 72 h by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) after ethidium bromide staining. A significant inhibition of the fungal adherence and biofilm development was observed on Ti-Enamel layers. The antifungal results demonstrated that the use of new Ti-Enamel composite layers could represent a promising perspective for the prevention of fungal biofilms associated implant infections.

1667. LTCC-based Ceramic Microsystems with Integrated Fluidic Elements and Sensors

Authors: Belavic, D; Hodnik, M; Santo, M; Bolado, P; Ursic, H; Bradesko, A; Malic, B; Mercioniu, IF; Bencan, A; Makarovic, K; Ciobanu, RC; Schreiner, C

Published: 2016, PROCEEDINGS OF THE 2016 INTERNATIONAL CONFERENCE AND EXPOSITION ON ELECTRICAL AND POWER ENGINEERING (EPE 2016), 46, DOI: 10.1109/ICEPE.2016.7781299

In this contribution the design and fabrication of ceramic microsystems with integrated different microfluidic elements and sensors will be presented. Ceramic microsystems are based on unconventional application of low-temperature co-fired ceramic technology and materials. This unconventional application is related to three-dimensional ceramic structures, such as cantilevers, ledges, bridges, diaphragms, valleys, channels, holes and cavities, valves, mixers, diffusors, distributors, collectors, flow limiters, sensors, and actuators.

1668. Tailored electric and optical properties of Nd doped ZnO: from transparent conducting oxide to photon down-shifting thin films

Authors: Nistor, M; Mihut, L; Millon, E; Cachoncinlle, C; Hebert, C; Perriere, J

Published: 2016, RSC ADVANCES, 6, 41472, DOI: 10.1039/c6ra07669f

Nd-doped ZnO films with highly tunable properties were grown by pulsed electron beam deposition at 500 C on Si and c-cut single crystal substrates under oxygen gas. The effects of a slight change in the oxygen pressure (10(-2) to 2 x 10(-2) mbar) on the composition, structure and physical properties of the films were studied. Films grown at 10(-2) mbar present a low resistivity (5 x 10(-3) S-2 cm) and high transparency in visible range and do not show any near -infrared emission due to Nd3+ ions. On the contrary, films grown at 2 x 10(-2) mbar have high resistivity (>16 S-2 cm), high optical transparency and near infrared emission of the Nd3+ ions is observed under indirect excitation at 335 nm (i.e. absorption by the ZnO matrix and transfer to Nd3+ ions). These significant changes in physical properties, leading from transparent conducting oxide to photon down -shifting thin films, are related to growth mode in pulsed -electron beam deposition.

1669. XPS Analysis of AuGeNi/Cleaved GaAs(110) Interface

Authors: Negrila, CC; Lazarescu, MF; Logofatu, C; Cotirlan, C; Ghita, RV; Frumosu, F; Trupina, L

Published: 2016, JOURNAL OF NANOMATERIALS, 2016, DOI: 10.1155/2016/7574526

The depth composition of the thin layer alloy, AuGeNi, devoted to acting as an ohmic contact on n-GaAs(110) has been investigated by in situ XPS combined with Argon ion sputtering techniques. The fresh cleaved surfaces, supposed to be free of oxygen, were usually deposited with a 200nm metallic layer in high vacuum conditions (better than 10(-7) torr), by thermal evaporation, and annealed at a 430-450 degrees Celsius temperature for 5 minutes. About 18 sessions of ion Ar surfaces etching and intermediate XPS measurements were performed in order to reveal the border of the metal/semiconductor interface. The atomic concentrations of the chemical elements have been approximated. Au4f, Ga3d, Ga2p, As3d, As2p, Ni2p(3/2), Ge3d, O1s, and C1s spectral lines were recorded. The Au, Ge, and Ni have a homogenous distribution while Ga and As tend to diffuse to the surface. Oxygen is present in the first layers of the surface while carbon completely disappears after the second etching step. The existence of an Au-Ga alloy was detected and XPS spectra show only metal Ni and Ge within the layer and at the interface. We tried to perform a study about the depth chemical composition profile analysis of AuGeNi layer on cleaved n-GaAs(110) by X-Ray Photoelectron Spectroscopy (XPS) technique.

1670. INVESTIGATIONS ON THE PROPERTIES OF A TWO-DIMENSIONAL NANOPATTERNED METALLIC FILM

Authors: Breazu, C; Preda, N; Socol, M; Stanculescu, F; Matei, E; Stavarache, I; Iordache, G; Girtan, M; Rasoga, O; Stanculescu, A

Published: OCT-DEC 2016, Digest Journal of Nanomaterials and Biostructures, 11, 1229, DOI:

This paper presents some investigations of the effect of nanopatterning on the properties of aluminum layer deposited by sputtering. UV-Nanoimprint Lithography technique has been used for the realization of a 2D array of nanostructures (pillars) in aluminum film characterized by cylindrical shape and the following structural parameters: diameter between 400 nm and 490 nm, depth between 320 nm and 420 nm and periodicity of 1.1 mu m, which have been revealed by SEM and AFM measurements. The UV-Vis transmission, reflection and photoluminescence measurements have evidenced the effect of the nanopatterning on the optical properties of the A1 layer.