National Institute Of Materials Physics - Romania

Publications

860 articles found

421. Preliminary Ultrasound Studies On Magnetic Fluids Based on Iron Oxide Nanoparticles

Authors: Popa, CL; Predoi, D; Soare, M; Petre, CC; Predoi, MV

Published: 2016, VIII INTERNATIONAL CONFERENCE ON TIMES OF POLYMERS AND COMPOSITES: FROM AEROSPACE TO NANOTECHNOLOGY, 1736, DOI: 10.1063/1.4949715

The study of various types of nanoparticles with different biomedical applications is of high interest in the last decades. For this purpose, among other techniques, ultrasounds have been used to characterize the aqueous solutions. A non-invasive method is preferable for the characterization of these materials, due to the fact that they are designed to be used for targeted delivery of a chemotherapeutic solution to the tumor site. The present research is focused on ultrasound characterization of solutions based on maghemite and 5-fluorouracil.

422. Characterisations of collagen-silver-hydroxyapatite nanocomposites

Authors: Ciobanu, CS; Popa, CL; Petre, CC; Jiga, G; Trusca, R; Predoi, D

Published: 2016, VIII INTERNATIONAL CONFERENCE ON TIMES OF POLYMERS AND COMPOSITES: FROM AEROSPACE TO NANOTECHNOLOGY, 1736, DOI: 10.1063/1.4949723

The XRD analysis were performed to confirm the formation of hydroxyapatite structure in collagen-silver-hydroxyapatite nanocomposites. The molecular interaction in collagen-hydroxyapatite nanocomposites was highlighted by Fourier transform infrared spectroscopy (FTIR) analysis. The SEM showed a nanostructure of collagen-silver-hydroxyapatite nanocomposites composed of nano needle-like particles in a veil with collagen texture. The presence of vibrational groups characteristics to the hydroxyapatite structure in collagen-silver-hydroxyapatite (AgHApColl) nanocomposites was investigated by FTIR.

423. ANTIMICROBIAL ACTIVITY OF EUROPIUM DOPED HYDROXYAPATITE POWDERS AFTER IMMERSION IN SBF SOLUTION

Authors: Andronescu, E; Surugiu, A; Badea, ML; Ciobanu, CS; Iosif, A

Published: 2016, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN SERIES B-CHEMISTRY AND MATERIALS SCIENCE, 78, DOI:

The europium doped hydroxypatite samples were obtained by an adapted coprecipitation method. After the synthesis, the samples were immersed in simulated body fluid (SBF) solution for 6 and 24 h respectively. After the immersion in the SBF solution, the morphology and antimicrobial activity of the powders were studied. Our antimicrobial studies revealed that all the samples exhibit antimicrobial activity against gram positive and gram negative strains.

424. Influence of Thermal Treatment on the Antimicrobial Activity of Silver-Doped Biological Apatite

Authors: Popa, CL; Ciobanu, CS; Voicu, G; Vasile, E; Chifiriuc, MC; Iconaru, SL; Predoi, D

Published: DEC 29 2015, NANOSCALE RESEARCH LETTERS, 10, DOI: 10.1186/s11671-015-1211-x

In this paper, we report the structural and morphological properties of silver-doped hydroxyapatite (AgHAp) with a silver concentration x(Ag) = 0.5 before and after being thermal treated at 600 and 1000 degrees C. The results obtained by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy suggest that the structure of the samples changes gradually, from hydroxyapatite (AgHAp_40) to a predominant beta-TCP structure (AgHAp_1000), achieved when the thermal treatment temperature is 1000 degrees C. In the AgHAp_600 sample, the presence of two phases, HAp and beta-TCP, was highlighted. Also, scanning electron microscopy studies suggest that the shape and dimension of the nanoparticles begin to change when the temperature increases. The antimicrobial activity of the obtained compounds was evaluated against Klebsiella pneumoniae, Staphylococcus aureus, and Candida albicans strains.

425. The influence of heating rate on superconducting characteristics of MgB2 obtained by spark plasma sintering technique

Authors: Aldica, G; Burdusel, M; Popa, S; Enculescu, M; Pasuk, I; Badica, P

Published: DEC 15 2015, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 519, 189, DOI: 10.1016/j.physc.2015.10.004

Superconducting bulks of MgB2 were obtained by the Spark Plasma Sintering (SPS) technique. Different heating rates of 20, 100, 235, 355, and 475 degrees C/min were used. Samples have high density, above 95%. The onset critical temperature T-c, is about 38.8 K. There is an optimum heating rate of similar to 100 degrees C/min to maximize the critical current density J(c0), the irreversibility field H-irr, the product (J(c0) x mu H-0(irr)), and to partially avoid formation of undesirable flux jumps at low temperatures. Significant microstructure differences were revealed for samples processed with low and high heating rates in respect to grain boundaries. (C) 2015 Elsevier B.V. All rights reserved.

426. Correlation of optical reflectivity with numerical calculations for a two-dimensional photonic crystal designed in Ge

Authors: Husanu, MA; Popescu, DG; Ganea, CP; Anghel, I; Florica, C

Published: DEC 10 2015, EUROPEAN PHYSICAL JOURNAL D, 69, DOI: 10.1140/epjd/e2015-60478-7

A two dimensional photonic crystal (2DPhC) with triangular symmetry is investigated using optical reflectivity measurements and numerical calculations. The system has been obtained by direct laser writing, using a pulsed laser (lambda = 775 nm), perforating an In-doped Ge wafer. A lattice of holes with well-defined symmetry has been designed. Analyzing the spectral signature of PBGs recorded experimentaly with finite difference time domain theoretical calculations one was able to prove the relation between the geometric parameters (hole format, lattice constant) of the system and its ability to trap and guide the radiation in specific energy range. It was shown that at low frequency and telecommunication ranges of transvelsal electric modes photonic band gap occur. This structure may have potential aplications in designing photonic devices with applications in energy storage and conversion as potential alternative to Si-based technology.

427. Effect of thermal treatments on the structural and magnetic transitions in melt-spun Ni-Fe-Ga-(Co) ribbons

Authors: Tolea, F; Sofronie, M; Crisan, AD; Enculescu, M; Kuncser, V; Valeanu, M

Published: NOV 25 2015, JOURNAL OF ALLOYS AND COMPOUNDS, 650, 670, DOI: 10.1016/j.jallcom.2015.07.296

The effect of thermal treatments on the martensitic transformation in three representative Ni-Fe-Ga alloys with or without Co substitutions has been studied by calorimetry, X-ray diffractometry, scanning electron microscopy and magnetometry. The alloys were prepared as ribbons, by the melt spinning technique. The thermal treatments promote a reduction of the martensitic transformation temperature in all investigated samples, with the most pronounced decrease for the alloys with lower Ga content. Three different mechanisms induced by specific thermal treatments and responsible for the characteristic behaviour of the martensitic transformation, with respect to temperature and heat of transition, were observed and discussed in details. (C) 2015 Elsevier B.V. All rights reserved.

428. Surface topography to reflectivity mapping in two-dimensional photonic crystals designed in germanium

Authors: Husanu, MA; Ganea, CP; Anghel, I; Florica, C; Rasoga, O; Popescu, DG

Published: NOV 15 2015, APPLIED SURFACE SCIENCE, 355, 1191, DOI: 10.1016/j.apsusc.2015.07.218

Light confinement in a two dimensional photonic crystal (2D PhC) with hexagonal symmetry is studied using infra-red reflectance spectromicroscopy and numerical calculations. The structure has been realized by laser ablation, using a pulsed laser (lambda = 775 nm), perforating an In-doped Ge wafer and creating a lattice of holes with well-defined symmetry. Correlating the spectral signature of the photonic gaps recorded experimentally with the results obtained in the finite difference time domain and finite difference frequency domain calculations, we established the relationship between the geometric parameters of the structure (lattice constants, shape of the hole) and its efficiency in trapping and guiding the radiation in a well-defined frequency range. Besides the gap in the low energy range of transversal electric modes, a second one is identified in the telecommunication range, originating in the localization of the leaky modes within the radiation continuum. The emerging picture is of a device with promising characteristics as an alternative to Si-based technology in photonic device fabrication with special emphasize in energy storage and conversion. (C) 2015 Elsevier B.V. All rights reserved.

429. Superior biofunctionality of dental implant fixtures uniformly coated with durable bioglass films by magnetron sputtering

Authors: Popa, AC; Stan, GE; Enculescu, M; Tanase, C; Tulyaganov, DU; Ferreira, JMF

Published: NOV 2015, JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS, 51, 327, DOI: 10.1016/j.jmbbm.2015.07.028

Bioactive glasses are currently considered the suitable candidates to stir the quest for a new generation of osseous implants with superior biological/functional performance. In congruence with this vision, this contribution aims to introduce a reliable technological recipe for coating fairly complex 3D-shaped implants (e.g. dental screws) with uniform and mechanical resistant bioactive glass films by the radio-frequency magnetron sputtering method. The mechanical reliability of the bioactive glass films applied to real Ti dental implant fixtures has been evaluated by a procedure comprised of "cold" implantation in pig mandibular bone from a dead animal, followed by immediate tension-free extraction tests. The effects of the complex mechanical strains occurring during implantation were analysed by scanning electron microscopy coupled with electron dispersive spectroscopy. Extensive biocompatibility assays (MTS, immunofluorescence, Western blot) revealed that the bioactive glass films stimulated strong cellular adhesion and proliferation of human dental pulp stem cells, without promoting their differentiation. The ability of the implant coatings to conserve a healthy stem cell pool is promising to further endorse the fabrication of new osseointegration implant designs with extended lifetime. (C) 2015 Elsevier Ltd. All rights reserved.

430. Sulfur treatment on n-GaSb (100) and surface antibacterial evaluation

Authors: Ghita, R; Iconaru, SL; Frumosu, F; Logofatu, C; Badea, ML; Holban, AM

Published: OCT 16 2015, TOXICOLOGY LETTERS, 238, S199, DOI: 10.1016/j.toxlet.2015.08.599