National Institute Of Materials Physics - Romania

Publications

5840 articles found

1841. Nematic ionic liquid crystals based on pyridinium salts derived from 4-hydroxypyridine

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

Published: 2016, CRYSTENGCOMM, 18, 5069, DOI: 10.1039/c6ce00618c

A series of pyridinium salts with various counterions (Br-, NO3-, BF4-, PF6-, OTf- and SCN-) and different spacer chain lengths, which display a nematic phase, have been designed and prepared. They are derived from 4-hydroxypyridine and possess two mesogenic cyanobiphenyl groups attached to the pyridinium unit via a flexible long alkyl spacer (6, 9, 10). These salts exhibit solely a nematic phase with the thermal range influenced by the counterion employed and spacer length.

1842. BST thin film capacitors integrated within a frequency tunable antenna

Authors: Rammal, M; Huitema, L; Crunteanu, A; Passerieux, D; Cros, D; Monediere, T; Madrangeas, V; Dutheil, P; Champeaux, C; Dumas-Bouchiat, F; Marchet, P; Nedelcu, L; Trupina, L; Banciu, G; Cernea, M

Published: 2016, 2016 IEEE INTERNATIONAL WORKSHOP ON ANTENNA TECHNOLOGY (IWAT), 47, DOI:

Ferroelectric (FE) thin film varactors can be a convenient technology for tuning miniature antennas. In this paper we present the design of a compact, agile, wire patch antenna integrating barium strontium titanate (Ba(1-x)SrxTiO3, BST) thin film interdigitated capacitors (IDC). The IDCs values were measured at different temperatures and bias voltages ranging from 0 to 120 V showing a capacitance variation of more than 40% between 11-13 GHz and up to 28% in the 2-3 GHz frequency interval. Their integration within a compact antenna design allows tuning its operating frequency on the whole WiFi band, with efficiencies higher than 70%.

1843. MAGNETIC AND MOSSBAUER SPECTROSCOPY STUDY OF Fe-Cr-Al THIN FILMS SPUTTERED ON Si SUBSTRATES

Authors: Greculeasa, SG; Schiniteie, G; Palade, P; Filoti, G; Ghita, IS; Kuncser, V

Published: 2016, ROMANIAN REPORTS IN PHYSICS, 68, 258, DOI:

Fe and Fe-Cr-Al thin films, both as sputtered on Si substrates as well as after subsequent annealing treatments in hydrogen atmosphere, have been investigated by means of X-ray reflectometry, magneto-optic Kerr effect and Mossbauer spectroscopy with respect to structural and related magnetic characteristics. The as deposited films are showing chemically disordered bcc structures, assigned to Fe-Si and Fe-Cr-Al-Si phases, respectively, with soft magnetism and magnetic texture, both influenced by the presence of Si, Cr and Al atoms. The softness of the films as well as the magnetic texture are strongly modified via hydrogenation treatments. In addition, such treatments induce the expulsion of Si, Cr and Al atoms from the as deposited phases, providing almost pure Fe films of much well crystallized bcc structure.

1844. Fast atomic diffusion in amorphous films induced by laser pulse annealing

Authors: Teodorescu, VS; Ghica, C; Maraloiu, AV; Kuncser, A; Lepadatu, AM; Stavarache, I; Ciurea, ML; Scarisoreanu, ND; Andrei, A; Dinescu, M

Published: 2016, 2016 39TH INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 158, DOI:

Fast atomic diffusion was evidenced in the surface layer of amorphous thin films of oxides and semiconductors irradiated with low fluence UV pulse laser. This process takes place in a surface layer with a thickness related to the laser radiation absorption depth in the target material and was revealed by the cross section transmission electron microscopy studies. These high values of diffusivity can be explained by supposing the glass transition transformation in the amorphous structure, triggered by the action of the laser pulse field. This effect can have application for controlling structural modifications at nanoscale of the thin films surface and also for inducing structural modification of interfaces between the film and substrate.

1845. Screen-printed Pb(Mg,Nb)O-3-PbTiO3 Thick Tilms on Ceramic Substrates for Sensor Applications

Authors: Ursic, H; Khomyakova, E; Drnovsek, S; Malic, B; Mercioniu, IF; Bencan, A; Makarovic, K; Schreiner, C; Ciobanu, R; Belavic, D; Bolado, P

Published: 2016, PROCEEDINGS OF THE 2016 INTERNATIONAL CONFERENCE AND EXPOSITION ON ELECTRICAL AND POWER ENGINEERING (EPE 2016), 58, DOI:

In this work the screen-printed piezoelectric 0.65Pb(Mg1/3Nb2/3)O-3-0.35PbTiO(3) thick films were prepared on metalized low-temperature co-fired ceramic substrates. Such substrates are interesting for micro-electro mechanical systems, for example for piezoelectric sensors and actuators. The prepared thick films exhibit the piezoelectric coefficient d(33) equal to 120 pC/N.

1846. STRUCTURAL CHARACTERIZATION AND OPTICAL PROPERTIES OF HYDROXYAPATITE/COLLAGEN MATRIX

Authors: Popa, CL; Albu, M; Bartha, C; Costescu, A; Luculescu, C; Trusca, R; Antohe, S

Published: 2016, ROMANIAN REPORTS IN PHYSICS, 68, 1158, DOI:

This paper presents the synthesis and characterization of hydroxyapatite (HAp) and hydroxyapatite embedded in a collagen matrix (C-HAp6). The aim of this study was to investigate the influence of collagen on the structure and morphology of hydroxyapatite. According to the XRD patterns, the samples have the structure characteristic to hydroxyapatite. The FTIR and Raman spectra proved the successfully embedding of hydroxyapatite in the collagen matrix. Morphologically, the collagen increases the porosity of HAp. The collagen influences the structure and morphology of the hydroxyapatite causing a decrease of the mean particle size and/or a decrease of crystallinity while increasing the porosity.

1847. 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.

1848. Tissue Engineering Scaffolds from La2O3 - Hydroxyapatite\Boron Glass Composites

Authors: Sych, O; Gunduz, O; Pinchuk, N; Stan, GE; Oktar, FN

Published: 2016, JOURNAL OF THE AUSTRALIAN CERAMIC SOCIETY, 52, 110, DOI:

Bioactive composites of bovine derived hydroxyapatite and boron containing bioactive glass were doped with 5, 10 and 15 wt.% lanthanum oxide (La2O3). Results showed that at low sintering temperatures (800 degrees C) the doping oxide of La2O3 promoted transformation to crystalline phases. Formation of secondary phases, such as rhenanite, NaCaPO4, and calcium silicate, Ca2SiO4, were also found. La was found to act as modifier and influenced the viscosity. The increase of La2O3 content led to decrease of pore size. Porosity amount 48.1 %, at 15-240 mu m size range were reduced, to 34.4 %, with 5-80 mu m size range and particle sizes of 0.3-6 mu m to 0.09-2 mu m, respectively. In addition to that compression strength (MPa) and microhardness (HV) of the performed composite bioceramics were in the range of 25 - 110 MPa, and 121 - 364 HV, respectively. Our investigations suggested that the porosity type has a strong influence on the compressive strength and microhardness properties of the final bioceramic products.

1849. NANOTUBES OF Ba0.95Ce0.05Ti0.9875O3 PREPARED BY SOL-GEL CHEMISTRY

Authors: Cernea, M; Ianculescu, AC; Vasile, BS; Vasilescu, CA

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

Nanotubes of Ba0.95Ce0.05Ti0.9875O3 with an average diameter of 80 nm and wall thickness of similar to 8 nm were prepared from the precursor sol using as template a polycarbonate membrane with the pores diameter size of 100 nm. The Ce doped-BaTiO3 nanotubes calcined at 700 degrees C, 1h in air crystallized on the lattice of BaTiO3 cubic phase as indicated the high resolution transmission electron microscopy and selected area electron diffraction analyses. The nanotubes showed a polycrystalline structure with crystallites of 3-5 nm size. The results prove that we can prepare BaTiO3 doped with 5 at.% Ce nanotubes for future capacitor applications.

1850. 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.