Book of Abstracts - National Institute of Research and … Book of Abstracts... · 2005-08-28 ·...

Book of Abstracts

National Institute of R & D for Technical PhysicsIaşi, ROMANIA

March 24-25, 2005

NANOMAT 2005National Mobilization Workshop

Network for Nanostructured Materials of ACCEuropean Project INCO-CT-2003-510363

NANOMAT 2005 Mobilization Workshop - Programme

March 24, 2005

9:00 – 9:30 OPENING SESSION (H. Chiriac)

9:30 – 10:00 O.1

NANOSCIENCES AND NANOTECHNOLOGIES IN ROMANIA. CHANCES FOR SUCCESS. RESPONSABILITIES AND RISKS. Gh. Popa ”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi

10:00 – 10:30 O.2 A TENTATIVE SWOT ANALYSIS OF ROMANIAN RESEARCH Bogdan C. Simionescu “Petru Poni” Institute of Macromolecular Chemistry, Iasi

10:30 – 11:00 O.3

RAINS – STARTING POINT FOR A STRONGER REGIONAL CO-OPERATION Valeria Harabagiu “Petru Poni” Institute of Macromolecular Chemistry, Iasi

11:00 – 11:15 COFFEE BREAK

11:15 – 11:45 O.4

MAGNETIC RESONANCE AT NANOSCALE: NANOMETROLOGY AND SPIN DYNAMICS L. M. Giurgiu National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca

11:45 – 12:15 O.5

MAGNETIC PROPERTIES AND GMR EFFECT IN NANOSTRUCTURED ELECTRODEPOSITED THIN FILMS V. Georgescu ”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi

12:15 – 12:30 O.6

MICRO-STRUCTURE AND MAGNETIC PROPERTIES OF Fe-Cu NANOCOMPOSITES, AS POTENTIAL CANDIDATES FOR RE-FREE PERMANENT MAGNETS M. Sofronie(1), V. Kuncser(1), A. Jianu(1), M. Codescu(2), F. Lifei(1), N. Stancu(2), J. Pintea(2), M. Valeanu(1), W. Kappel(2), G. Filoti(1) (1)National Institute for Materials Physics, Bucharest (2)S.C. ICPE-CA SA, Bucharest

12:30 – 12:45 O.7

RATE DEPENDENCE HYSTERESIS IN SPIN CROSSOVER SOLIDS ANALYZED USING FORC DIAGRAMS C. Enachescu(1), R. Tanasa(1), Al. Stancu(1), F. Varret(2), J. Linares(2) (1)”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi (2)Universite Saint Quentin en Yvelines, Versailles, France

12:45 – 13:45 LUNCH

13:45 – 14:00 O.8

MAGNETOSTRICTIVE PROPERTIES OF SOME AMORPHOUS AND NANOCRYSTALIZED ALLOYS Ioan Mihalca(1), A. Ercuta(2) (1)University ”Politehnica”, Timisoara (2)West University of Timisoara

14:00 – 14:15 O.9

THE MAGNETIC AND MORPHOLOGICAL CHARACTERIZATION OF NANOGRANULAR [FeCoB/(SiO2] x n THIN FILMS M. Urse, H. Chiriac, M. Grigoras National Institute of Research and Development for Technical Physics, Iasi

14:15 – 14:45 O.10

CARBON BASED NANOSTRUCTURES THROUGH INTERACTION LASER-REACTIVE GASEOUS MIXTURES C.T. Fleaca, L. Albu, R. Alexandrescu, F. Dumitrache, I. Morjan, E. Popovici, I. Sandu, M. Scarisoreanu, I. Soare, I. Voicu NILPRP, Bucharest

14:45 – 15:15 O.11

NANOSTRUCTURED CALCIUM PHOSPHATES COATINGS FOR BIOMEDICAL IMPLANTS C. Ristoscu, G. Socol, E. Axente, S. Grigorescu, G. Dorcioman, I. N. Mihailescu National Institute for Lasers, Plasma and Radiation Physics, Bucharest

15:15 – 15:30 O.12

PHYSICAL CHARACTERISATION OF CdMnS NANOCRYSTALLINE FILMS OBTAINED BY CHEMICAL BATH DEPOSITION F. Iacomi, A. Vasile, N. Apetroaei, M. R. Craus, I. Caraman ”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi

15:30 – 15:45 O.13

NANO-SCALE THERMOELECTRIC MATERIALS FOR DIRECT THERMAL-TO-ELECTRIC ENERGY CONVERSION V. Cimpoca(1), I. Bancuta(1), A. Gheboianu(1), Gh. Brezeanu(2), I. Cernica(3), M. Cimpoca(3), I. Grozescu(4) (1)Valahia State University, Targoviste (2)”Politechnica” University of Bucharest (3)National Institute for Microtechnologies, Bucharest (4)National Institute for Condensed Materials, Timisoara

15:45 – 16:15 O.14

NANOMATERIALS APPLICATION IN HYDROGEN TECHNOLOGY AND FUEL CELLS D. Stoenescu, L. Patularu, M. Culcer, R. E. Lazar, E. Carcadea, D. Mirica, M. Varlam, I. Stefanescu National Institute of Research and Development for Cryogenics and Isotopic Technologies – ICIT, Rm Valcea

16:15 – 16:30 O.15

NANOSTRUCTURED METAL OXIDES FOR OPTICAL GAS SENSING APPLICATIONS C. Ristoscu, G. Socol, E. Axente, S. Grigorescu, G. Dorcioman, I. N. Mihailescu National Institute for Lasers, Plasma and Radiation Physics, Bucharest

16:30 – 16:45 O.16

GRANULAR GMR LAYERS AS DEPOSITED BY THERMIONIC VACUUM ARC TECHNOLOGY (TVAT) O. Brinza, I. Mustata, C. P. Lungu, A. M. Lungu, V. Zaroschi National Institute for Lasers, Plasma and Radiation Physics, Bucharest


17:00 – 19:00 POSTER SESSION

March 25, 2005 9:00 – 9:30 O.17 NANOSCIENCES AND NANOTECHNOLOGIES IN EUROPEAN

PROGRAMMES: FROM FP6 TO FP7 Dan Dascalu National Institute of Research and Development for Microtechnologies, Bucharest

9:30 – 10:00 O.18 NANOSPHERE LITHOGRAPHY AND SELF-ASSEMBLY – TWO VERSATILE ROUTES FOR FABRICATION OF PERIODIC ARRAYS OF NOBLE METAL NANOPARTICLES S. Astilean, M. Baia, D. Maniu, F. Toderas, C. Farcau “Babes-Bolyai” University, Faculty of Physics, Cluj-Napoca

10:00 – 10:30 O.19 POLIMERS AS CRYSTALLIZATION REGULATORS FOR NANO/BIOAPPLICATIONS Gabrielle Charlotte Chitanu “Petru Poni” Institute of Macromolecular Chemistry, Iasi

10:30 – 11:00 O.20 SUBSTITUTED ANIONIC CLAYS WITH TAILORED TEXTURAL PROPERTIES: EFFECT OF THE NATURE OF THE THIRD CATION IN THE CLAY LAYER G. Carja(1), H. Chiriac(2), N. Lupu(2) (1)Technical University ”Gheorghe Asachi”, Department of Physical Chemistry, Faculty of Industrial Chemistry, Iasi (2)National Institute of Research and Development for Technical Physics, Iasi


11:15 – 11:30 O.21 FERROMAGNETIC RESONANCE PARAMETERS OF BALL MILLED Ni-Zn FERRITE NANOPARTICLES B. Parvatheeswara Rao(1), O. F. Caltun(2), I. Dumitru(3), L. Spinu(3) (1)Department of Physics, Andhra University, India (2)”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi, Romania (3)Advanced Materials Research Institute, University of New Orleans, USA

11:30 – 11:45 O.22 WATER AT NANOSCOPIC CONTACTS L. Sirghi(1), E. Riedo(2) (1)”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi (2)School of Physics, Georgia Institute of Technology, USA

11:45 – 12:00 O.23 NEW MAGNETIC NANOMATERIALS AT NIRDTP IAŞI: PREPARATION, PROPERTIES, APPLICATIONSN. Lupu, H. Chiriac National Institute of Research and Development for Technical Physics, Iasi

12:00 – 13:00 National Institute of Research and Development for Technical Physics (NIRDTP) VISIT

13:00 – 14:00 LUNCH

POSTER SESSION, March 24, 2005 (17:00 – 19:00)

P.1

POROUS SILICON SURFACE FUNCTIONALIZATION FOR BIOMOLECULES ATTACHEMENT A. Bragaru, I. Kleps, A. Angelescu, M. Miu, M. Simion, T. Ignat, F. Craciunoiu, M. Avram National Institute for Microtechnologies, Bucharest

P.2

PS CONDUCTIVE AND BIOCOMPATIBLE COMPOSITE NANOSTRUCTURES FOR ELECTRODE APPLICATIONS T. Ignat, A. Bragaru, I. Kleps, A. Angelescu, M. Miu, M. Simion National Institute for Microtechnologies, Bucharest

P.3

PREPARATION OF Fe-TiO2 NANOCRYSTALS BY HYDROTHERMAL METHOD USED HIGH PRESSURES AND TEMPERATURES M. Miclau, R. Baies, C. Lazau, I. Grozescu National Institute of Research and Development for Electrochemistry and Condensed Matter, Timisoara

P.4

NEON ATOMS NANOTUBES AS 1D QUANTUM REGISTERS C. I. Ciubotariu(1), C. Ciubotariu(2), Corneliu Ciubotariu(3) (1)Department of Electrical and Computer Engineering, University of Calgari, Alberta, Canada (2)Universite Laval, Faculte des Sciences de l’Administration, Quebec, Canada (3) Technical University “Gheorghe Asachi”, Iasi

P.5 STRUCTURAL AND OPTICAL PROPERTIES OF CdO THIN FILMS R. S. Rusu, P. Prepelita, I. Vlascianu, G. I. Rusu ”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi

P.6 ON THE MECHANISM OF ELECTRONIC TRANSPORT IN CdO THIN FILMS R.S. Rusu, N. Rezlescu, P. Prepelita, C. Dantus, G. I. Rusu ”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi

P.7

ON THE ELECTRICAL AND OPTICAL CHARACTERISTICS OF POLYCRYSTALLINE ZnTe THIN FILMS P. Prepelita, R. S. Rusu, N. Apetroaie, G. Oniciuc, M. Lesenciuc, G. I. Rusu “Alexandru Ioan Cuza” University, Faculty of Physics, Iasi

P.8

AFM AND XRD INVESTIGATIONS OF CdTe THIN FILMS DEPOSITED BY STACKED LAYER METHOD G. G. Rusu ”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi

P.9

SEM STUDIES ON THIN STRUCTURE SAMPLES OF Al-Ni EUTECTIC P. Olaru(1), D. Hui(2) (1)INAV Aviation Institute, Bucharest (2)University of New Orleans, USA

P.10 ACOUSTIC EMISSION IN ADHESION MEASURMENT OF THIN FILMS C. Gheorghies, M. Bucsa, L. Gheorghies “Dunarea de Jos”University of Galati, Galati

P.11

FTIR RECOGNITION OF NANO-IRON CENTERS IN Fe-ZSM-5 BASED CATALYST M. T. Nechita, G. Apostolescu, I. Rosca Technical University “Gheorghe Asachi”, Iasi

P.12 PREPARATION OF SILVER NANOPARTICLES BY γ AND ELECTRON IRRADIATION IN SOLUTION: INFLUENCE OF SURFACTANT ON PARTICLE SIZE

G. Apostolescu, G. Carja, m. T. Nechita, N. Apostolescu, I. Rosca Technical University “Gheorghe Asachi”, Iasi

P.13

PILLARED LAPONITE CLAY-BASED FER NANOCOMPOSITE AS PHOTO-FENTON CATALYST M. M. Bobu, I. Siminiceanu Technical University “Gheorghe Asachi”, Iasi

P.14

HEXAFERRITE NANOPOWDERS FOR RECORDING MEDIA PREPARED BY A MODIFIED COPRECIPITATION TECHNIQUE C. Doroftei, E. Rezlescu, P. D. Popa, N. Rezlescu National Institute of Research and Development for Technical Physics, Iasi

P.15

ULTRA-FINE NICKEL-COBALT FERRITE DOPED WITH MAGNANESE FOR ACETONE GAS SENSOR N. Iftimie, N. Rezlescu, E. Rezlescu, P. D. Popa National Institute of Research and Development for Technical Physics, Iasi

P.16

COMPLEX PERMEABILITY SPECTRA OF HIGH FREQUENCY Ni-Zn FERRITES DOPED WITH V2 O5/ Nb2O5 B. Parvatheeswara Rao(1), O. F. Caltun(2), L. Spinu(3), I. Dumitru(3) (1)Department of Physics, Andhra University, India (2)”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi (3)University of New Orleans, SUA

P.17

MAGNETIZATION PROCESS IN SOFT MATERIALS UNDER DIFFERENT WAVEFORM OF THE APPLIED MAGNETIC FIELD O. F. Caltun(1), Al. Stancu(1), P. Andrei(2) (1)”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi (2)Electrical and Computer Engineering, Florida State University and Florida A&M University, Tallahasse, USA

P.18

THE MICROSTRUCTURE OF THE SOFT FERRITE THIN FILMS DEPOSITED BY PLD ON SILICON SUBSTRATE O. F. Caltun(1), Li-Shing Hsu(2) (1)”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi (2)National Chang Hua University of Education, Department of Physics, Taiwan

P.19

STRUCTURAL AND MAGNETIC PROPERTIES OF Fe-Co EMBEDDED NANOSTRUCTURES F. Brinza, N. Sulitanu ”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi

P.20

REALISTIC REPRESENTATION OF THE REVERSIBLE MAGNETIZATION PROCESSES IN SCALAR PREISACH MODELS OF HYSTERESIS L. Stoleriu, Al. Stancu ”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi

P.21

LOCAL HYSTERESIS LOOPS ANALYSIS IN A SYSTEM OF INTERACTING SINGLE-DOMAIN PARTICLES R. Tanasa, Al. Stancu ”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi

P.22

IDENTIFICATION PROCEDURES FOR PREISACH-TYPE MODELS BASED ON FORC DIAGRAMS Al. Stancu ”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi

P.23

DYNAMIC INTERACTIONS IN NANOSTRUCTURED PARTICULATE SYSTEMS D. Cimpoesu, Al. Stancu ”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi

P.24

PRELIMINARY DATA REGARDING THE SYNTHESIS AND CHARACTERIZATION OF AN AQUEOUS FERROFLUID M. Racuciu(1), D. E. Creanga(2), Gh. Calugaru(3)

(1)“Lucian Blaga” University, Sibiu (2)”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi (3)Technical University “Gheorghe Asachi”, Iasi

P.25

INVESTIGATION OF NANOSTRUCTURES IN FERROFLUIDS BY STATIC MAGNETIZATION AND BIREFRINGENCE RELAXATION MEASURMENTS V. Badescu(1), L. E. Udrea(1), G. Fosa(2), R. Badescu(2) (1)National Institute of Research and Development for Technical Physics, Iasi (2)Technical University “Georghe. Asachi”, Iasi

P.26

PREPARATION AND MAGNETIC PROPERTIES OF Ni, Co AND Co-Ni NANOPARTICLES FOR BIOMEDICAL APPLICATIONS H. Chiriac, A. Moga, C. Gherasim, G. G. Nedelcu National Institute of Research and Development for Technical Physics, Iasi

P.27

PREPARATION AND MAGNETIC PROPERTIES OF Co-P AND Co-Ni-P AMORPHOUS NANOWIRES ARRAYS H. Chiriac, A. Moga, C. Gherasim National Institute of Research and Development for Technical Physics, Iasi

P.28

SOFT MAGNETIC PROPERTIES AND STRUCTURAL CHARACTERIZATION OF Fe-Co-B-N THIN FILMS M. Urse, H. Chiriac, M. Grigoras National Institute of Research and Development for Technical Physics, Iasi

P.29

MAGNETO-OPTICAL PROPERTIES OF Fe-BASED AMORPHOUS THIN FILMS M. Dobromir(1), M. Neagu(1), G. Popa(1), H. Chiriac(2), Gh. Singurel(1), K. Teliou(3), A. Kakaroglou(3) (1)”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi (2)National Institute of Research and Development for Technical Physics, Iasi (3)National Technical University, Athens, Greece

P.30 MAGNETIC PROPERTIES IN FePt3 NANOSTRUCTURED THIN FILMS V. Georgescu, R. Musat, C. Sirbu ”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi

P.31

EDDY CURRENT NONDESTRUCTIVE EVALUATION METHODS OF DEFECTS IN AMORPHOUS AND NANO-CRYSTALLINE MATERIALS R. Grimberg(1), A. Savin(1), R. Steigmann(1), A. Andreescu(1), S. S. Udpa(2), T. Hogan(2) (1)National Institute of Research and Development for Technical Physics, Iasi (2)Michigan State University,USA

P.32 GMI MAGNETIC SENSOR FOR BIOMEDICAL DETECTION H. Chiriac, M. Tibu, A. Moga, D. D. Herea National Institute of Research and Development for Technical Physics, Iasi

P.33

NEW FeNbB BASED BULK AMORPHOUS AND NANOCOMPOSITE SOFT MAGNETS FOR APPLICATIONS N Lupu, H. Chiriac National Institute of Research and Development for Technical Physics, Iasi

P.34

FLUXGATES USING ZERO MAGNETOSTRICTIVE FeCoSiB NANOCRYSTALLINE RIBBONS J. Petrou(1), J. Patronos(1), H. Chiriac(2), E. Hristoforou(1) (1)National Technical University, Athens, Greece

(2)National Institute of Research and Development for Technical Physics, Iasi

P.35

MAGNETOSTRICTIVE DELAY LINES IN ENGINEERING APPLICATION BASED ON AMORPHOUS Fe-RICH ALLOYS G. Loris(1), H. Chiriac(2), E. Hristoforou(1) (1)National Technical University, Athens, Greece (2)National Institute of Research and Development for Technical Physics, Iasi

P.36

MAGNETIC AND MAGNETOELASTIC UNIFORMITY MEASURMENTS ON Fe78Si7B15 AMORPHOUS RIBBONS A. Teliou(1), H. Chiriac(2), E. Hristoforou(1) (1)National Technical University, Athens, Greece (2)National Institute of Research and Development for Technical Physics, Iasi

P.37

SMART MULTI-SENSOR BASED ON AMORPHOUS ALLOYS A. Kakaroglou(1), H. Chiriac(2), E. Hristoforou(1)

(1)National Technical University, Athens, Greece (2)National Institute of Research and Development for Technical Physics, Iasi

P.38

SMART NANOSTRUCTURES SIMULATED DESIGN BY NEURAL-NETS METHOD FOR SPATIAL BIOTECHNOLOGIES APPLICATIONS S. Mohorianu, F. V. Rusu National Institute of Research and Development for Technical Physics, Iasi

P.39

CONTRIBUTIONS TO METALLIC MATRIX COMPOSITES PROCESSING BY POWDER METALLURGY M. Mangra, O. Gingu, G. Sima, N. Dumitru, L. Gruionu, N. Coman University of Craiova, Faculty of Engineering and Management of Technological Systems, Drobeta Turnu Severin

P.40 NANOWIRES IN POROUS TEMPLATES M. Daub Max-Planck Institute for Microstructure, Halle, Germania

1 of 82

O-1

NANOSCIENCES AND NANOTECHNOLOGIES IN ROMANIA. CHANCES FOR SUCCESS. RESPONSABILITIES AND RISKS.

Gh. Popa

“Al. I. Cuza” University, Faculty of Physics, 700506, Iasi Abstract not available.

2 of 82

O-2

A TENTATIVE SWOT ANALYSIS OF ROMANIAN RESEARCH

Bogdan C. Simionescu

“Petru Poni” Institute of Macromolecular Chemistry, Romanian Academy, Aleea Grigore Ghica Voda 41A, 700487 Iasi, Romania

Abstract not available.

3 of 82

O-3

RAINS – STARTING POINT FOR A STRONGER REGIONAL COOPERATION

Valeria Harabagiu

“Petru Poni” Institute of Macromolecular Chemistry, Romanian Academy, Aleea Grigore Ghica Voda 41A, 700487 Iasi, Romania

Abstract not available.

4 of 82

O-4

MAGNETIC RESONANCE AT NANOSCALE: NANOMETROLOGY AND SPIN DYNAMICS

L.M. Giurgiu*

National Institute for Research and Development of Isotopic and Molecular Technologies, P.O. Box 700, R-400293, Cluj-Napoca, Romania

Electron Paramagnetic Resonance (EPR) is shown to be a powerful tool for studying microscopic details of nanometer metallic/magnetic particles and nanostructured materials. Regarding the metrology in nanoscaled particles I will concentrate on the following informations revealed by EPR: (i) metallic particle’s mean size evaluation and (ii) orientational degree of magnetic particles. From the EPR experiments on Pt-nanoparticles electrodeposited in the channels of porous Al2O3 membranes, the integral intensity which is proportional to the electronic susceptibility, follows a Curie law. It is a characteristic feature of a quantum size effect confirming that the condition hνe < δ is satisfied for Pt – nanoparticles. Taken into account a theoretical model, the Pt – particles mean diameter, d ≈ 6 nm, could be evaluated. The analysis of the temperature dependencies of the resonance field and the linewidth appropriate to αFe2O3 magnetic nanoparticles embedded in conducting polymers (PPy), could give distinct indication on the degree of the orientation corresponding to these particles. In accordance with the phenomenological model ultrafine magnetic particles, we have estimated that αFe2O3 particles are partially oriented ( n = 2.28). As far as the EPR investigations on nanostructured materials are concerned, we have investigated nanometric La0.67Ca0.33MnO3 manganites with colosal magnetoresistence. I will point at those highlights as the spin dynamics in the paramagnetic regime and the influence of the grain size reduction on the exchange coupling integral between Mn spins, J, and the polaron activation energy, Ea. The temperature dependencies of the EPR linewidth and integral intensity have been analysed in terms of the bottlenecked spin relaxation, small polaron hopping and core-shell scenarios. The degradation of the double-exchange interaction as the grain size decreases results in the decrease of J with the reduction of grain size. It could be due to (i) an increase influence of the magnetically disordered surface layer in smaller grains and probably (ii) the structural changes upon annealing at different temperatures. The observed decrease of Ea with decreasing grain size could be attributed to two opposite contributions arising from the inner core and outer shell of the granular particles.The polaron activation energy decreases with increasing the Mn4+ content (inner core contribution) while an increased disorder in the surface layer of the smaller grains results in the increase of Ea. Since the overall effect is the decrease of Ea, the inner core contribution to Ea is dominant.

*E-mail: [email protected].

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O-5

MAGNETIC PROPERTIES AND GMR EFFECT IN NANOSTRUCTURED ELECTRODEPOSITED THIN FILMS

Violeta Georgescu

“Al. I. Cuza” University, Faculty of Physics, 11 Carol I Blvd, Iasi - 700506, Romania During the last several years, interest in the study of nanostructured materials has been increasing at an accelerating rate, stimulated by recent advances in materials preparation and characterisation techniques and the realisation that these materials exhibit many potential technological applications. Nanostructured materials have structural or chemical restrictions on the nanometer scale along one or more of the dimensions. Due to the complexity of nanostructures, low dimensionality, and interplay among constituents, they exhibit new and enhanced functional properties by comparison with the similar bulk materials. We used electrodeposition to produce nanostructured multilayers, magnetic thin films and ordered nanostructures of transition metals. Various electrodeposited magnetic films (such as Co-Pt, Fe-Pt, Ni-Pt, Co-Ni-Mg-N, Co-Ni-P, Co-Cr, Cu-Cr, and Cu-Co) have been studied to elucidate the relationship between electrodeposition conditions and resulting deposit magnetic properties. In this report, we will exemplify the preparation and characterization of electrodeposited Co/Pt and Fe/Pt nanostructured materials, together with their magnetic properties. We have studied the transition from multilayer to alloy in the Co-Pt system, using films prepared by pulse electrodeposition. Recently, we prepared random arrays of electrodeposited Co/Pt multilayered nanowires and Fe-Pt nanowires into the pores of anodised aluminium oxide films. The magnetic anisotropy, interface anisotropy, interlayer exchange coupling, magnetoresistance, the coercive field and the magnetic susceptibility have been investigated in several series of multilayered films, with thickness of component layers of nanometric scale, with the aim to correlate changes in the microstructure of electrodeposited multilayers with magnetic properties. It was important to study the correlation between the microstructural properties in nanostructured multilayers and functional properties, by using complementary analysis techniques. The multilayers were characterised using XRD, EDAX, SEM and AFM techniques. Magnetic measurements were carried out by torque magnetometry and by an induction method using a digital scope interfaced to computer. Measurements of the magnetoresistance were performed for current-perpendicular-to-plane (CPP) geometry and current-in-plane (CIP) geometry. The nanostructured FePt3 films and the Co/Pt multilayers exhibit a giant magnetoresistive effect. Our research demonstrates that electrodeposition is a promising and inexpensive preparation method for obtaining nanostructured magnetic materials with controllable and adequate functional properties for technological applications.

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O-6

MICRO-STRUCTURE AND MAGNETIC PROPERTIES OF Fe-Cu NANOCOMPOSITES, AS POTENTIAL CANDIDATES FOR RE-FREE

PERMANENT MAGNETS

M. Sofronie1, V. Kuncser1, A. Jianu1, M. Codescu2, F. Lifei1, N. Stancu2, J. Pintea2, M. Valeanu1, W. Kappel2, G. Filoti1

1 National Institute for Materials Physics, P.O. Box Mg-7, 76900 Bucharest, Romania 2S.C.ICPE-CA SA 74204, Bucharest, Romania

The Rare-Earth (RE) based intermetallics rich in 3d transition elements represent to date highest performance magnets. There are more complex systems involving exchange spring phenomena, which also contain as a main constituent a RE based phase. Intense efforts are presently done in the search for cheaper RE-free permanent magnets with similar or even improved magnetic properties. Enhanced energy products can be reached by increasing both the coercivity and the remanent magnetization. The RE ions are responsible for the strong intrinsic anisotropy. Therefore, due to their absence, complementary effects should induce the preferred orientation of the magnetic moments along an easy axis. In particular, the anisotropy produced by shape effects might be exploited. This work reports on a micro-structural and magnetic study of the Fe-Cu nanocomposite system in respect to their magnetic performances as potential candidate for a RE-free permanent magnet. Fe20Cu80 ribbons were prepared by the melt spinning method, choosing different conditions to better control the degree of Fe dispersion in the fcc-Cu matrix. Subsequent annealing treatments were performed on the composites, in the presence or absence of an external applied magnetic field, in order to growth nano-particles of metallic iron with various shapes. Structural properties and phase composition have been analyzed by Mossbauer spectroscopy and X ray diffractometry and corroborated with magnetic measurements data, at each stage of preparation. The α-Fe phase was present in all initial melt spun ribbons, the amount and the dispersion degree was dependent on the selected parameters of the quenching procedure. There are structural and magnetic texture effects along the ribbon plane as evidenced by corroborating Mossbauer and X-ray data. The crystallization process was suitable controlled via annealing parameters. The specific characteristics depend on the magnitude and direction of the applied magnetic field, having also a direct influence on the magnetic parameters of the composites.

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O-7

RATE DEPENDENT HYSTERESIS IN SPIN CROSSOVER SOLIDS ANALYZED USING FORC DIAGRAMS

Cristian Enachescu*, Radu Tanasa, Alexandru Stancu

“Alexandru Ioan Cuza” University, Faculty of Physics, Department of Solid State and Theoretical Physics, 700506, Iasi, Romania

Francois Varret, Jorge Linares

Laboratoire de Magnétisme et d’Optique, Universite Saint Quentin en Yvelines, UMR-CNRS 8634, 78035, Versailles, France

In this paper we propose the light induced thermal hysteresis (LITH) of spin crossover solids as a good candidate for the experimental exploration of the ability of the First Order Reversal Curves (FORC) diagram method to evidence rate-dependent effects. To the best of our knowledge, systematic studies of the rate-dependent phenomena in magnetic systems (nanometric or nanostrutured systems) within the framework of the FORC diagram method have not yet been published, due to the difficulties in extending the field rate in a sufficient wide range. The spin transition solids [1] are molecular compounds, commutable between two states in thermodynamic competition: the low spin state (LS) and the high spin state (HS). The optical, magnetic and volume properties are different for these two states. The commutation is accompanied by hysteresis, property at the base of applications for information storage [2]. In order to characterize the system, one uses the high spin fraction, nHS, i.e. the fraction of molecules that are in the high spin state. One FORC starts on the Major Hysteresis Loop at a certain temperature, named reversal temperature TB and contains the data up to the saturation of the sample. A set of FORCs (usually up to 100) are obtained for different reversal temperatures. The value of the high spin fraction in a certain point on a FORC depends on the actual temperature and on the reversal temperature [3]. The FORC distribution is defined as the second mixed derivative of the high spin fraction for all these curves, ( ) ( )( , ) ,2

A B HS A B A BT T n T T T Tρ = −∂ ∂ ∂ . LITH can be observed at lower temperatures (where LS is the stable state) under permanent irradiation, and was explained [4] as a result of the non-linear competition between photo-excitation, and relaxation, a cooperative self-accelerated process. In Fig. 1 we present three sets of FORCs obtained for a thin sample of [Fe0.6Zn0.4(btr)2(NCS)2]H2O (1 mg), starting from the lower temperature branch, obtained using different temperature scan rate and/or light intensity. The corresponding derived switching temperatures distribution are shown in Fig. 2. To understand the qualitative features of the experimental FORC distributions associated with the LITH loops, we have proceeded to various simulations using the Macroscopic Master equation approach and based on the static parameter distributions determined by the thermal hysteresis investigation. We considered distributions of cooperativity parameter α and activation energies aE obtained previously, in terms of interaction parameter ( / )J T 2α= and energy barrier ∆ , from the treatment of thermal hysteresis FORCs [5].

References [1] P. Gütlich, H.A. Goodwin, Topics in current chemistry, 233 (2004) 1. [2] O. Kahn, C. J. Martinez, Science, 279 (1997) 44.

*Corresponding author. E-mail: [email protected].

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[3] C. R. Pike, A. P. Roberts, and K. L. Verosub, Journal of Applied Physics, 85(9) (1999) 6660. [4] A. Desaix et al, Eur. Phys. J. B, 6 (1998) 183. [5] R. Tanasa, C. Enachescu, A. Stancu, E. Codjovi, J. Linarès, F. Varret , J. Haasnoot, Phys. Rev. B,

71 (2005) 014431.

Fig. 1. Experimental FORC/LITH data of [ ]( )0.6 0.4 2 2

( )Fe Zn btr NCS Fig. 2. Derived FORC/LITH distribution of

switching temperatures

30 35 40 45 50 55 60 65 700,0

0,2

0,4

0,6

0,8

1,0

0.42K/min, I1 0.42K/min, I2>I1 0.3K/min, I2

n HS

T [K]

4 5

5 0

4 5

5 0

4 5 5 0 5 5 6 0 6 5 7 0

4 5

5 0

Tβ

Tβ

Tβ

Tα

Tβ

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O-8 MAGNETOSTRICTIVE PROPRIETES OF SOME AMORPHOUS AND

NANOCRYSTALIZED ALLOS

Ioan Mihalca1, Aurel Ercuta2

1University “Politehnica”Timisoara, Physics Department 2West University of Timisoara, Electricity Department

The magnetic and magnetostrictive proprietes of feromagnetic TM-M and RE-TM-M amorphous alloys can be varied within large limits by chemical composition modification. Thermally activated structural relaxation or nanocrystalization processes can be also used in order to optimize the macoscopic magnetic and magnetoelasic properties. The paper presents a comparative study of the magnetostriction changes of some Fe-based and RE-Fe-B (Gd, Dy, etc.) induced by annealig at appropriate temperatures. Magnetoelastic behaviour was studied by using Villari effect. Structural characterization was made by XRD, DSC and Mossbauer spectroscopy. If nanocrystallization process determines a decrease of magnetostriction in FINEMET alloy (λs~ 0), large values ~ 250 ppm can be obtained in some Dy-Fe-B nanocrystallized alloy.

References [1] G.Herzer, IEEE Trans. Magn., 26 (1990)1397. [2] S.H.Lim et al., J. Appl. Phys., 76 (1994) 7021.

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O-9

THE MAGNETIC AND MORPHOLOGICAL CHARACTERIZATION OF NANOGRANULAR [FeCoB/(SiO2)]× n THIN FILMS

M. Urse*, H. Chiriac, and M. Grigoras

National Institute of Research and Development for Technical Physics, 47 Mangeron Blvd., 700050 Iasi, OP3, CP 833, Romania

The granular metal – insulator films are composite materials consisting of metallic nanograins embedded in an insulating matrix. Their electrical and magnetic properties are strongly dependent on their composition and microstructure. The hetero-amorphous structure of metal /insulator thin films exhibits much higher resistivity in contrast to the conventional nanocrystalline structures because it holds magnetic softness without exchange interaction between the metal particles [1-3]. The ferromagnetic metal/insulator thin films with very high electrical resistivity are an excellent candidate for high permeability cores in thin film inductors that can be used for R.F - Integrated Circuit. This paper reports some results concerning the influence of the FeCoB and SiO2 layers thickness and annealing temperature on the electrical, magnetic and microstructural properties of [FeCoB/(SiO2)]×n multilayer thin films, in view of their utilization for manufacturing magnetic thin film inductors which can operate at high frequencies. A comparison between the magnetic and microstructural properties of FeCoB and [FeCoB/(SiO2)]×n thin films is also reported. The FeCoB and [FeCoB/(SiO2)]×n thin films were prepared by deposition in vacuum using a conventional R.F. diode sputtering system. The as-deposited samples with a total thickness of FeCoB layers about 300 nm were annealed at temperatures between 200oC and 400oC, for 1h, in vacuum of 2 x 10-3 Pa. The electrical resistivity of the samples was measured using the D.C. four – point probe technique and the magnetic characteristics were measured using a vibrating sample magnetometer (VSM) in a magnetic field of 1.8 kOe. The crystallographic structure was investigated using X-ray diffraction (XRD) analysis and microstructure was investigated with a transmission electron microscopy (TEM). Supplementary, the morphology and magnetic structure of the samples was investigated by atomic force microscopy (AFM) and magnetic force microscopy (MFM).

The [FeCoB/SiO2]×n (n ≥10) thin films exhibit high resistivity over 300 µΩ⋅cm while superior soft magnetic properties, specific for FeCoB thin films are maintained. The [FeCoB(10nm) /SiO2(2nm)]×30 thin films after annealing at 300oC show good resistive and magnetic properties of the resistivity ρ ≅ 810 µΩ⋅cm, saturation magnetization Ms ≅ 170 emu/g and coercive field Hc ≅ 4 Oe. The good resistive and soft magnetic properties of these materials were due to the granular microstructure. TEM image for as-deposited [FeCoB(10nm)/

SiO2(2nm)]x5 thin film, presented in figure, displays nanometric spherical particles, with the average sizes are about 10 nm, embedded in a SiO2 amorphous matrix. In order to improve

*Corresponding author. Phone: +40-232-430680 / Fax: +40-232-231132 / e-mail: [email protected].

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the structural and magnetic properties of [FeCoB/SiO2]×n thin films, further investigations are developing concerning the utilization of magnetic or non-magnetic underlayers.

References [1] K. Ikeda, K. Kobayashi and M. Fujimoto, J. Ceram. Soc., 85 (2002) 169. [2] X.N. Jing and X. Yan, J. Appl. Phys., 83(11) (1998) 6530. [3] K. Ikeda, K. Kobayashi, K. Ohta, R. Kondo, T. Suzuki, and M. Fujimoto, IEEE Trans.Magn.,

39(5) (2003) 3057.

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O-10

CARBON-BASED NANOSTRUCTURES THROUGH INTERACTION LASER-REACTIVE GASEOUS MIXTURES

C.T. Fleaca*, L. Albu, R. Alexandrescu, F. Dumitrache, I. Morjan, E. Popovici I. Sandu, M. Scarisoreanu, I. Soare, I. Voicu

National Institute for Lasers, Plasma and Radiation Physics, P.O. Box MG-36, 0077125 Bucharest-Magurele

Carbon-made materials have been the field of major discoveries over the past fifteen years, with the identification of new phases, beyond the well known diamond, graphite and amorphous structures. These novel morphologies include building blocks in the nanometer size range, such as fullerene molecules, the carbon onions or the carbon nanotubes. They have stimulated a huge effort to understand the atomic arrangements and bonds involved in these nano-objects, to master new routes for improving the production of selected species, to measure their mechanical and electronic properties or to identify fields of application. Continuously demanded by the applied research, these carbon nanostructures are mainly obtained by methods based on the systems containing carbon and an inert gas or under the conditions of a fuel-rich hydrocarbon/oxygen flame. This last technique is based on a high temperature C/H/O system of well-established composition. Laser pyrolysis of hydrocarbons leads to soots containing different carbon nanostructures.Our method allows to obtain nanostructures from the amorphous carbon and particles with a turbostratic structures up to those characterized by a high degree of curvature. The continuous synthesis method by laser pyrolysis of hydrocarbon-based mixture differs from that of combustion by the heat supply to the chemical system: a CW CO2 laser is used as an energetic controlled source. The process that we use is based on the interaction between laser radiation and at least one of the gaseous reactants ; formation of carbon nanostructures in the flames of laser pyrolysis and the synthesis of macroscopic quantities were already demonstrated. The high temperature gradients and very rapid reaction time involved in the process of laser pyrolysis are characteristic of the process leading to very fine powders with uniform and controllable particle size distribution. The variation of the experimental parameters could control the final particle morphology providing useful functional properties. We believe that the utilization of a CW CO2 laser and continuous flow reactor makes the installation, in principle, scaleable to pilot plant dimensions. Conversely, the negligible radiation absorption by the precursors requires the addition of a reaction sensitizer, an energy transfer gas, which we show that can either react or interfere, thus altering the expected reaction path. The formation of different nanostructures is related to the presence of heteroatoms in the reactants. Some heteroatoms can be found in sensitizers. The same or other heteroatoms can play an oxidative/catalytic role. In our opinion, the non-controlled presence of these heteroatoms should be deleterious to the formation of all-carbon compounds as their effective participation in the process can yield strong carbon-heteroatom bonds and thus inhibiting the formation of useful final product. Focusing, in the context of necessary presence of these heteroatoms in the gas composition, on the present questions concerning the rational synthesis of nanostructures with controlled dimensionality, size and potentially properties, the aim of our work was to investigate, mainly by diffraction methods, significant changes in soot morphology produced by these, sometimes unavoidable, heterogeneous atoms.

*Corresponding author. Phone: (0421)4574467 ext.1819/1879 / Fax: (0421)4574467 / email: [email protected].

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O-11

NANOSTRUCTURED CALCIUM PHOSPHATES COATINGS FOR BIOMEDICAL IMPLANTS

Carmen Ristoscu, Gabriel Socol, Emanuel Axente, Sorin Grigorescu, Gabriela Dorcioman, Ion N. Mihailescu

Laser-Surface-Plasma Interactions Laboratory National Institute for Lasers, Plasma and Radiations Physics, Bucharest, Romania

We report recent progress in Pulsed Laser Deposition of bioactive calcium phosphates thin structures. The coatings are well-suited for biomimetic medical implants. The depositions were performed on titanium substrates with a pulsed KrF* UV (248 nm, 6 ns) laser source. Our important result reported with this contribution is the first successful deposition of nanostructured layers of hydroxyapatite (Ca10(PO4)6(OH)2 - HA) doped with Mn2+ and carbonates (Mn-CHA) and octacalcium phosphate(Ca8H2(PO4)6 x 5H2O - OCP). Biological apatites are always carbonated. To improve the metallic implants properties, we synthesized carbonated hydroxyapatite enriched with Mn2+ ions to be used as coating material. Mn2+ ions activate integrins, a family of receptors which mediate cellular interactions with extra-cellular matrix and cell surface ligands. In Mn2+ ions presence the ligand binding affinity of integrin increases and cell adhesion is activated. Consequently, the presence of Mn2+ in coatings should promote the interaction with the host bone tissue. We mention that OCP, due to its structural resemblance to HA and its frequent occurrence in pathological and physiological calcifications, is considered the most likely precursor of biological apatites. The best deposition conditions for both HA and Mn-CHA thin films were 13 Pa O2, 400 °C with post deposition treatment of 6h in air enriched with water vapors. The coatings were stoichiometric and crystalline. For OCP, deposition at 150°C in 50 Pa water vapors atmosphere, annealed for 6h in hot flux of water vapors, resulted in stoichiometric, but partially nano-crystallized films. XRD analyses indicate the same composition for targets and for the “as deposited” structures while SEM investigations prove that the films are rough and exhibit an extended active surface, a good prerequisite for cells proliferation. We observed a fast degradation for OCP while HA presents an increased physico-chemical resistance in SBF presence. In-vitro tests (Cell proliferation (WST1 test), Alkaline phosphatase (ALP), Collagen type I (CICP), Transforming growth factor beta 1 (TGF-b1)) prove that human osteoblasts proliferate, reach a normal morphology and remain viable when cultured on CaPs coatings. In-vivo pull-out tests on OCP, Mn-CHA and HA coated implants demonstrated that the CaP coatings activate and enhance the bone repairing (with about 50%).

Acknowledgements The authors acknowledge the financial support of the EU through the contract SIMI G5RD-2000-00423 and of the Ministry of Education and Research through the contract CERES 3-124.

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O-12 PHYSICAL CHARACTERISATION OF CdMnS NANOCRYSTALLINE

FILMS OBTAINED BY CHEMICAL BATH DEPOSITION

F. Iacomi*, A. Vasile, N. Apetroaei, M.L. Craus, I. Caraman

Faculty of Physics, “Al.I. Cuza“ University, Iasi, Romania Diluted magnetic semiconductors have attracted much attention because they permit to tune the energy gap, the effective mass and the lattice constant by varying the concentration of the magnetic material. The Mn – based diluted magnetic semiconductors can be grown over a wide composition range and are excellent candidates for fabrication of quantum wells and superlattice. The introduction of large mole Mn fraction can move the intrinsic edge through the visible region. The deposition solution was prepared by mixing CdSO4 and MnSO4 (0.5 mol-1) and potassium nitriloacetate (0.7mol-1) and adjusting the pH to 8.5 with 10% KOH solution. This solution was mixed with thiourea (0.4 mol-1), diluted with distilled water and the pH was adjusted to 11. The CdSO4 and MnSO4 were mixed in various molar rations: x = 0.05, 0.10, 0.20, 0.30, and 0.40. Glass slides were degreased and rinsed thoroughly with distilled water and placed at an angle of cca. 200 of normal in final solution and kept at room temperature in the dark, 12 and 24 h, respectively. The samples were characterized by XRD, AFM and optical absorption. The surface morphology of one of as – deposited films is shown in Fig.1. The grain size of CdMnS thin

films was found to decrease with an increase in Mn concentration. The RMS surface roughness decreases with the increases in Mn concentrations. The absorption spectra are dependent on the Mn concentration but also by the particle size. The blue shift of band gap of thin films might be ascribed to the size effect of the small grains. The band gaps of CdMnS thin films as determined from the absorption spectra are listed in Table 1. The dependence of the band gap on the Mn content can be ascribed to the fact that Cd was substituted by Mn in the CdS’s structure.

Table 1 Mn concentration 0.00 0.05 0.10 0.20 0.30 0.40 Eg (eV) 4.24 4.00 4.07 4.15 4.21 4.30

The minimum of the band gap energy could be attributed to exchange interactions of the conduction and valence bands electrons of the Mn2+ d electrons. Mn2+/Mn2+ and Mn2+/band electrons interactions are stronger than of the bulk phase.

References


Fig. 1. AFM of Cd0.9Mn0.1S.

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[1] P. Nemec, I. Nemec, P. Nahilkova, K. Knizek, P. Maly, J. of Crystal Growth, 240 (2002) 484. [2] D. S. Chun, Y.C. Chang, C.Y. Hsieh, Thin Solid Films, 304 (1987) 28.

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O-13

NANO-SCALE THERMOELECTRIC MATERIALS FOR DIRECT THERMAL-TO-ELECTRIC ENERGY CONVERSION

V. Cimpoca1), I. Bancuta1), Anca Gheboianu1), Gh. Brezeanu2) Ileana Cernica3), Maria Cimpoca3), I. Grozescu4)

1)Valahia State University, Targoviste, Romania 2)”Politechnica” Univerity of Bucharest, Bucharest, Romania

3)National Institute for Microtechnologies, Bucharest, Romania 4)National Institute for Condensed Material, Timisoara, Romania

Many electronic and optoelectronic components dissipate large amount of heat in a small area, creating a high temperature rise that affects the device performance and reliability. Thin-film thermoelectric devices have potentially higher efficiency than bulk ones due to quantum and classical size effects of electrons and phonons. In this paper, we discuss the design of thin-film thermoelectric microcoolers and microgenerators for achieving high performance. The devices considered are membrane structures based on electron transport along the film plane. A model is developed to include the effects of heat loss and leg shape. Design optimization is performed based on the modeling results. The efficiency of a thermoelectric (TE) device is determined by the materials used in making the device. A number of new theories to increase the figure of merit in TE materials have been developed in recent years, and the effectiveness of some approaches are being proved by increasing experiment results. In general, there are two types of approaches. In the first approach, the current and heat flow perpendicular to the film plane, i.e. the crossplane device, this is similar to the traditional TE device. In the second approach, both heat and current flow parallel to the film plane, i.e. the in-plane device. For the in-plane devices, an increase in Z has been calculated to arise from a number of factors, including an increase in the electronic density of states per unit volume for small well widths (several nanometers), as well as an increase in carrier mobility if modulation doping is exploited.

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O-14

NANOMATERIALS APPLICATION IN HYDROGEN TECHNOLOGY AND FUEL CELLS

Daniela Stoenescu*, Laurentiu Patularu, Mihai Culcer, Roxana Elena Lazar, Elena Carcadea, Dumitru Mirica, Mihai Varlam, Ioan Stefanescu

National R&D Institute for Cryogenics and Isotopic Technologies – ICIT Rm. Valcea The recent ecological and economical critical aspects of human development have called into question the new sphere of the hydrogen energy economy. The necessity of effective control of the environment quality and sustainable development impose with urgency upon the replacement of traditional ways of energy production with high performance Proton Exchange Membrane Fuel Cells (PEMFC). The remarkable properties shown by different types of nanomaterials, i.e. electrical, thermal, chemical and mechanical suggest that they are one of the most promising solution in domain of hydrogen energy. This paper presents the results obtained by ICIT-Rm. Valcea in an experimental-demonstrative conversion energy system and the future perspectives for the development of new materials and technologies for hydrogen storage and the Membrane Electrode Assembly’s (MEA’s) design.


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O-15 NANOSTRUCTURED METAL OXIDES FOR OPTICAL GAS SENSING

APPLICATIONS

Carmen Ristoscu, Gabriel Socol, Emanuel Axente, Sorin Grigorescu, Gabriela Dorcioman, Ion N. Mihailescu

Laser-Surface-Plasma Interactions Laboratory, Lasers Department National Institute for Lasers, Plasma and Radiations Physics, Bucharest, Romania

Nano-structured optical sensors offer a novel route for gas detection, which has recently become attractive for potential users. The main envisaged advantages are simplicity, compactness and resistance to electromagnetic interference. Metal oxides thin films can successfully be used in waveguides design and selective gas sensing. We performed Pulsed Laser Deposition (PLD) experiments with a KrF* (248 nm, 6 ns) laser source for producing nanostructured photonic sensors of metallic oxides with different composition and morphological characteristics. We deposited two types: undoped metal oxides (ZnO, TiO2 or WO3), or doped with Au, Pd, Pt or Ag, respectively. The behavior of coatings having the best waveguide properties was tested for different concentrations of butane. All structures were complementary characterized by Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS), Energy Dispersive X-ray Spectrometry (EDS), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). Our main result reported here is the detection of 100 ppm of butane in a super-atmospheric N2 or N2+air mixtures. For optical interrogation measurements in reaction with gas we used m-line technique, a method able to detect small variation of refractive index (∆n=10-5–10-4). We observed that the structural and morphological coatings’ characteristics are affected by growth conditions which can strongly influence the sensitivity to gas exposure. The deposited structures were optimized with respect to their sensitivity to each gas under investigation, through deposition parameters’ control and post-deposition treatments. Acknowledgements The authors acknowledge with thanks the financial support of the EU through the contract NANOPHOS IST-2001-39112 and of the Ministry of Education and Research through the contract PN 03 17.01.03.

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O-16

GRANULAR GMR LAYERS AS DEPOSITED BY THERMIONIC VACUUM ARC TECHNOLOGY (TVAT)

O. Brinza*, I. Mustata, C.P. Lungu, A.M. Lungu, V. Zaroschi

Low Temperature Plasma Laboratory, National Institute of Lasers, Plasma and Radiation Devices,

P.O. Box MG-36, Magurele-Bucharest We produced granular GMR films depositions by two simultaneous discharges in high vacuum conditions (10-5 mBar) in two kind of metal vapors exclusively, which were evaporated from the respective anodes by strong electronic bombardment. The bombarding electrons were thermo emitted by two externally heated cathodes made of tungsten wire. The magnetic metal together with the noble non magnetic metal were deposited on many glass probes having different positions relative to the two discharges. The resistance variations of the so deposited probes were measured against the values of a variable magnetic field induction (B). The as deposited probes were thermally treated in vacuum at different temperature and treatment durations. The magneto-resistive effect increased together with the wing steepness of the curves. The most used metal compositions were made of copper together with either iron or nickel or cobalt or, lastly, with permalloy. The principal characteristics of the vacuum plasmas were: - Cathode heating current for the copper discharge: 23-26 A; - Discharge current in copper vapors: 300 mA; - Copper anode voltage against the earthen cathode: 200-400 V; - Cathode heating current for the magnetic metal (Fe, Co, Ni, Permalloy) discharge: 100-

120 A; - Discharge current in magnetic metal vapors: 0.8-1.5 A; - Magnetic metal anode voltages: 600-1000V. The obtained results could be summarized as follows: 1. The greatest GMR effect defined as [R(H)-R(0)]/R(0)] was obtain for the CoCu

combinations and varied from some percentages to 32% when using magnetic induction variation from 0 to 1 T. The square like dependence of these dependencies can induce the idea of very narrow distribution of the granule dimensions;

2. The most sensitive probes were obtained with the Cu-Permalloy combination (Sensitive for field with the induction as low as some Gauss);

3. Very good result was obtained with the CuFe combination deposited on a Kapton substrate (38% without post-deposition treatment);

4. The X ray studies of the magnetic metal concentration in copper structure shown a continuous decrease from the magnetic metal discharge to the copper one, the maximum GMR effect being obtained for 35-45 % value.

*Corresponding author. Email: [email protected].

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O-17

NANOSCIENCES AND NANOTECHNOLOGIES IN EUROPEAN PROGRAMMES: FROM FP6 TO FP7

Dan Dascalu

National Institute for Research and Development in Microtechnologies, Bucharest, Romania Abstract not available.

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O-18

NANOSPHERE LITHOGRAPHY AND SELF-ASSEMBLY – TWO VERSATILE ROUTES FOR FABRICATION OF PERIODIC ARRAYS

OF NOBLE METAL NANOPARTICLES

S. Astilean*, M. Baia, D. Maniu, F. Toderas, and C. Farcau

Faculty of Physics, Babes-Bolyai University, Cluj-Napoca, Romania During the past decades, various nanoparticles of polystyrene, silica, metal, semiconductor and magnetic materials, nearly monodisperse in terms of their size, shape, internal structure, and surface chemistry, are being produced through a reliable manufacturing process. The fabrication of ordered nano-architectures by self-assembling such building blocks has become an increasingly popular topic in nanoscience and nanotechnology. For manipulating photons on the nanoscale and sensing molecular interaction, noble-metal nanostructures are of particular interest. They can support electromagnetic surface modes (surface plasmons) able to concentrate light field to a small fraction of wavelength and enhance the local field by several orders of magnitude. Here, we report the fabrication and characterization of long-range-ordered monolayers of noble-metal nanoparticles and other nanostructured materials via nanosphere lithography - a new emerging technique based on self-assembling procedure [1]. (A) Ordered arrays of self-assembled polystyrene nanospheres on solid substrate were used

as deposition mask through which gold or silver was deposited by thermal or e-beam evaporation. After the removal of the nanospheres, a regular array of metallic nanoparticles was left on the substrate. We used nanosphere lithography together with other techniques like thermal annealing and reactive ion etching in order to vary the array period, nanoparticle size and shape, as well as to create regular arrays of nanoholes into a metallic film.

(B) Gold and silver colloids of controlled size, density, optical response and morphology were self-assembled on fused silica substrates by employing an aminofunctional silane as a coupling agent.

Such nanostructures are highly desirable in several applications including optical energy and information transport, photonic crystals, near-field scanning optical microscopy, surface-enhanced spectroscopy, chemical and biological sensing. We currently exploit these fabricated noble-metal nanostructures in nanophotonics and surface – enhanced Raman spectroscopy (SERS) due to their unique optical response dominated by the excitation of surface plasmons [2,3].

References [1] C.L. Haynes and R.P. Van Duyne, J. Phys. Chem., B 105, (2001) 5599. [2] W.A. Murray, S. Astilean, and W.L. Barnes, Phys Rev B, 69 (2004) 165407. [3] M. Baia, L. Baia, S. Astilean, Chem. Phys. Lett., (2005) in press.


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O-19

POLYMERS AS CRYSTALLIZATION REGULATORS FOR NANO/BIOAPPLICATIONS

Gabrielle Charlotte Chitanu*

“Petru Poni” Institute of Macromolecular Chemistry, Romanian Academy of Sciences Aleea Grigore Ghica Voda 41A, 700487 Iasi, Romania

In nature structures of complex shape are often formed in processes, where the self-assembly properties of complex organic molecules are combined with the rigidity of inorganic compounds. In the last decade it has been an intensive focus to synthesize higher ordered inorganic crystals or hybrid inorganic/organic materials with a specific size, shape, orientation, organization, in order to design new materials and devices in various fields such as medicine, electronics, ceramics, catalysis, pigments, and cosmetics. Recently, bio-inspired morphosynthesis strategies have been emerging as an important tool for crystallization, taking advantage of using self-assembled organic superstructures to template inorganic materials with controlled morphologies and hierarchy. Usually, organic additives and/or templates with complex functionalization patterns are used to control the nucleation, growth, and alignment of inorganic crystals. Recently, it was shown that double hydrophilic block copolymers can exert significant effects on the crystal growth of inorganic and organic crystals. These functional polymers can adopt different functions ranging from the temporary stabilization of precursor phases to direct crystal growth via face selective adsorption. The role of water soluble polymers especially polyelectrolytes as crystal growth regulators was already investigated in several papers. In our contribution we analyze the influence of these polymers on the crystallization/separation of inorganic or organic low molecular salts in the processes which are involved in the biomineralization or in other processes/phenomena.


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O-20

SUBSTITUTED ANIONIC CLAYS WITH TAILORED TEXTURAL PROPERTIES: EFFECT OF THE NATURE OF THE THIRD CATION

IN THE CLAY LAYER

Gabriela Carja1, Horia Chiriac2, Nicoleta Lupu2

1Technical University of Iasi, Department of Physical Chemistry, Faculty of Industrial Chemistry, 71 D. Mangeron Boulevard, 700050 Iasi, Romania

2National Institute of Research and Development for Technical Physics 47 Mangeron Boulevard, 700050 Iasi, Romania

Layered double hydroxides (LDH) anionic clays in which magnesium was partially substituted by Fe(II) or Cu(II) and aluminium was partially substituted by V(III) were synthesized by a coprecipitation method. The resulting materials were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The introduction of the third cation in the brucite - like layer preserved the layered double hydroxide structure though the textural properties: e.g. the size, shape and the interconnection pattern of the obtained nanoparticles modified. The particle sizes increased from an average value equal to 75 nm for FeLDH, to 100 nm for VLDH and reached 150 nm for CuLDH. The changes of the textural properties give rise to altered porous properties of the studied clays. The introduction of iron as a layer cation induces soft magnetic properties for the derived clay structure; the saturation magnetization (M) is a function of iron content of the sample.

References [1] G. Carja, R. Nakamura, T. Aida, H. Niiyama, Microp. Mesopor. Mater., 47 (2001) 275. [2] G. Carja, R. Nakamura, T. Aida, H. Niiyama, J. Catal., 218 (2003) 104.

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O-21 FERROMAGNETIC RESONANCE PARAMETERS OF BALL MILLED

Ni-Zn FERRITE NANOPARTICLES

B. Parvatheeswara Rao1, O.F. Caltun2, I. Dumitru3, L. Spinu3 1Department of Physics, Andhra University, Visakhapatnam 530 003, India

2Department of Electricity and Electronics, A.I. Cuza University, 700506 Iasi, Romania 3Advanced Material Research Institute, University of New Orleans,

New Orleans, LA 70148, USA Among various methods reported for preparation of ferrite nanoparticles in the literature, the high-energy ball milling method has certain advantages as it provides a good control over the particle size and produces samples in relatively short times. The aim of this study is to prepare and and report various structural, magnetic and resonance parameters of ball milled Ni-Zn-In-Ti ferrite nanoparticles. Sintered pellets of the ferrite system, Ni0.65Zn0.375InxTi0.025Fe1.95-xO4, where x takes the values of 0.10, 0.15, 0.20 and 0.25 have been ground to make ultra fine particles of few nanometer size using a ball mill for 5 hours with a ball-to-powder ratio of 10:1. The powder samples were characterised by XRD, VSM and FMR techniques. The samples showed all major peaks related to a cubic spinel structure reported for ferrites, but smaller intensities and larger peak broadening were observed compared to their bulk samples. Particle sizes for these samples are estimated using Scherrer equation while taking into account of instrumental broadening and they are found to be around 5-6 nm. The obtained magnetic parameters from the hysteresis loops of the samples are very different from those of their bulk samples and are indicative of a typical superparamagnetic nature (Fig. 1). The FMR spectra of the samples show a single resonance peak at a field of the order of 2 kOe (Fig. 2). The data on the resonance field were used to estimate the magnetic parameters and these were analysed in combination with the structural and magnetic parameters from XRD and VSM studies.

Fig. 1. Hysteresis loops of Ni0.65Zn0.375InxTi0.025Fe1.95-xO4 particles.

Fig. 2. FMR spectra of Ni0.65Zn0.375InxTi0.025Fe1.95-xO4 particles.

The results of different indium concentrated samples are discussed in comparison to their bulk magnetic properties and the differences in various parameters are understood in terms of the particle size and associated small particle magnetism.

-10000 -5000 0 5000 10000-30-25-20-15-10-505

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0 2000 4000 6000 8000-1,5

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References [1] R. Krishnan, IEEE Trans. Magn., MAG-7 (1971) 202. [2] N. Venkataranani and C. M. Srivastava, IEEE Trans. Magn., 23(5) (1987) 2221. [3] W.A. Kaczmarek, A. Calka and B.W. Ninham, IEEE Trans. Magn., 29(6) (1993) 2649. [4] M. Rojo, J. Margineda and J. Munoz, IEEE Trans. Instr. Meas., 42 (1993) 56.

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O-22

WATER AT NANOSCOPIC CONTACTS

Lucel Sirghi† and Elisa Riedo‡ †Faculty of Physics, “Al. I. Cuza” University, Blvd. Carol I, no. 11, 700506 Iasi, Romania

‡School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, GA 303032, USA

Because of capillary condensation, nanoscopic contacts in atmospheric air are surrounded by water menisci. The phenomenon has received recently a great deal of attention because of its relevance to the fields of nanolitography [1,2], nanotribology [3] and biochemistry [4]. This work presents results of a theoretical and experimental study of behavior of the water menisci formed at nanoscale contacts when contacts break down. Atomic force microscopy (AFM) pull-off experiments were performed with silicon tips on atomically flat mica in controlled-humidity atmosphere. The experiments revealed characteristics of the contact water meniscus that allowed us to construct a theoretical model for the water meniscus behavior during contact breakdown.

References [1] Richard D. Piner, Jin Zhu, Feng Xu, Seunghun Hong, Chad A. Mirkin, Science, 283 (1999) 661. [2] M. Tello, R. Garcia, Appl. Phys. Lett., 79 (2001) 424. [3] Bharat Bhushan, Wear, 225–229 (1999) 465. [4] Z.F. Shao, J. Mou, D.M. Czajkowsky, J. Yang, J.Y. Yuan, Adv. Phys., 45 (1996) 1.

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O-23

NEW MAGNETIC NANOMATERIALS AT NIRDTP IASI: PREPARATION, PROPERTIES, APPLICATIONS

N. Lupu and H. Chiriac

National Institute of Research and Development for Technical Physics 47 Mangeron Blvd., 700050 Iasi, Romania

Nowadays, magnetic materials are present everywhere in our life. Recently, the introduction of the nanomaterials concept opened up new research directions in the development of magnetic nanomaterials as nanodimensional ones (nanowires, nanopowders, thin films with thicknesses of a few atomic layers) or by inducing nanostructures within the bulk materials and changing essentially the specific physical properties. This paper will focus on the recent results obtained at NIRDTP Iasi on the preparation, characterization and applications of magnetic nanomaterials, which represent international priorities. Arrays of 20-200 nm diameter polycrystalline Ni, Co and NiFe nanowires have been made by electrodeposition into the nanometer–sized pores of track–etched polycarbonate or anodic alumina oxide (AAO) membranes using a two-electrode electrochemical cell. The pore diameters and the thickness of both the polycarbonate and AAO membranes were 20-200 nm and about 6 µm, respectively. We succeeded for the first time in the world making amorphous Ni100-xPx and Co100-xPx nanowires arrays with very interesting magnetic properties. Nanopowders, including the ones in amorphous state, were prepared by chemical reduction and arc discharge in Fe, Co, NiCo and other complex systems. Due to their specific magnetic properties, which are completely different in comparison with their bulk counterparts, the nanopowders could be used successfully in applications as soft or hard magnets, but also as magnetic carrier for medical and biotechnological applications. Recently we succeeded making new magnetic materials with nanostructures induced directly during the preparation process from the melt or by applying suitable thermal treatments. Structures as “atomic clusters” obtained in RE-TM-Al(Si) systems lead to remarkable magnetic properties (high coercivities in the as-cast state in different bulk amorphous samples), but also opened up perspectives to develop a new class of materials with local magnetic properties structurally controlled at the nanodimensional level. We designed and manufactured new magnetic materials with large glass-forming ability for applications as soft and hard magnets. All these results are included in national and international patents or scientific papers published in prestigious international journals.

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P-1

POROUS SILICON SURFACE FUNCTIONALIZATION FOR BIOMOLECULES ATTACHEMENT

A. Bragaru, I. Kleps, A. Angelescu, M. Miu, M. Simion, T. Ignat, F. Craciunoiu, M. Avram

National Institute for Research and Development in Microtechnologies, Bucharest, Romania Abstract. Porous silicon (PS) can be used as smart transducer material in sensing application, and in particular in the detection of vapors, liquids and biochemical molecules. This material is sensitive to organic and biological molecules, either in vapor and liquid state. PS has a porous sponge-like structure with a specific area in the range of 200 ÷ 500 m2·cm-3, so that it can assure a very effective interaction with several adsorbates. PS is an available, low cost material, and it could usefully be employed in the realization of smart sensors and microsystems. In particular, PS thin layers have been used as substrate in order to attach oligonucleotides for biosensing purposes. A generally functionalization method is the reaction between organic acids molecules and hydrogen terminated porous silicon surface in order to obtain a more stable organic layer covalently attached to the PS surface through Si-C bonds. Our experimental work is related to surface functionalization of the etched silicon, with different polymers. The ideal polymer should have at least two reactive groups, one for binding the biomolecule and one for its attach at the substrate. In our laboratory, we studied oligonucleotides immobilisation on silicon chip, for “in vitro” DNA amplifications. The methods used for DNA molecules attachement on porous surfaces includes poly-lysine as an intermediate. The wafers are usually coated with compounds like poly-lysine before DNA is printed because poly-lysine gives the slide an overall positive charge. Poly-lysine is a basic poly-amino acid with a net positive charge which is often used to coat biomaterials surfaces. Poly-lysine has a carbonil group, for binding to the substrate, and an amino group, necessary for binding the oligonucleotides.The polylysine coating goal is to ensure DNA fixation through electrostatic interactions. Other polymers used for surface functionalization includes both synthetic and natural polymers, either non-biodegradabile or biodegradabile. Representative synthetic polymers include polyethylene glycol (PEG), polymethacrilates, polyacrylic acids. Representative natural polymers include albumin, chitosan, cellulose. Preferred hydrophilic polymers include PEG, polylysine.

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P-2

PS CONDUCTIVE AND BIOCOMPATIBLE COMPOSITE NANOSTRUCTURES FOR ELECTRODE APPLICATIONS

Teodora Ignat*, Adina Bragaru, Irina Kleps, Anca Angelescu, Mihaela Miu, and Monica Simion

National Institute for Research and Development in Microtechnologies, P.O. Box 38-160, 72225 Bucharest, Romania

Conducting materials as solid contacts have been prepared and investigated on the top of the porous silicon PS layers for different optical or biomedical devices. It is important to characterize the conducting material/PS composite interface which determines the properties of PS optical device or sensor / biosensor. The contact layers preparation on optical devices need special precautions to avoid the PS luminescent properties deterioration; it is indicated to use a method to fill the pores with some material, such as the electrochemical processing. On the other hand, contact layers for biomedical applications need to be biocompatible with the biological material: cells, DNA, etc. Polymers such as polypyrrole (PP) (Fig.1) were deposited on PS as solid contacts. This process is conducted in a liquid solution which penetrates over the entire depth of the pores and is stimulated by an electric field, thus making it possible to form a contact layer at the pore bottom where the maximum electric field is localized. The experimental data and the electrical properties of PP/PS/p-Si are summarized in the Table 1.

Fig. 1. Conductive composite material: electrochemical polypyrole-PS.

Table 1. The experimental data and the electrical properties of PP/PS/p-Si. Contact layer Porosity (%) RS (kΩ) IO (A) ϕB (eV) Ideality Factor, n Pyrrole:C2H5OH (1:1) 60 2 0.6 - 5 0.6 0.83 Pyrrole:C2H5OH (1:1) + 0.05 M InCl3

60 80

0.75 - 1.5 0.75 - 1.5

3 – 5 3 - 5

1-2 1

0.87-1.05 0.87-0.9

The experiments emphasize little differences between the different types of solid-state contacts on PS. These contacts show a rectifying behavior (all our samples have a small PS layer thickness). The structures with doped polipyrrole present high series resistance values and they are not indicated for LED. The experimental data show that porous silicon covered with polypyrrole is a good biomaterial with no citotoxicity. We have cultivated B16F1 mouse melanocytes in normal conditions (at 370C in 5% CO2 atmosphere in RPMI 1640 medium supplemented with 10%

*Corresponding author. Tel. +40214908412 / Fax: +40214908238 / e-mail: [email protected].

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fetal calf serum) using PP/PS as substrates. Usually, these cells are cultivated in special conditions on plastic materials pretreated with polilysine, a compound that stimulates cell adhesion. Biocompatible PP/PS conducting composite layers can be used to investigate electrical cell behavior to various stimuli.

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P-3 PREPARATION OF Fe-TiO2 NANOCRYSTALS BY HYDROTHERMAL

METHOD USED HIGH PRESSURES AND TEMPERATURES

M. Miclau, R. Baies, C. Lazau, and I. Grozescu

National Institute R&D for Electrochemistry and Condensed Matter, Timisoara, Romania Iron–ion-doped anatase titanium dioxide (TiO2) nanocrystalline samples were prepared by hydrothermal method used high pressures and temperatures. The samples were characterized by X-ray diffraction, TEM analyses and UV-Vis spectroscopy. It was found that the amount of doped iron plays a signifificant role in affecting its photocatalytic activity and iron doped with optimum content can enhance photocatalytic activity, especially under visible light irradiation. Also, the dimension and shape of Fe-TiO2 nanocrystals can be modified by the pressure and temperature chosen in during of the growth process.

Keywords: hidrothermal, nanocrystals, TiO2, photocatalytic.

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P-4

NEON ATOMS IN NANOTUBES AS 1D QUANTUM REGISTERS

Carmen-Iuliana Ciubotariu1, Ciprian Ciubotariu2, and Corneliu Ciubotariu3,∗ 1Department of Electrical and Computer Engineering, University of Calgary,

Alberta T2N 1N4, Canada 2Université Laval, Faculté des Sciences de l'Administration, Québec G1K 7P4, Canada

3Department of Physics, TechnicalUniversity “Gh. Asachi” Iasi, Blvd. Mangeron 67, 700050-Iasi, Romania

We report the effects of interacting neon atoms confined (by physisorbtion or by ‘physical doping’ with ‘physical impurities’, not a nano-peapod system) to nanotubes on the conductance of individual conducting SWCNT -single-walled carbon nanotubes (or of ropes). We have chosen the neon atom because its De Boer quantum parameter has a value of the order 0.5, i.e. the theory can be semiclassical (or semiquantum), and thus we can define a new type of flying qubit for quantum computing (QC) register and also a flying semiquantum bit (‘squbit’) for quantum cellular automata (QCA). Suitable chosen nanotubes (or 1D interstices between tubes in ropes) act as waveguides which avoid the spontaneous transitions, the decoherence time of the system being considerably lengthened by Purcell-Casimir effects. Furthermore, the correlations (including quantum entanglement) are more sensitive in such a reduced spatial dimensionality, and this is an important property for QC, QCA and nanosensors (e.g. a read-out quantum device). As an example we place neon atoms inside a (5,5) nanotube, and apply a 1D (no phase transition) statistics (nonlinear Tonks equation). Generalization to quantum statistical interactions is carried out for the case where the de Broglie thermal wave length is on the order of the interparticle spacing along the nanotube. The quantization of the nanotube conductance is analysed using the universal conductance fluctuations and the Landauer (-Büttiker) approach to conduction, as resulting from the discreteness of the number of propagating modes (open channels) in the nanotube (electron) waveguide. Point contact conductance as a staircase function of gate voltage is similar with the variation in steps of conductance when the width of the electron nanoguide is increased and more electron modes are able to propagate. Also, some irregular conductance fluctuations can arise because of a classical chaotic scattering (‘electron billiard’). At this point we note that we also investigated another approach to our problem in which the neon atoms are approximated by pointlike (Dirac-delta potential) physical impurities inside a nano-waveguide. Also in this case the wave functions should fulfill Dirichlet boundary condition on the walls of the nanotube. The conclusion is that in the case of few neon atoms ( 100≤ ), due to the non-interacting character of random matrix theory (RMT), it is not possible to describe the system semiclassically, and the conductance of the nanoguide as a regular staircase function (integrable system) of the impurity strength and the number of impurities is described by a Landauer-Büttiker approach. However, by increasing the impurity strength and the number of impurities, the system becomes (non-integrable) quantum-chaotic or quantum disordered and can be described in the framework of RMT. The final conclusion is that the presence of (quasi) free neon atoms in 1D nanotubes leads to a variation of conductance due to the inelastic quantum electron-atom collisions similar to that displayed by a Franck-Hertz (F-H) tube filled with a neon gas. This result may be exploited in order to define a F-H (s)qubit with a long coherence time in the framework of DeVincenzo criteria. As a first experiment which can confirm our approach we propose a F-H experiment with neon atoms physisorbed inside a nanotube. The current-voltage characteristics of such a F-H nanotube ∗Corresponding author. Tel: +40721645917 / E-mail: [email protected].

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may represent a new type of quantum read-out which can be related to the stochastic measurement (wave function collapse) processes.

Keywords: Nanotubes, Quantum Computing, Quantum Cellular Automata, Qubit, Conductance Read-Out.

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P-5

STRUCTURAL AND OPTICAL PROPERTIES OF CdO THIN FILMS

R.S. Rusu, Petronela Prepelita, I. Vlascianu, and G.I. Rusu*

Faculty of Physics, “Alexandru Ioan Cuza”University, R-7000506, Iasi, Romania In recent years, cadmium oxide (CdO) are studied due their interesting characteristics which are considered relevant for its applications: solar cells, gas sensors, transparent electrodes, photodetectors, etc. Cadmium oxide (CdO) thin films were deposited onto glass substrates by thermal evaporation under vacuum (quasi-closed volume technique). The structural investigations performed by means of X-ray diffraction (XRD) technique showed that as-deposited samples have an polycrystalline or an amorphous structure. After a heat treatment the films with amorphous structure becomes polycrystalline and have a cubic (natrium chloride) structure. Crystallite size, interplanar distances and density of thin films was calculated. The morphology of thin films was analyzed by AFM. The spectral dependences of the transmission and absorption coefficients were investigated in the range 300-1400nm. The values of optical energy gap, calculated from absorption spectra, were in the range 2.20-2.70eV. Using the Swanepoel’s method was determined the dispersion of the refractive index. The influence of heat treatment (in the temperature range ∆T=300-575K) on the transmission and absorption spectra is also studied.


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P-6 ON THE MECHANISM OF ELECTRONIC TRANSPORT IN CdO THIN

FILMS

R.S. Rusu, N. Rezlescu, Petronela Prepelita, C. Dantus, G.I. Rusu*

Faculty of Physics, “Alexandru Ioan Cuza” University, R-7000506, Iasi, Romania Cadmium oxide in thin films has a large field of applications being an important material for many solid-state devices: solar cells, gas sensors, transparent electrodes, photodetectors, etc. In this paper, some electronic transport properties of CdO thin films are investigated. Cadmium oxide (CdO) thin films were deposited onto glass substrates by thermal evaporation under vacuum (quasi-closed volume technique). Temperature dependence of the electrical conductivity, σ, was investigated for a large number of samples prepared under various deposition conditions. The effect of the heat treatment (performed after film deposition) on the electrical conductivity was studied, too. The values of thermal activation energy of electrical conduction, ∆E, was calculated from lnσ=f(103/T) dependences. Using the Seto’s model was calculated the donors concentration, concentration of surface-states and the traps energy. For this model was used the value of optical energy bandgap calculated from the absorption spectra in the spectral domain 300-1400nm.


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P-7

ON THE ELECTRICAL AND OPTICAL CHARACTERISTICS OF POLYCRYSTALLINE ZnTe THIN FILMS

Petronela Prepelita, R.S. Rusu, N. Apetroaei, G. Oniciuc, M. Lesenciuc, G.I. Rusu*

Faculty of Physics, “Alexandru Ioan Cuza”University, R-7000506, Iasi, Romania In the last two decades zinc telluride (ZnTe) thin films are widely used in technology of thin film heterojunction solar cells as CdSe-ZnTe. Zinc telluride (ZnTe) is an important semiconductor material for the development of various modern technology of solid-state devices (blue light emitting diodes, solar cells, microwave devices, etc). ZnTe thin films ( d = 0.23 - 2.15 µm ) were deposited onto glass substrates by the quasi-closed volume technique under vacuum. It was established that the films with stable structure can be obtained if they, after deposition are submitted to a heat treatment. For heat-treated samples the temperature dependences of the electrical conductivity, Hall coefficient and carrier mobility were studied for films with different thickness, deposited under different deposition conditions. The structure analysis of the film was performed by X-ray diffraction (XRD) technique and atomic force microscopy (AFM). The films are polycrystalline and have a würtzit (hexagonal) structure. The root mean square roughness ranged between 1.47 nm and 2.73 nm. The thermal activation energy of electrical conduction varied from 0.38 eV to 0.70 eV. The polycrystalline structure of the films strongly influences the electronic transport mechanism. By studying optical properties (transmission and absorption spectra, refractive index) of ZnTe thin films very useful information have been obtained about the energy gap, characteristics of optical transitions. Optical energy gap, calculated from the absorption spectra (for allowed band-to-band transitions) was in the range 1.70eV – 2.40eV.


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P-8

AFM AND XRD INVESTIGATIONS OF CdTe THIN FILMS DEPOSITED BY STACKED LAYER METHOD

G.G. Rusu*

“Alexandru Ioan Cuza“ University, Faculty of Physics, 11 Blvd. Carol I, Iasi 700506, Romania

CdTe thin films (d = 270 – 575 nm) were prepared by thermal evaporation under vacuum by quasi-closed volume technique onto unheated glass substrates using an experimental procedure similar to those for evaporating multilayered films. During the evaporation process, the substrates holder were periodically passed (by rotational moving) over the CdTe evaporating source. As result of step by step deposition, multi-layered films were formed. For samples deposited in various conditions, AFM and XRD investigations were performed. The obtained results revealed a strong dependence of film surface morphology and film cristallinity on the source temperature and rotational speed. At lower temperature source (925 K), the surface roughness decreases with increase of rotational speed, v, while at greater source temperature (1165 K) the surface roughness increase with v. The XRD studies revealed that with the increase of source temperature, the film structure varied from a preferred (111) orientation of the film crystallites to a nanocrystalline structure without preferred orientation.


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P-9 SEM STUDIES ON THIN STRUCTURE SAMPLES OF Al-Ni EUTECTIC

Paul Olaru* and David Hui**

*INAV Aviation Institut, Bucharest, Romania **University of New Orleans, USA

Recently, it has been shown that Electron Backscatter Diffraction (EBSD) and Orientation Imaging Microscopy (OIM) are very useful tools to investigate the microstructure of thin Al-Ni eutectic directional solidified materials samples. In this paper we present some of our recent results in this field.

D8 DISCOVER with GADDS for diffraction measurements.

Keywords: SEM, EBSD, OIM, Eutectic, Solidification.

The authors would like to thank BRUKER AXS GMBH KARLSRUHE GERMANY for supporting this work.

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P-10

ACOUSTIC EMISSION IN ADHESION MEASUREMENT OF THIN FILMS

C. Gheorghies*, M. Bucsa and L. Gheorghies

“Dunarea de Jos” University of Galati, Romania Many testing techniques are continuing to be developed to estimate adhesion of thin films or coatings to a substrate. Some techniques are non-destructive, but other are considered destructive. The adhesion testing is considered a destructive technique because it involves peel tests which depend on careful control of the peel angle, peel rate, thickness of the coating and modulus of the coating. Micro-indentation or nano-indentation testing becomes an usual technique in order to estimate the adhesion of thin film or coating to a substrate. A triboindenter is a stand-alone nanomechanical characterization instrument allowing the measurement of force and displacement of a probe relative to a fixed sample. The triboindenter is equipped with a sphero-conical diamond probe having a radius of 650nm and subjected to a normal load in range of 0-50N. During indentation test some micro-cracks or cracks can appear that are accompanied of a noise having a spectral complicated form. By analyzing of the emitted noise that has a frequency in range of ultrasounds can be estimated the adhesion level of thin film or coating to substrate. The experimental set-up includes beside triboindenter an acoustic (AE) detector in range of 150 KHz with 100-300 KHz band pass and a PC that coordinates the movement of scratch indenter on surface sample and analyzing the acoustic signal emitted when a crack appeared in thin film or coating. Using this technique, we studied the behavior of a TiN layer obtained by PVD method deposited on a steel substrate. The used set-up is presented in Fig. 1, whereas the tested speciments and the shape of acoustic signal are shown in Fig. 2 and Fig. 3, respectively. The experiment was performed at Ecole des Mines, Nancy, France.

Fig. 1. The experimental set-up.

*Corresponding author. Email: [email protected].

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Fig. 2. The scratch on sample and cracks.

Fig. 3. Acoustic emission signal.

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P-11 FTIR RECOGNITION OF NANO-IRON CENTERS IN Fe-ZSM-5 BASED

CATALYST

Mircea Teodor Nechita*, Gabriela Apostolescu, Ioan Rosca

Department of Inorganic Chemistry, Faculty of Industrial Chemistry, Technical University “Gh. Asachi” Iasi, Blvd. D. Mangeron no. 71, Iasi 700050, Romania

Most of the zeolites might be considered as nano-scale reactors, where isolated redox nano-sites, dispersed in narrow zeolite channels, can play their redox activity with high selectivity. Due to the high industrial interest in partial oxidation reaction, Fe-ZSM-5 catalysts have been extensively studied in the past decade. Several preparation procedures were employed to disperse iron species into ZSM-5 channels, and many studies have been published on the characterization of Fe-ZSM-5 catalysts. Despite the high interest on these materials, the problem of iron active sites is still under scientific debate, and less information is available on the nature of the encapsulated iron species formed by migration in extra-framework positions. The versatility of iron species (Fe2+ ↔ Fe3+) and their affinity to oxygen and water are making their characterization very difficult. An additional hitch might be the low content of iron required in some catalysts, which make the characterization problem even harder. Recently, a new route to iron functionalization of ZSM-5 zeolites has been founded [1,2]. Low iron content Fe-ZSM-5 catalysts have been obtained by ion exchange in ferric oxalate solutions. Owing to the low iron content of thus prepared catalysts the detection of iron itself was quite difficult and classical characterization techniques such SEM-EDX and XRD have failed on this task. Using the FTIR spectroscopy with nitric oxide as probe molecule, by a method proposed by Spoto and co-workers [3-5], three unsaturated iron species were identified inside the zeolite channels after the thermal treatment: [Fe2+(NO)3], [Fe2+(NO)2] and oxo-clusters [FexOy(NO)].

References [1] M.T. Nechita, G. Ricchiardi, G. Berlier, A. Zecchina, European Research Conference on Zeolite

Molecular Sieves, March 20-25, Hattingen, Germany (2004). [2] M.T. Nechita, S. Bordiga, G. Ricchiardi, G. Berlier, A. Zecchina, 14th International Zeolite

Conference (14th IZC), Recent Research Reports, April 23-30, Cape Town, South Africa (2004). [3] G. Berlier, G. Spoto, G. Ricchiardi, S. Bordiga, C. Lamberti, A. Zecchina, J. Molec. Catalysis A -

Chemical, 182 (2002) 359. [4] G. Berlier, F. Bonino, A. Zecchina, S. Bordiga, C. Lamberti, Chem. Phys. Chem, 4 (2003), 1073. [5] G. Spoto, A. Zecchina, G. Berlier, S. Bordiga, M.G. Clerici, L. Basini, J. Molec. Catalysis A -

Chemical, 158 (2000) 107.


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P-12

PREPARATION OF SILVER NANOPARTICLES BY γ AND ELECTRON IRRADIATION IN SOLUTION: INFLUENCE OF

SURFACTANT ON PARTICLE SIZE

Gabriela Apostolescu*, Gabriela Carja, Mircea Teodor Nechita, Nicolae Apostolescu, Ioan Rosca

Faculty of Industrial Chemistry, Technical University “Gh. Asachi” Iasi, Bd. Dimitrie Mangeron No. 71, Iasi 700050, Romania

Metal colloids are one of important nano-size materials because of the need for the micro miniaturization of electronic devices, and partly because of their unique character differing from those in the bulk state [1,2]. Also, their optical properties and high catalytic activity have been interested. It has recently been demonstrated that irradiation in solutions is a new promising technique to obtain metal colloids. One advantage of irradiation compared to other conventional method for preparing metal colloids is absence of chemical reagents in solutions [3-5]. Colloidal solutions of silver nanoparticles were prepared in water by irradiation with electron beam or γ-rays in order to investigate influences of radiation nature and surfactant on the particle size. Particles were characterized by using an electron microscope and UV-Vis spectrometry. The mean diameter of particles became smaller from 50 to 12 nm with change of the radiation type and for the same radiation, with change of the surfactant. Therefore, pure colloids, which will be useful for further applications, can be produced by irradiation method [6]. Control of particle size is a very important factor in colloid synthesis, because the character of nano-size metal particles is much sensitive to their size.

References [1] W. Eberhardt, Surface Science, 500 (2002) 242. [2] H. Yin, T. Yamamoto, Y. Wada, S. Yanagida, Materials Chemistry and Physics, 83 (2004) 66. [3] T. Tsujia, K. Iryo, N. Watanabe, M. Tsuji, Applied Surface Science, 202 (2002) 80. [4] I. Texier, M. Mostafavit, Radiation Physics and Chemistry, 49(4) (1997) 459. [5] M.J. Rosemary, T. Pradeep, Journal of Colloid and Interface Science, 268 (2003) 81. [6] G. Apostolescu, G. Carja, M.T. Nechita, N. Apostolescu, National Conference of Applied

Physics, Iasi, Romania (2004).


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P-13

PILLARED LAPONITE CLAY-BASED FER NANOCOMPOSITE AS PHOTO-FENTON CATALYST

Maria Magdalena Bobu and Ilie Siminiceanu*

Technical University “Gh.Asachi” of Iasi , Bd. Mangeron 71, Iasi 700050, Romania Photoassisted Fenton reaction proved to be the most effective process for the degradation and the mineralization of organic pollutants in water [1]. However, the homogeneous photo- Fenton reactions have a big drawback: the large volume sludge generated at the end of the treatment by neutralization and precipitation of Fe ions. The recovery of Fe ions by separation and re- dissolution is rather costly. To eliminate this major disadvantage studies have been done to find a solid support for the Fe catalyst. The Nafion-based catalysts, studied by Fernandez et al. [2], proved to have a low catalytic activity , and to be too expensive for an industrial application. Pillared clay minerals have been used as catalyst supports because of their particular properties and structures as well as of their abundance and low cost [3]. A laponite RD-based Fe nanocomposite has been recently synthesized and tested for the Orange II degradation in water by the photo- Fenton reaction [4]. But they did not compare the results with those for the homogeneous photo-Fenton process in similar conditions. The first objective of this work was to prepare the laponite RD clay-based Fe nanocomposite by the pillaring technique experimented previously for montmorillonite [5]. The XRD characterization of the product revealed the crystallites of Fe2O3 as pillars and of Fe2SiO10(OH)2. The second objective was to taste the photocatalytic activity of the Fe-Lap-RD nanocomposite for the degradation of the Monuron herbicide in water. Kinetic curves have been generated for a 0.2 mM aqueous Monuron solution at pH 3, UV-C (254 nm) radiations, 9 mM H2O2 dose, and catalyst doses between 0.1 and 1.0 g/L. Parallel probes have been taken for the homogeneous process , in identical conditions, but using doses of soluble FeSO4. The pollutant, analysed by HPLC, has been almost completely removed after 60 minutes in both processes. The mineralization degree (% TOC removal ) after 120 minutes of irradiation reached 65% in the heterogeneous, while only 51% in the homogeneous process, under the optimal conditions. Despite the encouraging results a major question arises: how many cycles the catalyst could be reused?

Acknowledgements. The physical tests of the catlyst have been done in the Chemistry Laboratory, University of Oslo.

References [1] I. Siminiceanu, Procese fotochimice aplicate la tratarea apei, Tehnopres, Iasi, 2003. [2] J. Fernandez, M.R. Djananjeyan, J. Kiwi, Y. Senuma, and J. Hilborn, J. Phys. Chem., B104

(2000) 5298. [3] P.L. Yue, J.Y. Feng, and X. Hu, Water Sci. & Tech., 49 (2004) 85. [4] J.Y. Feng, X. Hu, P.L. Yue, H.Y. Zhu, and G.Q. Lu, Chem. Eng. Sci., 58 (2003) 679. [5] A. Azzouz, I. Siminiceanu, and D. Nistor, Pontage des argilles de type montmorillonite, Actes du

Colloque Franco- Roumain de Chimie Appliquée - CoFrRoCA (ISBN 973-8392-04-07) (2002) 289.

*Corresponding author. Fax: 0040 232 271311 / e-mail: [email protected].

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P-14

HEXAFERRITE NANOPOWDERS FOR RECORDING MEDIA PREPARED BY A MODIFIED COPRECIPITATION TECHNIQUE

C. Doroftei, E. Rezlescu, P.D. Popa, and N. Rezlescu

National Institute of Research and Development for Technical Physics, 47 Mangeron Blvd., 700050 Iasi, Romania

In the last time, the importance of the hexaferrites (BaFe12O19 and SrFe12O19) in the magnetic media industry has increased. This application requires materials to be prepared with strict control of particle size and magnetic properties. In order to obtain Sr and Ba hexaferrite powders with submicron crystallites, we used a new method, self combustion, and heat treatments. This method is an improved variant of the coprecipitation enabling a rapid preparation of pure and homogeneous hexaferrite powders by using the thermal energy given out in a very exothermic solid state reaction. By combustion it was obtained magnetic powders having a nanometer granular structure and characterized by the followings: M = 44.7 emu/g and Hc= 520 Oe for SrFe12O19 and M = 31 emu/g and Hc= 350 Oe for BaFe12O19 and nanosized crystallites (about 50 nm). The combusted powders were subjected to heat treatments for different times. It was investigated the effect of the annealing time on the grain size and several magnetic properties (magnetization and coercivity). After a short annealing time (5 – 10 minutes) at 10000C the coercivity achieved an important increase, to about 5000 Oe for Ba hexaferrite and to about 3400 Oe for Sr hexaferrite, whereas the grain size does not exceed 300 nm. By doping with 1 mol CaO, it was obtained a spectacular increase of coercivity of SrFe12O19, to about 6000 Oe by annealing at 8000C for 5 – 10 minutes. Smaller magnetization for Ca-doped samples than that of the undoped samples can be explained by rearranging Fe ions in the distorsioned structure, if one supposed that Ca2+ ions enter into hexagonal structure.

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P-15

ULTRA-FINE NICKEL-COBALT FERRITE DOPED WITH MAGNANESE FOR ACETONE GAS SENSOR

N. Iftimie, N. Rezlescu, E. Rezlescu, and P.D. Popa


The sensitivity to some reducing gases (acetone, ethanol, methane and liquefied petroleum gas-LPG) of calcia doped nickel ferrite (NiFe2O4 + 1% CaO) and cobalt and manganese doped nickel ferrite, Ni0.99Co0.01 MnxFe2-xO4-δ (x = 0.01 and 0.02), was investigated. Starting from nitrates, as raw materials, the samples were prepared by selfcombustion method. This method offers the advantage to produce ultra-fine, homogeneous and reproducible ferrite powders using aqueous solutions of salts of constituent ions (metal nitrates) in comparison with ceramic technology. By quick combustion, the nanosized powders were obtained. After heat treatment at 10000C for 30 minutes of the compacted powders in a disc shape, some investigations of the samples were carried out by X-ray diffraction, scanning electron microscopy and sensitivity measurements of the electrical resistivity to the four test gases. It was studied the response time, too. The gas sensitivity largely depends on the composition, temperature and the test gas species. The ferrite compounds doped with Co and Mn are selective to detect reducing gases at low operating temperature. The mixed ferrite with Ni0.99Co0.01 Mn0.02Fe1.98O4-δ composition is sensitive and selective for the detection of acetone gas.

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P-16

COMPLEX PERMEABILITY SPECTRA OF HIGH FREQUENCY Ni-Zn FERRITES DOPED WITH V2O5/Nb2O5

B. Parvatheeswara Rao*, O.F. Caltun**, L. Spinu***, I. Dumitru***

*Department of Physics, Andhra University, Visakhapatnam 530 003, India **Department of Electricity and Electronics, “Alexandru Ioan Cuza” University,

700506 Iasi, Romania ***Advanced Material Research Institute, University of New Orleans,

New Orleans, LA 70148, USA Nickel-zinc ferrites with the formula, Ni0.65Zn0.35Fe2O4 + x V2O5/Nb2O5, where x values ranging from 0 to 1.5 wt% in steps of 0.03 wt% have been prepared by standard ceramic preparation technique to examine their response at high frequencies. Sintering of the samples was done at 12500C for 4 hours in case of niobium samples and 12100C for vanadium samples in air atmosphere followed by natural cooling. X-ray studies confirm single phase spinel structure in all the samples. Complex permeability measurements reveal that the frequency response of real permeability is stable up to a few megahertz and beyond which it decreases. The frequency at which the real part of the permeability starts decreasing coincides with the point at which the imaginary part starts increasing (Fig. 1). Fig. 1. Complex permeability versus frequency for different vanadium concentrations of the system of

Ni0.65Zn0.35Fe2O4 + x V2O5 for x values from 0 to 1.5 wt % in steps of 0.3 wt %.

Table 1. Sintered density, saturation magnetization and grain size data of Ni0.65Zn0.35Fe2O4 + Nb2O5/V2O5

Sintered density (g/cm3) Ms (emu/g) Grain size (µm) wt. % Nb2O5 V2O5 Nb2O5 V2O5 Nb2O5 V2O5

0.0 4.910 4.921 73.5 78.5 - 4.9 0.3 4.717 4.939 78.3 78.0 - 4.9 0.6 4.796 4.903 79.2 78.3 5.7 4.9 0.9 4.992 4.896 78.2 77.9 7.3 4.9 1.2 4.865 4.900 77.7 77.1 9.7 4.9 1.5 4.771 4.872 78.3 75.5 13.2 7.8

Though the vanadium doped samples resulted better densities with the aid of liquid phase sintering, the niobium containing samples have resulted higher values of real permeability

106 107 108 109

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largely due to their microstructural contributions. The results are discussed in terms of the changes in composition, microstructure and the associated processes of resonance and relaxation due to domain wall movements and damping of spin rotations contributing to the variations in permeability.

References [1] D. Arcos and M. Vazquez, J. Mater. Res., 14 (1999) 861. [2] D.P. Rao, S.B. Raju, S.R. Vadera, and D.R. Sharma, Bull. Mater. Sci., 26 (2003) 505.

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P-17

MAGNETIZATION PROCESS IN SOFT MATERIALS UNDER DIFFERENT WAVEFORM OF THE APPLIED MAGNETIC FIELD

Ovidiu Florin Caltun*, Alexandru Stancu, Petru Andrei*

Department of Solid State Physics and Theoretical Physics, Faculty of Physics, “Alexandru Ioan Cuza” University, Blvd. Carol I no. 11, 700506 Iasi, Romania

*Electrical and Computer Engineering Florida State University and Florida A&M University, Tallahassee, FL 32310, USA

There are two ways to measure hysteresis curves. The moment of magnetic materials can be determined either directly by using sensors (Hall probe for field strength meters, coils for flux meter) [1] or indirectly by measuring current-voltage characteristics [2]. In this paper, we present a technique based on the second approach. This technique has been introduced by us in Ref. [3], and then up-graded and improved in Ref. [4]. The test core, part of an RL circuit, is driven by a voltage applied to the primary winding. The current through the primary coil is proportional to the magnetic field applied to the magnetic core. Complex magnetization process can be studied by using predefined (computer generated) waveforms of the current in the primary coil. The induced voltage measured in the secondary winding is proportional with the magnetic flux density. By integrating the induced signal with respect to time and representing the magnetic induction versus the magnetic field strength the hysteresis loops can be plotted. In our measurements we use a digital storage oscilloscope (Tektronix TDS 3000B) to digitize the secondary voltage and primary current and to transfer the data via Internet. All further calculations, such as numerical integrations and scaling, are carried out on a personal computer. Specialized software was implemented (see the figure below). The magnetization curves and the hysteresis loops measured in various experimental conditions can be obtained. Several waveforms can be compared in the same time by loading them in the same or separate windows.


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References [1] V.J. Thottuvelil, T.G. Wilson, H.A. Owen Jr., IEEE Trans. Power Electron., 5(1) (1990) 41. [2] N. Schmidt, H. Güldner, IEEE Trans. Magn., 33(2) (1996) 489. [3] A. Stancu, O. Caltun, P. Andrei, J. Phys. IV France, Collq. C1, Suppl. J. Phys. III (1997) 209. [4] O. Caltun, C. Papusoi, A. Stancu, P. Andrei, W. Kappel, IOS Series "Studies in Applied

Electromagnetics and Mechanics" (Editors V. Kose and J. Sievert), (1998) pp. 594.

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P-18

THE MICROSTRUCTURE OF THE SOFT FERRITE THIN FILMS DEPOSITED BY PLD ON SILICON SUBSTRATE

Ovidiu Florin Caltun* and Li-Shing Hsu**

*”Alexandru Ioan Cuza” University, Faculty of Physics, 700506 Iasi Romania **National Chang Hua University of Education, Department of Physics,

Chang-Hua 50058 TAIWAN A wide variety of materials can be deposited by pulsed laser deposition (PLD) technique. Many attempt were done in PLD of soft and hard magnetic thin ferrite films. PLD deposition of crystalline and amorphous, oriented or no uniform soft ferrite thin films was reported where different stoichiometries were achieved. Usually the films are post annealed to reach the spinel structure. In our work, a few NiFe2O4, NiZnFe2O4 and ZnFe2O4 ferrite crystalline and amorphous films were grown on silicon. The energy of the laser beam, the O2 pressure, the substrate temperature, and the distance between the target and the substrate were varied in order to establish the optimal deposition conditions. The microstructures of the thin films were characterized by XRD, SEM, EDAX, SIMS and AFM analysis. The XRD patterns of the thin films as deposited feature small peaks corresponding to the spinel phase. By annealing, the peaks become evident and show the high crystallinity of the samples. The results of SIMS analysis presented in figs. 1a-c prove the high stoichiometry of thin films obtained by PLD technique. a) b) c)

Fig. 1. The SIMS anlysis of the thin films: a) NiFe2O4; b) NiZnFe2O4; c) ZnFe2O4. Great deposition rate, 9nm/min, was registered for 1.5cm distance target – substrate, but in this case the films hasn’t homogeneity and many aggregates were observed in the thin film surface. Increasing the target – substrate distance to 5cm the deposition rate becomes lower, 2.5nm/min, but the homogeneity is good and rarely aggregates were observed on the thin surface. The microstructure of the film grown in optimal condition has a smooth surface and the average grain size is in sub micrometer range. The thin films kept the stoichiometry of the target as was demonstrated by the EDAX and SIMS analysis. The results suggest that the crystallized ferrite films fabricated in our study are

a mixture of amorphous phase and crystallites with the spinel structure. Annealing for fully crystallization may achieve a further improvement in microstructure and XRD patterns.

References [1] M. Nakano, K. Tomohara, J.M. Song, and H. Fukunaga, J. Appl. Phys., 87(9) (2000) 6217. [2] B. Negulescu, L. Thomas, Y. Dumont, M. Tessier, N. Keller and M. Guyot, J. Mag. Magn.

Mater., 242-245 (2002) 529.

0 50 100 150 200 250 300100

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ndar

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unts

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100

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Zn

NiO

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[3] N. Matsushita, C.P. Chong, T. Mizutani, and M. Abe, J. Appl. Phys., 91(10) (2002) 7376. [4] M. Desai, S. Prasad, N. Venkataramani, I. Samajdar, A.K. Nigam, N. Keller, R. Krishnan, E.M.

Baggio-Saitovitch, B.R. Pujada, and A. Rossi, J. Appl. Phys., 91(10) (2002) 7592. [5] H. Yahiro, H. Tanaka, Y. Yamamoto, and T. Kawai, Solid State Commun., 123 (2002) 535.

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P-19 STRUCTURAL AND MAGNETIC PROPERTIES OF Fe-Co EMBEDDED

NANOSTRUCTURES

Florin Brinza*, Nicolae Sulitanu

Faculty of Physics, Department of Solid State & Theoretical Physics, "Alexandru Ioan Cuza" University, Blvd. Carol I, 11, 700506, Iasi, Romania

In this paper, we intend to describe a suitable method for embedding ferromagnetic materials in porous membrane of polyethylene using electrochemical processes. Magnetic materials containing Fe and Co in composition were deposited in pores of polyethylene membrane. The size and shape of membrane’s pores are variables. Embedded ferromagnetic clusters were characterized using SEM, TEM and HRTEM methods. Magnetic properties was investigated using VSM and torque magnetometer. The new material exhibit Fe-Co clusters with spherical shapes and nanocrystalline structure inside of pores. Strong anisotropy, correlated with pores directions was detected.


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P-20

REALISTIC REPRESENTATION OF THE REVERSIBLE MAGNETIZATION PROCESSES IN SCALAR PREISACH MODELS OF

HYSTERESIS

Laurentiu Stoleriu* and Alexandru Stancu


Any magnetisation process is the result of both irreversible and reversible processes. The irreversible processes are usually associated with the dissipation of energy and with the switching of the magnetic moment from one equilibrium position to another while the reversible magnetisation processes are quasi-static. Both these processes are involved, for example, in the magnetic recording. The writing is taking place when a magnetic head brings the medium into the desired magnetised state associated to irreversible changes in the medium. When the head leaves a certain area, its magnetic field acts no more on the medium and therefore, the magnetisation in the absence of an external magnetic field is more relevant for the recording performance than the magnetisation during the application of the field.

E asy ax is

M agn e tic fie ldd irec tio n

Mreve rsib le

irrevers ib le

Fig.1 Trajectory of the magnetic moment vector for a single domain particle

Fig. 2: The modified reversible function used to simulate Stoner-Wohlfarth-type behavior in Preisach-

type models. Stoner-Wohlfarth model [1] is widely used to describe 2D and 3D magnetization processes for single domain ferromagnetic particles (see Fig. 1). As most of the magnetic measurements are made on one direction, what we observe in the experiment is a 1D projection of the 2D or 3D processes. The most difficult problem in the modelling of the scalar hysteresis of a system *Corresponding author. E-mail: [email protected].

H frev

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of interacting single domain particles is to correctly separate the reversible and irreversible processes in order to evaluate the part which is due only to pure switching. In this paper we are proposing a new method to associate to the Preisach plane [2-4] a SW hysteresis loop with the reversible part given by a function, as presented in Fig. 2. The pure irreversible switching processes are given by the classical Preisach distribution and the reversible processes are described by a supplementary singular distribution given by a special function, similar to the one presented in Fig. 2, which is changing as a function of the magnetic moment of the sample. As a test, this Preisach model can reproduce identically the results given by SW for various angles between the easy axis and the direction of the applied field.

References [1] E.C. Stoner and E.P. Wohlfarth, Phil. Trans. Roy. Soc., 240 (1948) 599. [2] P. Preisach, Zeitschrift für Physik, 94 (1938) 277. [3] I.D. Mayergoyz, Mathematical models of hysteresis, Springer-Verlag, 1990. [4] A. Stancu, L. Stoleriu, P. Postolache, and M. Cerchez, IEEE Trans. Magn., 40(4) (2004) 2113.

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P-21

LOCAL HYSTERESIS LOOPS ANALYSIS IN A SYSTEM OF INTERACTING SINGLE-DOMAIN PARTICLES

Radu Tanasa, Alexandru Stancu*

“Alexandru Ioan Cuza” University, Faculty of Physics Department of Solid State and Theoretical Physics, 700506, Iasi, Romania

Recent studies [1,2] have been addressing the problem of the relation between well known Ising-type hysteresis models, like Edwards Anderson Spin Glass (EASG) and Random Field Ising (RFI) models, and the Classical Preisach Model (CPM). Using the First Order Reversal Curves (FORC) diagram method, a distribution was calculated from data obtained with the EASG and RFI models. We have shown that the interaction field distribution in Ising-type systems is strongly dependent on the magnetic state [3] which is not compatible with a CPM system. In this paper one present a method of reconstruction of the Preisach distribution starting from the hysteresis loops of the individual particles in the system (local hysteresis loops – see Figure). If one takes into account the changes in the position of the moments in the Preisach plane, one can reconstruct identically any magnetization process of the system. In this way one can identify the sources of the differences between Ising and Preisach descriptions of system’s hysteresis. Essentially, one observes that the Preisach distribution is not stable in most cases. In the paper one compare the Preisach and FORC distributions for an Ising system and discuss the differences. In this paper one also give a systematic analysis of the local loop hysteresis and the dependence of the switching fields on the magnetization process in which they are measured. As the local hysteresis loops can be measured experimentally, this study offers a tool of understanding the results of this kind of experiment.

References [1] H.G. Katzgraber et al., Phys. Rev. Lett., 89 (2002) 257202. [2] H.G. Katzgraber, G. Friedman, G.T. Zimanyi, Physica B, 343 (2004) 10. [3] R. Tanasa, C. Enachescu, A. Stancu, E. Codjovi, J. Linares, F. Varret, J. Appl. Phys., 95(11)

(2004) 6750.


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-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0-3

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Hα

m/ms

P-22

IDENTIFICATION PROCEDURES FOR PREISACH-TYPE MODELS BASED ON FORC DIAGRAMS

Alexandru Stancu*


The renewed interest in the use of the First Order Reversal Curves (FORC) method to characterize magnetic materials have conducted in many cases to the conclusion that the FORC diagram represents the real distribution of coercive and interaction fields in the studied samples [1]. The occurrence of negative regions in the FORC distribution has been seen as an indication of the fact that this method is essentially more general as the well known Preisach distribution. In this paper one analysis the links between the FORC diagram and the Preisach distribution and one show the limits of the direct use of the FORC diagram. A special attention is given to the case of structured magnetic systems (e.g. patterned media or nanowire systems) for which a very simple Preisach-type model have been developed recently (named Preisach Model for Patterned Media – PM2) that can take into account for two peaks interaction field distribution with the amplitude dependent on the magnetic state of the system [2]. In the paper we also evaluate the errors due to the concrete experimental conditions in the calculation of the FORC distribution (e.g. non saturated samples) and discuss the possibility to extend the FORC method to minor loops (Multiple Order Reversal Curves = MORC) to scan certain regions of the major hysteresis loop of a magnetic system (see Figure). The MORC distributions are obtained with a similar methodology as the FORC distribution. The results obtained with the FORC and MORC methods, are compared and the links with the Preisach distribution & model are presented. The results of the simulations show that within certain error limits, the constrictions usually considered in the FORC methodology can be relaxed without a major increase of the errors in the distribution evaluation. However, both FORC and MORC methods offers a static image of the interaction field distribution which is a major problem especially for the magnetic characterization of structured materials.

References [1] A. Stancu, C. Pike, L. Stoleriu, P. Postolache, D. Cimpoesu, J. Appl. Phys., 93(10) (2003) 6620. [2] A. Stancu, L. Stoleriu, P. Postolache, M. Cerchez, IEEE Trans. Magn., 40(4) (2004) 2113.


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P-23 DYNAMIC INTERACTIONS IN NANOSTRUCTURED PARTICULATE

SYSTEMS

Dorin Cimpoesu, Alexandru Stancu*


Recently we have proposed a statistical criterion to identify the superparamagnetic particles within a particulate system [1]. We have used the stochastic Landau-Lifshitz-Gilbert (SLLG) equation to simulate systems of a few thousands single-domain ferromagnetic particles and observed the evolution of the interaction field distribution as a function of temperature on the Zero Field Cooled (ZFC) and Field Cooled (FC) magnetization processes (see Figure). The simulated system had a distribution of the volumes, anisotropies and easy axes directions. We have observed that the statistical interactions in the system are mainly linked to the blocked particles. As a consequence, when the temperature of the sample increases, the interaction field distribution variance decreases. This was evidenced experimentally, as well. In this paper we are extending the analysis to structured nanoparticulate systems. Systematically, we have generated samples increasingly structured, with the standard deviations of the mentioned distributions smaller and smaller. In each case one study the distribution of interaction fields during a number of magnetization processes and one analyze separately the contributions of the superparamagnetic and blocked particles. As the distribution of the particles tends towards a perfect structured medium, the distinction between the superparamagnetic and blocked particles is more difficult to make and the usual critical volume approach is more difficult to apply. The effect of this fact on the phenomenological Preisach-Neel type models (PNM) [2,3] is also presented and the results are discussed.

References [1] D. Cimpoesu et al., IEEE Trans. Magn., 40(4) (2004) 2125. [2] A. Stancu, L. Spinu, IEEE Trans. Magn., 34 (1998) 3867. [3] I.D. Borcia et al., J. Appl. Phys., 93(10) (2003) 6823.


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P-24

PRELIMINARY DATA REGARDING THE SYNTHESIS AND CHARACTERIZATION OF AN AQUEOUS FERROFLUID

M. Racuciu1,*, D.E. Creanga2, Gh. Calugaru3

1“Lucian Blaga”University, 10 Victoriei Blvd., Sibiu, Romania 2Faculty of Physics, “Al. I. Cuza” University, 11A Blvd. Carol I, 700506 Iasi, Romania

3“Gh. Asachi”University, Physics Department, Bd. D. Mangeron 68, 700050, Iasi, Romania Ferrofluids are stable colloidal dispersions of ultra-fine particles of a magnetic material, such as magnetite, in a liquid, which may be chosen to conform to a particular application. Since in future the applications of the ferrofluids will focus more toward the biological uses where the ultra-fine ferrophase is particularly important for the penetration of the cell structures. Also, in these applications, it is proper to have a biocompatible solvent such as water at optimum pH. Ferrofluids containing Fe3O4 particles have been prepared by a controlled co-precipitation method. Using citric acid prevented the aggregation of the ferrophase. The ferrophase from the ferrofluids prepared by us is consistent with magnetic particles (magnetite and maghemite) obtained by chemical precipitation from ferric and ferrous salts (FeCl3 and FeSO4) with ammonia hydroxide in excess. Citric acid (10% volume) has been used to stabilize the ferrophase particles (about 5% volume), while water (85% volume) was the carrier liquid. Physical tests have been performed on three samples of the ferrofluid prepared by us in similar conditions. The ferrofluid density (picnometric method), viscosity (capillary method) and surface tension (stalagmometric method) have been measured using standard methods. The pH measurements were carried out with universal indicative paper (Merck). The ferrofluid macroscopic homogeneity was obvious following the visual inspection upon the reaction vial when submitted to the action of a relatively weak magnetic field (provided by the magnetic stirrer). The values of the measurements carried out on three ferrofluid samples (yielded using basically the same protocol) are presented in figures below in comparison with water (the ferrofluid carrier liquid). The preliminary results are concordant with the data reported in literature. Further investigation is designed aiming to reveal the magnetic properties of the colloid produced following this methodology.

Fig. 1. The superficial tension and density. Fig. 2. The viscosity and pH.


66

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supe

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)

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In conclusion, stable magnetic colloid, prepared by using the citric acid as stabilizer in water dispersion, was adjusted in order to get physical parameters concordant with the literature data. Its future destination for living tissues applications will be accompanied by adequate measurements of the biological effects.

References [1] C. Groβ, K. Büscher, E. Romanus, C.A. Helm, W. Weitschies, European Cells and Materials, 3,

suppl. 2 (2002) 163. [2] A. Halbreich, J. Roger, J.N. Pons, D. Geldwerth, M.F. da Silva, M. Rodier, J.C. Bacri, Biochimie,

80 (1998) 379. [3] C. Cotae, S. Istrate, M. Agop, Gh. Calugaru, The Annals of the “Dunarea de Jos” University of

Galati, Fasc. II, tom. XVI (XXI) (1998) 29. [4] A. Goodarzi, Y. Sahoo, M.T. Swihart, P.N. Prasad, Mat. Res. Soc. Symp. Proc., vol. 789 (2004)

N6.6.1.

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P-25

INVESTIGATION OF NANOSTRUCTURES IN FERROFLUIDS BY STATIC MAGNETIZATION AND BIREFRINGENCE RELAXATION

MEASUREMENTS

V. Badescu1, Laura Elena Udrea1, Gabriela Fosa2, and Rodica Badescu2 1National Institute of Research and Development for Technical Physics,

47 Mangeron Blvd., 700050 Iasi, Romania 2“Gheorghe Asachi” Technical University, Department of Physics,

71 Mangeron Blvd., 700050 Iasi, Romania Static magnetization curves and the field free relaxation of birefringence was used to study the nanostructural properties (steric stabilization efficiency and agglomerate formation) in some ferrofluids with magnetite particles stabilized with oleic acid in transformer oil. The degree of steric stabilization was altered using a polar agent less compatible with the carrier liquid. Using the theoretical model developed by Zubarev et al. [1] for the static magnetization of ferrofluids with chain-like aggregates we explain some experimental findings, such as the nonlinearity of volume fraction dependence of the static magnetization and the log-normal dimensional distribution dependence on the degree of stabilization). Studying the magneto birefringence effect we have observed that the field-free decay curve of this effect do not fit to a single exponential decay, as one would expect for a monodisperse distribution of nanoparticles in ferrofluid. This deviation is attributed to the distribution of hydrodynamic size of the nanoparticles and microaggregates that relax in the ferrofluid. Considering these, we have proceeded to an analysis of the relative contributions to the relaxation time by the “peeling” method.

References [1] Zubarev et al., J. Exp. Theor. Phys., 80 (1995) 857.

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P-26 PREPARATION AND MAGNETIC PROPERTIES OF Ni, Co AND Co–Ni

NANOPARTICLES FOR BIOMEDICAL APPLICATIONS

H. Chiriac, A. E. Moga, C. Gherasim, G. G. Nedelcu


Magnetic nanoparticles find a wide range of in vivo and in vitro biomedical applications. The in vivo applications include drug delivery, magnetic resonance imagining contrast enhancement, and magnetic fluid hyperthermia. For these applications the nanoparticles must be water dispersible and biocompatible. In this work we present our experimental results on the preparation and magnetic properties of Ni, Co and Co-Ni nanoparticles. The nanoparticles were obtained by a chemical method called the polyol process [1]. The morphology and size of the nanoparticles were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The micrographs reveal that the nanoparticles are mostly spherical. The size of the nanoparticles ranges between 80 – 400 nm for Ni, 600 – 900 nm for Co, and 100 – 500 nm for Co–Ni alloy. Room temperature magnetic characteristics of the nanoparticles were determined by using a vibrating sample magnetometer (VSM), in an external magnetic field of 15 kOe. The saturation magnetization (Ms) and coercive field (Hc) of the as-prepared nanoparticles were determined to be 34 emu/g and 506 Oe for Ni, 160 emu/g and 493 Oe for Co, and 118 emu/g and 490 Oe for Co–Ni alloy, respectively. To ensure the stability and biocompatibility, the as-prepared nanoparticles were coated with a thin layer of polyvinylpyrrolidone (PVP). The values of the apparent saturation magnetization and the coercive field for the coated particles were 5.9 emu/g and 329 Oe for Ni, 43 emu/g and 411 Oe for Co, and 49 emu/g and 443 Oe for Co–Ni alloy, respectively.

References [1] P. Tartaj, M.P. Morales, S.V. Verdaguer, T.G. Carreno, C.J. Serena, J. Phys. D: Appl. Phys., 36

(2003) R182.

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P-27

PREPARATION AND MAGNETIC PROPERTIES OF Co-P AND Co-Ni-P AMORPHOUS NANOWIRE ARRAYS

H. Chiriac*, A. E. Moga*, C. Gherasim*, **

*National Institute of Research and Development for Technical Physics, 47 Mangeron Blvd., 700050 Iasi, Romania

**”Al. I. Cuza” University, Faculty of Physics, 11 Carol I Blvd., 700506 Iasi, Romania Magnetic nanowire arrays fabricated by electrodeposition into cylindrical pores of a porous membranes are intensively studied in order to understand their magnetic behavior and to estimate their potential applications in fields such as optics, electronics, bio-medical diagnostics, information processing and storage [1,2]. In this work, we report some results about the preparation and magnetic properties of amorphous Co-P and Co-Ni-P nanowire arrays with diameters of 20, 100 and 200 nm and length between 20 and 45 µm. The Co-P and Co-Ni-P nanowire arrays have been made by electrochemical deposition into nanosized pores of anodic aluminum oxide membranes (AAO), using a two-electrode electrochemical cell. The growth of nanowires was performed at 60˚C from two kinds of solution containing cobalt sulfate and chloride, nickel sulfate and chloride, phosphorous acid and boric acid. The pH of the solution varied between 1 and 1.5. The employed current densities varied between 50 and 150 mA/cm2. The morphology and the length of nanowires were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM), after the dissolution of the AAO membrane in sodium hydroxide (NaOH). Fig. 1 shows a SEM image of Co-Ni-P amorphous nanowire arrays. The sample amorphicity was checked by X-ray diffraction (XRD). Magnetic characteristics of Co-P and Co-Ni-P amorphous nanowires were determined at room temperature by using a vibrating sample magnetometer (VSM), in an external magnetic field of 15 kOe. The obtained Co-P and Co-Ni-P amorphous nanowire arrays are magnetically soft.

Fig. 1. SEM micrograph of Co-Ni-P nanowire arrays with 20 nm diameter. The coercive fields of Co-P and Co-Ni-P amorphous nanowire arrays are dependent on the nanowire diameter and their length. The value of coercive fields of Co-P nanowires of different lengths varied between 341 and 430 Oe for the applied field perpendicular to membrane plane, and between 348 and 474 Oe for the applied field parallel to membrane plane. The coercive fields of the Co-Ni-P nanowire arrays were between 329 and 462 Oe for the applied field perpendicular to membrane plane, and varied between 272 and 411 Oe for the applied field parallel to membrane plane, respectively.

References [1] P. Aranda, J.M. Garcia, J. Magn. Magn. Mater., 249 (2002) 214. [2] H. Chiriac, A.E. Moga, M. Urse, I. Paduraru, N. Lupu, J. Magn. Magn. Mater., 272-276 (2004)

1678.

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P-28

SOFT MAGNETIC PROPERTIES AND STRUCTURAL CHARACTERIZATION OF Fe-Co-B-N THIN FILMS

M. Urse*, H. Chiriac, and M. Grigoras

National Institute of Research and Development for Technical Physics, 47 Mangeron Blvd., 700050 Iasi, OP3, CP 833, Romania

Nanocrystalline soft magnetic materials have been widely used in modern electromagnetic devices such as recording heads, integrated inductors and micromachined motors. Demands for soft magnetic thin films operating at higher frequencies have been continuously increased because electro-magnetic devices are obligated to decrease the size and to increase the efficiency [1]. Recently, Fe-Co thin films with additions of B and N have received much attention because of their high resistivity and good soft magnetic properties that play a critical role in improving the high frequency characteristics. The Fe-Co-B-N thin films exhibited very good electrical and soft magnetic properties, attributed to microstructural changes, from columnar to randomly oriented nanograins of (Fe,Co) [2]. Electrical and magnetic properties of these materials are very sensitive to preparation and annealing conditions. In this paper we report some results concerning the effects of composition and preparation conditions such as N2 partial pressure and input R.F power on the structural, electrical and magnetic properties of as-deposited and annealed Fe-Co-B-N thin films, in view of their utilization for manufacturing magnetic thin film inductors which operating at high frequencies. The optimization of the magnetic properties of Fe-Co-B-N thin films is also made by their growth on suitable underlayers. The Fe-Co-B-N thin films with a thickness of about 150 nm, grown on Ti underlayer (20 nm), show good electrical and magnetic properties of resistivity ∼ 165 µΩ×cm / ∼ 220 µΩ×cm, saturation magnetization ∼ 17.8 kG/ ∼18.4 kG, coercivity ∼ 5 Oe/ ∼ 2 Oe and zero – magnetostriction, when the composition of each film is 1,5 - 4 at.% B, 8,5 – 6 at.% N and balanced Fe0.65Co0.35. These good electrical and magnetic properties were due to the decrease of the FeCo grains size by mixed effect of the intergranular amorphous phase and metallic - based nitride precipitates.

References [1] S. Han, I. Kim, J. Kim, K.H. Kim, M. Yamaguchi, J. Magn. Magn. Mater., 272-276 (2004) 1490. [2] I. Kim, J. Kim, K.H. Kim, and M. Yamaguchi, Phyica Status Solidi, A201 (2004) 1777.

*Corresponding author. Tel: +40 232 430680 / Fax: +40 232 231132 / e-mail: [email protected].

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P-29

MAGNETO-OPTICAL PROPERTIES OF Fe-BASED AMORPHOUS THIN FILMS

M. Dobromira, M. Neagua, Gh. Popaa, H. Chiriacb, Gh. Singurela, K. Teliouc, and A. Kakaroglouc

a"Al. I. Cuza" University, Faculty of Physics, 11 Carol Blvd., 700506 Iasi, Romania bNational Institute of R&D for Technical Physics, 47 Mangeron Blvd., 700050 Iasi, Romania

cPhysical Metallurgy Lab., National Technical Univ., Zografou Campus, Athens, Greece The soft magnetic amorphous thin films have outstanding magnetic and magnetoelastic properties which make them particularly suitable for a wide range of sensor applications [1,2]. The control of the surface magnetic properties in these materials is very important in order to obtain miniaturised magnetic devices with improved performances. The amorphous thin films were prepared by evaporation in vacuum (10-6 Torr) from amorphous ribbons of nominal composition Fe77.5Si7.5B15. Films with thickness in the range 100-300 nm, were deposited onto water-cooled glass and silicon substrates. Using magneto-optical Kerr effect the surface magnetic properties of as-deposited and thermal/magnetic annealed Fe77.5Si7.5B15 amorphous thin films are investigated [1]. The treatments were made at temperatures between 370-3900C, with and without applied magnetic field. The amorphous state of the obtained films was examined by X-ray diffraction, while the surface topography was investigated by atomic force microscopy. The magneto-optical Kerr measurements were taken with an EL X-01R ellipsometer at 632.8 nm laser wavelength, equipped with a pair of Helmholtz coils which provide the biasing magnetic field for the studied samples. The hysteresis loops were obtained by plotting the Kerr rotation as function of the applied magnetic field. The minimum value of the coercive field for the as-deposited thin films samples was about 350 A/m. The optimum heat treatment and magnetic annealing are inducing better soft magnetic characteristics, determining a decrease of the coercive magnetic field value up to 95% with respect to the as-deposited state. Researches on the utilization of the obtained amorphous thin films as sensing elements are under work.

References [1] M. Ali, R. Watts, W.J. Karl, M.R.J. Gibbs, J. Magn. Magn. Mater., 190 (1998) 199. [2] A.Yu. Toporov, P.I. Nikitin, M.V. Valeiko, A.A. Beloglazov, V.I. Konov, A.M. Chorbanzadeh,

A. Perrone, A. Luches, Sensors and Actuators A, 59 (1997) 323.

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P-30

MAGNETIC PROPERTIES AND GMR EFFECT IN FePt3 NANOSTRUCTURED THIN FILMS

Violeta Georgescu, Raluca Musat, Cristina Sirbu

Faculty of Physics, “Alexandru Ioan Cuza” University, 11 Carol I Blvd., 700506 Iasi, Romania

Magnetism in nanostructured materials and the study of the interaction between the electron charges and magnetic spins have become an important topic from both scientific and technological points of view. Granular nanostructured (inhomogeneous) alloy films are the focus of attention due to the existence in them of an isotropic giant magnetoresistance (GMR) effect. Our goal was to study nanostructured granular Fe-Pt films in a view to obtain by electrolysis materials with GMR effect. The electrodeposition technique has major advantages over other methods of thin film production, namely, the possibility of performing deposition at normal conditions of pressure and temperature, requiring relatively inexpensive equipment. The system of Fe-Pt alloys was chosen because there is a competition between ferro- and antiferro-magnetism in Fe-Pt, which could favour the GMR existence. This work is concerned to films in the composition range of ordered (L12) FePt3 phase. There are only few studies on magnetism of electrodeposited Fe-Pt films [1-2]. The Fe-Pt films were electroplated on a copper substrate using an iron anode. Iron and platinum ions were introduced in a single bath, containing: Fe (NH4)2(SO4)2.6H2O, K2PtCl6, H3BO3 and NaCl, in double distilled water. The composition and thickness of the electrodeposited film from the solution containing Fe and Pt ions was controlled by varying deposition parameters such as the cathode potential, the current density, the electrolysis duration and the concentration of the substances included in the electrolyte. The magnetic properties of the films were studied at room temperature using a torque magnetometer in fields up to 300 kA.m-1 and an a.c. induction type device with computerised data acquisition (50 Hz, maximum field of 57,3 kA/m applied in the plane of the samples). The DC magnetoresistance measurements were performed applying the current-at-an-angle-to-plane (CAP geometry), and the external magnetic field was applied in the plane or perpendicular to the film plane. Field dependence of the magnetoresistance (MR) was defined as ( ) ( )[ ] ( )ss HRHRHRHMR −=100)( , where HS denotes the saturation magnetic field. The experimental torque curves exhibit mainly a twofold symmetry and a shape indicating that the easy magnetisation direction is perpendicular to the film plane and that an antiferromagnetic type coupling between crystallites could be present in the nanostructured film. Due to a very strong spin-orbit interaction and a strong polarisation of the Pt d states induced by Fe atoms, the FexPt1-x films, with x ≈ 30 – 38 % exhibit values of the magnetoresistance (of about 11.8 ÷ 7.8% in CAP geometry). The electric resistance of such samples in zero or low magnetic field, when the magnetic moments are preferentially antiferromagnetic coupled, is different from their resistance in a magnetic field, when the magnetic moments are ferromagnetic aligned, parallel to the field direction. We suppose that electrodeposited nanostructured alloys near to stoichiometric composition FePt3 contain antiferromagnetic clusters in addition to ferromagnetic ones, i. e., they are in a mixed ferro- antiferro-magnetic state (mixomagnetic state). The local concentration fluctuations generated during the film preparation results in a spatially inhomogeneous magnetic structure. The magnetic inhomogeneity has a common feature; namely, it contains

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ferromagnetic phases separated by nonferromagnetic ones. Therefore, the enhancement of the magnetoresistance can be attributed to the spatially inhomogeneous magnetic structure having different magnetic component and to the exchange interaction between neighbouring interfaces.

References [1] V. Georgescu, Analele Stiintifice ale Universitatii “Al. I. Cuza” din Iasi, Tom XXXII, s. I. B,

Fizica, (1986) 9. [2] E.B. Svedberg, J.J. Mallet, S. Sayan, A. Shapiro, W.F. Egelhoff, Jr., and T. Moffat, Appl. Phys.

Lett., 85 (2004) 1353.

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P-31 EDDY CURRENT NONDESTRUCTIVE EVALUATION METHODS OF

DEFECTS IN AMORPHOUS AND NANO-CRYSTALLINE MATERIALS

R. Grimberg*, Adriana Savin*, Rozina Steigmann*, A. Andreescu*, S.S. Udpa**, and T. Hogan**

*Nondestructive Testing Department, National Institute of R&D for Technical Physics, 47 D. Mangeron Blvd., 700050 Iasi, Romania

**Department of Electric and Computer Engineering, Michigan State University, 2120 Engineering Building, East Lansing, MI 48824

The aim of this paper is to present transducers, signal processing and post processing algorithmes able to eddy current nondestructive evaluation of Indium-Antimony nano-wires used for many applications, including gases and hazardous chemicals, and potentially low-cost biological sensors such as for detection of cystic fibrosis or prostate cancer. Indium-Antimony nano-wires (Fig. 1) were obtained by Pulsed Laser Deposition (PLD) at The Electronic Materials Pulsed Laser Deposition and Transport Characterisation, Electric and Computer Engineering Dept., MSU.

Fig. 1. Indium-Antimony nano-wires obtained by PLD. The pulsed laser deposition (PLD) system utilizes a KrF excimer laser. This outputs a 248 nm wavelength, 25 ns pulse, with a repetition rate up to 100Hz and output energy adjustable up to 1J. The PLD system is capable of depositing a wide range of materials while maintaining the stoichiometry of the target, even for three or four elements. The problem consist in nondestructive evaluation of nanowires existance, taking into acccount their conductivity 25 S/m while the support in insulator, having conductivity 10-6 S/m. The coating zone is 1µm2. For this, a 2D sensors array is used. The emission par is made from a rectangular coil having 5mm each side, 2 turns and 125µm width, by gold coating with 1µm thickness, on silicon support. The reception part is made from 5x5 coils with one turn each, having inner diameter 25µm, 10µm width and 1µm thickness. The electric connection are made with gold wires having 10µm diameter. The work frequency is 100 MHz. The signals delivered by array are measured with alock-in amplifier. type Agilent 77064D, the injection being made with signal generator Agilent 770102. The useful information is the amplitude, (Fig. 2) that is post processed by maximum likelihood super-

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resolution algorithm (Fig. 3). Thus, through an inversion method, the location and nanowires concentration zones can be determined.

Fig. 2. Signal delivered by nanowires array. Fig. 3. Signal processing by maximum likelihood super resolution method.

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P-32

GMI MAGNETIC SENSOR FOR BIOMOLECULES DETECTION

H. Chiriac, M. Tibu, A.E. Moga, and D.D. Herea


A magnetic sensor based on Giant Magnetoimpedance Effect (GMI) for biomolecules detection is presented. The sensing element of the sensor is a CoFeSiB amorphous magnetic microwire. Such a sensor presents a significantly high sensitivity in low magnetic field range. Using Co soft ferromagnetic microparticles and GMI-based sensor with field sensitivities of the impedance of about 2.5%/A·m-1 in the very low field region (less than 200 A·m-1) at frequencies close to 10 MHz we obtained a good response of the sensor required for low biomolecule concentrations.

Keywords: magnetic sensor, giant magnetoimpedance, magnetic microparticles, biomolecules.

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P-33

NEW FeNbB BASED BULK AMORPHOUS AND NANOCOMPOSITE SOFT MAGNETS FOR APPLICATIONS

Nicoleta Lupu and Horia Chiriac

National Institute of Research and Development for Technical Physics, 47 Mangeron Boulevard, 700050 Iasi, Romania

Nowadays there are tremendous efforts to design and manufacture soft magnets with excellent physical properties and high corrosion resistance for industrial applications. To be considered for engineering applications these materials should be low cost, easy to prepare and highly competitive with the already existent ones used in such applications. Bulk amorphous and nanocrystalline materials could be a good prospective because of their 2 main advantages: the ease of formation in different 3-D bulk shapes by casting due to their large glass-forming ability and the low costs implied in their manufacture. This paper deals with the presentation of our very recent results on the preparation and magnetic characterization over a wide frequency range of (Fe,Co,Ni)70Nb10B20 bulk amorphous and nanocomposite alloys. Master alloys of 5-10 g each prepared by induction melting the pure components (99.99%) in high vacuum were used to cast torroids with Dext = 5 mm; Dint = 3 mm; t = 1 mm, discs with t = 1 mm and bars with diameters ranging from 0.4 to 0.9 mm by Cu mould casting method. XRD and DSC measurements shown that the samples are either fully amorphous or consists of very fine 5 to 10 nm α-Fe(Co) nanoparticles embedded within the amorphous matrix. Magnetic measurements indicate saturation inductions of about 0.85 T and relative permeabilities of 7 x 104 (at 80 Hz) in the as-cast state and after annealing in the temperature range Tx1-Tx2, i.e. 540-7400C (Tx1 and Tx2 are the first and the second crystallization temperature, respectively, as indicated from the DSC curves). Coercive fields of 40 A/m were determined for Fe-Nb-B-based bulk amorphous torroids, whereas in nanocomposite cast bars Hc varies between 180 and 360 A/m in the as-cast state and decreases about 2 times when the refined nanocrystalline structure is achieved. Hc and µe are increasing and respectively decreasing drastically during the secondary crystallization. The frequency variation of the MHL curves indicates these materials as good candidates for applications in the frequency range 50 Hz – 2 Hz. Moreover, in this frequency range the magnetic permeability decreases from 7 x 104 to 1 x 104, which is quite an expected good result at high frequencies for Fe-based amorphous and/or nanocomposite alloys prepared directly in the desired 3D-shape. The potential engineering applications in which the new Fe-Nb-B-based bulk amorphous and nanocomposite soft magnets could be used will be presented in connection with their specific magnetic behavior.

Acknowledgements This work was funded by the Romanian Ministry of Education and Research – Department of Research under Contract no. 08N/2003.

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P-34

FLUXGATES USING ZERO MAGNETOSTRICTIVE FeCoSiB NANOCRYSTALLINE RIBBONS

J. Petrou, J. Patronos, H. Chiriac*, and E. Hristoforou*

National Technical University of Athens, Laboratory of Physical Metallurgy, School of Mining and Metallurgy Engineering, Zografou Campus, Athens 15780, Greece

*National Institute of R&D for Technical Physics, 700050 Iasi, Romania In this paper we present new results on magnetic fluxgate sensors using zero magnetostrictive Fe-Co-Si-B alloy ribbons. The sensors have a race track and a toroidal shape. Their sensitivity has been studied in both types of sensors using as-cast core material and core material after stress relief by means of thermal annealing in 3500C in Argon atmosphere for 1 hour. In these measurements, the best recorded sensitivity has been determined to be 1 nT at 1 Hz for stress relieved sensing cores, having the race truck shape. Consequently, nanocrystallization of the sensing core ribbons in 6500C in Argon atmosphere for 1 hour resulted in a sensitivity of 100 pT at 1 Hz, for those sensing cores having the race truck shape. The better sensitivity is attributed to the smaller Barkhausen jumps in the nanocrystalline ribbons with respect to the amorphous state.

Keywords: Fluxgates, Magnetostriction, Barkhausen noise.


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P-35

MAGNETOSTRICTIVE DELAY LINES IN ENGINEERING APPLICATION BASED ON AMORPHOUS Fe-RICH ALLOYS

G. Loris, H. Chiriac*, and E. Hristoforou*

Laboratory of Physical Metallurgy, School of Mining and Metallurgy Engineering, National Technical University of Athens, Zografou Campus, Athens 15780, Greece,

*National Institute of R&D for Technical Physics, 700050 Iasi, Romania Current research activities at the Electronic Material Group of the Laboratory of Physical Metallurgy, National Technical University of Athens include investigation of magnetic nano-structures, like nano-crystalline Fe-Co-Nb-Si-B ribbons, nano-magnetic shape memory alloys and particulate media as well as NDT&E in metallic materials. A special topic in magnetic research concerns the magnetostrictive delay line (MDL) technique and corresponding sensing applications. In this presentation new results on tensile stress and displacement sensors are illustrated, designed for mining & civil engineering. Additionally, a coagulation sensor for chemical and biomedical applications is also presented.


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P-36

MAGNETIC AND MAGNETOELASTIC UNIFORMITY MEASUREMENTS ON Fe78Si7B15 AMORPHOUS RIBBONS

A. Teliou, H. Chiriac* and E. Hristoforou*

Laboratory of Physical Metallurgy, National Technical University of Athens, Zografou Campus, Athens 15780, Greece

*National Institute of R&D for Technical Physics, 700050 Iasi, Romania In this paper we present results on magnetic and magnetoelastic uniformity measurements on Fe78Si7B15 amorphous ribbons. The measurements are performed using an automatic instrumentation device, with the ability to determine the B(H) and λ(H) functions along the length of a ribbon with parametric control of field and frequency. The device has been calibrated with respect to standard Ni wires. According to these results, it has been determined that magnetic and magnetoelastic uniformity functions are in agreement and they are also subject to the history of the under test samples. These measurements may allow the structural non destructive evaluation on the under test samples in real time, which may be usable in industrial NDT testing and sensing applications.


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P-37

SMART MULTI-SENSOR BASED ON AMORPHOUS ALLOYS

A. Kakaroglou, H. Chiriac*, E. Hristoforou*

Laboratory of Physical Metallurgy, National Technical University of Athens, Zografou Campus, Athens 15780, Greece

*National Institute of R&D for Technical Physics, 700050 Iasi, Romania In this paper a new smart sensor is proposed, based on three different magnetic effects or operational modes, using the same sensor topology, which consists of a magnetic wire as sensing core, two coils as excitation or search means and two electric contacts at the ends of the magnetic wire. The currently involved magnetic effects are magnetostriction, magneto-impedance and re-entrant flux reversal. Operating the sensor in these three different modes separately and sequentially, one can obtain the response of the sensor related to three different physical quantities, such as stress, temperature and field. It has been experimentally observed that the total output of the sensor in each one of the three different modes is equal to the product of each corresponding physical quantity function concerned, provided that a given threshold of ambient field and preloaded stress is used to bias the sensing element. Therefore, the three unknown parameters of stress, temperature and field can be determined from a 3x3 matrix equation. Other magnetic effects may also be involved. Furthermore, other physical quantities may also be determined, such as position, pressure, load, etc.

Keywords: Magnetostriction, magneto-impedance, re-entrant flux reversal, magnetostrictive delay lines.


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P-38

SMART NANOSTRUCTURES SIMULATED DESIGN BY NEURAL-NETS METHOD FOR SPATIAL BIOTECHNOLOGIES

APPLICATIONS

Sergiu H. Mohorianu1 and Florin V. Rusu 1National Institute of R&D for Technical Physics, 700050 Iasi, Romania

In Space Water Purification is still a difficult problem, not only because of no-gravity. Nishida [1] proposed some methods but for instance we have focused one: Magnetically Agitated Photocatalytic Reactor (MAPR). The nano-magnetic particles are coated with silica and TiO2 to photocatalytically degrade organics. This enhance the capture organics through traditional adsorption with TiO2 coated activated carbon. On the other hand the external magnetic field fluidizes particles to enhance mixing and destruction rates. The structure of nanophase materials on a variety of length scales have an important bearing on their special physical properties. A variety of computational methods have been developed to perform theoretical studies of the properties of nanomaterials. Tehnologically important nanomaterials come in all shapes and sizes. They can range from small molecules to complex composites and mixtures. Depending upon spatial dimensions of the system and properties under investigation, computer modeling of such materials can range from first-principle Quantum Mechanics to Neural-Network method. The last one was that we used in our last research. Neural computation has now “legally” a style. Unlike more analytically based information processing methods, neural computation effectively explores the information contained within input data, without further assumptions. Neural Networks are an expanding and interdisciplinary field bringing together many adjacent fields. We imagine this method, using the Neural-Net program we have, to simulate the design of the smart nanostructures used in MAPR. So, for Water Recovery we think we create new frame for a future research.

References [1] T. Nishida, M.E. Law, “Integrated Smart Nanosensors for Space Biotechnology Applications”,

NASA Research Briefing, September 25, 2002.

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P-39

CONTRIBUTIONS TO METALLIC MATRIX COMPOSITES PROCESSING BY POWDER METALLURGY

M. Mangra, O. Gingu, G. Sima, N. Dumitru, L. Gruionu, N. Coman

University of Craiova, Faculty of Engineering and Management of Technological Systems, Calugareni 1, 220037 Drobeta Turnu Severin, Romania, www.imst.ro

The paper is an overview of the AEG research group from Faculty of IMST, Dr. Tr. Severin regarding the processing of advanced materials, modelling and simulation of their behaviour during different mechanical tests. The researched composite materials are Al-based, discontinuously reinforced by SiC and/or graphite. The materials are processed by Powder Metallurgy (PM) technology, as composite powders, as layers and as bulk materials. The research level is in micro- and nano-scale, especially regarding the nanocomposite powders processed by mechanical alloying process (specific to PM). Also, there have been achieved composite layers by laser deposition technology on common Al alloy substrate. Regarding the modelling and simulation, AEG group was involved in nanoscale monitoring of nanoindentation process.

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P-40

NANOWIRES IN POROUS TEMPLATES

Mihaela Daub

Max-Planck Institute for Microstructure Physics, Halle, Germany Nanowires became in the recent years a very interesting topic of research both for fundamental studies and many technological applications. The method used in this work for obtaining nanowires consists in synthesizing the desired structures by electrochemical deposition into the pores of a membrane. In the first case, polycarbonate foils were irradiated with single swift heavy ions. After irradiation, a thin gold layer was sputtered on one foil side to be used as a cathode. The ion track etching was performed with a solution of NaOH with methanol, by applying a pulsed square-shaped voltage between a gold electrode and the cathode. The electrochemical deposition of the wires was performed in a cell with two-electrode arrangement. In the second case, alumina membranes were anodized in one or two steps in order to obtain the pores. For perfectly ordered pores, an imprint stamp was used before anodizing the membranes. Different types of nanowires were electrochemically grown in these membranes using the method of reducing the barrier layer or the direct contact method. By removing the membrane using chemical methods, free standing nanowires were obtained.

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AUTHORS INDEX

A Albu L………………………………………………………………………………………...12 Alexandrescu R.………..……………………………………………………………………..12 Andreescu A.…………………………………………………………………………….……67 Andrei P.………………………………………………………………………………….…..48 Angelescu A.……………………………………………………………………………...28, 29 Apetroaei N.……………………………………………………………………………....14, 36 Apostolescu G.…………………………………………………………………………....41, 42 Apostolescu N.…………………………………………………………………………….….42 Astilean S..…………………………………………………………………………………....21 Avram M..………………………………………………………………………………….…28 Axente E..………………………………………………………………………………....13, 18

B Badescu R..……………………………………………………………………………….…...60 Badescu V..…………………………………………………………………………………...60 Baia M..……………………………………………………………………………………….21 Baies M..……………………………………………………………………………………...31 Bancuta I..…………………………………………………………………………………….16 Bobu M.M..…………………………………………………………………………………...43 Bragaru A..………………………………………………………………………………..28, 29 Brezeanu I..…………………………………………………………………………………...16 Brinza F..……………………………………………………………………………………...52 Brinza O..……………………………………………………………………………………..19 Bucsa M..……………………………………………………………………………………..39

C Caltun O..…………………………………………………………………………24, 46, 48, 50 Calugaru Gh.………………………………………………………………………...………..58 Caraman I..……………………………………………………………………………..……..14 Carcadea E..…………………………………………………………………………………..17 Carja G..…………………………………………………………………………………..23, 42 Cernica I..……………………………………………………………………………………..13 Chiriac H..…………………………………….10, 23, 27, 61, 62, 63, 64, 69, 70, 71, 72, 73, 74 Chitanu G..………………………………………..…………………………………………..22 Cimpoca M..…………………………………………………………………………………..16 Cimpoca V..…………………………………………………………………………………..16 Cimpoesu D.…………………………………………………………………………………..57 Ciubotariu Ciprian.……..……………………………………………………………………..32 Ciubotariu Corneliu.…………………………………………………………………………..32 Ciubotariu C.I..………………………………………………………………………………..32 Codescu M..……………………..……………………………………………………………..6 Coman N..…………………………...………………………………………………………..76 Craciunoiu F..………………………..………………………………………………………..28 Craus M.L..…………………………….……………………………………………………..14 Creanga D.E..…………………………..……………………………………………………..58 Culcer M..……………………………………………………………………………………..17

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D Dantus C..……………………………………………………………………………………..35 Dascalu D..……………………………………………..……………………………………..20 Daub M..……………………………………………………..………………………………..77 Dobromir M..…………………………………………………..……………………………..64 Dorcioman G..…………………………………………………...………………………..13, 18 Doroftei C..…………………………………………………………..………………………..44 Dumitru I..…………………………………………………………….…………………..24, 46 Dumitru N..……………………………………………………………….…………………..76 Dumitrache F..…………………………………………………………….…………………..12

E Enachescu C..…………………………………………………………………………………..7 Ercuta A..……………………………………………………………………………..………..9

F Farcau C..……………………………………………………………………………………..21 Filoti G..………………………………………………………………………………………..6 Fleaca C..……………………………………………………………………………………...12 Fosa G..……………………………………………………………………………………….60

G Georgescu V..………………………………………………………………………………5, 65 Gheboianu A..………………………………………………………………………………...16 Gherasim C..…………………………………………………………………………..…..61, 62 Gheorghies C..………………………………………………………………………….……..39 Gheorghies L..………………………………………………………………………….……..39 Gingu O..……………………………………………………………………………………...76 Giurgiu L.M..…………………………………………………………………………………..4 Grigoras M..………………………………………………………..……………………..10, 63 Grigorescu S..……………………………………………………………………………..13, 18 Grimberg R..…………………………………………………………………………………..67 Grozescu I..……………………………………………………………………………….16, 31 Gruionu L..…………………………………………………………………………………....76

H Harabagiu V..…………………………………………………………………………………..3 Herea D.D..……………………………………………….…………………………………..69 Hogan T..……………………………………………………….……………………………..67 Hristoforou E..…………………………………………………...………………..71, 72, 73, 74 Hsu L.-S..……………………………………………………………………………………..50 Hui D..………………………………………………………………………….……………..38

I Iacomi F..……………………………………………………………………………………..14 Ignat T..…………………………………………………………………………………...28, 29 Iftimie N..……………………………………………………………………………………..45

J Jianu A.……………………………………………………………………….………………..6

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K Kakaroglou A.………………………………………………………………...…………..64, 74 Kappel W.………………………………………………………………………….…………..6 Kleps I.………………………………………………………………………………..…..28, 29 Kuncser V.………………………………………………………………………………….…..6

L Lazar R.E..………………………………………………………………………………….....17 Lazau C.………………………………………………………………………..……………..31 Lesenciuc N.…………………………………………………………………………………..36 Lifei F.……………………………………………………………………………………...…..6 Linares J.……………………………………………………………………...………………..7 Loris G.……………………………………………………………………………...………..72 Lungu A.M.…………………………………………………………………………….……..19 Lungu C.P.…………………………………………………………………………………....19 Lupu N.……………………………………………………………………………….23, 27, 76

M Mangra M.………………………………………………………………………………...…..76 Maniu D.………………………………………………………….…………………………..21 Miclau M.……………………………………………………………………………………..31 Mihalca M.……………………………………………………………………………………..9 Mihailescu I.N.……………………………………………………………………..……..13, 18 Mirica D.………………………………………………………………………………….…..17 Miu M.………………………………………………………………………………….....28, 29 Moga A.……………………………………………………………………………….61, 62, 69 Mohorianu S.…………………………………………………………………………...……..75 Morjan I.…………………………………………………………..…………………………..12 Musat R.…………………………………………………………………..…………………..65 Mustata I.……………………………………………………………………….……………..19

N Neagu M.…………………………………………………………………………….………..64 Nechita M.T.……………………………………………………………………….……..41, 42 Nedelcu G.G.………………………………………………………………………...………..61

O Olaru P.…………………………………………………………………………………….....38 Oniciuc G.…………………………………………………………………………...………..36

P Paratheeswara R.………………………………………………………………………….24, 46 Patularu L.…………………………………………………………………………………….17 Patronos J.………………………………………………………...…………………………..71 Petrou J.…………………………………………………………………...…………………..71 Pintea J.…………………………………………………………………………….…………..6 Popa Gh.………………………………………………………………………………..…..1, 64 Popa P.D.………………………………………………………………………………….44, 45 Popovici E.…………………………………………………………………………………....12 Prepelita P.…………………………………………………………………..………..34, 35, 36

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R Racuciu M.……………………………………………………………………..……………..58 Rezlescu E.………………………………………………………………………………..44, 45 Rezlescu N.………………………………………………………………….………..35, 44, 45 Riedo E.……………………………………………………………………………...………..26 Ristoscu C.………………………………………………………………………………..13, 18 Rosca I.…………………………………………………………………………………....41, 42 Rusu G.G.……………………………………………………………………………………..37 Rusu G.I.……………………………………………………………………………...34, 35, 36 Rusu R.S.……………………………………………………………………………...34, 35, 36 Rusu F.V.……………………………………………………………………………………..75

S Sandu I.………………………………………………………...……………………………..12 Savin A.………………………………………………………………...……………………..67 Scarisoreanu M.……………………………………………………………………...………..12 Sima G.……………………………………………………………………………………......76 Siminiceanu I.………………………………………………………………………………...43 Simion M.………………………………………………………………………………....28, 29 Simionescu B.C.………………………………………………………………………………..2 Singurel Gh.…………………………………………………………………………………..64 Spinu L.……………………………………………………………………………….…..24, 46 Sirbu C.………………………………………………………………………………...……..65 Sirghi L.………………………………………………………………………..……………..26 Soare I.………………………………………………………………………………………..12 Socol G.………………………………………………………….………………………..13, 18 Sofronie M.…………………………………………………………...………………………..6 Stancu N.……………………………………………………………………...………………..6 Stancu A.…………………………………………………………….……..7, 48, 53, 55, 56, 57 Steigmann R.…………………………………………………………...……………………..67 Stoenescu D.…………………………………………………………………………………..17 Stoleriu L.……………………………………………………………………………………..53 Stefanescu I.…………………………………………………………………………………..17 Sulitanu N.……………………………………………………………………………...……..52

T Tanasa R.……………………………………………………………………….…………..7, 55 Teliou K.………………………………………………………………………...………..64, 73 Tibu M.………………………………………………………………………………………..69 Toderas F.……………………………………………………………………………………..21

U Udpa S.S.……………………………………………………………………………….……..67 Udrea L.E.……………………………………………………………………...……………..60 Urse M.……………………………………………………………………………..……..10, 63

V Valeanu M.……………………………………………………………………………………..6 Varlam M.……………………………………………………………………………...……..17 Varret F.………………………………………………………………………………………..7 Vasile A.………………………………………………………………………………….…..14

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Vlascianu I.……………………………………………………………………………….…..34 Voicu I.………………………………………………………………………………………..12

Z Zaroschi V.…………………………………………………………………………..………..19

Book of Abstracts - National Institute of Research and … Book of Abstracts... · 2005-08-28 ·...

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