Morphology of flux avalanches in patterned superconducting films

It is well known that under certain circumstances, magnetic fields applied perpendicularly to the plane of superconducting films can trigger flux avalanches. In such cases, the penetration has a tree-like profile. However, in samples where a regular array of antidots, ADs, is present, the avalanches follow the rows of ADs as if they were guiding lines for the abrupt penetration. In this work, we used the magnetooptical imaging technique to study the morphology of flux avalanches in two Nb films with a square lattice of square ADs, each one with a different lateral size, and a plain film for reference. We show that the morphology of the flux avalanches is greatly influenced by the size of the interstitial region. © 2012 Springer Science+Business Media, LLC.

Effect of precursor solution on the formation of perovskite phase of Pb(Mg-1/Nb-3(2/3))O-3 thin films

Precursor solutions for Pb(Mg1/3Nb2/3)O-3 (PMN) synthesis were obtained by Pechini's method. The influence of the concentration of organic materials on the phase formation has been studied. For this purpose, PMN solutions were prepared with different precursors and were characterized by thermogravimetric and differential thermal analysis. The obtained solutions were deposited onto a Si (100) substrate by dip coating and pre-treated in a hot plate at 300 degreesC for 1 h. The films were annealed at 600, 700, 800 and 900 degreesC for 1 h and characterized by X-ray diffraction. The perovskite phase was formed after annealing at 600 and 700 degreesC when the solution of PMN was prepared with a lower amount of organic material and starting with mobium oxide. By increasing the temperature to 800 or 900 degreesC, only the formation of pyrochlore phase was observed. With the solution prepared from mobium ethoxide, only the presence of pyrochlore phase was observed independently of the annealing temperature. (C) 2002 Elsevier B.V. B.V. All rights reserved.

The effect of Nb doping on ferroelectric properties of PZT thin films prepared from polymeric precursors

Pure and Nb doped PbZr0.4Ti0.603 thin films was prepared by the polymeric precursor method and deposited by spin coating on Pt/Ti/SiO2/Si (100) substrates and annealed at 700 degreesC. The films are oriented in (1 1 0) and (1 0 0) direction. The electric properties of PZT thin films show strong dependence of the crystallographic orientation. The P-E hysteresis loops for the thin film with composition PbZr0.39Ti0.6Nb0.103 showed good saturation, with values for coercive field (E-c) equal to 60 KV cm(-1) and for remanent polarization (P-r) equal to 20 muC cm(-2). The measured dielectric constant (epsilon) is 1084 for this film. These results show good potential for application in FERAM. (C) 2004 Elsevier B.V. All rights reserved.

Structural, dielectric and ferroelectric properties of Nb-doped PZT thin films produced by oxide precursor method

Recently, was proposed a chemical method for preparation of ferroelectric thin films based on oxide precursors. In this work, PZT thin films were prepared to attest the viability of this method for cation-substitution. In this study, a small concentration of Nb (5 mol%) was selected as substitute of B-site in ABO 3 structure of PZT. Dielectric and ferroelectric properties of PZT films were studied as a function of cation-substitution. Results for Nb-PZT were compared with PZT films undoped. The values of dielectric constant, at typical 100 kHz frequency, were 358 and 137, for PZT and Nb-PZT films respectively. Remanent polarizations of these films were respectively 7.33 μ C/cm 2 and 13.3 μ C/cm 2 , while the measured coercive fields were 101 kV/cm and 93 kV/cm. As a result, changes on observed dielectric and ferroelectric values confirm the Nb substitution in PZT thin film produced by oxide precursor method. © 2002 Taylor & Francis.

Ligas Ti-Al-Nb como biomaterial: elaboração, caracterização, modificação eletroquímica da superfície e estudo da biocompatibilidade utilizando culturas primárias de células da medula óssea humana

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Preparação de filmes finos ferroelétricos de SrBi2'('TA IND.1-x''NB IND.x)ÍND.2 'O IND.9' puro e dopado com tungstênio, obtidos pelo método dos precursores poliméricos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Corrosion properties of Fe-Cr-Nb-B amorphous alloys and coatings

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Synthesis of poly(styrene-co-methyl methacrylate)-based ionomers and their Langmuir and Langmuir-Blodgett (LB) film formation

Poly(styrene-co-methyl methacrylate) (PS-PMMA) ionomers with several degrees of sulfonation were synthesized and characterized by infrared, UV-vis, and NMR spectroscopies, elemental analysis, and differential scanning calorimetry (DSC). Stable Langmuir films could be produced with PS-PMMA with 3 and 6 mol % of sulfonation, while PS-PMMA 8% exhibited material loss to the water subphase, probably due to its higher solubility. Surface pressure and surface potential isotherms with PS-PMMA 3% spread onto salt-containing subphases pointed to a film behavior characteristic of the polyelectrolyte effect, where charge repulsion governs the film properties. The Langmuir-Blodgett films of this ionomer were successfully transferred onto various substrates, as confirmed by UV-vis and FTIR spectroscopies. Using cycling voltammetry, we show that LB films from PS-PMMA 3% can be applied in selective sensing of dopamine, even in the presence of interferents such as ascorbic acid.

A layer-by-layer film of chitosan in a taste sensor application

Chitosan is alternated with sulfonated polystyrene (PSS) to build layer-by-layer (LBL) films that are used as sensing units in an electronic tongue. Using impedance spectroscopy as the principle method of detection, an array using chitosan/PSS LBL film and a bare gold electrode as the sensing units was capable of distinguishing the basic tastes - salty, sweet, bitter, and sour - to a concentration below the human threshold. The suitability of chitosan as a sensing material was confirmed by using this sensor to distinguish red wines according to their vintage, vineyard, and brands.

An electrochemical sensor for (L)-dopa based on oxovanadium-salen thin film electrode applied flow injection system

An oxovanadium-salen complex (NAP-ethylene-bis(salicylidenciminato) oxovanadium) thin film deposited on a graphite-polyurethane electrode was investigated with regard to its potential use for detection of L-dopa in flow injection system. The oxovanadium(IV)/oxovanadium(V) redox couple of the modified electrode was found to mediate the L-dopa oxidation before its use in the FIA system. Experimental parameters, such as pH of the carrier solution, flow rate, sample volume injection and probable interferents were investigated. Under the optimized FIA conditions, the amperometric signal was linearly dependent on the L-dopa concentration over the range 1.0 x 10(-1) to 1.0 x 10(-4) mol L-1 (I-anodic, mu A) = 0.01 + 0.25 [L-dopa mu mol L-1]) with a detection limit (S/N = 3) of 8.0 x 10(-7) mol L-1 and a sampling frequency of 90 h(-1) was achieved. For a concentration of 1.0 x 10(-5) mol L-1 L-dopa, the R.S.D. of nine consecutive measurements was 3.7%. (c) 2006 Elsevier B.V. All rights reserved.

Electrochemical sensor for sulfite determination based on a nanostructured copper-salen film modified electrode

The electrochemical preparation described herein involved the electrocatalytic oxidation of sulfite on a platinum electrode modified with nanostructured copper salen (salen=N,N'-ethylenebis(salicylideneiminato)) polymer films. The complex was prepared and electropolymerized at a platinum electrode in a 0.1 mol L-1 solution of tetrabutylammonium perchlorate in acetonitrile by cyclic voltammetry between 0 and 1.4V vs. SCE. After cycling the modified electrode in a 0.50 mol L-1 KCI solution, the estimated surface concentration was found to be equal to 2.2 x 10(-9) Mol cm(-2). This is a typical behavior of an electrode surface immobilized with a redox couple that can usually be considered as a reversible single-electron reduction/oxidation of the copper(II)/copper(III) couple. The potential peaks of the modified electrode in the electrolyte solution (aqueous) containing the different anions increase with the decrease of the ionic radius, demonstrating that the counter-ions influence the voltammetric behavior of the sensor. The potential peak was found to be linearly dependent upon the ratio [ionic charge]/[ionic radius]. The oxidation of the sulfite anion was performed at the platinum electrode at +0.9V vs. SCE. However, a significant decrease in the overpotential (+0.45V) was obtained while using the sensor, which minimized the effect of oxidizable interferences. A plot of the anodic current vs. the sulfite concentration for chronoamperometry (potential fixed = +0.45V) at the sensor was linear in the 4.0 x 10(-6) to 6.9 x 10(-5) mol L-1 concentration range and the concentration limit was 1.2 x 10(-6) mol L-1. The reaction order with respect to sulfite was determined by the slope of the logarithm of the current vs. the logarithm of the sulfite concentration. (C) 2009 Elsevier Ltd. All rights reserved.

Development of an electrochemical sensor for determination of dissolved oxygen by nickel-salen polymeric film modified electrode

An amperometric oxygen sensor based on a polymeric nickel-salen (salen = N,N'-ethylene bis(salicylideneiminato)) film coated platinum electrode was developed. The sensor was constructed by electropolymerization of nickel-salen complex at platinum electrode in acetonitrile/tetrabutylammonium perchlorate by cyclic voltammetry. The voltammetric behavior of the sensor was investigated in 0.5 mol L-1 KCl solution in the absence and presence of molecular oxygen. Thus, with the addition of oxygen to the solution, the increase of cathodic peak current (at -0.25 V vs. saturated calomel electrode (SCE)) of the modified electrode was observed. This result shows that the nickel-salen film on electrode surface promotes the reduction of oxygen. The reaction can be brought about electrochemically, where the nickel(II) complex is first reduced to a nickel(I) complex at the electrode surface. The nickel(I) complex then undergoes a catalytic oxidation by the molecular oxygen in solution back to the nickel(II) complex, which can then be electrochemically re-reduced to produce an enhancement of the cathodic current. The Tafel plot analyses have been used to elucidate the kinetics and mechanism of the oxygen reduction. A plot of the cathodic current vs. the dissolved oxygen concentration for chronoamperometry (fixed potential = -0.25 V vs. SCE) at the sensor was linear in the 3.95-9.20 mg L-1 concentration range and the concentration limit was 0.17 mg L-1 O-2. The proposed electrode is useful for the quality control and routine analysis of dissolved oxygen in commercial samples and environmental water. The results obtained for the levels of dissolved oxygen are in agreement with the results obtained with a commercial O-2 sensor. (C) 2012 Elsevier B.V. All rights reserved.

Electrochemical investigation of the dimeric oxo-bridged ruthenium complex in aqueous solution and its incorporation within a cation-exchange polymeric film on the electrode surface for electrocatalytic activity of hydrogen peroxide oxidation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Film based on Y2O3: Eu3+ (5 mol% of Eu3+) for flat panel display

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Development of an electrochemical sensor for potassium ions based on KSr(2)Nb(5)O(15) modified electrode

In the work described by this paper, we studied the development of a selective potassium ion sensor constituted of a carbon paste electrode modified (CPEM) with a novel KSr(2)Nb(2)O(15). The material KSr(2)Nb(2)O(15) is an oxide with the tetragonal tungsten bronze structure (TTB) type are in forefront both in the area of research as well as in industrial applications. The sensor response to potassium ions was linear in the concentration range 1.26 x 10(-5) at 1.62 x 10(-3) mol L(-1) (E (mV) = 32.7 + 51.1 log [K(+)]). The sensor based KSr(2)Nb(2)O(15), of the TTB-type presented very good potentiometric response, with a slope of 51.1 mV/dec (at 25 degrees C) and detection limit for the potassium ions of 7.27 x 10(-5) mol.L(-1)