Nanostructured hybrid films containing nanophosphor: Fabrication and electronic spectral properties

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

Filmes nanométricos de FeN e ALN crescidos por sputtering e aplicações do efeito peltier

This study will show the capability of the reactive/nonreactive sputtering (dc/rf) technique at low power for the growth of nanometric thin films from magnetic materials (FeN) and widegap semiconductors (AlN), as well as the technological application of the Peltier effect using commercial modules of bismuth telluride (Bi2Te3). Of great technological interest to the high-density magnetic recording industry, the FeN system represents one of the most important magnetic achievements; however, diversity of the phases formed makes it difficult to control its magnetic properties during production of devices. We investigated the variation in these properties using ferromagnetic resonance, MOKE and atomic force microscopy (AFM), as a function of nitrogen concentration in the reactive gas mixture. Aluminum nitride, a component of widegap semiconductors and of considerable interest to the electronic and optoelectronic industry, was grown on nanometric thin film for the first time, with good structural quality by non-reactive rf sputtering of a pure AlN target at low power (≈ 50W). Another finding in this study is that a long deposition time for this material may lead to film contamination by materials adsorbed into deposition chamber walls. Energy-dispersive X-ray (EDX) analysis shows that the presence of magnetic contaminants from previous depositions results in grown AlN semiconductor films exhibiting magnetoresistance with high resistivity. The Peltier effect applied to commercially available compact refrigeration cells, which are efficient for cooling small volumes, was used to manufacture a technologically innovative refrigerated mini wine cooler, for which a patent was duly registered

Fases magnéticas de sistemas nanoestruturados de terras-raras

There is presently a worldwide interest in artificial magnetic systems which guide research activities in universities and companies. Thin films and multilayers have a central role, revealing new magnetic phases which often lead to breakthroughs and new technology standards, never thought otherwise. Surface and confinement effects cause large impact in the magnetic phases of magnetic materials with bulk spatially periodic patterns. New magnetic phases are expected to form in thin film thicknesses comparable to the length of the intrinsic bulk magnetic unit cell. Helimagnetic materials are prototypes in this respect, since the bulk magnetic phases consist in periodic patterns with the length of the helical pitch. In this thesis we study the magnetic phases of thin rare-earth films, with surfaces oriented along the (002) direction. The thesis includes the investigation of the magnetic phases of thin Dy and Ho films, as well as the thermal hysteresis cycles of Dy thin films. The investigation of the thermal hysteresis cycles of thin Dy films has been done in collaboration with the Laboratory of Magnetic Materials of the University of Texas, at Arlington. The theoretical modeling is based on a self-consistent theory developed by the Group of Magnetism of UFRN. Contributions from the first and second neighbors exchange energy, from the anisotropy energy and the Zeeman energy are calculated in a set of nonequivalent magnetic ions, and the equilibrium magnetic phases, from the Curie temperature up to the Nèel temperature, are determined in a self-consistent manner, resulting in a vanishing torque in the magnetic ions at all planes across the thin film. Our results reproduce the known isothermal and iso-field curves of bulk Dy and Ho, and the known spin-slip phases of Ho, and indicate that: (i) the confinement in thin films leads to a new magnetic phase, with alternate helicity, which leads to the measured thermal hysteresis of Dy ultrathin films, with thicknesses ranging from 4 nm to 16 nm; (ii) thin Dy films have anisotropy dominated surface lock-in phases, with alignment of surface spins along the anisotropy easy axis directions, similar to the known spin-slip phases of Ho ( which form in the bulk and are commensurate to the crystal lattice); and (iii) the confinement in thin films change considerably the spin-slip patterns of Ho.

Efeito Kerr magneto-óptico; Ressonância ferromagnética; Acoplamento bilinear; Acoplamento biquadrático

In this work, we investigated the magnetic properties of a monocrystalline Fe thin film and of Fe(80 Å)/Cr(t)/Fe(80 Å) tri-layers, with the nonmagnetic metallic Cr spacer layer thickness varying between 9 Å < t < 40 Å. The samples were deposited by the DC Sputtering on Magnesium Oxide (MgO) substrates, with (100) crystal orientation. For this investigation, experimental magneto-optical Kerr effect (MOKE) magnetometry and ferromagnetic resonance (FMR) techniques were employeed. In this case, these techniques allowed us to study the static and dynamical magnetization properties of our tri-layers. The experimental results were interpreted based on the phenomenological model that takes into account the relevant energy terms to the magnetic free energy to describe the system behavior. In the case of the monocrystalline Fe film, we performed an analytical discussion on the magnetization curves and developed a numerical simulation based on the Stoner-Wohlfarth model, that enables the numerical adjustment of the experimental magnetization curves and obtainment of the anisotropy field values. On the other hand, for the tri-layers, we analyzed the existence of bilinear and biquadratic couplings between the magnetizations of adjacent ferromagnetic layers from measurements of magnetization curves. With the FMR fields and line width angular dependencies, information on the anisotropy in three layers was obtained and the effects of different magnetic relaxation mechanisms were evidenced. It was also possible to observe the dependence of the epitaxy of the multilayers with growth and sputtering parameters. Additionally it was developed the technique of AC magnetic susceptibility in order to obtain further information during the investigation of magnetic thin films

Synthesis and characterization of Fe(III)-doped ceramic membranes of titanium dioxide and its application in photoelectrocatalysis of a textile dye

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

Material processing by plasma shock wave generated in an inverse Z-pinch plasma expander

The applicability of plasma shock wave for material processing was investigated using modified inverse Z-pinch device. Shock wave expanding speed and plasma spectral analysis were studied using an internal magnetic,probe and spatially collimated light spectroscopy. The material processing capability of the device was shown by many different surface analysis techniques such as AES, IRS, EPM and SEM. The interactions between a plasma shock wave of similar to4x10(6) cm/s speed with a Si substrate surface shows some ion implantation capability using a nitrogen plasma and thin film formation using a methane plasma.

Obtaining of Nanoapatite in Ti-7.5Mo Surface After Nanotube Growth

Titanium and their alloys have been used for biomedical applications due their excellent mechanical properties, corrosion resistance and biocompatibility. However, they are considered bioinerts materials because when they are inserted into the human body they are cannot form a chemical bond with bone. In several studies, the authors have attempted to modify their characteristic with treatments that changes the material surface. The purpose of this work was to evaluate obtaining of nanoapatite after growing of the nanotubes in surface of Ti-7.5Mo alloy. Alloy was obtained from c.p. titanium and molibdenium by using an arc-melting furnace. Ingots were submitted to heat treatment and they were cold worked by swaging. Nanotubes were processed using anodic oxidation of alloy in electrolyte solution. Surfaces were investigated using scanning electron microscope (SEM), FEG-SEM and thin-film x-ray diffraction. The results indicate that nanoapatite coating could form on surface of Ti-7.5Mo experimental alloy after nanotubes growth.

Dielectric relaxation of vegetable-based polyurethane

Vegetable-based polyurethane (PU) was prepared in the thin film form by spin coating. This polymer is synthesised from castor oil, which can be extracted from the seeds of a native plant in Brazil called mamona. This polymer is biocompatible and is being used as material for artificial bone. The PU was characterised by dielectric spectroscopy in a wide range of frequency (10(-5) Hz to 10(5) Hz) and by thermally stimulated discharge current (TSDC) measurements. The glass transition temperature (T-g=39degreesC) was determined and using the initial rise method the activation energy was found to be 1.58 eV. (C) 2003 Kluwer Academic Publishers.

Electromechanical properties of 0-3 vegetable based polyurethane and lead zirconate titanate composite.

Composite made of Lead Zirconate Titranate (PZT) ceramic powder and castor oil based polyurethane (PU) were prepared in the thin film form with 0-3 connectivity by spin coating. The composite films were obtained in the thickness range of 100 mum to 300 mum using 33-vol.% of ceramic. The samples mechanical resistance. The material was characterised by dielectric spectroscopy, thermally stimulated discharge current (TSDC), hysteresis measurements and laser-intensity-modulation method (LIMM). The pyroelectric coefficient at 343 K was 7x10(-5) C.m(-2) K-1 for the sample poled with 10 MV/m at 373 K for Ih. The results show that this new composite can be used as suitable piezo and pyroelectric sensors.

Dielectric and pyroelectric properties of a composite of ferroelectric ceramic and polyurethane

Flexible piezo- and pyroelectric composite was made in the thin film form by spin coating. Lead Zirconate Titanate (PZT) ceramic powder was dispersed in a castor oil-based polyurethane (PU) matrix, providing a composite with 0-3 connectivity. The dielectric data, measured over a wide range of frequency (10(-5) Hz to 105 Hz), shows a loss peak around 100 Hz related with impurities in the polymer matrix. There is also an evidence of a peak in the range 10(-4) Hz, possibly originating from the glass transition temperature T of the polymer. The pyroelectric coefficient at 34 K is 7.0x10(-5) C(.)m(-2.)K(-1) which is higher than that of P-PVDF (1X10(-5) C(.)m(-2.)K(-1)).

Deposição de filmes de ZrO2 modificados sobre substratos metálicos

This work makes use of the Pechini process for synthesis of the solutions and the dip-coating process for the addition of zirconium oxide films pure and doped cerium metal substrates. The metals with ceramic substrates were subjected to severe conditions of salinity. The x-ray fluorescence of the substrate showed a great diversity of chemical elements. The x-ray diffraction of the samples showed the phase of iron substrate because the thickness of nano-thin film. Tests using an LPR probe showed that the film presents with zirconia corrosion independent of film thickness. The substrates of ZrO2-doped ceria showed low chemical attack of the salt in films with less than 15 dives. The results imply that ultrathin films are shown in protecting metallic substrates

Construção de um sistema de caracterização das propriedades de transporte de filmes finos pelo efeito Hall

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

Propriedades magnéticas e magnetorresistência em filmes finos de Ni81Fe19

The ferromagnetic materials play an important role in the development of various electronic devices and, have great importance insofar as they may determine the efficiency, cost and, size of the devices. For this reason, many scientific researches is currently focused on the study of materials at ever smaller scales, in order to understand and better control the properties of nanoscale systems, i.e. with dimensions of the order of nanometers, such as thin film ferromagnetic. In this work, we analyze the structural and magnetic properties and magnetoresistance effect in Permalloy-ferromagnetic thin films produced by magnetron sputtering. In this case, since the magnetoresistance effect dependent interfaces of thin films, this work is devoted to the study of the magnetoresistance in samples of Permalloy in nominal settings of: Ta[4nm]/Py[16nm]/Ta[4nm], Ta[4nm]/Py[16nm]/O2/Ta[4nm], Ta[4nm]/O2/Py[16nm]/Ta[4nm], Ta[4nm]/O2/Py[16n m]/O2/Ta[4nm], as made and subjected to heat treatment at temperatures of 160ºC, 360ºC e 460ºC, in order to verify the influence of the insertion of the oxygen in the layer structure of samples and thermal treatments carried out after production of the samples. Results are interpreted in terms of the structure of the samples, residual stresses stored during deposition, stresses induced by heat treatments and magnetic anisotropies

Úlceras crônicas dos membros inferiores: avaliação pela fotografia digital

OBJETIVO: Avaliar o desempenho da análise de imagem digital na estimativa da área acometida pelas úlceras crônicas dos membros inferiores. MÉTODOS: Estudo prospectivo em que foram mensuradas úlceras empregando o método planimétrico clássico, utilizando desenho dos seus contornos em filme plástico transparente, medida sua área posteriormente por folha milimetrada. Esses valores foram utilizados como padrão para a comparação com a estimativa de área pelas fotografias digitais padronizadas das úlceras e dos desenhos das mesmas em filme plástico. Para criar um referencial de conversão dos pixels em milímetros, foi empregado um adesivo com tamanho conhecido, adjacente à úlcera. RESULTADOS: foram avaliadas 42 lesões em 20 pacientes portadores de úlceras crônicas de membros inferiores. As áreas das úlceras variaram de 0,24 a 101,65cm². Observou-se forte correlação entre as medidas planimétricas e as fotos das úlceras (R²=0,86 p<0,01), porém a correlação das medidas planimétricas com as fotos digitais dos desenhos das úlceras foi ainda maior (R²=0,99 p<0,01). CONCLUSÃO: A fotografia digital padronizada revelou-se método rápido, preciso e não-invasivo capaz de estimar a área afetada por úlceras. A avaliação das medidas fotográficas dos contornos das úlceras deve ser preferida em relação à análise de sua fotografia direta.

Estratégias para redução de girassol ornamental para comercialização em vaso

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