Effect of thermal treatment on the morphology of PLZT thin films prepared from polymeric precursor method

Lead lanthanum zirconate titanate (PLZT) thin films with (9/65/35) stoichiometry were prepared by dip coating from polymeric precursor method. The films deposited on silicon (100) substrates, were thermally treated from 450° to 700°C for 6 hours in order to study the influence of thermal treatment on the crystallinity, microstructure, grain size and roughness of the final film. X-ray diffraction results showed that PLZT phase crystallizes at low temperature (500°C) and present preferential orientation. It was observed by scanning electron microscopy (SEM) that it is possible to obtain dense thin films at temperatures around 650°C. The atomic force microscopy (AFM) studies showed that the grain size and roughness are strongly influenced by the annealing temperature.

Erbium-activated HfO2-based waveguides for photonics

70SiO2 - 30HfO2 planar waveguides, activated by Er3+ concentration ranging from 0.3 to 1 mol%, were prepared by solgel route, using dip-coating deposition on silica glass substrates. The waveguides showed high densification degree, effective intermingling of the two components of the film, and uniform surface morphology. Propagation losses of about 1 dB/cm were measured at 632.8 nm. When pumped with 987 nm or 514.5 nm continuous-wave laser light, the waveguides showed the 4I 13/2→4I15/2 emission band with a bandwidth of 48 nm. The spectral features were found independent both on erbium content and excitation wavelength. The 4I13/2 level decay curves presented a single exponential profile, with a lifetime between 2.9-5.0 ms, depending on the erbium concentration.

Electrical devices obtained from polymeric precursors process

Nowadays, many investments have been made in the area of superconductor materials, with the aim to improve their potential technological applications. Applications on the energy transport using cables, to get high resolution images in the medicine use high magnetic fields, high speed signals use superconductor devices all of them are in crescent evidence and they are showing that the future is coming and next for this new kind of materials. Obviously that everything of this is possible due to the increasing of research with new materials, where the synthesis, characterization and applications are of the mainly objective of these researches. The production of cable for the energy transport has been in advanced stage as the bulks production is too. However, the film production that to aim at the electronic devices area is not as developed or it still need expensive investments. Thinking about that, we are developing a research where we may increase the relation of cost/benefits. Thereby, we are applying the polymeric precursors method to obtain films that will be used in the built of electronic devices. Thin films (mono and multilayers, on crystalline or metallic substrates, controlled thickness) of the BSCCO system have been obtained from dip coating deposition process with excellent results in terms of preferential orientation, controlled thickness, a large area, which may indicate future applications. Based on these results, we present an electrical circuit and their principal characteristics as superconductor transition (85K), transport current density and structure. DC four probes method, scanning electron microscopy, digital optical microscopy and X-ray diffractometry were some techniques used for the characterization of this superconductor electric device. © 2006 Materials Research Society.

Effect of scandium on the structural and photocatalytic properties of titanium dioxide thin films

Pure and scandium doped-TiO2 thin films were prepared by the sol-gel process and coated by dip coating. The effects of scandium on the phase formation, optical properties and photoactivity of the TiO2 thin films were investigated. The lattice parameters and the crystallinity of the anatase phase, characterized by the Rietveld method, demonstrated that scandium doping affected the structural parameters and crystallinity of the films, modifying the absorption edge. A direct correlation was found between band gap energy and photodegradation efficiency, with lower values of band gap energy augmenting this efficiency. Moreover, a significant improvement in the catalyst's photodegradation efficiency was attained with a scandium concentration of 5.0 mol%. © 2007 Springer Science+Business Media, LLC.

Effect of pressure-assisted thermal annealing on the optical properties of ZnO thin films

ZnO thin films were prepared by the polymeric precursor method. The films were deposited on silicon substrates using the spin-coating technique, and were annealed at 330°C for 32h under pressure-assisted thermal annealing and under ambient pressure. Their structural and optical properties were characterized, and the phases formed were identified by X-ray diffraction. No secondary phase was detected. The ZnO thin films were also characterized by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, photoluminescence and ultraviolet emission intensity measurements. The effect of pressure on these thin films modifies the active defects that cause the recombination of deep level states located inside the band gap that emit yellow-green (575nm) and orange (645nm) photoluminescence. © 2012 John Wiley & Sons, Ltd.

Carbon nanotube-reinforced siloxane-PMMA hybrid coatings with high corrosion resistance

Siloxane-polymethyl methacrylate hybrid films containing functionalized multiwall carbon nanotubes (CNTs) were deposited by dip-coating on carbon steel substrates from a sol prepared by radical polymerization of methyl methacrylate and 3-methacryloxy propyl-trimethoxysilane, followed by hydrolytic co-polycondensation of tetraethoxysilane. The correlation between the structural properties and corrosion protection efficiency was studied as a function of the molar ratio of nanotubes carbon to silicon, varied in the range between 0.1% and 5%. 29Si nuclear magnetic resonance and thermogravimetric measurements have shown that hybrids containing carbon nanotubes have a similar degree of polycondensation and thermal stability as the undoped matrix and exhibit and excellent adhesion to the substrate. Microscopy and X-ray photoelectron spectroscopy results revealed a very good dispersion of carbon nanotubes in the hybrid matrix and the presence of carboxylic groups allowing covalent bonding with the end-siloxane nodes. Potentiodynamic polarization curves and electrochemical impedance spectroscopy results demonstrate that CNTs containing coatings maintain the excellent corrosion protection efficiency of the hybrids, showing even a superior performance in acidic solution. The nanocomposite structure acts as efficient corrosion barrier, increasing the total impedance by 4 orders of magnitude and reducing the current densities by more than 3 orders of magnitude, compared to the bare steel electrode. © 2013 Elsevier B.V. All rights reserved.

Síntese e caracterização de nanopartículas e filmes finos de óxidos semicondutores

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização de filmes finos de YBa2Cu3O7-x e La0.7Ca0.3MnO3 produzidos via síntese química

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Preparação e caracterização de filmes finos do tipo 'Pb IND. 1-x-yCa IND. xSr IND.yTiO IND. 3'

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

Estudo da fotossensibilidade de materiais híbridos de sílica dopados com heteropoliânions de tungstênio

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Preparação e caracterização estrutural e elétrica de células solares sensibilizadas por corantes empregando anodos nanoestruturados à base de 'TiO IND. 2'

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese e caracterização de nanoesferas de sílica monodispersas para obtenção de filmes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desenvolvimento de revestimentos híbridos do sistema siloxano-PMMA com aplicações anticorrosivas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Recobrimentos cerâmicos bioativos pelo processo sol-gel sobre Ti c.p. modificado por laser empregados em implantes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Imobilização de peroxidase em filme de titânio

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)