Colheita de energia usando dispositivos baseados em materiais piezoelétrico

Recently, research on energy harvesting has increased substantially. Many researchers have concentrated their efforts to find the best configuration for these systems and to optimize their output power. In the process of energy harvesting, the electric energy is obtained by converting mechanics energy created by an environment vibration source by a transducer, for example, a thin piezoceramic film. That vibration source is, for example, a beam suffering some mechanic force able to generate a vibration in it, an oscillating beam is the best properly used example. Different mechanisms of electromechanical coupling have been developed to harvesting devices, and a particular interest has been given to the use of models that transform the mechanical vibration into electrical current using a piezoelectric element. In this paper we propose a model to energy harvesting from vibrations, from an oscillating beam, including non-linearities in the piezoelectric coupling and a non-ideal excitation in the material. From this model, it was developed a system to obtain some results about the harvested power by the material. It was demonstrated that the power captured was influenced by the effect of the nonlinearities of the piezoelectric coupling, modifying the system dynamic behavior

Surface characterization of lithium disilicate ceramic after nonthermal plasma treatment

Statement of problem. Surface transformation with nonthermal plasma may be a suitable treatment for dental ceramics, because it does not affect the physical properties of the ceramic material.Purpose. The purpose of this study was to characterize the chemical composition of lithium disilicate ceramic and evaluate the surface of this material after nonthermal plasma treatment.Material and methods. A total of 21 specimens of lithium disilicate (10 mm in diameter and 3 mm thick) were fabricated and randomly divided into 3 groups (n=7) according to surface treatment. The control group was not subjected to any treatment except surface polishing with abrasive paper. In the hydrofluoric acid group, the specimens were subjected to hydrofluoric acid gel before silane application. Specimens in the nonthermal plasma group were subjected to the nonthermal plasma treatment. The contact angle was measured to calculate surface energy. In addition, superficial roughness was measured and was examined with scanning electron microscopy, and the chemical composition was characterized with energy-dispersive spectroscopy analysis. The results were analyzed with ANOVA and the Tukey honestly significant difference test (alpha=.05).Results. The water contact angle was decreased to 0 degrees after nonthermal plasma treatment. No significant difference in surface roughness was observed between the control and nonthermal plasma groups. Scanning electron microscopy and energy-dispersive spectroscopy images indicated higher amounts of oxygen (O) and silicon (Si) and a considerable reduction in carbon (C) in the specimens after nonthermal plasma treatment.Conclusions. Nonthermal plasma treatment can transform the characteristics of a ceramic surface without affecting its surface roughness. A reduction in C levels and an increase in 0 and Si levels were observed with the energy-dispersive spectroscopy analysis, indicating that the deposition of the thin silica film was efficient.

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.

Numerical simulation of the liquid phase in SnO2 thin film deposition by sol-gel-dip-coating

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Growth of Al2O3 thin film by oxidation of resistively evaporated Al on top of SnO2, and electrical properties of the heterojunction SnO2/Al2O3

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Nanohardness of a Ti thin film and its interface deposited by an electron beam on a 304 SS substrate

The results of nanohardness measurements at a film surface and film-substrate interface are presented and discussed. An electron beam device was used to deposit a Ti film on a 304 stainless steel (304 SS) substrate. The diluted interface was obtained by thermal activated atomic diffusion. The. Ti film and Ti film-304 SS interface were analyzed by energy dispersive spectrometry and were observed using atomic force microscopy. The nanohardness of the Ti film-304 SS system was measured by a nanoindentation technique. The results showed the Ti film-304 SS interface had a higher hardness value than the Ti film and 304 SS substrate. The Ti film surface had a lower hardness due to the presence of a TiO2 thin layer.

Thermal treatment of superconductor thin film of the BSCCO system using domestic microwave oven

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

Photoelectrocatalytic treatment of p-nitrophenol using Ti/TiO2 thin-film electrode

The photoelectrochemical degradation of p-nitrophenol (PNP) was investigated using titanium dioxide thin-film photoelectrode. The effects of different supporting electrolytes, pH, applied potential and PNP concentration were examined and discussed. Complete photodegradation was obtained in perchlorate medium at pH 2 when the photoanode was biased at +1.0 V (versus SCE) during a 3-h experiment. Under these conditions, carbon removal of approximately 60% was achieved. (C) 2005 Elsevier B.V. All rights reserved.

Fabrication of coaxial TiO2/Sb2S3 nanowire hybrids for efficient nanostructured organic- inorganic thin film photovoltaics

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influence of particle size on the photoactivity of Ti/TiO2 thin film electrodes, and enhanced photoelectrocatalytic degradation of indigo carmine dye

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

Nanoporous of W/WO3 Thin Film Electrode Grown by Electrochemical Anodization Applied in the Photoelectrocatalytic Oxidation of the Basic Red 51 used in Hair Dye

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

Grain size effect on the electrical response of SnO2 thin and thick film gas sensors

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

Influence of strains and defects on ferroelectric and dielectric properties of thin-film barium-strontium titanates

Pristine, W and Mn 1% doped Ba(0.6)Sr(0.4)TiO(3) epitaxial thin films grown on the LaAlO(3) substrate were deposited by pulsed laser deposition (PLD). Dielectric and ferroelectric properties were determined by the capacitance measurements and X-ray diffraction was used to determine both residual elastic strains and defect-related inhomogeneous strains-by analyzing diffraction line shifts and line broadening, respectively. We found that both elastic and inhomogeneous strains are affected by doping. This strain correlates with the change in Curie-Weiss temperature and can qualitatively explain changes in dielectric loss. To explain the experimental findings, we model the dielectric and ferroelectric properties of interest in the framework of the Landau-Ginzburg-Devonshire thermodynamic theory. As expected, an, elastic-strain contribution due to the epilayer-substrate misfit has an important influence on the free-energy. However, additional terms that correspond to the defect-related inhomogeneous strain had to be introduced to fully explain the measurements.

Microstructure and dielectric properties of (Ba,Sr)TiO3 thin film produced by the polymeric precursor method

BaxSr1-xTiO3 (x = 0.6) (BST) thin films were successfully prepared on a Pt(111)/TiO2/SiO2/Si(100) substrate by spin coating, using the polymeric precursor method. BST films with a perovskite single phase were obtained after heat treatment at 700 degrees C. The multilayer BST thin films had a granular structure will a grain size of approximately 60 nm. A 480-nm-thick film was obtained by carrying out five cycles of the spin-coating/heating process. Scanning electron microscopy and atomic force microscopy analyses showed that the thin films had a smooth, dense, crack-free surface with low surface roughness (3.6 nm). At room temperature and at a frequency of 100 kHz, the dielectric constant and the dissipation factor were, respectively, 748 and 0.042. The high dielectric constant value was due to the high microstructural quality and chemical homogeneity of the thin films obtained by the polymeric precursor method.

Ferroelectric and optical properties of Ba0.8Sr0.2TiO3 thin film

Barium strontium titanate (Ba0.8Sr0.2TiO3) thin films have been prepared on Pt/Ti/SiO2/Si substrates using a soft solution processing. X-ray diffraction and also micro-Raman spectroscopy showed that the Ba0.8Sr0.2TiO3 thin films exhibited a tetragonal structure at room temperature. The presence of Raman active modes was clearly shown at the 299 and 725 cm(-1) peaks. The tetragonal-to-cubic phase transition in the Ba0.8Sr0.2TiO3 thin films is broadened, and suppressed at about 35 degreesC, with a maximum dielectric constant of 948 (100 kHz). Electrical measurements for the prepared Ba0.8Sr0.2TiO3 thin films showed a remnant polarization (P-r) of 6.5 muC/cm(2), a coercive field (E-c) of 41 kV/cm, and good insulating properties. The dispersion of the refractive index is interpreted in terms of a single electronic oscillator at 6.97 eV. The direct band gap energy (E-g) and the refractive index (n) are estimated to be 3.3 eV and n = 2.27-2.10, respectively. (C) 2002 American Institute of Physics.