Influence of the concentration of Sb2O3 on the electrical properties of SnO2 varistors

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electrical Properties at Grain Boundaries Influenced by Cr3+ Diffusion in SnO2.ZnO.Nb2O5-Films Varistor Prepared by Electrophoresis Deposition

SnO2-based varistors are strong candidates to replace the ZnO-based varistors due to ordering fewer additives to improve its electrical behavior as well as by showing similar nonlinear characteristics of ZnO varistors. In this work, SnO2-nanoparticles based-varistors with addition of 1.0 %mol of ZnO and 0.05 %mol of Nb2O5 were synthesized by chemical route. SnO2.ZnO.Nb2O5-films with 5 μm of thickness were obtained by electrophoretic deposition (EPD) of the nanoparticles on Si/Pt substrate from alcoholic suspension of SnO2-based powder. The sintering step was carried out in a microwave oven at 1000 °C for 40 minutes. Then, Cr3+ ions were deposited on the films surface by EPD after the sintering step. Each sample was submitted to different thermal treatments to improve the varistor behavior by diffusion of ions in the samples. The films showed a nonlinear coefficient (α) greater than 9, breakdown voltage (VR) around 60 V, low leakage current (IF ≈ 10-6 A), height potential barrier above 0.5 eV and grain boundary resistivity upward of 107 Ω.cm.

Sugarcane Bagasse Ash as a Reinforcing Filler in Thermoplastic Elastomers: Structural and Mechanical Characterizations

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

Supramolecular organization-electrical properties relation in nanometric organic films

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

Rietveld refinement, cluster modelling, growth mechanism and photoluminescence properties of CaWO4: Eu3+ microcrystals

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

Rietveld refinement and optical properties of SrWO4:Eu3+ powders prepared by the non-hydrolytic sol-gel method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A joint experimental and theoretical study on the electronic structure and photoluminescence properties of Al-2(WO4)(3) powders

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of humidity on the electrical properties of thermal inkjet-printed films of copper tetrasulfonated phthalocyanine (CuTsPc) onto paper substrates

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

Investigation of photoinduced electrical properties in the heterojunction TiO2/SnO2

TiO2/SnO2 thin films heterostructures were grown by the sol-gel dip-coating technique. It was found that the crystalline structure of TiO2 depends on the annealing temperature and the substrate type. TiO2 films deposited on glass substrate, submitted to thermal annealing until 550 degrees C, present anatase structure, whereas films deposited on quartz substrate transform to rutile structure when thermally annealed at 1100 degrees C. When structured as rutile, this oxide semiconductor has very close lattice parameters to those of SnO2, making easier the heterostructure assembling. The electrical properties of TiO2/SnO2 heterostructure were evaluated as function of temperature and excitation with different light sources. The temperature dependence of conductivity is dominated by a deep level with energy coincident with the second ionization level of oxygen vacancies in SnO2, suggesting the dominant role of the most external layer material (SnO2) to the electrical transport properties. The fourth harmonic of a Nd:YAG laser line (4.65 eV) seems to excite the most external layer whereas a InGaN LED (2.75 eV) seems to excite electrons from the ground state of a quantized interfacial channel as well as intrabandgap states of the TiO2 layer.

Synthesis, structure and magnetic properties of Y3Fe5-xAlxO12 garnets prepared by the soft chemical method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Comparative analysis between biogas flow in landfill and electrical resistivity tomography in Rio Claro city, Brazil

The biogas originated from anaerobic degradation of organic matter in landfills consists basically in CH4, CO2, and H2O. The landfills represent an important depository of organic matter with high energetic potential in Brazil, although with inexpressive use in the present. The estimation of production of the productive rate of biogas represents one of the major difficulties of technical order to the planning of capture system for rational consumption of this resource. The applied geophysics consists in a set of methods and techniques with wide use in environmental and hydrogeological studies. The DC resistivity method is largely applied in environmental diagnosis of the contamination in soil and groundwater, due to the contrast of electrical properties frequent between contaminated areas and the natural environment. This paper aims to evaluate eventual relationships between biogas flows quantified in drains located in the landfill, with characteristic patterns of electrical resistivity in depth. The drain of higher flow (117 m3 /h) in depth was characterized for values between 8000 Ω⋅m and 100.000 Ω⋅m, in contrast with values below 2000 Ω⋅m, which characterize in subsurface the drain with less flow (37 m3 /h), besides intermediary flow and electrical resistivity values, attributed to the predominance of areas with accumulation or generation of biogas.

First-principles simulation of elastic constants and electronic properties of GaN

The electronic and structural properties and elastic constants of the wurtzite phase of GaN, was investigated by computer simulation at Density Functional Theory level, with B3LYP and B3PW hybrid functional. The electronic properties were investigated through the analysis of the band structures and density of states, and the mechanical properties were studied through the calculus of the elastic constants: C11, C33, C44, C12, and C13. The results show that the maximum of the valence band and the minimum of the conduction band are both located at the Γ point, indicating that GaN is a direct band gap semiconductor. The following constants were obtained for B3LYP and B3PW (in brackets): C11 = 366.9 [372.4], C33 = 390.9 [393.4], C44 = 99.1 [96.9], C12 = 143.6 [155.2], and C13 = 107.6 [121.4].

Opto-electrical properties of single layer flexible electroluminescence device with ruthenium complex

In this work, a ruthenium hexafluorophosphate complex, [Ru(bpy)(3)](PF6)(2) in poly(methylmethacrylate) (PMMA) was employed to build a single layer light electrochemical cell on indium tin oxide polyester flexible substrate. The electroluminescence spectrum features a relatively broad band peaked near 625 run, with CIE (x,y) color coordinates of (0.61,0.39). The driving voltage is only 3 V, and for the maximum electrical current of 10 mA the brightness reaches 1 cd/m(2). Regarding the useful application of the device, its opto-electrical behavior under mechanical strain was studied considering the central curvature. In these situations, both electrical characterization in DC mode and luminance were analyzed. (C) 2007 Elsevier B.V. All rights reserved.

Processing and mechanical properties evaluation of glass fiber-reinforced PTFE laminates

A specific manufacturing process to obtain continuous glass fiber-reinforced RIFE laminates was studied and some of their mechanical properties were evaluated. Young's modulus and maximum strength were measured by three-point bending test and tensile test using the Digital Image Correlation (DIC) technique. Adhesion tests, thermal analysis and microscopy were used to evaluate the fiber-matrix adhesion, which is very dependent on the sintering time. The composite material obtained had a Young's modulus of 14.2 GPa and ultimate strength of 165 MPa, which corresponds to approximately 24 times the modulus and six times the ultimate strength of pure RIFE. These results show that the RIFE composite, manufactured under specific conditions, has great potential to provide structural parts with a performance suitable for application in structural components. (C) 2012 Elsevier Ltd. All rights reserved.

Interaction between bradykinin potentiating nonapeptide (BPP9a) and beta-cyclodextrin: A structural and thermodynamic study

Herein, we demonstrate the physical and chemical characterizations of the supramolecular complex formed between beta-cyclodextrin (beta CD) and bradykinin potentiating nonapeptide (BPP9a), an endogenous toxin found in Bothrops jararaca. Circular dichroism results indicate a conformational change in the BPP9a secondary structure upon its complexation with beta CD. Nuclear magnetic resonance results, mainly from NOESY experiments, and theoretical calculations showed a favorable interaction between the tryptophan residue of BPP9a and the beta CD cavity. Thermodynamic inclusion parameters were investigated by isothermal titration calorimetry, demonstrating that beta CD/BPP9a complex formation is an exothermic process that results in a reduction in entropy. Additionally, in vitro degradation study of BPP9a against trypsin (37 degrees C, pH 7.2) showed higher stability of peptide in presence of beta CD. This beta CD/BPP9a complex, which presents new chemical properties arising from the peptide inclusion process, may be useful as an antihypertensive drug in oral pharmaceutical formulations. (C) 2011 Elsevier B.V. All rights reserved.