Structural characterization of blends containing both PVDF and natural rubber latex

Films containing different volumes of latex of natural rubber (NR) in a fixed mass of poly (vinylidene fluoride) (PVDF) powder were fabricated by compressing under annealing a mixture of both materials without using any solvent. This is an important issue keeping in mind that these films have to be used in the future as biomaterials in different applications once the solvents that are used to dissolve the PVDF become toxic to human. The films with different percentage of latex in PVDF were characterized using microRaman scattering and Fourier transform infrared absorption (FTIR) spectroscopies, thermomechanical techniques using thermogravimetry (TG), differential scanning calorimetry (DSC), dynamical-mechanical analysis (DMA) and scanning electron microscopy (SEM). The results showed that the latex of NR and PVDF do not interact chemically, leading to the formation of a polymeric blend with high thermal stability and mechanical properties suitable for applications involving bone (prostheses, for instance). Besides, the results recorded using the micro-Raman technique revealed that for a fixed amount of PVDF the higher the amount of latex in the blend, the better the miscibility between both materials. Copyright (c) 2005 John Wiley & Sons, Ltd.

EXAFS investigation on Sb incorporation effects to electrical transport in SnO2 thin films deposited by sot-gel

The effect of Sb doping in SnO2 thin films prepared by the sol-gel dip-coating (SGDC) process is investigated. Electronic and structural properties are evaluated through synchrotron radiation measurements by EXAFS and XANES. These data indicate that antimony is in the oxidation state W, and replaces tin atoms (Sn4+), at a grain surface site. Although the substitution yields net free carrier concentration, the electrical conductivity is increased only slightly, because it is reduced by the high grain boundary scattering. The overall picture leads to a shortening of the grain boundary potential, where oxygen vacancies compensate for oxygen adsorbed species, decreasing the trapped charge at grain boundary. (c) 2007 Elsevier Ltd. All rights reserved.

Thermal characterization of an ultrasonic density-measurement cell

An ultrasonic density-measurement cell is experimentally characterized as a function of temperature. The measurement of propagation velocity and density of several liquids is performed in the 15 degrees C-40 degrees C temperature range. Results are compared to the tabulated values in the case of distilled water, showing an accuracy of 0.07% for the propagation velocity. The cell was tested with distilled water, alcohol, and homogenized milk, and density values are compared to those obtained with a pycnometer, showing 0.2% accuracy in density measurement for stabilized temperature and 0.4% accuracy under thermal gradient conditions.

Effect of magnesium on the properties of LiNbO3 thin films prepared from polymeric precursors

The effect of magnesium addition on the phase formation, microstructure and electric and ferroelectric properties of LiNbO3 thin films prepared through polymeric precursors was analyzed. By X ray diffraction no secondary phase was observed with the increase of magnesium concentration. Comparing to pure LiNbO3, the addition of 0.5 and 1.0 mol% of Mg+2 increased of the dielectric constant, while 2.0 mol% decreased it. It was noticed that the increase in additive concentration decreases the ferroelectric remanent polarization and increases the coercive field.

Effect of preannealing on the morphology of LiTaO3 thin films prepared from the polymeric precursor method

Lithium tantalate (LiTaO3) thin films with 50:50 stoichiometry were deposited on silicon (100) substrates with two layers by the spin coating method using a polymeric organic solution. In order to study the influence of preannealing on the crystallinity, microstructure, grain size and roughness of the final film, two annealing procedures, slow preannealing and fast preannealing, were used. X-ray diffraction (XRD) results showed that LiTaO3 thin films are polycrystalline. It was observed by scanning electron microscopy (SEM) that the thin film, which had been thermally treated using slow preannealing, was characterized by a dense and homogeneous surface. The atomic force microscopy (AFM) studies showed that the roughness is strongly influenced by preannealing temperature. (C) 2003 Elsevier B.V. All rights reserved.

Characterization of an all sol-gel electrochromic device WO3/Ormolyte/CeO2-TiO2

Electrochemical lithium intercalation in thin films of CeO2-TiO2 and WO3, prepared by the sol-gel technique was investigated with cyclic voltammetry and spectroelectrochemical techniques in propylene carbonate solutions. A solid state system having the configuration WO3/Ormolyte/CeO2-TiO2 has been assembled. The solid electrolyte, an organically modified electrolyte (ormolyte), was prepared with different [O]/[Li] ratios. The transmittance variation of this system during a potentiostatic step from -0.7 V to 0.8 V was about 35% at 550 nm.

Characterization of tin oxide based sol-gel coatings on borosilicate glasses by X-ray reflectivity

The X-ray reflectivity technique was applied in the study of tin oxide films deposited by sol-gel dip-coating on borosilicate glasses. The influence of the withdrawal speed and temperature of thermal treatment on the film structure was analyzed. We have compared the thermal evolution of the density and the shrinkage of the films with these properties measured for the monolithic xerogel by helium picnometry and thermomechanical analysis. In agreement with the Landau-Levich model, the layer thickness increases by increasing the withdrawal speed. Nevertheless, it decreases with the increase of the thermal treatment temperature, due to the densification process. The values of apparent density are smaller than the skeletal density, which shows that the films are porous. The comparison between the film and the monolith indicates that shrinkage during firing is anisotropic, occurring essentially perpendicular to the coating surface.

Microstructure and electrical properties of perovskite (Pb, La)TiO3 thin film deposited at low temperature by the polymeric precursor method

High-quality (Pb, La)TiO3 ferroelectric thin films were successfully prepared on a Pt(111)/Ti/SiO2/Si(100) substrate for the first time by spin coating, using the polymeric precursor method. The X-ray diffraction patterns show that the films are polycrystalline in nature. This method allows for low temperature (500 degrees C) synthesis, a high quality microstructure and superior dielectric properties. The effects on the microstructure and electrical properties were studied by changing the La content. The films annealed at 500 degreesC have a single perovskite phase with only a tetragonal or pseudocubic structure. As the La content is increased, the dielectric constant of PLT thin films increases from 570 up to 1138 at room temperature. The C-V and P-E characteristics of perovskite thin films prepared at a low temperature show normal ferroelectric behavior, representing the ferroelectric switching property. The remanent polarization and coercive field of the films deposited decreased due to the transformation from the ferroelectric to the paraelectric phase with an increased La content. (C) 2001 Kluwer Academic Publishers.

Crystallographic, dielectric and optical properties of SrBi2Ta2O9 thin films prepared by the polymeric precursor method

Strontium bismuth tantalate thin films were prepared on several substrates (platinized silicon (PvTi/SiO2/Si), n-type (100)-oriented and p-type (111)-oriented silicon wafers, and fused silica) by the solution deposition method. The resin was obtained by the polymeric precursor method, based on the Pechini process, using strontium carbonate, bismuth oxide, and tantalum ethoxide as starting reagents. Characterizations by XRD and SEM were performed for structural and microstructural evaluations. The electrical measurements, carried on the MFM configuration, showed P-r values of 6.24 muC/cm(2) and 31.5 kV/cm for the film annealed at 800 degreesC. The film deposited onto fused silica and treated at 700 degreesC presented around 80 % of transmittance.

Characterization of dense lead lanthanum titanate ceramics prepared from powders synthesized by the oxidant peroxo method

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

The effect of TiO(2) on the microstructural and electrical properties of low voltage varistor based on (Sn,Ti)O(2) ceramics

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influence of TiO2 and AI(2)O(3) on the electrical and microstructural properties of SnO2 ceramics obtained by the Pechini method

Tin oxide has wakened up great scientific and technological interest for its potential use in varistors production and as gas sensor. In order to improve the microstructural and electrical properties in SnO2 varistor ceramics, the influence of differents dopants used, like TiO2 and Al2O3, is under research. The effect of TiO2 and Al2O3 on the properties of Sn-Co-Nb varistor systems obtained by the Pechini method has been investigated in this work. Characterization of synthesized raw material was performed by X-Ray Diffraction (XRD) and Scanning Electronic Microscopy (SEM). The microstructural and electrical characterization of sintered samples show that the TiO2 favors the grain growth and the Al2O3 contributes to the decrease it, effect that is manifested in the Sn-Co-Nb varistor systems. Breakdown field increase up to 6300V/cm with increasing Al2O3 content and non-linear coefficients with alpha=22 were obtained.

Microstructure and phase evolution of SrTiO3 thin films on Si prepared by the use of polymeric precursors

The use of polymeric precursors was employed in preparing SrTiO3 thin films by dip coating using Si (111) as substrate. Crack free films were obtained after sintering at temperatures ranging from 550 to 1000°C. The microstructure, characterized by SEM, shows the development of dense polycrystalline films with smooth surface and mean grain size of 52 nm, for films sintered at 1000°C. Grazing incident angle XRD characterization of these films shows that the SrTiO3 phase crystallizes from an inorganic amorphous matrix. No intermediate crystalline phase was identified.

Properties of BaBi2Ta2O9 thin films prepared by chemical solution deposition technique for dynamic random-access memory applications

We report on the properties of BaBi2Ta2O9 (BBT) thin films for dynamic random-access memory (DRAM) and integrated capacitor applications. Crystalline BBT thin films were successfully fabricated by the chemical solution deposition technique on Pt-coated Si substrates at a low annealing temperature of 650°C. The films were characterized in terms of structural, dielectric, and insulating properties. The electrical measurements were conducted on Pt/BBT/Pt capacitors. The typical measured small signal dielectric constant and dissipation factor, at 100 kHz, were 282 and 0.023, respectively, for films annealed at 700°C for 60 min. The leakage current density of the films was lower than 10-9 A/cm2 at an applied electric field of 300 kV/cm. A large storage density of 38.4 fC/μm2 was obtained at an applied electric field of 200 kV/cm. The high dielectric constant, low dielectric loss and low leakage current density suggest the suitability of BBT thin films as dielectric layer for DRAM and integrated capacitor applications.

Electrode poling of cellular polypropylene films with short high-voltage pulses

Recently, piezoelectric cellular polypropylene (PP) was proposed as a new type of quasi-ferroelectric. The observed hysteresis of the charge density as a function of the electric field could be explained as field-dependent charging inside the gas-filled voids. Interestingly enough, the measurable poling behavior of the macroscopic dipoles formed by charges that are trapped at the internal void surfaces is phenomenologically completely identical to the cooperative poling behavior of microscopic molecular dipoles in ferroelectric polymers. Therefore, it can be assumed that charge separation (or charge redistribution) and subsequent trapping in cellular PP is a rather fast switching process. In order to examine the poling dynamics, we developed an experimental setup for pulsed poling. High-voltage pulses with a duration of 45 μs (FWHM) were applied in direct contact to two-side metallized cellular PP films. The pulsed poling yields piezoelectricity in the cellular PP. We study and discuss the dependence of the resulting piezoelectricity on the poling field. We also characterize the charge separation during application of higher electric poling fields of up to -10 kV in direct contact to the two-side metallized films for longer times.