This paper discusses the applicability of an electronic tongue (e-tongue) based on capacitance measurements to determine the water content in ethanol. The e-tongue consisted of an array of interdigitated electrodes coated with ultrathin films of gallium nitrate and titanium dioxide, which were robust against attack by ethanol. Principal Component Analysis (PCA) was used to treat the capacitance data for discriminating ethanol/water mixtures even in cases with very small water contents. Discrimination is easier if the water added to ethanol contains ions, as is the case of tap water or if NaCl is added to the mixtures. With this e-tongue we were able to quantify the water content through a linear relationship between the first principal component (PC1) and the added water to the biofuel. Therefore, we have proven to be possible to measure the water content precisely, which is one of the major problems in ethanol biofuel adulteration nowadays.

The Mg2+ homovalent substitution by Li+/Sc3+ cations at the B-site sub-lattice of the lead magnesium niobate (PMN) perovskite structure was studied in this work. Through structural and electrical analyses, it was observed that the dopant pair effectively substituted the Mg cation, although an addition limit close to 2.5mol% of dopants was observed. Up to this concentration level, the dopant pair does not affect the perovskite phase stability, and thus, pyrochlore free ceramics with a Tm value of −6°C and 19,000 of electric permittivity were obtained. As a consequence of the substitution, the 1:1 chemical ordering at the B-site was changed, leading to a less diffuse ferroelectric–paraelectric phase transition even despite the increase of the relaxor character. However, a 5.0mol% addition of Li/Sc provoked the precipitation of a small quantity of pyrochlore phase that caused a deterioration of the ceramic electrical properties.

The effects of silver insertion on the TiO2 photocatalytic activity for the degradation of diclofenac potassium were reported here. Techniques such as X-ray diffraction, scanning electron microscopy and UV-Vis spectroscopy were used to comprehend the relation between structure and properties of the silver-modified TiO2, thin films obtained by the sol-gel method. The lattice parameters and the crystallinity of TiO2 anatase phase were affected by inserted silver, and the film thickness increased about 4 nm for each 1 wt.% of silver inserted. The degradation of diclofenac potassium and by-products reached an efficiency of 4.6 mg(C) W-1 when the material was modified with silver. Although the first step of degradation involves only the photochemical process related to the loss of the chlorine and hydrogen atoms. This cyclization reaction leads to the formation of intermediate, which degradation is facilitated by the modified material. (C) 2007 Elsevier B.V. All rights reserved.

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%.

Nickel nanoparticles into silica–carbon matrix composites were prepared by using the polymeric precursor method. The effects of the polyester type and the time of pyrolysis on the mesoporosity and nickel particle dispersion into non-aqueous amorphous silica–carbon matrix were investigated by thermogravimetric analysis, adsorption/desorption isotherms and TEM. A well-dispersed metallic phase could be only obtained by using ethylene glycol. Weightier polyesters affected the pyrolysis process due to a combination of more amounts of carbonaceous residues and delaying of pyrolysis process. The post-pyrolyzed composites were successfully cleaned at 200°C for 1h in oxygen atmosphere leading to an increase in the surface area and without the occurrence of carbon combustion or nickel nanoparticles oxidation. The matrix composites presented predominantly mesoporous with pore size well defined in 38Å, mainly when tetraethylene glycol was used as polymerizing agent.

The present work reports the effects caused by barium on phase formation, morphology and sintering of lead magnesium niobate–lead titanate (PMN–50PT). Ab initio study of 0.5Pb(Mg1/3Nb2/3)O3–0.5(BaxPb(1−x)TiO3) ceramic powders, with x=0, 0.20, and 0.40 was proposed, considering that the partial substitution of lead by barium can reestablish the equilibrium of monoclinic–tetragonal phases in the system. It was verified that even for 40mol% of barium, it was possible to obtain pyrochlore-free PMN–PT powders. The increase of the lattice parameters of PMN–PT doped-powders confirmed dopant incorporation into the perovskite phase. The presence of barium improved the reactivity of the powders, with an average particle size of 120nm for 40mol% of barium against 167nm for the pure sample. Although high barium content (40mol%) was deleterious for a dense ceramic, contents up to 20mol% allowed 95% density when sintered at 1100°C for 4h.

The influence of lithium on the structural characteristics of PMN-PT ceramic was studied. The synthesis of PMN-PT powders using this precursor leads to the formation of high amount of perovskite phase. The insertion of Li+ ions in B-site affects the microstructure because the rise in mass transport changes the mechanical characteristics of sintered ceramic. Higher values of K m and T m were gotten when lithium is inserted into perovskite phase. Secondary phase was found when lithium content increase beyond 1 mol%, besides the occurrence of transgranular fractures in sintered ceramic. Also, the additive acts increasing the relaxor behavior.

This study aims to demonstrate how the chemical homogeneity of B cations affects the microstructure and electrical responses of (1-x) PMN-xPT ceramics. Two methodologies were employed to synthesize three different compositions, with x assuming the values 0.10, 0.28, and 0.35. If compared to conventional method, the Ti-modified columbite route, which is characterized by higher B cation homogeneity, leads to PMN-PT powders and ceramics with lower content of PNT pyrochlore phase and, for 0.65PMN-0.35PT composition, minor amount of tetragonal phase is found. Conclusively, PMN-PT ceramics obtained by modified route favors B cations homogeneity, enhancing the dielectric, ferroelectric and piezoelectric properties.

This study proposes to synthesize (1-x)PMN-xPT powders, where 0.10 < x < 0.45, using the T-modified columbite route. This methodology consists in the preparation of the MNT columbite precursor via the polymeric precursor method, followed by the solid state reaction with PbO to get the PMN-PT powders. It was verified that from 15 mol% of Ti, the MNT presents the coexistence of two main phases with different crystal symmetry: Rutile and Columbite. However, the synthesis of (1-x)PMN-xPT powders is not affected by this event. A detailed study of structural effects in MNT and PMN-PT powders as function of Ti content was made using the Rietveld method. It was also demonstrated that powders possess high chemical and microstructural homogeneity.

A recent and innovative method to include Ti into the columbite precursor has permitted to synthesize 0.9PMN–0.1PT powders with high homogeneity. The present work describes this methodology, named modified columbite method, showing that the reaction between MNT and PbO at 800°C for 2h results in perovskite single-phase. The crystal structure alterations in the columbite and perovskite phases obtained by this methodology and the effects of potassium doping were investigated by the Rietveld method. Changes in the powder morphology, density and weight loss during the sintering process were also studied. Conclusively, potassium does not affect significantly the perovskite amount, but reduces the particle and grain sizes. This dopant also changes the relaxor behavior of 0.9PMN–0.1PT ceramic, reducing the dielectric loss and enhancing the diffuseness of the phase transition.

The complex perovskite compound 0.9PbMg1/3Nb2/3O3-0.1PbTiO3 is one of the most promising relaxor ceramic because the addition of lead titanate increases Tm by about 5°C/mol% from intrinsic Tm value for pure PMN (near –7 to -15°C). A Ti-modified columbite precursor was used to prepare PMN-PT powders containing single perovskite phase. This variation on columbite route includes Ti insertion in MgNb2O6 orthorhombic structure so that individual PT synthesis becomes unnecessary. Furthermore, effects of Li additive on columbite and PMN-PT structures were studied by XRD to verify the phase formation at each processing step. XRD data were also used for the structural refinement by Rietveld method. The additive acts increasing columbite powders crystallinity, and the amount of perovskite phase was insignificantly decreased by lithium addition. By SEM micrographs it was observed that Li presence in PMN-PT powders leads to the formation of rounded primary particles and for 1mol% of additive, the grain size is not changed, different from when this concentration is enhanced to 2mol%.

The solid solution 0.9PbMg(1/3)Nb(2/3)O(3-)0.1PbTiO(3) is one of the most widely investigated relaxor ceramic, because of its high dielectric constant and low sintering temperatures. PMN-PT powders containing single perovskite phase were prepared by using a Ti-modified columbite precursor obtained by the polymeric precursor method. Such precursor reacts directly with stoichiometric amount of PbO to obtain pyrochlore-free PMN-PT powders. The structural effects of K additive included in the columbite precursor and 0.9PMN-0.1PT powders were also studied. The phase formation at each processing step was verified by XRD analysis, being these results used for the structural refinement by the Rietveld method. It was verified the addition of K in the columbite precursor promotes a slight increasing in the powder crystallinity. There was not a decrease in the amount of perovskite phase PMN-PT for 1mol% of K, and the particle and grain size were reduced, making this additive a powerful tool for grain size control.

Single-phase perovskite 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 (PMN–PT) powders were prepared by using a Ti-modified columbite precursor (MNT) obtained by the polymeric precursor method. The innovation consists in the preparation of Ti-modified columbite in order to react directly with a stoichiometric amount of PbO to obtain pyrochlore-free PMN–PT powders. It has been shown that titanium oxide forms a solid solution with columbite (MN) and does not affect the obtaining of a single-phase columbite precursor. Thus, a high amount of perovskite phase can be obtained by reaction with PbO at 800°C for 2h. Effects of K and Li additives on the structure of MNT and PMN–PT were studied. X-ray diffraction studies were carried out to verify the phase formation at each processing step and these data were used for structural refinement by the Rietveld method. Both K and Li additives increase the crystallinity of MNT powders, being this effect more intense for the Li-doped samples. For PMN–PT samples the additives cause an insignificant decrease in the amount of perovskite phase. The morphology of the PMN–PT powder depends on the type of the additive.

The effect of lead excess on the pyrochlore-type formation in Pb(Mg1/3Nb2/3)O3 (PMN) powders has been investigated. The polymeric precursor method was used in the synthesis of the columbite in association to the partial oxalate method to synthesize the PMN powder samples. Structure refinement of the columbite precursor and PMN powders was carried out using the Rietveld method. The quantitative phase analysis showed that the amount of perovskite phase is not affected by PbO excess, but a great excess drives the pyrochlore-type formation so that 3wt.% of PbO causes the predominance of Mg-containing pyrochlore phase. Using the refined data obtained from the Rietveld refinement, the compositional fluctuation in the perovskite phase was calculated from Nb/Mg ratio values and Pb occupation factor. Mg inclusion occurs concomitant with Pb one into PMN perovskite phase and this effect is directed by PbO excess during powder synthesis.

The grain size distribution shape did not change during normal grain growth but this distribution widened and flattened during the abnormal grain growth. The initial smaller mean size of carbonitrides and/or the highest homogeneity of niobium carbonitride size distribution of the samples submitted to thermal cycles (“sc”) in comparison with the normalized samples (“sn”) increased the abnormal grain growth temperature from 1373 K at “sn” series to 1473 K at “sc” series.

A study to achieve the control of polymer particles obtained by propylene polymerization with Ziegler-Natta catalyst based on TiCl3 was carried out. Two different catalysts were employed: Cat. A was made through TiCl4 reduction with diethylaluminium chloride (DEAC) in the presence of di-n-butyl ether (DBE) as first internal base and Cat.B was prepared through TiCl4 reduction with DEAC in the presence of DBE as first internal base and ethyl benzoate (EB) as second internal base, added after the reduction and before the thermal treatment at 70°. The progress of propylene polymerization was evaluated. Fragmentation of catalyst particles and a “replica” phenomenon were observed during the polymerization. The rupture of polypropylene particles was attributed to their friability and to the uncontrolled kinetics of the polymerization.

Blends of thermoplastic polyurethane elastomer (TPU) and ABS resin (acrylonitrile-butadiene-styrene) were observed by SEM (scanning electron microscopy) before and after their treatment with methyl ethyl ketone (MEK). Samples were treated with MEK for different periods of time and dried at two temperatures in order to optimize the etching conditions. It was found that 3 h of etching is adequate to reveal the phase morphology of these blends. In contrast, a 4 h period has provoked serious artifacts in the samples and no information about phase structure could be obtained. At appropriate conditions, this technique can be used to quantitatively estimate the component dispersion in these blends.