[en] Short communication

[en] Orthorhombic zirconia was partially or totally stabilized with niobia by using a zirconium hydroxide gel and niobium ammonium oxalate. The Zr₈ Nb₂ O₂₁ superstructure type was obtained for 11.1 mol% of niobia. (author)

[en] The PZT thin film thickness (< 3 μm)determines the electrical, ferro electrical and electro optical properties of these materials. Several analytical techniques have been used to determine the film thickness as ellipsometry, X-ray diffraction and scanning electronic microscopy (SEM). We have prepared thin films from citrate solution (Pechini's method) and they have dip coating deposited on glass substrates. Solutions with different viscosity were used and the number of dips were varied in order to produce films with several thickness. In this work X-ray fluorescence was used to measure the film thickness using values of thickness obtained by SEM to produce a calibration curve: fluorescent intensity versus thickness. (author)

[en] Currently, the removal of contaminants such as wastewater dye has become an essential task. In view of this, improving the performance of the adsorbents in order to improve the adsorption technique and reduce the total cost of the adsorption process is of great interest to the industrial sector. This study investigated the adsorption process of natural and purified bentonite clay adsorbents, using rhodamine B in an aqueous media. Rhodamine B is very toxic to aquatic organisms and may cause long-term adverse effects in the aquatic environment. These clays were used both in the natural form and after purification by centrifuge. All adsorbents were characterized. The kinetics and equilibrium isotherms were studied. In equilibrium, the Freundlich isotherm model was the best fit to the experimental data. In kinetics study, the data were best fit by the pseudo-second order model. The purified clays efficiently removed the rhodamine B. (author)

[en] α-TCP microspheres were obtained by atomizing aqueous slurries containing 50 wt% of low crystallinity α-TCP and 1 wt% of citric acid. Poly(ethylene glycol) and poly(vinyl alcohol) were tested as a binder. The spray drying process yielded to microspheres with mean diameter around 20 μm and sphericity (horizontal and vertical length ratio) closest to one, which is essential to many applications, such as drug delivery and injectability of cements. The addition of binders was necessary to decrease the amount of loose particles and to improve powder flowability but it also caused a reduction in wettability and surface area. Best results were achieved with 3 wt% of PVA, as the microspheres presented the highest specific surface area, wettability, and sphericity. The microspheres prepared in this study may be used as injectable bone cements precursor since their geometry and flowability would favor paste homogeneity and injectability overcoming many drawbacks of today’s injectable bone cements. (author)

[en] The study and development of ceramic composites are important because of the properties that these materials can provide, such as high dielectric constant and low dielectric loss in the RF and microwave range. Such characteristics make this type of material appropriate to several segments, such as in the telecommunication sector, especially in dielectric resonator antenna (DRA). Ceramic composites provide new materials with a range of properties that can be controlled through the phases to meet the specifications of a given application. This study aimed to synthesize and characterize the composite based on hexaferrite (BFO) and ceramics based on bismuth (BZN), aiming application as DRA. The composites were characterized by FTIR, XRD, and SEM. The composites presented a compact and heterogeneous microstructure, indicating that the sintering at 1000 °C/150 min was adequate for obtaining the ceramic composites; besides, BFO-BZNβ composite was shown to be less porous than the composite BFO-BZNα. (author)

[en] In this study, the production of a technical porcelain, for the ceramic dielectric applications by using economical natural raw materials, was investigated. The basic porcelain composition was selected consisting of 30 wt% kaolin, 45 wt% potash-feldspar and 25 wt% quartz. The obtained phases in the sintered samples were investigated by X-ray diffraction, Fourier transform infrared spectroscopy analysis, and scanning electron microscopy images. It has been confirmed by these techniques that the main crystalline phases were quartz and mullite. Dielectric measurements of technical porcelains have been carried out at 1 kHz from room temperature to 200 °C. The dielectric constant, loss factor, dielectric loss tangent, and resistivity of the porcelain sample sintered at 1160 °C were 22-25, 0.32-1.80, 0.006-0.07, and 0.2-9 x 10"1"3 Ω.cm, respectively. The value of dielectric constant was significantly high when compared to that of conventional porcelains which did not exceed generally 9. (author)

[en] Ni_0_._7Zn_0_._3Fe_2O_4 ferrospinel was synthesized by combustion and its catalytic performance in methyl and ethyl esterification of the soybean oil was investigated. The samples were characterized by X-ray diffraction, Rietveld refinement analysis, energy dispersive X-ray fluorescence spectroscopy, Fourier transform infrared spectroscopy, textural analysis, scanning electron microscopy, density by picnometry, particle size analysis, thermogravimetric analysis, magnetic measurements, and catalytic tests. The synthesis was efficient resulting in a ferrospinel with single phase Ni_0_._7Zn_0_._3Fe_2O_4 with crystallite size of 20 nm, high surface area (86 m"2/g) and saturation magnetization of 18 emu/g. The ferrospinel had promising catalytic activity in both reaction conditions studied, being more active in the conversion of soybean oil to biodiesel in methyl esterification with an average conversion of 93.9±2.8%. (author)

[en] Short communication

[en] Short communication