Abstract Heterogeneous catalysts, especially those produced with functionalized clays, can be used for methyl transesterification at moderate temperatures. The use of bentonite clay functionalized by potassium compounds (KF, KOH, K2CO3, KCl and K2SO4) in the methyl transesterification of cottonseed oil is the object of the present study. The catalysts were produced by contacting aqueous solutions with the clay and subsequent drying. The catalysts were characterized by Hammett indicators to determine alkalinity. The methyl transesterification reactions were made in a flask with stirring and reflux at 70°C for 2 h. The performance evaluation of the reaction was carried out using regression between the absorption band area and the concentration of a biodiesel-oil mixture by infrared spectroscopy. The catalytic activity is directly associated with the alkaline character of the catalysts. The catalysts produced with KCl and K2SO4 did not show conversion in the methyl transesterification reaction, while the catalysts produced with KF, KOH and K2CO3 showed a conversion greater than 90%.

This paper evaluates the effect of adding glycerol to the electrodeposition bath on the deposition efficiency and characteristics of Ni-Mo coating in concentrations ranging from 0.07 to 0.82 mol.L-1. Evaluation of the corrosion resistance was performed by means of weight loss tests in four different periods of immersion. Electrochemical techniques, such as obtaining polarization curves, linear polarization resistance, corrosion current density, corrosion potential, and electrochemical impedance spectroscopy were applied. Corrosion measurements were obtained in 0.5 mol.L-1 NaCl acid solution and 0.5 mol.L-1 NaOH alkaline solution. The morphology and microstructures of electrodeposited were analyzed using Scanning Electron Microscopy and Spectrometry X-Ray Diffraction. The effect of glycerol on Ni-Mo hardness was evaluated by Vickers microhardness measurements. The presence of glycerol in the electrodeposition bath increased the grain size and decreased the hardness of the coating. However, it promoted the formation of a more compact and less porous coating, increasing the corrosion resistance of the coating. Moreover, the addition of 0.82 mol.L-1 glycerol increases current efficiency, thereby reducing the amount of energy consumed during electroplating.

High density polyethylene and high density polyethylene-clay nanocomposites were produced using direct solvent polymerization and a Ziegler catalyst system (TiCl4 and triethylaluminum in hexane). The produced polymer has a high average molecular weight and a multimodal molecular weight distribution composed of four distributions including a very high molecular weight component. The laboratory polymer has a thermal stability in inert atmosphere similar to the commercial high density polyethylene produced by Braskem. In oxidant atmosphere the produced polymer presents three thermal oxidation events above 400ºC due to the combustion of low, medium and high molecular weight molecules. The thermal oxidation of the nanocomposites is shifted and reduced for high temperatures indicating an improvement in the thermal stability of the polymeric matrix due to the clay barrier effect for gases and volatile compounds.

Zinc electrodeposition is an economical process of Zn coating compared to conventional galvanic process. The galvanizing process is used in various industrial sectors to protect ferrous alloys during the corrosion process. In buildings, the galvanizing process is widely used to coat mortar protective screens. The electrodeposition of zinc has a relatively low cost compared to other coating materials for the same purpose; however, its corrosion resistance is lower than that of most protective deposits. This study evaluated the effect of adding glycerol to the electrodeposition bath on the corrosion resistance, deposition efficiency, morphology and microstructure of the zinc electrodeposit in concentrations ranging from 0.03 to 0.82 M. The electrodeposition was performed on carbon steel AISI 1020 with a current density of 10 mA.cm-2. The electroplating solution composition was 0.10 M ZnCl2, 2.80 M KCl and 0.32 M H3BO3. Electrodeposition time was 17.56 min, 5 µm thick coating, equivalent to the mass of 7.166E-3 g of zinc on the steel surface. Evaluation of the corrosion resistance was performed by means of the electrochemical tests of Anodic Voltammetry, Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) as well as Weight Loss tests in NaCl 0.5 M in 4 (four) different period of immersion. The morphology and microstructures of electrodeposited were analyzed using the techniques of Scanning Electron Microscopy (SEM) and Spectrometry X-Ray Diffraction (XRD). The presence of glycerol in the electrodeposition bath decreased the deposition efficiency; however, it increased corrosion resistance and promoted the formation of more compact and refined electrodeposited coatings. Moreover, the results showed that the corrosion rate does not vary linearly with the addition of glycerol.

In the present work the effect of substituting Mo with Nb on the glass forming ability and corrosion resistance of Fe-Co-Cr-M-Si-B-Y (M=Mo, Nb) ribbons with high corrosion resistance is investigated. The X-ray powder diffraction pattern indicates that the alloy containing both Nb and Mo presented greater glass forming ability than the alloy containing either of these elements separately. The results obtained indicate that Mo is more effective in enhancing corrosion resistance than the Nb in 4.0 M HCl solution. The alloy containing both Nb and Mo presented greater overall corrosion resistance than the alloy containing only one of these elements.

Electric-arc furnace dust (EAFD) is a by-product of steel production and recycling. This fine-grained material contains high amounts of zinc and iron as well as significant amounts of potentially toxic elements such as lead, cadmium and chromium. Therefore, the treatment and stabilization of this industrial residue is necessary. Concrete is a well-known suitable environment for stabilization/solidification of materials which have leachable elements in need of fixation. The effect of the EAFD content on the mechanical and chemical performance of Portland cement concrete is investigated in this paper. The effect of the EAFD content on the setting time of cement slurry was also analyzed. The axial compressive strength of the concrete samples increases with the EAFD addition in the range of 10 to 20 wt. (%) EAFD; also the tensile strength increases with the EAFD addition. An increase in EAFD content significantly increases the setting time of the concrete. The acetic acid leaching and water solubilization tests indicate low mobility of the potentially toxic elements from the EAFD concrete composite. The results of the immersion tests show that the addition of EAFD to the concrete seems to reduce chloride penetration, which may help prevent pitting corrosion in reinforced concrete.

Conventional sample holder cells used to the electric characterization of ceramics at high temperature consists of an alumina tube and platinum wires and plates using a complex design. The high cost materials used in the conventional sampler holder cell were replaced by stainless steel and conventional ceramics. The sample holder was validated by characterizing yttria-stabilized-zirconia in a temperature range of 25 to 700 ºC. The results do not present variations, discontinuity or unusual noise in the electric signals. Several samples were characterized without maintenance, which demonstrates that the sample holder is electric and mechanic adequate to be used to electrical characterization of ceramics up to 700 ºC.