Materials Science Forum Vols. 775-776

Abstract: Nanocomposites are a class of materials formed by hybrids of organic and inorganic materials, where the inorganic phase is dispersed at the nanometer level in a polymeric matrix. Several polymers have been used as matrices for the preparation of polymer / clay nanocomposite, among which, polyamide 6.6, by presenting excellent chemical, thermal and mechanical. The nanocomposites exhibit excellent properties the point of view optical, electrical and barrier, and reduced flammability. In this research, micro-porous membranes were obtained from the polyamide 6.6/argila montmorillonite nanocomposite, in order to verify its application in the separation water / oil. The results obtained by scanning electron microscopy (SEM) showed that the obtained membranes have a dense layer and a porous layer, and that after the test oil-water separation was observed that the relative flow (J/J0) was greater in compositions with 3% clay, 1.5 bar pressure.

Abstract: Modified montmorilonite additivated films of poly 3 (hydroxybutyrateco-8%-hydroxyvalerate) were formulated by solvent evaporation technique and then characterized by means of X-ray diffraction, scanning electron microscopy, atomic force microscopy and scanning differential calorimetry. A preliminary characterization using these analyses revealed the formation of nanocomposites with partially exfoliated and interlayered structures. These nanocamposites display changes in the crystalline structure of the precursor biodegradable polymer.

Abstract: The physico-chemical characteristics of attapulgite clay confer appropriate properties to their different industrial uses, such as: Drilling fluid, bleaching of vegetable oils, mineral and animal grease and oil absorbents, pet waste absorbents (pet litter), purification of drinking water etc. The aim of this study was the chemical modification of attapulgite originally from state of Piauí, for applications in polyester-based composites. The unmodified and modified clay were characterized by X-ray diffraction (XRD). In order to evaluate the interaction of clays with organic solvents, the test of Foster swelling with gasoline, diesel and toluene was conducted. The polyester resin-based composite and clay unmodified and modified in different percentages were molded by hand lay up technique and they were characterized by water sorption.

Abstract: Malignant tumors are caused by uncontrolled multiplication of cells in the body. It is possible to stop the growth of atypical cells by overheating (hyperthermia). By the magnetization process of magnetite nanoparticles, energy is dissipated as heat (Joule effect), producing increase of temperature. This causes the rupture of cancer cells. In this work, magnetic nanoparticles were synthesized by coprecipitation method and coated by biocompatible material (chitosan or castor oil). The samples showed required characteristics of nanocrystallinity, superparamagnetism and biocompatibility. This was deduced from hysteresis curve, thermal analysis and X-ray Diffraction data. Thus, the nanocomposite exhibits excellent features for use in vivo.

Abstract: A F138 austenitic stainless steel was solution heat treated, deformed by equal-channel angular pressing (ECAP) at 25, 100, 200, and 300°C. The equivalent strain was ~0.7 per pass and the applied equivalent strain varied from 0.7 to 4.2. The same material was also deformed by high pressure torsion (HPT) at 300 and 480°C, applying 6GPa pressure and 5 turns; the equivalent strain was ~ 4.5 at r/2 and ~5.2 at the vicinity of the disk edge. Microstructure evolution was observed by transmission electron microscopy (TEM) electron back-scattered diffraction (EBSD) and X ray diffraction. The effect of severe plastic deformation was studied at 25 and 300°C: at 25°C further deformation led to the formation of grain subdivision inside deformation bands and the onset of new grains formation after 2 ECAE passes. The deformation at 300 and 400°C up to 6 passes lead to the formation of recrystallized grains of the order of 100 nm size.

Abstract: Obtaining membranes from polymer nanocomposites have attracted interest of researchers because they use low levels of charge for improvement in barrier properties. In this study, membranes from poly (imide ether) (PEI) and poly (sulfone ether) (PES) were produced by the solvent evaporation technique, using as solvent: chloroform to PEI and dimethylformamide (DMF) to PES; and the clay Brasgel PA was used as load. The results showed that, by XRD, PEI membranes have apparently a structure of micro-composites and / or interleaved structure. Those obtained with PES had an exfoliated structure and / or partially exfoliated one. However, for the composition of PES with 5% clay, there was a small shoulder, therefore demonstrating perhaps an intercalated structure and/or an exfoliated part. By SEM, it was observed that all the membranes are apparently dense, but the behavior is differentiated by changing the matrix of the membranes.

Abstract: The bentonite clay fillers are mostly used for the development of nanocomposites, due to having characteristics which provide to obtain in nanometric particles. The bentonite clay was treated with an ammonium quaternary salt to modify it to organophilic clay. The polymeric membranes and nanocomposites were prepared using the phase inversion technique. The bentonite and organophilic clays were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The membranes were characterized by XRD. The results of XRF, XRD and FTIR confirmed the presence of quaternary ammonium salt in the organoclay structure. The XRD diffraction patterns of nanocomposites membrane showed exfoliated and/or partially exfoliated structure. According to the obtained results, it could be seen that the treatment performed on the surface of the clay was quite promising and efficient to be added as nanofillers on polymeric membranes.

Abstract: In this work, were obtained nanocomposite membranes polyamide66/Paraíba bentonite clay, treated with a quaternary ammonium salt in order to make it organophilic. The membranes were prepared as thin films using the technique of phase inversion from the nanocomposites obtained by solution. The membranes were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TG) and scanning electron microscopy (SEM). By means of X-ray diffractogram, it was revealed that the membranes remained organically treated clay presented exfoliated and/or partially exfoliated structure. From curves of DSC and TG, it was observed that membrane of PA66 with 3% w/w of with treatment clay showed higher thermal stability compared with the same content of clay without treatment. From the SEM photomicrographs, there was a selective layer (skin filter) on top and one porous layer at the bottom of all membranes studied. Moreover, it was verified that the presence of clay provided a significant structural modification in the membranes of polymer nanocomposites.

Abstract: The ferritic stainless steels have been used in applications where suitable properties are required at high temperatures. These metallic materials are applied, for example, as interconnects in ITSOFC fuel cells (600-800 °C).The aim of this work is to produce a La, Sr and Co based coatings using the dip-coating and spray pyrolysis techniques, on an AISI 430 ferritic stainless steel. These coatings are known for acting as barriers, increasing the oxidation resistance when applied on stainless steel at high temperatures. The obtained coatings were heat treated at 800 °C for 120 min, seeking the formation of La_0,6Sr_0,4Co,and, then characterized regarding their morphology and microstructure using scanning electron microscopy (SEM) and X-ray diffraction. The results showed that the coatings obtained by spray pyrolysis covered regularly the surface while the ones obtained by dip-coating exhibited some crack formation.

Abstract: Platinum is known as the best catalyst for fuel cells reactions, because it presents the best catalytic activity and stability, mainly in acidic media. However, due to the high cost of platinum and its lower availability, the development of platinum-free catalysts for Alkaline Polymer Electrolyte Fuel Cells has been proposed. This work aims to compare catalysts characteristics obtained from two different synthesis methods. Ni catalysts were obtained by the impregnation/reduction method and by electroless deposition. The morphology of the electro-catalysts obtained were characterized by SEM-EDS and the electrochemical behavior was evaluated by Cyclic Voltammetry. And the composition of the catalysts obtained by the impregnation/reduction method was analyzed by Rutherford Backscattering Spectroscopy. The results obtained showed that the catalyst elaborated by the impregnation/reduction method developed higher current densities values than the catalyst elaborated by electroless deposition.