Materials Science Forum Vols. 775-776

Abstract: The worldwide demand for ornamental stones in building construction is motivating the use of their wastes, generated during fabrication, to produce synthetic stones. This work has as its objective to investigate the production of a synthetic ornamental marble (SOM) under vacuum and vibro-compression processing of a polyester matrix composite with addition of marble waste as a filler. Rectangular SOM composite plates were subjected to compression and flexural mechanical tests. Samples were analyzed to obtain the density, water absorption, and microstructure. The SOM composites presented properties within the expected range of an artificial stone, which indicates that the applied process is suitable for production of this type of material.

Abstract: The coconut fibers are an abundant source of natural materials, renewable, high-availability, accessibility and biodegradable. This great interest in developing and using materials made from renewable sources occurred mainly in response to the global attention for the use of natural products and the preservation of the environment. In this paper, coconut fibers received different surface treatments, environmentally friendly, based on high values of temperature and pressure. The coconut fibers were characterized by FTIR, SEM, water absorption, weight loss and wetting angle. The results indicated that the methods were effective, changing the chemical composition of the fiber as well as their surface morphology and raising the hydrophobic character. Thus, the compatibility between the fiber and the polymeric matrix should be increased, providing the application of these new fibers in the development of composite materials.

Abstract: . Polymeric materials based on petroleum have generated a major problem for the environment because they are produced by non-renewable sources. Many studies are being conducted to propose alternatives to obtain polymers from renewable raw materials sources. The disadvantage of this alternative is the use of food sources for polymer production but this is avoided when using the residual frying oil. Aiming to obtain polymer-based urethanes, pretreated residual frying oil samples were submitted to various conditions of hydroxylation and analyzed by FT-IR, where it was possible to observe the presence of-OH groups. To optimize the process of hydroxylation a new research was conducted to determine the concentrations of formic acid and hydrogen peroxide that can generate polyols with high levels of hydroxylation index, suitable for the formation of urethanes.

Abstract: The consumption of plastic products over the years has been producing large numbers of waste material, which accumulate by landfill generating considerable environmental problems. Among biodegradable polymers, there is the PHB (poly-3-hydroxybutyrate), which has attracted more attention once it is obtained from renewable sources. This study aimed to prepare biodegradable nanocomposites by melt intercalation of PHB polymer in the natural vermiculite clay, in the ratios of 1, 3 and 6 wt%. The nanocomposites were obtained in an internal mixer coupled to a torque rheometer by Haake-Blucher, operating at 170°C, 50 rpm for 10 minutes. The material was triturated and then films were molded by compression under the conditions: 3 tons at 170°C for 3 minutes. The films were characterized by X-ray diffraction (XRD) and Infrared (FTIR). These analyzes were used to evaluate the intercalation and / or exfoliation of nanocomposites. In general, results indicated changes in structure as a function of clay content employed in the systems of PHB / vermiculite.

Abstract: Stainless steels are materials used in specific applications where a good corrosion resistance property combined with high material mechanical resistance are required. The shot peening process has been used in order to improve the mechanical properties of metallic surfaces. Besides, it might has influence on the material electrochemical behavior, depending of the used parameters in the operational process. The purpose of this study is to evaluate the effect of the shot peening process in the corrosion resistance of AISI 430 ferritic stainless steel. Wettability test, atomic force microscopy (AFM), open circuit potential (OCP) and potentiodynamic polarization curves have been used in order to evaluate the behavior of AISI 430 ferritic stainless steel after the shot peening process. The aim of this study was to demonstrate the influence of shot peening on the surface properties of ferritic stainless steel AISI 430 and correlate them with the reactivity of the surface. The results showed that the shot peening process, contributes to avoid the localized corrosion resistance of the AISI 430 ferritic stainless steel.

Abstract: The aim of this work is to coat tin plate with a hybrid film obtained from a sol consisting of alkoxide precursors: 3 - (trimethoxysilylpropyl) methacrylate (TMSM), poly (methyl methacrylate) PMMA with and without tetraethoxysilane (TEOS) addition. The pH = 3 was adjusted with hydrochloric acid. The films were obtained by dip-coating process, cured for 3 hours at 160 ° C, and characterized for their electrochemical behavior. The hydrophobicity of the film was determined by the contact angle measurements and its morphology was evaluated by SEM. Results showed that the hybrid films studied presented good performance concerning their corrosion resistance in tin plate. Besides the addition of TEOS, it has contributed to the increase of the film thickness, however at the same time promoting the crack formation, which compromises the corrosion resistance of the coated tin plate.

Abstract: The state of Paraíba disposes of one of the largest deposits of smectites in the country. However, these smectites present in their composition elevated contents of accessory minerals, especially quartz. For these clays to become viable to determine technological use it is necessary the elimination of part of these minerals. The particle size analysis of a soil consists in the determination of the size of the particles that constitute it and their distribution in certain intervals. This work aims to study smectite clays from the city of Pedra Lavrada-PB, through the particle size analyses, for the use in water based drilling fluids. The determination of particle size was made by sieving and laser granulometer. Apparent and plastic viscosities were measured from the samples. The clays were left at rest before the test for periods of 7 and 28 days, with and without deflocculant. It was verified that there was no significant difference in the particle sizes in relation to the resting time of the samples.

Abstract: The improvement in the properties of nanocomposites is achieved with a load volume fraction of up to 10% due to the very high ratio of the load aspect. Moreover, they have the advantage of being processed with conventional equipment and techniques (extrusion, injection, etc.) used for polymers. In order for the clay to be uniformly dispersed in the polymer and there to be good interaction with the polymer matrix, superficial treatments of the clays with organic salts are essential for it to become organophilic, and, thus the material obtained has better performance. In this study, it was evaluated the influence of two speeds (100 and 200 rpm) of processing and thermo mechanical properties of nanocomposites with 3% of bentonite clay prepared with two speeds and two threads. The nanocomposites showed better properties as compared to properties of polyamide 6, especially the samples heated at screw speed of 100 rpm.

Abstract: This paper presents an investigation of the correlation between dielectric properties and microstructure and TiO2 crystalline-phase characteristics (rutile and anatase) in ZnO-TiO2-Nb2O5 system ceramics. Such ceramics were produced from powder mixtures of zinc oxide, niobium oxide and titanium oxide. Powder mixtures were compressed by pressing (100 MPa uniaxial and 300 MPa isostatic) and sintered at 1100, 1200 and 1250 °C. The sintered ceramics were characterized on the crystalline phases, density and microstructure and microwave frequencies. As for the microwave dielectric properties, dielectric constant, quality factor and thermal coefficient in the temperature range from-20 to 50 °C were measured. The results showed that the type of titanium oxide structure (rutile or anatase) causes influence on the type and quantity of crystalline phases in relative density of sintered ceramics and, consequently in their dielectric properties measurements.

Abstract: Ferrites are ceramic materials whose magnetic properties are very interesting used in various applications. This study evaluates the calcination on the characteristics of Ni_0.5Zn_0.5Fe_1.97Al_0.3O₄ ferrites synthesized by combustion reaction. The samples as synthesized and after calcination at 700 oC/1h in a muffle type furnace were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, magnetic measurements and determination of carbon content. The results showed the formation of the Ni_0.5Zn_0.5Fe₂O₄ ferrite phase for samples with and without calcination. The infrared spectra showed characteristic vibrations of HO and NO bonds, possibly attributed to the adsorbed water and residual nitrate. Morphologically there was the formation of soft agglomerates with interparticule porosity for both samples. The Ni-Zn ferrite doped with 0.3 mol of Al³⁺ showed superparamagnetic behavior without calcination and after calcination observing its behavior as a soft magnetic material (easy magnetization and demagnetization). Samples showed very low carbon content, indicating that urea used as a fuel was nearly completely consumed in the reaction and after calcination it wasnt observed the presence of carbon.