Materials Science Forum Vols. 727-728

Abstract: The ceramic sector is important to the economy in Rio Grande do Norte, Brazil. Overall, however, the manufacturing process is imperfect; leading to inappropriate use of raw materials, waste of energy, environmental degradation, nonconformity to the Brazilian and international standards, etc. So, its crucial improves the produced bricks. This work aims to contribute to quality control of the ceramic industry, raising the values of physical properties of their products. The main parameters that influence these values were determined by Weibull statistics. Ceramics were studied by measuring porosity, water absorption, linear shrinkage, bulk density and mechanical strength. Mechanical strength test data resulted in Weibull distributions. The Weibull statistic parameter was calculated to best evaluations of ceramic quality. The results support our initial considerations about current stands of low quality of ceramic products from Rio Grande do Norte and underline the importance of testing and improving these products.

Abstract: Electrorheological uids (ER) are commonly known as suspensions composed of semiconducting particles dispersed in insulating oil that respond to electric fields by gelling. The increase in suspension viscosity on application of the field is typically rapid and reversible and as a result, the ER response is amenable to applications where real time control of stress transfer properties is required. Ferroelectric particles are interesting in this application due to the presence of spontaneous polarization and high dielectric constant. Particularly, Bismuth Titanate (Bi₄Ti₃O₁₂ - BIT) is well-known as layer-structured ferroelectrics, so the typical morphology of these crystals is lamellar. Therefore, these particles dispersed in oil, in the presence of an electric field must produce an interesting ER response. Thus, BIT powders were prepared by the conventional solid state reaction method and the particles size was adjusted using ball milling process. Different ER fluids containing average particles size about 2.5 to 0.5 μm were dispersed in silicon oil about 10% vol and were submitted to AC and DC electric field. The relation between the BIT particles size with the ER response was observed, presenting an increase of the shear stress with the reduction on particle size.

Abstract: This work aims at the development of organoclay from two varieties of bentonite for use in organic media using ionic surfactants, studying the influence of process variables in the organophilization process. We used the following materials: natural bentonite clay from Cubati-PB District, and the ionic quaternary ammonium salt: Praepagen WB® with 45% active matter. The clays were benefited and then turned into sodium form and subsequently into organoclays. The bentonites were characterized by laser diffraction (GA) X-ray fluorescence chemical composition (EDX), thermogravimetric analysis (TGA), thermogravimetry (DTA) and X-ray diffraction (XRD). The organoclays were characterized by (XRD) thermogravimetric analysis (TGA) and thermogravimetry (DTA). The results showed that the clay has potential for application in the organophilization process and that there is influence of process variables.

Abstract: This work presents an experimental study focusing on the preparation and characterization of modified natural green clay-mud with quaternary ammonium salts of chloride and alkyl dimethyl benzyl ammonium chloride (Dodigen) and dimethyl stearyl ammonium chloride (Praepagen). X ray Diffraction (XRD), infrared spectroscopy (IR) and expansion tests (adsorption capacity and Foster swelling) measurements were performed in order to evaluate the performance of the ion exchange reactions and the degree of affinity with oil products. It is observed an increasing in the XRD basal spacing of the modified clays (1.96 nm and 2.25 nm for Praepagen and Dodigen salts, respectively) in comparison to the observed value (1.56 nm) for the natural clay. The IR results showed that salts were successfully incorporated to natural clay structure. Based on the expansion tests the organoclays presented the best efficiency independent on the kind of solvent used in comparison with the natural clay performance.

Abstract: The geopolymer although being a recently discovered material, it is already present in many industrial sectors. This range of applications is due to the commitment of the scientific community to understand and manipulate the material, seeking a contribution in this regard, it has produced geopolymer matrix composites with quasicrystalline and reinforcement, Al_62,2Cu_25,5Fe_12,3 in the proportion of 10%, 20% and 30% by volume. These composites were obtained by manual production and heat treated at 400 º C for two hours. The characterization was made with the aid of scanning electron microscopy (SEM) and x-ray diffraction (XRD). Diffractograms of composites without heat treatment showed characteristic peaks of the phases present in the matrix and reinforcement. For the composites with heat-treated, it was observed that besides the phases mentioned above the presence of diffraction peaks possibly associated phase silica sodium aluminate. The composite showed good interface quasicrystal / geopolymer, showing the existence of a phase with lamellar morphology in the treated material.

Abstract: Through different field of application and productive growth that membrane technology has been presented in the last years, the aim of this work is to prepare and characterize anisotropic porous ceramic membrane. The membrane were done with alumina, prepared by combustion reaction in microwave oven from urea as combustible and after deposited on support based on a commercial alumina. The results showed that it was obtained α-alumina as unique phase with average agglomerate size of 10µ and surface area of 33 m²/g. The alumina morphology was constituted by pre-sintering particles with hard agglomerates and/or aggregates. In relation to the membranes, it was observed a longitudinal section without cracks and uncovers support surface, also it can be observed grain formation well distributed and a layer of alumina with approximately 35.25µm. In relation to the permeate flux, the membrane presented initially values relatively high that is decrease with the permeation time, due to adsorption of water in the internal surface of the pores of the membrane, experiencing a decrease in size.

Abstract: The manufacture of ceramic products involves the knowledge of the whole process, starting with the raw materials that are traditionally treated as clays. The term clay according to Santos [1] means a material with earthy texture and low grain size, which develops plasticity when mixed with a limited amount of water. The clay (or mudstone from the geological point of view) is a finely divided rock, consisting mainly of clay minerals, plastic materials and minerals that may contain non-plastic, and some materials which are not considered clay minerals, such as calcite, dolomite, gibbsite, quartz, alumina, pyrite, and others. Chemically, clays are composed of hydrated silicates of aluminum and iron, containing also a certain amount of alkaline and earth alkaline elements.

Abstract: The structure of silicate glasses gets its charge stability through SiO₂, R₂O₃, R²⁺ and R⁺ groups arrangement. In these glassy structures, transition metals are usually used as dopants in small amounts. However, in soda-lime glass systems, transition metals can take part in the glassy network in larger quantities as secundary former or modifier, insted R²⁺ groups, if the charge balance conditions are made favorable by R₂O₃ groups additions. This paper studies transition metals (Cr, Ni, Fe, Cu, Zn, Pb, Ru) soda-lime-borosilicate glass network incorporation. This process was applied for many kinds of toxic metals containing vitrification waste. The glasses were obtaind by melt at temperature of 1300°C, and characterized by FT-IR and XRD techinics. The chemical stability was evaluated by hydrolytic attack test. The glasses showed a high chemistry and environmental stability like the soda-lime glass. Keywords: glass structure, electroplating waste, e-waste, nanowaste.

Abstract: The use of agricultural waste has become a necessity due to the high environmental cost derived from its improper disposal in nature. In this scenario, rice husks, as well as the ash produced by burning, became worrying in certain regions of the country due to the large volume produced annually [.

Abstract: ndustrial wastes recycling become attractive due to raw materials economy (sustainability) and environmental issues. This research objective was to characterize a residue generated during the alumina calcination process (electrostatic precipitator dust), to be applied on the development of tubular ceramic membranes. In this context, two samples were analyzed, a crude residue (sample A) as supplied by the industry and other calcined residue (sample B). As verified by X-ray fluorescence spectroscopy by dispersive energy (XDE), the samples A and B showed a high content of alumina in chemical compositions, both close to 96%. Gibbsite and α-alumina crystalline phases were identified by X-ray diffraction (XRD) in the samples. At scanning electron microscopy (SEM) images, could be observed agglomerates of particles with asymmetric shapes and a wide particle size distribution like was confirmed by laser diffraction, which showed that the particles diameters remained almost unchanged after calcination at 700°C. Results revealed no significant differences between samples characteristics, indicating that the crude and calcined residues could be used to prepare ceramic membranes.