Materials Science Forum Vols. 775-776

Abstract: This paper studies the technological feasibility of using iron ore tailings as additives in cement pavers for the optimization of the mechanical properties and color modulation.Thus, to study the physical, chemical, optical and morphological properties of the tailings, they were characterized for the composition, mineralogy and granulometry. To optimize the procedure of preparing iron ore tailings as additives in the production of new concrete pavers and to determine their effects on the properties of pavers they, were added in ratios of 0% to 50% in substitution of traditional aggregates. The pavers were characterized for hermeticity and mechanical properties.

Abstract: Basically, a traditional ceramic glaze is a thin layer of glass created on the ceramic surface to enhance the aesthetic appearance and also to waterproof the artifact. Almost all glazes are based on quartz, SiO₂, and a flux such as Na₂O or K₂O, similar to the composition of common glass, which contains approximately 72% SiO₂ and 15% Na₂O, and is widely used as windows or in glass packaging. The current work investigated the formulation of glazes using recycled waste glass powder for firing temperatures of 1100 and 1250°C. Three transparent base glaze formulations were developed and by adding coloring agents such as iron, cobalt or copper oxide several colored glazes could be successfully produced. In this way, up to 30% of recycled waste glass powder could be incorporated into the glazes.

Abstract: The addition of industrial residues into common red clay ceramic has been, from many decades, an alternative of using other low cost raw materials and, more recently, as an environmentally correct destination for polluting substances. An important residue, known as yellow sludge, is that generated at the water clearing stage (WCS) of a treatment plant by some heavy industries such as an integrated steel making. Since this yellow sludge residue is normally disposed in ways that pollutes water bodies, the objective of the present work was to characterize a WCS yellow sludge and investigate its addition into clay ceramics. The residue was characterized by X-ray fluorescence, particle size distribution and scanning electron microscopy. The addition was carried out up to 7.5 wt% followed by firing at 800oC. The added ceramics were evaluated in terms of water absorption, linear shrinkage, dry apparent density and flexural rupture strength. It was found that the residue addition does not practically alter the ceramic technical properties.

Abstract: The technology of subdividing stone blocks by diamond multi-wire sawing has recently been used by the ornamental stone industrial sector in the state of Espirito Santo, southeast of Brazil. The waste generated by this sawing procedure is iron free and relatively clean as compared to other stone processing operations. In principle, the diamond multi-wire sawn waste could be a viable alternative of incorporation into clays ceramics. The possibility of incorporating up to 40 wt% of a granite waste generated from diamond multi-wire sawing into clay ceramics, fabricated in the neighbor state of Rio de Janeiro, was investigated in this work. The incorporated ceramics were fired at 750, 950 and 1050oC. The apparent density, liner shrinkage and flexural strength were evaluated. The results indicated that the incorporation of the waste improved the ceramic properties, particularly at 1050oC.

Abstract: The kaolin residue presents in its composition significant levels of sílica and alumina, making it a material with chemical and physical properties appropriate to use as an alternative material with pozzolanic characteristics in substitution to the cement for grout utilization. Thus, this work aimed evaluate the influence from the addition of different amounts of kaolin residual calcined in partial substitution of Portland cement on grout in dash 1:2:6 (cement+%residue:lime:sand). It was evaluated grouts with and without residue substitution in the strengths of 0%, 5% and 30%, through resistor the simple compression at 30, 60 and 90 healing days. The results of resistor from the grouts were over the one required by NBR 13281 [, classifying them as type I e II.

Abstract: Polymer blends are better technological response to generate "new" high performance polymers from commercially available polymers and are an alternative to obtaining polymer materials with properties that generally are not found in a single material. The thermoplastic modified with elastomer and/or thermoplastic elastomers have attracted great interest from researchers and industries due to the attractive cost/benefit ratio and the possibility of a significant increase in the toughness of brittle polymers or temperatures subenvironment with the incorporation of a dispersed rubber phase. The destination of compound by recycled rubber has been one of the main problems faced by humanity, because its natural degradation occurs after a long time due to the presence of cross-links, stabilizers and other additives in their structure, causing damage to the environment. This study aimed to prepare blends of polyamide 6/PE-g-MA /compound by recycled rubber (SBRr).

Abstract: This article reports the results of a preliminary research work related to the rheological study of aqueous suspensions prepared from an industrial solid waste (ceramic shell) from the process of lost-wax casting. The results showed that the residue analyzed has a strong refractory character since it contains mostly mullite, zirconium silicate and quartz. The ceramic suspensions obtained, containing 70% (~ 23% vol.) residue, 5-7% of kaolin and 1.0-1.5% dispersant, showed a rheological behavior suitable for impregnation of polymeric foams for the production of filters for metal casting by the replication method.

Abstract: Lanthanum cobaltites doped with strontium and iron (La_1-xSr_xCo_1-yFe_yO₃) have been intensively studied as cathode materials for solid oxide fuel cells (SOFC). In this work, powders of composition La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF6428) were synthesized by a combination of citrate and hydrothermal methods. As-prepared and calcined powders were investigated by different material characterization techniques. LSCF films were obtained on gadolinium doped ceria substrates (CGO) after sintering at 1200 °C. The effects of the sintering conditions on the microstructure and electrochemical performance of the electrodes were evaluated by scanning electron microscopy and impedance spectroscopy. The electrochemical characterization was assessed using a symmetrical cell configuration (LSCF/CGO/LSCF) at temperatures ranging from 650 to 800 °C. The area specific resistance showed strong relationship with microstructure. The best electrochemical behavior (0.18 ohm.cm² at 800 °C) was obtained by using sintering dwell time of 2 h.

Abstract: The synthesis by combustion reaction stands as an alternative technique for preparing powders with high purity level, nanometric particle size and low cost. Therefore, this study had as objective the synthesis and characterization of ferrite powders with nominal composition NI_1-xZn_xFe₂O₄ (x = 0.6, 0.7 and 0.8 mol) prepared by combustion reaction using urea as fuel. The influence of the quantity of zinc in the final characteristics of the powders was also investigated. The powders were characterized by X-ray diffraction (XRD), nitrogen adsorption (BET) and scanning electron microscopy (SEM). All compositions resulted in nanometric powders of Ni-Zn ferrites with direct formation of the inverse spinel phase, showing the effectiveness of the synthesis method applied. The increase of zinc's concentration caused an increase in surface area, ranging 4 m²g^-1 from 23 m² g^-1. And the SEM micrographs show that the powders have thinner particle morphology with increasing zinc content.

Abstract: This work aims to investigate the glycerin from the biodiesel as fuel in the combustion synthesis into two routes, one for high temperature called direct route, in order to inhibit the formation of acrolein and compare it with the conventional combustion synthesis at low temperatures, using as fuels saccharose, pure glycerin, pure glycerin gel, glycerin from biodiesel, biodiesel from glycerin dried 24 h, biodiesel from glycerin gel dried 24 h to obtain the magnesium aluminate spinel (MgAl₂O₄). The synthesis was performed from the mixture of the precursors (Al (NO₃)₃.9H₂O and Mg (NO₃)₂.6H₂O) in water with the addition of the fuels. In the direct route case, the mixture was placed in a furnace heated to 500°C followed by calcination at different temperatures for 2 h. In the conventional route cases, the mixtures were slowly heated to 800°C for 2 h. The obtained powders, product of the combustion reactions, were characterized by X-ray diffraction (XRD), laser scattering particle size analyzer and scanning electron microscopy (SEM). The results showed that the product (powder) obtained by direct reaction was the MgAl₂O₄ as the only crystalline phase formed with particle sizes of approximately 41 μm. Even so, small particles with sizes of about 30 nm were also observed according to measurements on SEM images.