Materials Science Forum Vols. 798-799

Abstract: The objective of this work is to analyze ashes from a thermal power plant with the aim of determining its environmental aptitude for reutilization as aggregates in clay mixtures for ceramics production. To achieve this objective the waste material was characterized by different techniques: optical microscopy, scanning electronic microscopy, conductivity, pH, among others. Clay samples with bottom ash addition, up to 50%, were prepared. These samples were thermally treated at 950oC and then characterized with diverse techniques in order to determine their behaviour in service. The obtained results show the high feasibility of reutilization of the studied waste as raw material in the production of ceramic products.

Abstract: The lining of steel converters and ladles consists of magnesia-graphite refractories. The steel industry is the biggest consumer of refractories, about 70% of the total production of these materials. For this reason, it is very important to recycle them for the production process. The aim of this work is to carry out the physicochemical and microstructural characterization of post-mortem magnesia-graphite refractories from a steel plant, in order to achieve their incorporation to the manufacture of ceramic masonry to be used in the construction industry. The obtained results indicate acceptable properties in these industrial wastes in relation to the physicochemical and environmental characteristics and the feasibility of reusing them in the mentioned applications.

Abstract: In order to minimize the incorrect disposal of dust generated in the basic oxygen furnace (BOF) converter and to generate a new application for this solid residue, a simple characterization route was proposed. The powder residue is used to produce self-reducing pellets and can be used in the blast furnace process. The chemical analysis of the dust was carried out using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), and some elements as Fe, Si, P, Al and Ca were detected in high amount, as the iron which achieved about 65% concentration. Moreover, the X-ray diffraction analysis indicated that the iron was found in the phases, mainly, as magnetite (Fe₃O₄) and hematite (Fe₂O₃) while quartz (SiO₂) and calcite (CaCO₃) were the major impurities. The spectrometry dispersive energy (SDE) analysis confirmed the presence of such elements and the images obtained by SEM allowed visualizing the morphology of the particles. The average of particle size distribution of the dust was 0.053 mm which is suitable for self-agglomerates pellets.

Abstract: The use of waste to development of products has been an increasingly routine practice today. In this work was used rice husk ash from combustion boiler for energy for synthesis of sodium silicate. The silicate was obtained by means of ash fusion with sodium hydroxide at a temperature of 1200°C for 2 hours. For the synthesis of 4A-zeolite was performed hydrothermal reaction of sodium silicate, previously obtained with sodium aluminate and sodium hydroxide. The zeolite obtained was characterized by X-ray fluorescence, X-ray diffraction and scanning electron microscopy. The results have indicated the formation of 4A-zeolite.

Abstract: The problems caused by contamination of heavy metals generate a growing need to implement technologies to reduce or eliminate them. This work aims to evaluate the potential of gray clay, the process of removal of zinc and lead from synthetic effluents in finite bath system. The clay was characterized by: X-ray diffraction, X-ray Spectroscopy Energy Dispersive and Physical Adsorption of Nitrogen. The tests were performed finite bath following a 2² factorial design, with the variables: pH and initial concentrations of metal. The clays were evaluated for their removal capacity and rate of metal removal. After the characterization and evaluation, it was found that the gray clay comprises clay of the groups of kaolinite and mica. The results of the factorial design shown that the adsorption of the metals zinc and lead can be developed with good percentage of removal.

Abstract: Glass from computers’ LCD monitor screens were recovered, ground and used as filler for Polyamide-6. The composites contained 10 wt% of glass particles. Two particle sizes were tested: glass particles smaller than 106 μm (ABNT#150 sieve) and smaller than 53 μm (ABNT#270 sieve). The filler was evaluated by loss on ignition and the composites by tensile strength and Izod impact strength. The morphology was characterized by scanning electron microscopy (SEM). The value of Young’s modulus of composites processed with glass particles smaller than 53 μm was higher than the one for PA-6. The properties of impact strength, tensile strength, and elongation of PA-6 were reduced with the addition of filler, and the composite containing glass particles smaller than 53 μm showed the lowest reduction in mechanical properties (about 6% in the tensile strength and about 48% in impact strength). The micrographs of fracture surfaces of tensile strength specimens showed weak adhesion particle/matrix and uniform distribution of the particles in the matrix, especially in the composite with finest particle sizes.

Abstract: The yttria stabilized zirconia, ZrO₂ (Y₂O₃) has been widely used in dental prosthesis manufactured by CAD/CAM technique. This material is developed in the form of pre-sintered blocks, which are machined by extracting various customized prosthesis and generating a loss of about 30% of material. ZrO₂(Y₂O₃) is notably a toughening for other ceramics, and has a high cost, so reusing discards these applications less noble, is strategically interesting. In this work the proposal is to recover discharges of ZrO₂ (Y₂O₃) arising from prosthetic laboratories, reprocess them in order to reduce the particles size and subsequently sintering, demonstrating the potential use in applications less noble in dentistry. Discharges Residual of ZrO₂-(Y₂O₃) were fragmented and then sieved to particle size separation. Powders of smaller than 63 μm were uniaxially pressed at different pressures. The compacts were characterized by the relative density showing green density of the order of 40%. After characterization, compacts were sintered at 1550°C-2h. The sintered material was characterized as its relative density and crystalline phases.

Abstract: The civil construction industry in Brazil is an ever growing sector with relevant participation in the country’s economy. On the other hand, this sector, technically, is among those that generate the largest amount of undesirable rejects, waste and residues. Some of these residues are highly detrimental to the environment not only because of landscape degradation but also the possibility of pollution to rivers and lakes as well as ground waters. A typical example is that of the ornamental stone industry, which generates granite and marble residues from the several processing stages. Therefore the aim of the present work is to investigate the effect of direct addition of this kind of residues in concrete blocks for different applications in housing masonry. It was found that blocks added with 20 wt% of residue possess relatively higher compression strength in association with convenient water absorption below those presented by residue-free traditional blocks.

Abstract: Brazil follows the global trend to seek viable alternative energy sources that can improve the quality and secure supply of energy with environmental sustainability, allied to the necessity of facilitating a fitting end to the sludge treatment plants sewage. The biomass present in SS is emerging as an alternative to the country's energy matrix, through the Low Temperature Conversion process – LTC of the sludge in the production of biofuel (biooil and coal). This article aims to characterize the coal obtained through the Low Temperature Conversion and evaluate the thermal behavior. In this study physical and chemical studies were made: elemental analysis (CHNO), calorific power, Thermogravimetry (TG) at a heating rate of 10°C min^-1 under synthetic air atmosphere, and spectroscopic. The thermogravimetric study found a thermal stability at 300^oC. In the spectroscopy in the infrared (IR) regionit was observed bands related to the presence of water, organic matter and silicon oxides in the SS samples analyzed.

Abstract: Incomplete binder removal may introduce severe defects during ceramic processing. This work presents a new method to eliminate polyethylene glycol used as a binder in pre-sintering steps of alumina parts. The effectiveness of the proposed method was evaluated by density and pore size measurements, as well as thermogravimetry (TG), differential thermal analysis (DTA), volumetric physical adsorption analyzer (BET), and Fourier transformed infrared spectroscopy (FTIR). The results show that the new method, although relatively slow in comparison with traditional procedures, yields smaller pore sizes and better mechanical properties of the final products.