Materials Science Forum Vols. 727-728

Abstract: The aim of this work is to produce a stable suspension of iron oxide reinforced by different ceramic nanoparticles like SiO₂, TiO₂. Measurements of mean particle size, zeta potential and flow curves have been done. Additionally deflocculation curves and sedimentation were drawn to complement the study. The results showed that nanoparticles helped suspensions to maintain a deflocculated stable condition for longer periods of time.

Abstract: In this work, glasses with compositions, close to commercial borosilicate glasses, were developed. The main raw materials were residues of ornamental rock industries ( marbles and granites ). Beach sand was used in order to enrich the compositions with silica. Also, boron oxide was added to reach borosilicate glasses compositions. The obtained glasses were characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR), and hydrolytic resistance. The measured properties were compared to those of commercial glasses, available in the market, from two different brands. XRD results confirmed amorphous patterns of the produced glasses. The other tests revealed an excellent agreement between the obtained values and those from commercial glasses. Therefore, this study showed the possibility of using ornamental rocks residues as primary sources to produce borosilicate glasses. In addition, it became clear that an economic value could be aggregated to the residues, which otherwise would be discharged into nature causing pollution.

Abstract: The aim of this study is to evaluate the thickness and permeability of the membranes of TiO₂ supported on Al₂O₃. The TiO₂ samples were prepared by combustion reaction method using monohydrated citric acid, aniline and urea as fuel. It was prepared three samples with different morphological characteristics. The membranes were prepared by dip coating, and characterized by scanning electron microscopy (SEM), permeate flux and turbidity in laboratory test. The membrane obtained with urea presented layer formed at 16 µm of thickness. For membrane obtained with powder from citric acid and aniline do not presented layer formation. The membrane obtained with samples synthesized urea showed: higher permeated flux (185.46 kg/ h.m ²), higher particle rejection (97%) and lower turbidity (0.99 NTU) with contaminated water. The membrane obtained with powders from citric acid and aniline showed: permeated flux of 128.61 and 138.41 kg/h.m², rejection of 96 and 95% and turbidity of 1.33 and 1.13 NTU, respectively.

Abstract: Assuming that during the machining of stoneware tiles by flat grinding each grain on the abrasive wheel performs a single scratch, it is possible to simulate and analysis the effect generated by those employing esclerometry. This paper studied the effect between parallel scratches during brittle machining of stoneware tiles. Scratching tests were performed employing a CNC esclerometer; a Vickers indenter as abrasive tool; load of 10N by dead weight; three different configurations of sense in the same direction; three different configurations of spacing between the scratches incremented with a factor of 0.8, 1.0 and 1.2 times the average scratch width. The test samples were analyzed by optical microscopy and subsequent digital image analysis to quantify the worked area. The results showed variation of material removal as a function of the sense and spacing configuration. The sense configuration 1^st R-3^rd R-2^nd R had the highest improve in material remotion. The spacing arrangement 1.2 remain with many not worked areas between the scratches, needing rework to remove this material. The configuration with 0.8 was found a redundancy of work specially when used with the sense configuration of 1^st R-3^rd L-2^nd R.

Abstract: The pure oxides (yttria, zirconia, titania, alumina, etc.) pastes ceramics production by concentrate suspensions is interesting because differently than plastic ceramics (clays), where these behaviours are often empirical available, the rheological suspensions behaviour are extensively studied. Thus, controlling the concentrate slips rheological parameters, is possible extend these analysis for better understand and control the plastic pastes production, providing subsidies to obtain after shaping process, such as extrusion and calendering, suitable products for the desired application. Thus, alumina suspensions rheological behaviour, with high solids loading (> 50 vol.%) adequately stabilized, slip cast shaped are available in this work. High solids loading suspensions, up to 60 vol.%, presents adequate flow for thickeners/plasticizers elements adds to produce ceramic plastic pastes.

Abstract: The membrane separation processes present several advantages in relation to the traditional process, such as high selectivity, easy operation, good results in the effluent treatments, low energy consumption, small number of processing step, can be applied to thermo sensible substances, easy to combine with other process and scale up, great efficiency in the final product (PORTER, 1990; CAMPOS, 2000). The materials employed in the membrane preparation can be metals, ceramic, polymer or composites.

Abstract: The (La_0.60Sr_0.40)(Co_0.20Fe_0.80)O_3-δ - LSCF, (Ce_0.90Gd_0.10)O_1.95 - CGO composites and LSCF were deposited by wet powder spraying deposition method for the purpose of investigating their potential use in Intermediate Temperature Solid Oxide Fuel Cells. The interlayers are necessary between CGO electrolytes and LSCF cathodes in order to improve the performance of these materials. LSCF particles synthesized by citrate technique were calcined at 900 °C for 4 h and, their LSCF-CGO composites and LSCF suspensions deposited on CGO substrate and, sintered in 1100 °C for 1 h, were formed pseudo-perovskite. The ceramics materials were analyzed by X-ray diffraction (XRD) and chemical composition of different half-cells layers by scanning electron microscope with energy dispersive (SEM-EDS). The results are in agreement with the literature and indicate that route studied is adequate for crystal structures formation compatible with films the 35 µm thick total for study of conductivity between the cathode and the electrolyte.

Abstract: Hazardous byproducts emissions such as nitrogen oxides (NOx) and carbon monoxide (CO) might be controlled by the use of radiant porous burners. Those heaters require a solid porous matrix where combustion reaction takes place, reason why the heat transfer is much more efficient. This project was based on a rheology study of an alumina slurry, where parameters like viscosity and tixotropy were the guide to select the appropriate formulation to be used in the fabrication of ceramic foams by the replica method. Low strength samples were produced after the first thermal treatment, explained by the absence of a plasticizer when using PVA as a binder. Incomplete sintered foams were obtained due to an insufficient soak time.

Abstract: The high temperature solid oxide fuel cell (HTSOFC) can be manufactured in different configurations, which can to detach the planar and tubular. The HTSOFC are composed for four components that are cathode, electrolyte and anode for the formation of the unity cell; and interconnector, that establish connection these unity cells in series and parallel for bigger power generation. Different forming techniques are used for the manufacture of the components that need variable thicknesses for the forming ceramic films in the order of micrometers. In this work, the cathodic ceramic film of strontium-doped lanthanum manganite had been deposited on the electrolyte substrate of yttria-stabilized zirconia using the airbrush. In the forming ceramic film, the powder had been characterized by laser beam scattering granulometry and the suspension characterized by rheometry. The substrate and the ceramic film had been characterized by X-ray diffractometry and scanning electron microscopy. The conclusions of this work show that the airbrush allows flexibility in getting ceramic films with varied thicknesses with good adherence and low manufacture cost.

Abstract: The volume of waste generated by mining and mineral processing industries has escalated each day because of increased demand caused by global economic growth. The kaolin processing industries are important economic segments in the state of Paraiba, but generate huge amounts of waste. An alternative for the recycling of this waste is its use in mortars. The kaolin contained in wastes after thermal treatment can reduce the consumption of cement in the production of mortars. It was evaluated the influence of firing temperatures of the residue on its pozzolanic activity. The residue was fired at temperatures of 600°C, 700°C and 800°C for 2h and subjected to mineralogical analysis. The evaluation produced the mortar with a mixture of kaolin waste burned at temperatures of 600°C, 700°C and 800°C with lime delivering true a good mechanical performance, reaching values of compressive strength greater than the legislated.