Materials Science Forum Vols. 775-776

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 powders synthesized by citrate technique were calcined at 900 °C for 4 h and, their LSCFCGO 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: The inclusion of alternative materials in the composition of asphaltic masses aims to solve the problems arising from the disposal, in the environment, of industrial waste discarded; however, to ensure that such inclusion doesn't damage the characteristics and properties of the asphaltic mass, it is necessary that the mixtures, composed by mineral aggregates, PAC and filler, are previously submitted to the standardized essay. It is known that the filler is mainly responsible for the absorption of the PAC and that, the greater the amount of the PAC utilized on the asphaltic mass, the bigger the costs. Thus the characteristics of the filler, as well the rate of packing of the constituents of the asphaltic mass affects directly the cost and properties of the final product. Given the previous subject, in this work it was aimed to study the effect of the addition of low plasticity clay and peat in the final properties of the asphaltic masses.

Abstract: Beginning during the decade of 1920, the Brazilian highway system became the main way of transportation in the country, fomenting the search for asphaltic mix with better mechanical properties and resistance to the weather variations. The asphaltic mix is formed by minerals aggregates and binder (PAC Petroleum Asphaltic Cement). The aggregates are responsible for supporting the traffic weight and stability. The PAC is responsible for the attachment between the constituent particles and impermeable state. In this work it was investigated the formulation of asphaltic mix starting from the packing equations of the particles: Andreasen, Alfred and Alfred Inverted. It was produced bodies of proof varying the proportions of the aggregates and fillers, keeping constant the PAC (5% in weight) and the results were compared to an industrial standard formulation. The values obtained are in accordance with the DNIT norms, indicating that the equations of packing can be applied to the formulation of asphaltic masses.

Abstract: Brazil is currently one of the world leading producers and exporters of ornamental stones. The increasing production also generates a proportionally huge amount of wastes. Depending on stones such as granite, these wastes may be composed of relatively high content of alkaline oxides. This is a low melting point flux with advantage for a potential addition of the waste into common clay ceramic. Thus, the present work investigated the addition of a granite waste, generated during the sawing stage using the multi-wire technology, into clayey ceramics fired at 1200oC. This ceramic added with up to 30 wt% waste were evaluated in terms of linear shrinkage, water absorption and flexural strength. It was found that the waste fluxing compounds promoted a reduction in water absorption and increase in strength that are associated with an improved clayey ceramic.

Abstract: In this work, polypropylene (PP) and organophilic clay composites without and with PPgMA compatibilizer were obtained. The organoclay was incorporated into the PP matrix at concentrations of 0.5, 1.0, 3.0, 5.0 and 10 phr in order to obtain composites without compatibilizer. In the systems with compatibilizer, concentrations of 0.5 and 1phr of the organoclay were used. The systems were characterized by rheological measurements under steady and oscillatory shear flows. In the rheological characterization, it was observed that the viscosity and storage modulus at low frequencies increased with the increase in the clay content and with the compatibilizer. These results are relevant in the evaluation of the influence of the compatibilizer in the processability and in the degree of clay dispersion.

Abstract: Fibers obtained from de sugarcane bagasse are being investigated as possible engineering materials. Their application as reinforcement of polymer composites is of interest due not only to environmental benefits associated with a waste recycling but also to their biodegradable and renewable characterisitics. Since it is known that many lignocellulosic fibers present a tensile strength inverse dependence with the diameter, this possibility was investigated on bagasse fibers. By means of the Weibull analysis, it was found that the thinner the bagasse fiber, the greater the strength. Fracture observation of bagasse fibers by scanning electron microscopy, indicated possible mechanisms related to this inverse correlation.

Abstract: Lignocellulosic fibers with relatively unknowns mechanical properties such as those extracted from the sponge gourd, are being investigated as polymer composites reinforcement. The use of natural fibers are related to environmental , technical, economical and social advantages. An important possibility of improving the mechanical properties is the fact that lignocellulosic fibers may present tensile strength inversely correlated with their diameter. Therefore, this possibility was investigated in the present work regarding sponge gourd fibers by means of the Weibull statistic analysis. The results supported a hyperbolic inverse correlation between the strength of sponge gourd fibers with their diameter. Scanning electron microscopy observation of fibers with different diameters revealed possible mechanisms for the strength inverse correlation with diameter.

Abstract: In this work aqueous ceramic suspensions were prepared from a parent glass-ceramic powder (3.8 μm) belonging to the LZSA (Li₂O-ZrO₂-SiO₂-Al₂O₃) system without or with additions of different volume fractions (1.0-7.5%) of TiO₂ nanoparticles (25 nm). The obtained suspensions were rheologically characterized so that stable suspensions were defined e formed by slip casting. The obtained compacts were sintered (850-950°C/60 min) and their green and sintered densities were determined and related to linear shrinkage measurements. The results showed that samples sintered at 950oC for 60 min with 1.0% TiO₂ addicted presented linear shrinkage of 12% and relative densities of 97%.

Abstract: This paper describes the preparation and complementary characterization of a composite formed from the activation of titanium isopropoxide by phosphoric acid and deionized water (TiP).Techniques such as, X-ray diffraction (XRD), Raman , electronic (UV-vis) and Scanning electron microscopies (SEM) were used for characterization of this new composite formed. In the X-ray diffractogram of TIP was observed four intense peaks. A strong absorption was observed in the region 362-445 nm. The scanning electron microscopy of TiP, shows that the prepared material consists mostly of a cluster of spherical particles with diameters ranging from 2.35 to 2.60 μm.

Abstract: Sugarcane bagasse is a typical waste generated in the production of sugarcane and ethanol. This agro-industrial waste is commonly used as fuel in the industry boiler for the steam and energy generation. However, part of the bagasse waste is disposed and may pollute the environment. The fibers extracted from the sugarcane bagasse have been considered as addition to polymeric composites. In the present work epoxy composites incorporated with 30% in volume of continuous sugarcane bagasse fibers were evaluated in terms of their mechanical properties. As compared to the neat epoxy, the bagasse fiber displayed an increase in elastic modulus but a decrease in strength and ductility. The analysis of the composite microstructure by scanning electron microscopy revealed flaws and pores that could justify these preliminary obtained results.