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High-frequency measurements of wind, and temperature were made during the dry season of 2008 to study the development of an internal boundary layer at the main Brazilian space launching centre, Centro de Lançamento de Alcântara at Alcântara, Maranhão, Brazil. Turbulence measurements taken at the coast, in two different points 227 m apart show different daily cycles of turbulent kinetic energy friction velocity (u *), and buoyancy flux w' T ν '. Surface roughness change, surface heating change, and a gap in the natural vegetation seem to be the causes for the variation in these turbulent parameters. The mean wind cycle also shows distinct patterns. It seems that, first, internal boundary layers develop when the oceanic surface layer reaches the continent, and a second when the first internal boundary layer's flow encounters the gap. A direct implication is that turbulence is not horizontally homogeneous and measurements taken at single places are not spatially representative. Knowing how turbulence varies spatially is necessary information to understand the diffusion of pollutants exhausted by rockets near the coast.

This work developed a ceramic material for dental application, spinel-base (MgAl2O4), a ceramic material with recognized translucency. Spinel powders were uniaxially pressed at 100 MPa and pre-sintered in order to obtain porous ceramic blocks. The pre-sintered blocks were characterized and indicated 80% of relative density. X-ray diffraction (XRD) only showed MgAl2O4 phase. Samples with 15 x 15 x 1 mm were submitted to infiltration using glass rich in lanthanum (La). The products were characterized by scanning electron microscopy (SEM) and mechanical properties, as hardness and fracture toughness. Results were compared to the commercial product VITA-InCeram Spinell. Relative densities exceeding 92%, hardness around 900 HV and high toughness 2.5 MPa.m1/2 were obtained for both examined systems.

In this work, compacting powders of different ZrO2(Y2O3) are investigated relating the particle size, compaction pressure, and use of binders. Powders of ZrO2 stabilized with 3mol % Y2O3 with an average particle size of 0.15 to 0.7μm presence of both bonding and 0.15μm without addition of binder, were uniaxially compacted with pressures of 30 to 115MPa. Green density between 40% and 50% were obtained. The results indicate that powders sized less densification above 1400°C, while the larger sizes only after reaching full densification above 1500°C. Crystallographic characterization indicates that the powders have a percentage of monoclinic phases in the range of 15% to 26%, but only after sintering tetragonal phase is identified.

Currently the composite two-phase Al2O3-YAG laser has been widely exploited by having good properties such as high abrasion resistance and deformation in harsh environments. Thus, one can predict that this material has very attractive applications such as fins of jet engines and gas turbines. In this study, five mixtures were processed Y2O3-Al2O3-Nb2O5, in proportions of 0, 1, 5, 15 and 35 wt% Y2O3 and 4% by weight of Nb2O5. These samples were sintered at 1550 to 1650 °C in air where it was detected by X-Ray Diffraction (XRD) with Rietveld refinement training YAG and also two intermediate stages, and AlNbO4 YNbO4. Finally they were characterized by hardness by Vickers microindentation and fracture toughness. The highest hardness and fracture toughness were 15 GPa and 5.5 MPa.m1/2, respectively.

O presente trabalho destaca a aquisição de pelotas autofundantes na forma de briquetes consolidados a frio, utilizando para isto uma mistura fina de minério de ferro e manganês, CaO, CaCO3, dolomita, carvão e coque, aglomerados com escória de processo da refinação de aço de Tipo MRPL (Processo de Refino de Metal por Lance) como matéria-prima. Os resultados indicam que é possível produzir um aglomerado, com todos os resíduos gerados nas siderúrgicas integradas, pressionando e sujeitos a cura natural sem umidificação; A escória pode ser usada como um aglutinante, levando o briquete para apresentar uma resistência à compressão acima de 160 MPa, de acordo com os métodos ASTM C496 e ABNT 7222. Essa resistência é comparável ao valor do pellet e coque queimados. Essa qualidade permite ser carregada em um alto-forno grande e em outros equipamentos similares. Conclui-se que a briquetagem utilizando como ligante a escória de aço, permite atingir uma mistura de finos descartados.

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In this work, the preparation of Al2O3-TiO2 ceramics by high-energy ball milling varying the molar fraction in 1:1 and 3:1 was investigated. The powder mixtures were processed in a planetary mill at 250rpm and a ball-to-powder weight ratio of 5:1, for 120min. Compacts were obtained by cold pressing at 100MPa. These specimens were heated at 1000◦C for 30min to promote the water evaporation, and subsequently sintered at 1500◦C for 240min. Samples were characterized by relative density and X-ray diffraction. Hardness and fracture toughness were determined by Vickers Indentation Method. The crystallite sizes were lower than 420 and 560Å in Al2O3-TiO2 and 3Al2O3-TiO2 powders, respectively. After sintering, XRD analysis indicates Al2TiO5 and Al2O3/Al2TiO5 as major crystalline phases for Al2O3-TiO2 and 3Al2O3-TiO2 compositions, respectively. The relative density of the Al2O3-TiO2 ceramics was higher than 90% in both compositions. However, hardness and fracture toughness results of 10.7GPa or 10.5GPa and 3.2MPa.m1/2 or 2.6MPa.m1/2 for Al2O3-TiO2 and 3Al2O3-TiO2 mixtures respectively, indicates that microstructure duplex composed by Al2O3 and Al2TiO5 grains lead to improvement of toughness of these ceramics.