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Utilização da técnica de conformação por coagulação direta (direct coagulation casting) em massas refratárias de sílica para processos de fundição por cera perdida
(Universidade Federal de São Carlos, 2013-01-22) Alves Júnior, José Antonio; Baldo, João Baptista; https://lattes.cnpq.br/2410385643716370; https://lattes.cnpq.br/7449451997419254
Refractory masses for lost wax casting process of steel and alloys, especially for dental devices are constituted basically of silica (quartz and / or cristobalite). In these materials, the binding agent is generally based on magnesium phosphate cements, produced by acid-based reaction of NH4H2PO4 with MgO. The main product of the reaction is struvita (MgNH4PO46H2O). The presence of phosphates together with retarders, necessary to control the reaction kinetics, contributes to the sintering and adhesion of the silica investment to the metal material after solidification. Recently it was developed a consolidation process of ceramic powders by direct coagulation (DCC) of a stabilized slurry of high solids content and low viscosity. The direct coagulation is achieved by controlled destabilizing (flocculation/ coagulation) of the suspension either through the gradual change of the pH towards the isoelectronic point or increasing the ionic strength of the medium. In this work the change in pH was accomplished by two different routes. The first one by the use of buffer solutions whose pH controll was close to the one of silica IEP (innovative methodology). The second was made by using citric acid and sodium trypolyphosphate in a competing reaction changing slowly the medium pH towards the silica IEP. Both routes promoted the direct coagulation of silica refractory masses without the presence of phosphates or any other binder. The results were very satisfactory, since in all silica refractory masses (>99% SiO2) used, the coagulation occurred rapidly, at low initial viscosity, and low final water content to be eliminated. The masses kept the required refractory properties for high temperature castings, presenting excellent properties such as high expansion at the metal casting temperatures, excellent surface finishing, low adherence to the cast part and easiness upon demolding. This whole set of properties are ideal for lost wax investment casting processes.
Caracterização microestrutural e mecânica da liga de Al AA7050 reciclada por conformação por spray e extrusão
(Universidade Federal de São Carlos, 2013-01-22) Mazzer, Eric Marchezini; Kiminami, Claudio Shyinti; https://lattes.cnpq.br/5443002033733395; https://lattes.cnpq.br/7273276940567054
Aluminium alloys of the 7000 series are widely used in structural components in the aircraft industries due to their high strength and low density. However, a large amount of scraps is generated by the machining of the components, which achieves almost 90% of the alloy s initial mass. These wastes are normally used in low performance application, despite of the high quality of the AA7050 alloys. It occurs because is not possible to keep the good mechanical properties of the alloy when it is recycled by conventional casting, which generates high level of segregation of the alloy elements and a coarse microstructure. In this sense, the present work aims the recycling of the aluminium scraps by spray forming and hot extrusion. The spray forming process provides a rapid solidification, making possible to obtain a refined microstructure and a low level of segregation. The hot extrusion closes the pores arising from the previous process and increases the strength by reducing the grain size. After the spray forming the material was hot extruded in a industrial scale equipment in order to close the pores arising from the previous process and improve the strength. A combination of heat treatments concerning homogenization, solution and aging heat treatments were imposed during the process in order to optimize the mechanical properties. The microstructure characterization was carried out in a scanning electronic microscope (SEM) and in a transmission electronic microscope (TEM), combined with x-ray diffraction (XRD) and differential scanning calorimetry (DSC) . The mechanical properties were evaluated by tensile tests. By the analysis of the results we can conclude that the spray forming is a viable route to recycle the Al AA7050 alloys because it can generate refined microstructure and better mechanical properties than the original material.
A luta contra a desesperança: a experiência de gestantes com HIV
(Universidade Federal de São Carlos, 2013-01-22) Oliveira, Fernanda Ferreira Damaceno; Wernet, Monika; https://lattes.cnpq.br/6056127658896265; https://lattes.cnpq.br/7291591684066479
The discovery of the Human immunodeficiency virus (HIV) during pregnancy drives woman to experience prejudice, discrimination and the possibility to infect her child, promoting an existential reflection. Suffering is present, conducting to a hope experience. Hope is a dynamic and multidimensional process, focused in the possibility to achieve what is desired. Incorporate bases and force to exist, being reached in the moments of difficulty. Therefore, the routine with HIV during pregnancy connect itself to the experience of hope, for that reason the present study has hope as its component. The objective was to explore and describe hope experiences during pregnancy of woman that discovery her HIV seropositive at prenatal. This study had as theoretical reference the Symbolic Interactionism and narratives research as methodological reference. The strategy to data collection was semi-structured interview associated with hope s genogram and ecomap. It was part of this study seven pregnant women who discovered their HIV seropositivity during prenatal. The results are present and organized in the following thematic units: Life review ; be a mother , care of herself , surrender to divine intervention , social interaction and hope . The main phenomenon identified was fight against the lack of hope . It was conclude that the tendency to lack of hope is strongly present in the gestational routine of these women and that exist interactions that are hope promoters and others that restrict it. Woman try to valorize those that are hope promoter to reach what It was established as a goal in that period: contribute with her child s seronegativity.