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Estudo das propriedades estruturais dos catalisadores de Cu e Cu-Ce suportados em alumina aplicados à reação de deslocamento gás-água
(Universidade Federal de São Carlos, 2013-03-12) Caldas, Paula Cristina de Paula; Bueno, José Maria Corrêa; https://lattes.cnpq.br/0157452280626031; https://lattes.cnpq.br/3466253594165485
Particle size effect and Ce addition on the catalytic properties of Cu/Al2O3catalysts were investigated for the water gas shift reaction (WGS). The catalysts were prepared by dry impregnation of an aqueous solution of nitrates of the respective metals on alumina, synthesized by sol-gel method. Samples were prepared with 5, 10 and 15% w/w of metallic copper and 12% w/w of CeO2. The catalysts were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR) spectroscopy, X-ray absorption (XAS). The WGS reaction was performed with reagents ratio of H2O:CO = 1:3 with temperature range from 200 to 350° C. The crystallites CuO were not detected by XRD. As the Cu content increased, the crystallite size of CeO2 decreased with a fluorite type structure from 7.4 to 3.4 nm. The results of TPR showed that the interaction Cu-O-Al was crucial to reduce temperature and ceria addition on the catalysts did not affect the temperature reduction of the CuO. The XANES in situ results along the WGS reaction showed that metallic Cu predominated and ceria was partially reduced. EXAFS results showed that the Cu particle size increased from 0.65 to 0.91 nm with an increased load of copper from 5 to 15%, respectively. After the reduction, step prior to reaction, the catalysts were not completely reduced. The degree of reduction increased with the Cu particle size and it was also dependent on the temperature and the oxidation potential of mixing of the reactants. The addition of ceria did not change the degree of reduction of samples Cu/Al2O3. The results suggest that the Cu particles have a reduced Cu core covered with an oxide layer. The catalytic activity increased as the Cu particle size decreased, which can be associated with the presence of the redox couple Cu+/Cu0. This provides a possibility of CO oxidation and its reoxidation due to water activation. The ceria addition also increased catalytic activity and it is probably attributed to activation of the water on the surface of ceria, followed by transfer of oxygen from its structure to the oxidation of CO in an interface Cu-CeO2.
Microestrutura e propriedades mecânicas de vitrocerâmicos do sistema Li2O – CaO – SiO2
(Universidade Federal de São Carlos, 2013-03-12) Santos, Gisele Guimarães dos; Zanotto, Edgar Dutra; https://lattes.cnpq.br/1055167132036400; https://lattes.cnpq.br/0761705816463042
An interesting characteristic of the Li2O-CaO-SiO2 glass-forming system is the possibility of obtaining certain crystalline phases and morphologies that may lead to tough glass-ceramics. However, very few published works investigated this matter. Glass compositions within the range 30-50% CaSiO3 / 70-50% Li2SiO3 were studied to obtain appropriate microstructures. Heat treatments were conducted using the double treatment technique: nucleation at about the glass transition temperature followed by crystal growth within the temperature range 500 and 700°C. These temperatures were selected according to DSC data. The influence of the size, number and morphology of the crystals on certain mechanical properties of the glass-ceramics, such as hardness and indentation toughness, were estimated by Vickers indentation tests. The samples were also characterized by X-ray diffraction to identify the phases present and by MEV to examine the crystal size, percentage and morphology. The best results were obtained with a composition of 44% mol CaSiO3 using the following thermal treatment conditions: 498°C for 24 hours (nucleation) and 700°C for 2 hours (Crystal growth), that led to a glass-ceramic showing a toughness of 1,9 MPa.m1/2.
A educação escolar na arena do ciberespaço
(Universidade Federal de São Carlos, 2013-03-12) Oliveira, Alessandro Eleutério de; Zuin, Antônio Álvaro Soares; https://lattes.cnpq.br/5543562307373287; https://lattes.cnpq.br/3800768997086874
The objective of this study is to examine virtual communities dedicated to the School Education site relationships Orkut. Accordingly, we analyze written statements from teachers and students in order to apprehend the ways in which those involved in the teaching-learning perceive each other. That is, how students express themselves about their teachers, as teachers are manifested on students and how teachers and students are manifested on School Education. The rationale for this research is the need of understanding the ways in which the subjects' school experiences are expressed in cyberspace. The examination of the information contained in written statements made effective border methodological content analysis. Thus, the lucubrations are lit mainly by authors of Critical Theory, as Theodor Adorno and Walter Benjamin, by the confluence of the material collected in virtual communities on topics such as disorientation and semi-formation in contemporary as well as your reflexes in Brazilian School Education. Other authors provide important contributions to the construction of this paper are Richard Sennett, Charles Melman and Zygmunt Bauman. To date, the categories derived from the analysis of the data show the existence of largely negative perceptions of teachers on students, and vice versa, from experiences of these subjects in the teaching-learning process. This occurs in a context of reification and fragmentation of socio-cultural, which damages the formative experience. This process hinders the effectiveness of dialogic praxis, which is fundamental to the success of School Education
Desenvolvimento, perícia e poder no rural paulista : o caso do Programa Estadual de Microbacias Hidrográficas
(Universidade Federal de São Carlos, 2013-03-12) Gameiro, Mariana Bombo Perozzi; Martins, Rodrigo Constante; https://lattes.cnpq.br/6617183095074852; https://lattes.cnpq.br/5015952241455361
This research analyzes the relations established by agents with the expert knowledge in the context of a public policy for rural development, by reconstructing the experiences of those who took part of its processes of formulation and implementation. These processes are often mediated by funding institutions and rural extension agencies. Analyzing social phenomena from the perspective of mediations, and more specifically, from the perspective of expertise, assumes the centrality of power dimensions, the identification of its asymmetries and constant disputes over the construction of views about ruralities. The object of this study is the Land Management III Project (Programa Estadual de Microbacias de São Paulo - PEMH), one of the first public policies with a territorial, decentralized and participative approach for the sustainable rural development of the State of Sao Paulo. This program was partially financed by the World Bank and executed between 2000 and 2008 by the State Secretary of Agriculture, through its rural extension body, the Coordination of Integral Technical Assistance (CATI). The problematization of this research was designed from Anthony Giddens concept of systems experts, from whom we also extracted the notions of reflexivity, agency, time and space. Manuel Castells concepts of space of flows and space of places also assisted in the interpretation, as well as Michel Foucault's formulations on discourse. The field researches required the contributions of Luc Boltanski and Erving Goffman on trust and interaction processes. Techniques of social qualitative research, such as interviews and document analysis, were employed.