Sustentabilidade urbana e as certificações ambientais na construção civil

There is a huge debate surrounding the sustainability issues, especially urban sustainability. This article seeks to establish a critique of models of sustainable cities and postmodern city structured by dispersed city model produced by the logic of capital, it is an effort to confront methodological theoretical models of two cities, the capitalist model of production space and model sustainable city, the dispersed city model against a model of the compact city. For example it was used as environmental certifications for building a label denoting sustainable building when actually articulate a series of symbols that mask and reaffirm their production processes from the perspective of capital cities

In Situ Observation of the Thermal Decomposition of Weddelite by Heating Stage Environmental Scanning Electron Microscopy

The morphological and chemical changes occurring during the thermal decomposition of weddelite, CaC2O4·2H2O, have been followed in real time in a heating stage attached to an Environmental Scanning Electron Microscope operating at a pressure of 2 Torr, with a heating rate of 10 °C/min and an equilibration time of approximately 10 min. The dehydration step around 120 °C and the loss of CO around 425 °C do not involve changes in morphology, but changes in the composition were observed. The final reaction of CaCO3 to CaO while evolving CO2 around 600 °C involved the formation of chains of very small oxide particles pseudomorphic to the original oxalate crystals. The change in chemical composition could only be observed after cooling the sample to 350 °C because of the effects of thermal radiation.