Obtenção de multa nanométrica a partir de bentonitas delaminadas.

Abstract

Nanotechnology comprises a new paradigm in science, in which the dimensions and material properties are treated at the nanoscale. The nanosized ceramic materials has been investigated, with more intensity, from the 90's, with emphasis on ceramic materials muliti. The mullite ceramic phase is a thermodynamically stable crystalline SiO2.Al2O3 system and has excellent thermal properties, electrical, mechanical, optical and others, arousing interest in synthesizing it, mainly through a mixture of Al2O3 and SiO2 or from minerals these oxides present in its composition, between these minerals can be pointed out the bentonite. Bentonite addition to presenting the above oxides in its composition, delaminated when you can get the dimensions of nano-sized particles, which makes it a potential precursor for the production of nanopowders of mullite. Nanosized precursors are more reactive and facilitate the dissolution of aluminum ions in the liquid formed during the synthesis, favoring the formation of mullite phase in increasingly lower temperatures. The synthesis and processing of microwave sintering enables energy saving and obtaining a more refined microstructure, because the heating is volumetric and the heating rate is high, favoring the diffusion processes and chemical reactions. The objective of this study was to obtain nanosized powders and submicron mullite, using materials such as bentonite clay delaminated precursors for the synthesis and rapid heating in the microwave. The bentonites were processed and characterized chemically, physically and mineralogically. The synthesis process was conducted in a household microwave oven for 10, 15, 20 and 25 minutes and then there was the removal of the vitreous samples submitted to the above steps were characterized by x-ray diffraction scanning electron microscopy. Based on the results showed that: hydration and freezing favored the delamination of bentonite clay and that these procedures were more effective for clay containing low sodium oxide; delaminated samples showed better performance during the synthesis process, getting evidenced by the higher percentage of mullite phase formed and smaller average size of crystal and the heating process in a microwave oven favored the formation of mullite phase to the time of 25 minutes. Regarding the aspect of mullite microstructure, all samples showed acicular shapes and fiber.