Caracterização estrutural, físico-mecânica e dielétrica de compósitos mulita fase vítrea

Abstract

Mullite (3Al2O3.2SiO2) is an aluminosilicate of great technological importance commonly obtained by solid state between kaolinite and alumina at high firing temperatures. The main interest in the study of multi-layered and multi-matrix composite ceramics is due to the unique properties of this material, such as low density, low thermal conductivity, low thermal expansion, low dielectric constant, good chemical stability and good high temperature properties. However, due to its low availability in nature, in addition to the high value of its raw materials, it is increasingly necessary to search technologies that provide the best cost/benefit in obtaining these materials. In this context, the present work is focused on obtaining mullite/glass composites via reactive sintering of mixtures kaolinite clay- kaolin residue, both from the State of Paraíba. The raw materials were characterized by particle size analysis, X-ray fluorescence and X-ray diffraction. The samples were sintered at 1400 ° C and evaluated for apparent density, apparent porosity, water absorption, and flexural modulus as a function of the concentration of kaolin residue (0, 30, 50 and 70% by mass). The results indicated the predominance of the mullite phase, followed by an amorphous component (glassy phase) and quartz as minority phase. The morphological characteristics of the obtained composites were evaluated by scanning electron microscopy and evidenced the formation of dense material formed by acicular mullite immersed in a vitreous phase matrix at 1400 ° C. It was possible to observe that the addition of the residue improved the physical-mechanical properties of the composites. This improvement due to the addition of the kaolin residue is associated to a liquid phase assisted sintering process, activated by the presence of muscovite mica.