Comportamento físico, mecânico e microestrutural de massas contendo argilas e resíduo de alumina

Abstract

The pastes of the traditional ceramics are considered ideal for inertization of some residues, due to the chemical composition of these presents oxides that are present in many of the raw materials used in this sector. The study of the phase transformations during the heat treatment of clays and ceramic formulations is of fundamental importance, since the phases formed are responsible for the characteristics of the final products. The objective of this work was to investigate the phase transformations, physical-mechanical and microstructural behavior of pastes containing clay and alumina residue, when subjected to different thermal treatments, emphasizing the kinetics of mulitization. For the development of this work were used clays, kaolin, alumina and alumina residue. Based on the chemical composition of the raw materials and based on the stoichiometry of the mullite, compositions were formulated. Subsequently, rectangular and cylindrical specimens were formed by the uniaxial pressing and extrusion processes, respectively. Then, they were dried (110°C) and burned at 900, 1100, 1200, 1300 and 1400°C, with a heating rate of 5°C/min and 60min dwell time. The mineralogical phases formed were identified and quantified by the X- ray diffraction technique and the morphology was analyzed by scanning electron microscopy. The physical-mechanical properties of the specimens were also analyzed. The formation of mullite needles with average sizes varying from 2.70 to 5.88μm was also observed through scanning microscopic analysis, with the formulation with the highest percentage of flux oxides having higher mullite crystals. It was observed that formulations with better physical-mechanical properties were obtained for formulations containing alumina. For the compressed and sintered specimens, at 1400°C, mechanical strength was obtained between 50 and 72MPa. The best results with respect to permeate flow, 2000L/h.m2, were observed for the composition with alumina residue. With the accomplishment of this study, it was concluded that, the studied alumina residue can be used as an alternative raw material in pastes, that can be used in diverse applications in the manufacture of ceramic products.