Obtenção de cerâmicas porosas a partir de argila Ball Clay, alumina e talco.

Abstract

The porous ceramics have been used as filters, support of membranes, refractories, biomaterials and electronic components. This diversity of applications is related to a set of properties such as melting point, high permeability, low density, chemical stability and high mechanical strength. Thus, this work consists on preparation of porous ceramics from the sintering of mixtures containing ball clay, alumina, talc and chamotte. It were stuudied two compositions: C1 (ball clay, alumina and talc) and C2 (ball clay, alumina, talc and chamotte). Initially, C1 ceramic mass was characterized by X-ray fluorescence, X-ray diffraction, thermal analysis, particle size and plasticity. For the development of the composition C2, a chamotte was produced from the burning of the ceramic mass C1 at 1175 °C, which was characterized by X-ray diffraction and particle size, and studied in the following percentages: 10, 20, 30 and 40% by weight. The composition C1 was formed by pressing and extrusion. The firing was performed at seven temperatures: 1025, 1050, 1075, 1100, 1125, 1150 and 1175 °C. For the composition C2, only the pressing process was used. The firing was performed in four temperature ranges: 1025, 1050, 1075 and 1100 °C. Subsequently, the ceramic pieces were analyzed by X-ray diffraction and scanning electron microscopy. It were evaluated the linear retraction, water absorption, apparent porosity and mechanical resistance. Flow tests with distilled water were performed with the tubes of composition C1. As for the results, the X-ray diffraction showed the presence of α-cordierite (indialite) in samples sintered at 1175 °C. These samples presented the highest values of linear retraction and mechanical resistance. The highest values of water absorption and apparent porosity were found in sintered samples between 1025 and 1100 ° C. Regarding the samples of composition C2, the results indicated that the addition of chamotte favored lower retraction and low values of mechanical resistance. The images obtained by scanning electron microscopy allowed the analysis of pore evolution as well as the identification of the hexagonal crystals of the α-cordierite phase. A maximum value of 41.1 L.h/m2 was observed after the flow assays.