Influência das variáveis de processamento em formulações cerâmicas à base de argilas.

Abstract

Clays are key components of mass for production of traditional ceramic materials because they ensure plasticity in the shaping step and mechanical strength after firing, due to the phase and microstructural transformations that happen at high temperatures. Microstructural changes and properties of ceramic materials are dependent of the raw materials and the processing, from the beneficiation step to the final heat treatment. This work aims to analyze the influence of processing parameters, such as maturation time, shaping method and firing temperature, on the physico-mechanical properties and the microstructural aspects of ceramic pieces produced with clay-containing masses. The clays were characterized by particle analysis, chemical analysis, X-ray diffraction, differential thermal analysis and thermogravimetric analysis. The formulations were submitted to maturation for a period of one to four weeks and characterized, also evaluating plasticity. Then, the samples were shaped by the pressing and extrusion processes, which were then subjected to heat treatment at temperatures of 1200, 1300 and 1400oC, after which the following properties were analyzed: water absorption, apparent porosity, apparent density, linear firing shrinkage and flexural strength. The microstructural aspects obtained after firing were evaluated by: X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that for the maturation time factor, a standard behavior among the assays was not identified for the formulations. In terms of mechanical behavior, the pressing process was better than the extrusion process for the studied formulations. The firing temperature was the parameter that had the greatest influence on the evaluated properties, with the highest temperature (1400°C) exerting the most influence. Finally, it is verified that the processing variables influenced the orientation of the clay particles and the physical-mechanical properties of the sintered ceramic bodies.