Dilatometric study of ceramic formulations with added engobes reject marble

Full text:The application in the engobe ceramic aims at forming an overlying sublayer before the glaze that will mitigate different compositions between the two bodies (substrate and glaze) wishing to join, limit the risk of appearance of defects in the glaze, hide color substrate, waterproof ceramic piece before glazing and permit the use of thinner layers of glazes. The coefficient of thermal expansion is determined by analysis and can be calculated in different temperature ranges in the heating or cooling technique by dilatometry. This study aims to evaluate the dilatometric behavior of ceramic formulations with added engobes reject marble. Three types of ceramic bodies varying proportions of the following materials were prepared: light burning clay, phosphate, quartz, kaolin, zircon, feldspar, frit, carboxymethylcellulose (CMC) and the homogenized residue marble masses, initially characterized by the techniques of X-ray fluorescence (XRF) and X-ray diffraction (XRD). Bodies for each formulation rectangular specimens were fabricated using manual hydraulic press with a pressure of 25 MPa. They were placed in the dilatometer, in which the temperature may reach a maximum of 1100°C with a heating rate of 10°C/min. The results showed a considerable shrinkage caused by sintering beginning with the formation of the liquid phase and densification of the ceramic product. The well steep downward slope of the dilatometric curve from 900°C showed that there is a formation of a large mass transport and growth of the neck (solid densification) promoted by melting mineral oxides present in compounds. The shrinkage of the ceramic product occurred as a result of carbonization of organic matter and clay mineral dehydroxylation. References [1] PINHEIRO, B. C. A.; SILVA, A. G. P.; HOLANDA, J. N. F. Uso de Matérias-Primas do Rio Grande do Norte na Preparação de Massa Cerâmica para Grês Porcelanato. Cerâmica Industrial, v.15, p. 29-33, 2010. (author)