Thermodilatometry of Quartz Porcelain Mixture Under Tensile Loading

Abstract

Abstract Specimens composed of 50 wt.% kaolin, 25 wt.% quartz, and 25 wt.% feldspar were subjected to constant tensile stress during linear heating at 5 °C/min rate to measure their tensile deformation behavior. Deformation occurs at temperatures above 300 °C and depends on the tensile stress: higher external tensile stresses led to a more pronounced expansion of the sample during the dehydroxylation region. Consequently, at temperatures above 1100 °C, sintering of the samples in the liquid state and intense contraction occurred. The dilatation behaviour of the samples was governed by the combined effect of opposing forces. One of these forces originated from external loading and caused the elongation of the specimen. The other force resulted from surface tension, which resulted in the shortening of the specimen. At temperatures above 1100 °C, a distinct V-shaped minimum appeared on the dilatometric plot, indicating a balance between these forces. As the temperature increased, the viscosity of the glassy phase decreased, weakening the surface forces. Eventually, the external force prevailed, causing further elongation of the samples.