Relationship between Young's modulus and temperature in porcelain tiles

Abstract

A focused research was conducted on samples prepared from an industrial porcelain tile composition containing quartz, used to produce ceramic floor tiles, with the aim of evaluating the variation of fired specimens' Young's modulus with temperature. These samples were fired in controlled laboratory conditions so that specimens with pre-existing cracks were obtained and subject to non-destructive in situ thermo-mechanical measurements (impulse excitation technique) in the 22-700°C temperature range during heating and cooling processes in order to find evidences to explain the hysteresis phenomenon in the Young's modulus versus temperature curve. The observed irreversible Young's modulus may be directly related to the pre-existent cracks that on heating and cooling are closed and opened up respectively, changing thus the Young's modulus which is well characterized by a hysteresis cycle.

Young’s modulus of prefired quartz porcelain in a temperature range of 20–1200 °C

“…A different situation is noted for samples S600-S1200 (Figures 8, 9 and 10) where Young's modulus steeply increases over the temperature interval, in which the a ® b transition of quartz occurs. We met this phenomenon in our previous works 2, 5 and in the paper written by A. P. N. de Oliveira et al 3 where samples fired at temperatures sufficient for forming the glassy phase were measured. The quartz grains are not free here since they are encapsulated by the glassy phase.…”

“…If a fired ceramic mixture contains a sufficient amount of quartz, the relationship between Young's modulus and the temperature measured during the heating reflects the presence of quartz through a steep increase in the values of Young's modulus in a relatively narrow interval around the a ® b transition of quartz. This was found on quartz porcelain fired at 1320°C, 2,3 on corundum porcelain fired at 1330°C, 4 and also on illite-based tiles fired at 1100°C and 1200°C. 5,6 This increase in Young's modulus is caused by the closing of the circumference cracks around the quartz grains.…”

“…Similar results were also obtained for fired porcelain tiles. 3 After a decrease in the a ® b transition of quartz, Young's modulus of samples S400, S500 and S600 shows a moderate increase due to the solid-state sintering up to »950°C when the metakaolinite lattice collapses and a new phase (Al-Si spinel) is formed. 33 Its density is higher than that of metakaolinite; therefore, a steep increase in Young's modulus is observed above this temperature.…”

“…Thus, the quartz grains generate a compressive stress in their close surroundings. Since many quartz grains have circumferential microcracks around them, 3,30,31 the stress has a healing effect, leading to an increase in Young's modulus. Such a situation can be expected for samples S1100 and S1200.…”

Mechanical parameters identification for laminated composites based on the impulse excitation technique

“…When the resonant frequency is known and the dynamic Young's modulus and dynamic shear modulus can be calculated using their relationship with resonant frequencies respectively. However, so far only the dynamic Young's modulus and dynamic shear modulus detection methods for simple structures (beams of rectangular cross section and rods of circular cross section) are well established and the calculation formulas of dynamic Young's modulus and dynamic shear modulus are also reported [25][26]. The reason is that the correction factors depend the shape of structures are difficult to obtain accurately.…”