Abstract
Results obtained by mf-TMA during heating showed a direct relationship between the elastic properties of kaolin and green porcelain samples. Young's modulus and the mechanical strength of the green porcelain sample seem to be determined by the properties of the interfaces between kaolinite crystals.
Mechanical properties improve between 50 - 250 oC and then between 650 - 1100 oC, which can be explained by solid-phase sintering. Young's modulus and the mechanical strength in the cooling stage of firing are predominantly determined by the stresses created and relaxed between the glassy phase and the quartz grains.
They are a source of microcracks that are mostly located in the vicinity of the quartz grains. As a consequence, Young's modulus and the mechanical strength decrease.
Results obtained using the AE technique reveal several stages of microcracking. This process begins at the temperature of the glass transition.
At the temperature of the β RIGHTWARDS ARROW α transition, cracking is temporarily interrupted and a partial recovery of the structure occurs. Below this temperature circumferential cracks around the particles appear with less intensity, especially when the temperature is decreased below 300 oC.