Experimental study of deformations and state of tension in traditional ceramic materials

Abstract

Generally, the deformations of ceramic materials during and after firing may have a complex origin. If the products are made up of a single material, such deformations are mainly due to pyroplastic phenomena. In the case of multi-layer materials (like glazed ceramics or double charge technology products), two further factors must be considered: the state of tension established between layers, and their differences in behaviour during sintering. A novel optical contactless experimental technique providing bending data during the heating treatment, is presented. Combining it with optical dilatometry tests, a complete investigation of elastic and plastic deformations occurring in traditional ceramic materials is achievable. Being acquainted with the truth state of tension between layers, ordinary deflects like planarity problems and delayed crazing can be avoided. The results obtained show the possibility to get reliable and direct information on phenomena differently hard to predict with traditional contact techniques.