Kinetics of self-repair in inorganic glasses: modeling and experimental verification

A novel concept of self-repairable glass useful as seals in solid oxide fuel cells (SOFCs) is proposed, developed, and used for making metal-glass–ceramic seals for enhancing reliability and life. In this concept, cracks created during SOFC operation are repaired by the crack healing process driven by the viscous flow of the glass. An approach for studying the kinetics of crack healing in glasses responsible for the self-repair is described and used to study the crack healing behavior. The cracks are created by a microindenter, and the progression of healing of cracks thus created on a silicate glass surface is experimentally determined at different annealing temperatures and times. Sequential changes in the crack morphology during thermal healing are also studied to identify the three stages of crack healing process. A crack healing model, based on the relationship among crack length, time, temperature, glass viscosity, and its flow behavior is developed in order to describe and predict the time required for self-repair on a glass surface. The predictions from the developed model is then compared with the experimental data and found to be in good agreement. These results also demonstrated the relative importance of the different stages of crack healing on the overall healing or self-repair behavior.