Thermal cycling damage of silica refractories for high-temperature thermal energy storage (HT-TES) - Can it be healed?

Silica refractories are promising materials for high-temperature thermal energy storage (HT-TES), because they exhibit excellent thermal cycling properties, unless cooled below a critical temperature (usually assumed to be 600 degrees C). When cooling down to room temperature severe damage can occur, which can be conveniently monitored via the impulse excitation technique (IET). This damage is most severe when the cycling maximum temperature is low. The question is whether this damage can be healed again. In this short contribution we show that severe damage in silica refractories, caused by heating from room temperature to 300 degrees C and back again to room temperature, can indeed be healed by thermal cycling to 1300 degrees C. The healed material is actually better than the pristine material.