Electrochemically assisted room-temperature crack healing of ceramic-based composites

We demonstrated for the first time the room-temperature crack healing in ceramic-based composites. For this purpose, 20 and 30 vol% of fine titanium metal (Ti) were homogeneously dispersed in electrically insulating alumina (Al2O3) ceramic to obtain composites that exhibited excellent electrical conductivity. Electrochemical anodization at room temperature was used to successfully heal cracks induced in the Al2O3/Ti composites and recover their fracture strength and reliability. The bending strength of as-prepared, crack-induced, and electrochemically healed composites was measured to evaluate the crack-healing ability. Moreover, the effects of the anodization current density, crack size (including length and crack open distance), and the conductivity of the composites on their crack-healing behavior were investigated and discussed. The results indicate that the bending strength of crack-induced composites, which was approximately 61% of the crack-free composite strength, was completely recovered after the crack-healing procedure at room temperature under appropriate anodization conditions. The titanium oxides obtained after anodization formed bridges that healed the crack; this was considered to be the main strength recovery mechanism. By anodizing Al2O3/Ti composites, we developed a new and convenient approach to heal cracks and recover the fracture strength of cracked ceramics at room temperature.