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

Abstract

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 (Al 2 O 3 ) ceramic to obtain composites that exhibited excellent electrical conductivity. Electrochemical anodization at room temperature was used to successfully heal cracks induced in the Al 2 O 3 /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 Al 2 O 3 /Ti composites, we developed a new and convenient approach to heal cracks and recover the fracture strength of cracked ceramics at room temperature.

Role of CeAl11O18 in reinforcing Al2O3/Ti composites by adding CeO2

“…In addition, multifunctional applications of Al 2 O 3 /Ti composite were newly developed. For example, photocatalytic activity 18 and room temperature crack‐healing ability 19 …”

“…For example, photocatalytic activity 18 and room temperature crack-healing ability. 19 In spite of the improved fracture toughness, excellent electrical conductivity, and multifunctional applications, Al 2 O 3 / Ti composites show degraded flexural strength. In addition, interfacial reaction between Al 2 O 3 and Ti still exists which might harm the performances of these composites.…”

A review of some of experimental and numerical studies of self‐crack‐healing in ceramics

“…The obtained/formed oxides (TiO 2 ) after the anodization process could heal the cracks and seal its faces. 105 Takashi reported a complete rebonding of the cracks after heat treatment at a temperature of 600°C for a holding time of 10 minutes with high-temperature oxidation of the nonoxide interlayer healing agent as the main mechanism to heal the cracks 106 . Sitnikov et al discussed in their paper the basic concepts and mechanisms of self-healing in different types of materials including ceramics; in their paper, they provided a brief summary of the physical and chemical aspects of self-healing in materials.…”

“…Upon the sintering process chemical and physical reactions occur, which result in conversion process of the substances, the solid-state reaction can be described using analytical model, an example of such model is the master curve plot which uses/ employ the generalized time (ξ), which is the time required to obtain a function converted at infinite temperature, describe the isothermal or nonisothermal reactions respectively: 2.2 | Self-Healing Mechanism in Ceramics 98,104,105 In ceramics, the self-healing of the damage is initiated/induced through the thermal activation followed by the sintering process, rearrangement of the particles/atoms, viscous flow of the glassy phase(s) and hence sealing of the cracks and/or the solid-state oxidation reaction.…”

“…In this process, the composites were used as anodes and Pt as cathode, the distance between the cathode and anode is 15 mm. The obtained/formed oxides (TiO 2 ) after the anodization process could heal the cracks and seal its faces 105 . Takashi reported a complete rebonding of the cracks after heat treatment at a temperature of 600°C for a holding time of 10 minutes with high‐temperature oxidation of the nonoxide interlayer healing agent as the main mechanism to heal the cracks 106 .…”