Abstract
Self-crack-healing by oxidation of a pre-incorporated healing agent is an essential property of high-temperature structural ceramics for components with stringent safety requirements, such as turbine blades in aircraft engines. Here, we report a new approach for a self-healing design containing a 3D network of a healing activator, based on insight gained by clarifying the healing mechanism. We demonstrate that addition of a small amount of an activator, typically doped MnO localised on the fracture path, selected by appropriate thermodynamic calculation significantly accelerates healing by >6,000 times and significantly lowers the required reaction temperature. The activator on the fracture path exhibits rapid fracture-gap filling by generation of mobile supercooled melts, thus enabling efficient oxygen delivery to the healing agent. Furthermore, the activator promotes crystallisation of the melts and forms a mechanically strong healing oxide. We also clarified that the healing mechanism could be divided to the initial oxidation and additional two stages. Based on bone healing, we here named these stages as inflammation, repair, and remodelling stages, respectively. Our design strategy can be applied to develop new lightweight, self-healing ceramics suitable for use in high- or low-pressure turbine blades in aircraft engines.
Highlights
Strategies that confer self-healing properties may extend the applications of ceramic materials
We investigated the potential application of this approach in fabricating ceramics for use as turbine blades or other components in aircraft engines
We have fabricated a new bioinspired self-healing ceramic infused with a three-dimensional (3D) network of healing activator
Summary
Strategies that confer self-healing properties may extend the applications of ceramic materials. Damage exposes the healing agent to high temperatures or to the atmosphere, triggering an oxidation reaction that fills and bonds the damaged surface, allowing autonomous, complete recovery This strategy has been implemented using silicon carbide (SiC)[17,18,19,20,21,22,23,24,25], compounded MAX phases[26], and others. We have enhanced the already excellent self-healing capacity of an Al2O3/SiC composite ceramic[19,20,21,22,23,25] by producing a mobile phase enabling efficient oxygen delivery, and by incorporating an additional network of healing activator This approach significantly accelerates fracture gap filling and promotes regeneration of a mechanically strong crystal phase. We investigated the potential application of this approach in fabricating ceramics for use as turbine blades or other components in aircraft engines
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