Although activating toughening mechanisms during crack growth can postpone catastrophic fracture, a more potent toughening mechanism is to heal the cracks as they form.Ĭrack-healing requires local flow of material to close and heal the cracks by physical or chemical interactions ( 13). The quest to enhance damage tolerance also includes the development of nature-inspired ceramic-based (hybrid) materials with hierarchical structures that can trigger a combination of toughening mechanisms ( 7– 12). Traditional approaches to partially overcome this issue in ceramic materials rely on microstructure-specific toughening mechanisms such as crack-deflection, crack-bridging, microcracking, and stress-induced phase transformations ( 5, 6). In particular, at room temperature, ceramic materials readily undergo catastrophic fracture by cohesive bond breaking at the crack tip. While ceramic materials provide outstanding chemical and structural stability at high temperatures and in hostile environments, their insufficient plastic deformability and damage tolerance compared to metallic materials severely limit their applicability ( 5, 6). The lack of materials capable of withstanding extreme environments, more often than not, imposes the greatest technological barrier to the development and deployment of a host of next-generation technologies, such as efficient jet engines, hypersonic flights, and safer nuclear reactors ( 1– 4). This implies that the toughness of numerous other layered ceramic materials, whose broader applications have been limited by their susceptibility to catastrophic fracture, can also be enhanced by microstructural engineering to promote kinking and crack-healing. However, the onset of an abstruse mode of deformation, referred to as kinking in these materials, induces large crystallographic rotations and plastic deformation that physically heal the cracks. Crystals of this class of ceramic materials readily fracture along weakly bonded crystallographic planes.
Here, we demonstrate a more potent toughening mechanism that involves an intriguing possibility of healing the cracks as they form, even at room temperature, in an atomically layered ternary carbide. Traditional approaches to partially overcome this limitation rely on activating toughening mechanisms during crack growth to postpone fracture. Ceramic materials provide outstanding chemical and structural stability at high temperatures and in hostile environments but are susceptible to catastrophic fracture that severely limits their applicability.
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