A Gradient Enamel‐Mimetic Composite via Crisscross Assembly of Aligned Hybrid Nanowires for Excellent Mechanical Performance

Materials with excellent comprehensive mechanical properties (e.g., strength and toughness, stiffness and damping, fatigue et al.) are highly desirable for engineering applications, while it is still challenged for design. Tooth enamel is a typical biomaterial with outstanding mechanical properties that originate from its multiscale and gradient structure. Some composites with enamel-like multiscale structures are successfully synthesized, but mimicking the gradient structure of tooth enamel is still difficult to realize. Here, an enamel analog is fabricated with a gradient structure similar to inner enamel based on the crisscross assembly of aligned hybrid nanowires through a magnetic-assisted freeze casting and subsequent mechanical compression strategy. The gradient enamel-mimetic composites exhibited high strength and toughness surpassing the natural tooth enamel, and simultaneously high stiffness and damping comparable to those of enamel, as well as high fatigue resistance. The interface reinforcement of gradient structure, crystal/amorphous and organic/inorganic, fundamentally accounted for high mechanical performance. The gradient design strategy provides an avenue for the engineering of structural materials with excellent mechanical properties.