How do interlocked grains prevent cracks from spreading through ceramics?

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advanced ceramics Steps in doctor blading, a tape-casting process employed in the production of ceramic films. Ceramic powder and solvent are mixed to form a slurry, which is treated with various additives and binders, homogenized, and then pumped directly to a tape-casting machine. There the slurry is continuously cast onto the surface of a moving carrier film. The edge of a smooth knife, generally called a doctor blade, spreads the slurry onto the carrier film at a specified thickness, thereby generating a flexible tape. Heat lamps gently evaporate the solvent, and the dry tape is peeled away from the carrier film and rolled onto a take-up reel for additional processing.

In advanced structural ceramics, interlocked grains enhance toughness by engineering microstructures that actively resist crack propagation and absorb energy. They prevent cracks from spreading through two primary mechanisms:

Crack Deflection: The interlocked grain structure forces cracks to deviate from a straight path. This deflection significantly increases the total length of the crack, which requires more energy for the crack to continue growing.
Crack Bridging: As a crack advances, particles or grains located behind the crack tip act to bridge the gap. By exerting a force that tends to hold the crack closed, these grains effectively inhibit further opening and propagation.

Together, these processes increase the fracture surface area and lead to much greater energy absorption, helping to mitigate the inherent brittleness of the material.1