In ceramics under deformation, which atomic-scale process is associated with brittle fracture?

• A. Dislocation glide with minimal resistance
• B. Amorphization under stress
• C. Melting of grains at room temperature
• D. Slip with like-charged ion overlap leading to repulsion and fracture

Answer: (D)

In ceramics, brittle fracture happens because plastic deformation is very limited; the strong ionic or covalent bonds make dislocation motion difficult, so the material can’t soften by sliding grain boundaries. At the atomic level, when stress drives deformation, moving ions past each other would require bringing like-charged ions into close proximity, which causes strong electrostatic repulsion. That repulsion promotes bond breaking and crack propagation rather than stable, plastic slip. So the atomic-scale process tied to brittle fracture is slip that involves like-charged ion overlap leading to repulsion and fracture. The other ideas don’t fit because dislocation glide with little resistance would imply ductile, not brittle, behavior; amorphization under stress or room-temperature melting don’t capture the typical mode of failure seen in ceramics.