Twist-Activated Universal Kink Deformations Enabling High Plasticity in Layered Boron Nitride Ceramic

Ceramics inherently suffer from brittleness due to their covalent bonding structures, significantly limiting deformability and restricting applications in various engineering fields. Recent experiments demonstrated that twisted-layer boron nitride bulk ceramic (TS-BN) can achieve 8% compressive plastic strain at room temperature. Nevertheless, a clear understanding of nanoscale plastic deformation, specifically the role of twisted interfaces, remains elusive. Here, we performed large-scale molecular dynamics simulations to investigate how twisted interfaces govern nanoscale plastic deformation in twisted BN (tBN) multilayers, focusing on kink formation-mediated primary plasticity mechanisms compared to conventional hexagonal BN (hBN) multilayers. Kink deformation of hBN exhibits pronounced anisotropy due to the lattice direction-dependent in-plane slipping barriers. This anisotropy constrains bulk deformability owing to the high activation barriers for kink nucleation and formation. In contrast, tBN readily forms stable kink patterns under bending or axial compression, independent of in-plane direction. Compared to hBN, the twisted interfaces in tBN effectively reduce the interlayer shear modulus and sliding energy barrier by 2 orders of magnitude. Increasing the density of twisted interfaces lowers tBN's interlayer shear resistance, which enhances its omnidirectional kink deformation capabilities and facilitates universal kink deformation in bulk TS-BN. This work bridges significant knowledge gaps regarding the effect of twisted interfaces on kink behavior, in which the mechanistic insights propose a generalizable strategy for improving plastic deformation capacity in layered materials.