Synergistic toughening in layered nanotwinned diamond composites

XM Liu and YH Zhang and DL Zhang and XY Zhang and FX Tang and JS Liu and QJ Wang and F Dong and S Liu, INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, 307, 110901 (2025).

DOI: 10.1016/j.ijmecsci.2025.110901

Nanotwinned (NT) diamond achieves exceptional hardness but faces strength-toughness trade-offs. In this study, we propose layered NT diamond composites incorporating polytype phases within nanoscale twins to enhance fracture resistance. Through systematic atomistic simulations, we evaluate the fracture energy, crack progression patterns, and toughening mechanisms of these composites under uniaxial tension. Our results show that NT-2H diamond, among the layered NT diamond composites, exhibits 37 % greater fracture toughness and 19 % higher ultimate strength than conventional single-phase diamond systems, while maintaining advantages over traditional NT configurations. The enhanced performance arises from multiple toughening mechanisms: twin boundaries (TBs) and phase boundaries (PBs) work together to impede crack propagation through boundary pinning effects; hierarchical crystallographic deflection systems force tortuous crack paths; fracture-induced disordered atomic clusters promote continuous energy dissipation; and stress redistribution achieves both local shielding and global homogenization of stress. The layered architecture delivers superior crack deflection and interfacial stress redistribution compared to conventional NT diamond. The fracture toughness remains stable across polytype layer thicknesses (1.23-7.44 nm), suggesting versatile structural adaptability for engineering applications. Overall, this work offers a promising strategy for designing diamond composites with exceptional strength and fracture resistance.

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