Insights into the influence of three-dimensional interface on the high mechanical-electrical properties of BNNS/Cu(Ti) composites: experimental and computational evaluation

To overcome the strength-electrical conductivity trade-off in boron nitride nanosheet (BNNS) reinforced Cu matrix composites, 1.5 wt.% Ti was introduced into BNNS/Cu(Ti) material systems and triggered the solid-state interface reactions. The interface coherence orientation effectively minimized interface strain energy, ensured robust interface bonding and enhanced structural stability. Benefited from the typical three-dimensional interface, BNNS/Cu(Ti) composites achieved a tensile strength of 701 MPa and the electrical conductivity of 82 %IACS. Three-dimensional interface ensured both interfacial stability and efficient load transfer from BNNS during deformation. First-principles calculations showed that TiN transition layer induced a metallic transformation in the BNNS at the interface, which significantly enhanced the interface conductivity. Moreover, the low lattice mismatch between TiN and Cu promoted quasi-ohmic contact characteristics at the TiN/Cu interface, significantly reduced interface contact resistance and eliminated the Schottky barriers to electron transport as well as charge accumulation. Collectively, by in-situ constructed conductive ceramic phases to establish a three-dimensional interface, this work proposed a novel interface engineering strategy to overcoming the strength-conductivity dilemma in BNNS/Cu composites.