Strengthening boron carbide through lithium dopant

Abstract

AbstractThe high strength of boron carbide (B4C) is essential in its engineering applications such as wear‐resistance and body armors. Here, by employing density functional theory simulations, we demonstrated that the strength of B4C can be enhanced by doping lithium to boron‐rich boron carbide (B13C2) to form r‐LiB13C2. The bonding analysis on r‐LiB13C2 indicates that the electron counting rule (or Wade's rule) is satisfied in r‐LiB13C2 whose formula can be written as r‐Li+(B12)2‐(CB+C). The shear deformation on r‐LiB13C2 indicates that its ideal shear strength is larger than that of B4C because of the existing of Li dopant. The failure process of r‐LiB13C2 under ideal shear deformation initiates from breaking the icosahedral‐icosahedral B‐B bonds. Then these B atoms react with the middle B in the C‐B‐C chain, resulting in the disintegration of icosahedral clusters and brittle failure. More interesting, the nanotwinned r‐LiB13C2 is even stronger than r‐LiB13C2 because of the directional nature of covalent bonding at the twin boundaries. This suggests that the nanotwinned r‐LiB13C2 has a significant enhanced strength compared to B4C. Our simulation results illustrate the deformation mechanism of Li‐doped boron carbide and its nanotwinned microstructure. We proposed to improve the strength of boron carbide by doping Li into B13C2 and increasing its twin densities.