Densification of low‐density boron carbide by Li doping and its microstructural characterization

Abstract

AbstractLithium (Li)‐doped boron carbide (B4C) has generated widespread attention for its potential to enhance mechanical properties. Nevertheless, the influence of the Li solid solution on the microstructure and mechanical properties of B4C ceramics remain unclear. In this research, the microstructure of Li‐doped B4C was investigated in meticulous detail. Through X‐ray diffraction, X‐ray photoelectron spectroscopy, and Raman spectroscopy analysis, it was confirmed that Li successfully solubilized in B4C at 1 500°C under 50 MPa for an 8 min, resulting in lattice expansion. Further insights from electron energy loss spectroscopy revealed the integration of Li into the crystal lattice and alterations in the C–B–C chains. Furthermore, the Li2O content significantly affected the densification and microstructure of B4C. Relative density increased from 91.2% (B4C) to 99.2% (9 wt.% Li2O–B4C), accompanied by a transition from a few intragranular planar defects to high‐density twins. Mechanical property tests demonstrated that 9 wt.% Li2O–B4C exhibited optimal comprehensive mechanical performance, with a flexural strength of 533 ± 27 MPa, fracture toughness of 3.71 ± 0.29 MPa∙m1/2, hardness of 33.3 ± 0.6 GPa, and a density of just 2.45 g/cm3, surpassing that of pure B4C.