B4C ceramics with increased dislocation density fabricated by reactive spark plasma sintering via carbon nanotubes–boron mixture

Boron carbide with high relative density was prepared in situ using spark plasma sintering. Research on the in-situ reaction of boron and carbon nanotubes reveals that the reaction exhibits high reactivity at 1200 °C. Beyond this temperature, increasing the external pressure was beneficial for particle rearrangement, gas release, and dislocation formation. The result of mechanical properties shows that, the flexural strength and fracture toughness of the boron carbides are 656 ± 9 MPa and 5.0 ± 0.3 MPa·m1/2, respectively, when sintered at 1750 °C under continuous pressure ramping conditions–an increase of 64.1% and 46.6% compared to that prepared under constant pressure conditions. Increasing the magnitude of the external stress during the in-situ reaction process can also enhance the particle rearrangement efficiency, inducing the formation of twinning and stacking faults in boron carbide ceramics. High–density twinning and stacking faults dominated the toughening mechanisms of ceramic materials.