Effects of ZrB_2 contents on the mechanical properties and thermal shock resistance of B_4C-ZrB_2 ceramics

摘要

B_4C-ZrB_2 ceramics with different ZrB_2 contents were fabricated using hot-pressing technique. The introduction of ZrB_2 greatly promotes the sintering process, and all B_4C-ZrB_2 samples achieve full densification. With the ZrB_2 content increasing from 10 to 40 vol.%, the Vickers hardness ranges from 28.8 to 34.6 GPa, the flexure strength ranges from 233.3 to 523.4 MPa, and the fracture toughness ranges from 6.0 to 7.0 MPa m~(1/2), respectively. The thermal shock properties of B_4C-ZrB_2 ceramics were also investigated using water quenching method. The critical thermal shock temperature difference (ΔT_c) for B_4C-10 vol.% ZrB_2, B_4C-20 vol.% ZrB_2, B_4C-30 vol.% ZrB_2 and B_4C-40 vol.% ZrB_2 ceramics are 293.5, 337.5, 365.4 and 373.5 ℃, respectively. Considering the ceramic should maintain a relatively high initial strength, B_4C-30 vol.% ZrB_2 is found to exhibit the optimal thermal shock behavior.