Enhancing the hardness and thermal stability of submicron polycrystalline B₄C bulks through penetrating and intersected architectures

Existing pure B₄C bulk materials fabricated by conventional strategies generally suffer from impurity phases or grain growth. Here, we synthesized pure and dense submicron polycrystalline B₄C bulks using microcrystalline B and C precursors under HPHT conditions. Moreover, the sample synthesized at 5.5 GPa and 1900 °C for 30 min possesses the highest Vickers hardness (46.3 ± 4.3 GPa), compressive strain (6.11 %) and antioxidant temperature (859 °C) among in any known pure B₄C materials, and also exhibits high compressive strength (5.36 GPa), nanoindentation hardness (42.5–54.9 GPa) and elastic modulus (408.9–469.8 GPa) comparable to B₄C single crystal. The exceptional properties are attributed to the interaction between the penetrating structure (twins and stacking faults) and the intersected stacking faults architectures (nanostructured network cells and L-C locks). These findings develop a promising method for the preparation of high-performance superhard materials and hard ceramics by high-pressure reaction of microcrystalline precursors.