In-situ reaction-assisted high-pressure sintering of B6O/B4C composites with enhanced mechanical properties

Abstract

Boron suboxide (B₆O) and boron carbide (B₄C) ceramics are promising structure materials due to their remarkable hardness, but their practical applications are limited by insufficient fracture toughness. While composite strategies offer potential solutions, conventional direct sintering methods often fail to achieve optimal mechanical properties. Here, we report a novel approach using carbon-coated B₄C powders as precursors to synthesize B₆O/B₄C composite ceramics via high-pressure sintering. During high-pressure high-temperature (HPHT) processing, the carbon shells over B₄C powders reacted with B₆O to form B₄C in situ, resulting in enhanced grain boundary strength. The composites exhibited a synergistic enhancement in hardness and toughness with increasing B₄C content. The optimized B₆O/B₄C composite (containing 50 wt% B₄C) exhibits superior mechanical properties with a hardness of 40.5 GPa and toughness of 4.8 MPa·m^0.5, surpassing both pure phases. This work demonstrates an effective strategy for fabricating high-performance ceramic composites through in-situ reaction sintering, providing new opportunities for developing advanced structural ceramics.