Microstructural Evolution and Mechanical Properties Enhancement of B ₄ C Ceramics via BN‐Coated Powder Design

ABSTRACT This study presents a CVD synthesis strategy for BN‐coated B 4 C powder synthesis employing controlled nitridation of B 4 C in an NH 3 atmosphere for achieving a homogeneous hexagonal BN distribution in B 4 C/BN ceramics. Systematic temperature modulation (600°C–1200°C) led to different thickness progression with concurrent structural evolution from amorphous to turbostratic BN configurations, ultimately forming nanoflower‐like architectures. BN facilitated particle rearrangement through its lubricative two‐dimensional interlayers and induced phase transformation, which in turn reduced the densification temperature by 150°C. The composite nitrided at 800°C (B 4 C@BN08) exhibited superior comprehensive performance with a flexural strength, fracture toughness, and bulk density of 627 ± 41 MPa, 5.01 ± 0.17 MPa·m 1/2 , and 2.467 g/cm 3 , respectively. Mechanistic analyses revealed that this synergistic strengthening originated from BN nanosheet‐induced crack deflection/branching and pinning effect as well as high‐density defects at B 4 C and BN grains. These findings establish microstructure‐property relationships critical for designing next‐generation lightweight ceramic composites.