Sintering and characterization of additive-free B4C/SiCw composites using high-pressure techniques

Abstract

Dense B₄C-based ceramics reinforced with SiC whiskers (SiC_w) were successfully fabricated via high-pressure (4 GPa) and high-temperature sintering at 1650°C and 1850°C without any sintering additives. Composites containing 2.5–10 wt.% SiCw were systematically investigated to assess the influence of whisker content and sintering temperature on microstructure, densification, mechanical properties, and thermal diffusivity. Results showed that increasing SiCw content initially improved mechanical performance; however, excessive whisker addition caused a decline in both hardness and fracture toughness due to whisker agglomeration and microstructural inhomogeneities. The composite with 5 wt.% SiCw sintered at 1850°C exhibited the optimal balance, achieving the highest relative density (99.25%), Vickers hardness (30.97 GPa), and fracture toughness (3.24 MPa m^1/2). This sample demonstrated the most stable thermal diffusivity at elevated temperatures, with minimal degradation from room temperature up to 1400°C. Conversely, the 10 wt.% SiCw composite sintered at 1650°C showed the highest thermal diffusivity at room temperature (18.5 mm²/s) but suffered from reduced thermal stability at elevated temperatures. These findings underscore the crucial role of SiC whisker content and sintering conditions in tailoring the interplay between mechanical strength and thermal transport in B₄C-based ceramics, providing valuable insights for their application in extreme environments.