Microstructure and Properties of Porous SiC Ceramics Modified by CVI-SiC Nanowires

Sintered porous SiC ceramics are modified with SiC nanowires prepared via chemical vapor infiltration (CVI). SiC nanowires are successfully grown within sintered porous SiC ceramics following vapor–liquid–solid growth. The diameter of the SiC nanowires is in the range of 200 nm–1 μm, and first decreases with increasing input gas ratio (α = 50, 60, 70, and 80) and increases thereafter. The diameter of the nanowires decreases from the surface to the interior areas of the porous SiC ceramics. SiC nanowires effectively improve the mechanical properties of the porous SiC ceramics, and sample Ni-50 has the highest flexural strength of 33.91 MPa and fracture toughness of 0.79 MPa · m^1/2, which increases by 90.4% and 49.1% compared to an unmodified sample, respectively. Additionally, the presence of SiC nanowires leads to porous SiC ceramics with altered porosity and microstructure, and higher thermal conductivity. The porous SiC ceramics modified by CVI SiC nanowires satisfy the requirements of gas filtration applications and the pressure drop increases with decreasing apparent porosity. The porous SiC ceramics modified with CVI SiC nanowire has higher permeability than those resulting from the introduction of CVI-SiC matrix or CVD-SiC coating into porous SiC ceramics.