In situ growth of SiC wires on CVI densification of SiC foam

Silicon carbide (SiC) foam prepared by polymer infiltration and pyrolysis (PIP) process was further densified with beta-SiC by chemical vapor infiltration (CVI) technique. Scanning electron microscopy and high-resolution transmission electron microscopy images confirmed the presence of highly entangled and branched in situ grown SiC wires of uniform diameter (similar to 500 nm) over the struts of open-cell SiC foam. A uniform rate increase in diameter from nanometer to micron range (similar to 11 mu m) was observed with an increase in the CVI reaction period. X-ray diffraction results showed the formation of highly crystalline beta-SiC structure along the direction with stacking faults. The formation of SiC wires was explained by the vapor-liquid-solid mechanism and evenness of the surface and uniform growth rate of SiC confirmed the homogeneous concentration of gaseous species during CVI reaction. The compressive strength increased with relative density, with maximum values of 5.5 +/- 1.26 MPa for ultimate SiC foam (rho = 400 kg/m(3)) prepared by hybrid PIP/CVI technique. The thermo-oxidative stability of the resultant foam was evaluated up to 1650 degrees C under air and shows excellent thermal stability compared to SiC foam prepared by PIP route. The densified SiC foam can find potential applications in the field of hot gas filters, catalyst supports, microwave absorption properties, and heat insulation for high-temperature applications.

Automated summary

Silicon carbide (SiC) foam was densified with beta-SiC through chemical vapor infiltration (CVI) technique after polymer infiltration and pyrolysis (PIP) process. Highly entangled and branched SiC wires of uniform diameter were observed over the struts of open-cell SiC foam, showing a uniform diameter increase with CVI reaction period. The resultant foam exhibited good thermal stability and could be used in various high-temperature applications.