Preparation and properties of porous microcellular SiC ceramics by reactive infiltration of Si vapor into carbonized basswood

Highly porous microcellular SiC ceramics, a kind of biomorphic SiC with anisotropic pore structures, were prepared by reactive infiltration of Si vapor into porous carbon templates produced from basswood by high-temperature pyrolysis. The phase identification and morphology of the carbon templates and porous microcellular SiC ceramics were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The macroscopical properties of the resulting biomorphic SiC ceramics were characterized by pore size distribution, open porosity and bending strength. The process of the reactive infiltration of Si vapor into basswood carbon template was also introduced and analyzed. The SiC ceramics possessed a unique pore microstructure pseudomorphous to basswood charcoal. The SiC ceramics were composed of major crystal phase of β-SiC and secondary phase of unreacted carbon, and of a multimodal pore size distribution. Si vapor diffused through the primary β-SiC layer, which was reaction rate controlling step of the Si vapor infiltration/reaction process, and reacted with the inner carbon to form β-SiC at the SiC–C interface. The open porosity and bending strength of the porous SiC ceramics were above 50% and 50 MPa, respectively.