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Wood has strongly anisotropic cellular structure with 50-80 vol% porosity. It can be converted into porous ceramics (e.g., SiC, SiC/Si, TiC, C/C, and TiO2) replicating the wood structure by various processes. Previously porous cellular SiC ceramic was prepared by reaction of wood charcoal with gaseous SiO generated remotely from an equimolar mixture of Si and SiO2. In the present work, poplar charcoal was simply embedded in the powder mixture of Si and SiO2 and heated at 1600°C for 1 h in Ar to produce porous SiC. Samples were also prepared by infiltration of Si melt (1500-1600°C, 2 h) and vapor (1700°C, 2 h) into the charcoal for comparison. Samples prepared by Si melt infiltration showed 15-52% conversion to SiC. Samples prepared by Si vapor infiltration showed severe damage such that the conversion degree could not be measured. In contrast, samples prepared by the embedding process showed full conversion to SiC (mostly β form) with good retention of the cellular structure of the original wood. The embedding process is a simple and efficient way to produce porous cellular SiC from wood.

Porous ceramics are essential for a variety of technical applications such as thermal insulators, filters, catalyst supports, gas sensors, bone graft substitutes, etc. Of numerous processing methods, the slurry foaming method is advantageous in producing porous ceramics with a cellular structure with high degrees of shape complexity and control of pore size and connectivity. It combines foaming and setting of a ceramic slurry. The gelcasting employing in situ polymerization of organic monomers is superior to other setting methods utilizing thermal gelation of agar, carrageenan, gelatine, starch, or egg white in green strength and machinability. Previously unusual acrylic (or acrylate) monomer was used to produce porous Al2O3 and hydroxyapatite. In the present work, porous Al2O3 was prepared by the slurry foaming method with acrylamide monomer, commonly used in gelcasting for producing dense ceramics. The foaming and gelation behavior was investigated with the parameters such as the type and concentration of surfactant (i.e. foaming agent), solid loading, and the concentrations of initiator and catalyst. The density, porosity, microstructure, and strength of the resulting samples were characterized.

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