Emulsion processing of polymer-derived porous Si/C/(O) ceramic bodies

A novel route of miniemulsion processing was applied to preceramic polymers in order to fabricate porous Si/C/(O) bodies. Commercially available polysiloxane and polycarbosilane precursors and water were emulsified via intensive stirring or ultrasonication in the presence of surfactants, and subsequently shaped and cured in an autoclave. The resulting green bodies were dried and pyrolytically converted at 700 and 1050 °C under nitrogen into ceramic counterparts retaining their shape. A fine interconnected pore network derived from the aqueous phase allows escape of gaseous decomposition products during pyrolysis and avoids cracking. In the presence of transition metals such as Fe, Co, Ni or Pd nanofibers consisting of β-SiC/a-SiO2 are formed. Effects of polymer viscosity and processing parameters on the microstructures, porosities and pore sizes of the resulting products were investigated by means of DLS, mercury porosimetry, SEM, TEM, XRD and FTIR.