| Recent investigations in porous ceramics have remarkably increased due to the rapidly growing interests of porous ceramics as filters, catalyst supports, burners, gas diffusers and biomaterial for bone replacement. Since the distribution of size and shape of the pore space in porous ceramics directly relates to their ability to perform a desired function in a particular application, the need to establish uniformity of the cell size and shape in order to achieve superior part properties, has been strongly emphasized. Consequently, efficient manufacturing technologies for quality porous ceramics are in demand.;By controlling the viscosity of the polyolefin phase, polyolefin polymer content, compounding and foaming parameters, the polysiloxane-polyolefin foam morphology can be varied. Furthermore, with a deliberate control of the content and dispersion of polyolefin polymer, open-channels can be induced into the cell walls by burning out the sacrificial polyolefin phase at elevated temperatures; consequently, the open-cell content of porous ceramics can be adjusted. Gradient microcellular ceramics with continuously changed cell size and porosity have also been fabricated by using a laminating method. Furthermore, multi-phased microcellular ceramics are fabricated by adding selectable filler material into the staring blends of polysiloxane and polyolefin, followed by foaming and pyrolysis.;Our recent study demonstrated that an extremely fine and uniformly distributed microcellular structure could be developed from the blends of polysiloxane preceramic polymer and thermoplastic polymer. The following stages are involved in the research: (i) characterizing and modifying the rheological properties of polysiloxane preceramic polymer, (ii) foaming and shaping a mixture of polysiloxane, polyolefin polymer, and blowing agents by using a conventional polymer compounding and foaming method, (iii) cross-linking the foamed body, and (iv) transforming the foamed body into ceramic foams by pyrolysis. |
