Microcellular ceramics by using silicone preceramic polymer and PMMA polymer sacrificial microbeads

Microcellular silicon oxycarbides have been produced by pyrolysis of methylsilicone resin with the help of sacrificial microbeads of polymethyl methacrylate (PMMA). The PMMA microbeads were added in the range from 0 to 80 wt%, and the pyrolysis was performed at 800–1200 °C. The volume shrinkage resulting from the polymer-to-ceramic conversion becomes constant at the pyrolysis temperature above 1000 °C, and the shrinkage value reaches about 60% by a PMMA addition of 80 wt%. In the all range of PMMA additive ratios, the spherical micro pores with the wide range diameter from 1 to 10 μm are produced in the matrix. The open-cells, which are formed above 30 wt% of PMMA addition, have the open pores size bigger than 0.5 μm. The bending strength and the elastic modulus of the product exhibit the maximum values, i.e., 24.1 MPa and 16.0 GPa, respectively, when PMMA addition is 50 wt%.