Acicular porous mullite from diatom frustules

We report for the first time using diatom frustules, the porous silica shells of diatoms, as Si precursor for synthesis of porous mullite ceramics with fibrous pore morphology. The porous mullite ceramics prepared by mould pressing method without using any porogen and binder showed high open porosity (up to 60%) due to the highly porous nature of diatom frustules and near zero sintering shrinkage of mullite whiskers. The original circular pores of diatom frustules were turned into fibrous pores of mullite ceramics. The porous ceramics showed flexural strength of 38.6 MPa at the porosity of 55.5% when sintered at 1600 °C for 3 h.