From bulk to porous structures: Tailoring monoclinic SrAl2Si2O8 ceramic by geopolymer precursor technique

In this paper, monoclinic SrAl2Si2O8 ceramics with porous structures were prepared based on ion-exchanged geopolymer precursor technique. Micron-level pores with a homogeneous pore-size distribution were introduced into the inorganic framework using foaming agents. The results demonstrated that the apparent density, pore-size distribution and specific surface area of porous geopolymer precursors can be well-engineered via tailoring the category and concentration of the foaming agent. After being treated at 900 degrees C, hexagonal SrAl2Si2O8 first-crystallized from the amorphous geopolymer matrix and then gradually converted into monoclinic SrAl2Si2O8 between 1100 degrees C and 1200 degrees C. The resulting monoclinic SrAl2Si2O8 ceramics maintained the porous structures during high-temperature treatments and exhibited high porosity, specific surface area, and compressive strength. The aforementioned strategy not only achieves monoclinic SrAl2Si2O8 ceramics with well-defined and robust microstructures, but also provides an alternative route to prepare other porous ceramics, with potential applications in fields of high-temperature filters, adsorbents, and heterogeneous catalysis.