Tunable pore size and microstructure of hierarchical porous silica ceramics by freeze casting method using dual solvent as a template

Porous silica ceramics were prepared by a freeze-casting method using dual solvents as a template, and their microstructure can be regulated by different ratios of solvents. As the camphene content increases, the pore shape gradually changes from prismatic pores to spherical pores, and the pore size first decreases and then increases. A porous silica ceramic showed 76% porosity and a uniform pore size of 6 µm. It presents excellent thermal insulation properties (thermal conductivity ~0.17 W m-1 K-1), good compressive strength, and a stable dielectric constant (~1.48). The results of this work shed light on the promising aerospace application of porous ceramics prepared by freeze-casting using dual solvents as a template.