Synthesis of Al₂O₃–SiO₂–MgO ceramics with hierarchical porous structure

A series of asymmetric cordierite ceramics with hierarchical porous structure were prepared and characterized. The macroporous support was obtained from natural raw materials (bauxite, silica sand, kaolinite, talc, and alumina) via ceramic technology. The prepared ceramic discs were characterized by a narrow pore size distribution. The average pore size was about 9.5 µm, and the open porosity was estimated to be 30%. Coating the discs with micro/mesoporous cordierite layer was performed using the sol–gel approach. Three-component sols were obtained from organic or inorganic precursors. Corresponding gels were calcined at 1200 ℃ to form the cordierite structure. The nature of precursor was found to affect the pore volume distribution. Narrow pore volume distribution was observed when organic precursors were used. Another key factor to control the parameters of final material was the drying condition. Supercritical drying of the gels has allowed us to increase the surface area in two orders of magnitude comparing with conventional drying procedure.