Influence of cryogenic drying conditions on hierarchical porous structure of aluminum oxide systems

• We have developed a new method for the procedure of highly porous alumina system.
• The porous structure of cryogels is demonstrably maintained up to 1300 °C.
• The pore system of the cryogels is built up from open anisotropic macropores (2–20 μm Ø) and closed mesopores (7–9 nm Ø).
• The macropores can be characterized with channel-like (columnar) pore architecture.
• The pore structure of cryogels is demonstrated by 3D SEM images.

Highly porous alumina systems were aimed to produce by low energy-consuming sol–gel and freeze drying techniques. A 3D molecular gel structure derived by sol–gel method is provided as a precursor for vacuum freeze drying process. The typical inorganic precursor is an aqueous colloid solution such as sol or suspension. The new type of precursor results in a new columnar pore structure. The porous system keeps their high porosity even above 1500 °C in contrast with the reported heat resistance value (<800–1000 °C) of the porous alumina systems. The effects of the solvent content and other chemical additives as well as the drying conditions were studied on the porous structure. 3D SEM images represent the inner structure of porous materials.

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