Abstract
Porous materials are widely applied in various fields due to their diverse characteristics depending on the size, arrangement and shape of the pores, as well as the porosity and composition of the solid materials. The limitations are mainly due to the weak structure and mechanical property due to its high porosity. After million years of evolution, natural biological composites, such as bird beaks, feathers and bones, have developed optimal designs combining lightweight and superior mechanical strength. Based on bioinspired strategies and using natural diatomites as raw materials, hierarchically-structured porous scaffolds were synthesized by freeze casting technique and sintering process. The effect of parameters, such as slurry preparation, sintering temperature, cooling rate and solid content, on microstructural and mechanical properties were discussed. The normalized compressive strength indicated that this bioinspired strategy provided an efficient design for scaffolds with superior strength and high porosity. Owing to the chemical stability of diatomite, silica aerogel and PDMS were successfully infiltrated into the freeze-casted diatomite, and formed functional composites. Moreover, in order to avoid the porosity reduction caused by second phase infiltration, a novel one-step synthesis of ceramic-based organic/inorganic composites was developed. The mechanical strength and water retention of composite can be enhanced by introducing PVA and alginate, respectively. The anisotropic composites synthesized in this study, provide extraordinary axial compressive strength and radial thermal insulation properties and can be a promising materials for green building or package applications. The novel synthesis proposed in this study can be adapted to other material systems and develop multifunctional porous materials.