Soluble starch scaffolds with uniaxial aligned channel structure for in situ synthesis of hierarchically porous silica ceramics

Hierarchically porous silica ceramics with unidirectionally aligned channel morphology have been synthesized by in situ mineralization of soluble starch monolith. The procedure followed two steps. First, soluble starch monoliths with well-defined uniaxial macroporous structure were prepared by unidirectional solidification process of starch hydrosol or starch hydrogel. Second, such an as-prepared artificial monolith, used as template, was soaked into a surfactant-templated sol–gel solution to mineralize the existing channel structure. It was shown that the macropore size, wall thickness, and macropore morphology in obtained soluble starch materials may be tuned in a certain range, through adjusting the concentration of starch slurry. When initial concentration changed from 10 wt.% to 15 wt.%, the macropore size of soluble starch materials decreased, while the wall thickness increased. Through the second step, porous silica ceramics were obtained after drying and calcining of organic–inorganic hybrid silicate compounds from solution. These resulting products preserved template microstructure in great detail and exhibited narrow macropore size distributions. It was observed that when the soaking time increased from 36 h to 84 h, the average pore size of the silica ceramics was decreased from 4.1 μm to 3.6 μm. In addition, in nanopore regime, all the silica monoliths obtained presented a coexistence of uniform worm-like nanopore and lamellar phase feature, and large BET and microporous surface area.