Pore characteristics and mechanical properties of silica templated by wood

The pore characteristics and the mechanical properties of silica samples templated by wood were investigated. The wood samples had been either solely extracted with solvent, delignified or delignified and functionalized with maleic acid anhydride prior to infiltration with tetraethyl orthosilicate and subsequent calcination. All three samples show similar mesopore characteristics, while the one based on maleic acid anhydride functionalized wood exhibited also a large volume of micropores. These micropores are only partly accessible as shown by a combination of in situ small angle x-ray scattering and sorption experiments with n-pentane. Nanoindentation experiments reveal that the presence of the micropores decreases the indentation hardness of the material, while the reduced elastic modulus is similar for all three samples when taking mesoporosity properly into account. In addition, the micropores enhance the ductility index of the material. The microporosity introduced by this biotemplating approach proves to be advantageous for increasing the toughness of silica, as the material can dissipate more energy by irreversible collapse of the pores.