Nanosized Mesoporous Silica Coatings on Ceramic Foams:  New Hierarchical Rigid Monoliths

Silica-based rigid monoliths exhibiting a trimodal hierarchical pore system have been successfully prepared through coating of a ceramic foam (CF) with sub-micro-/nanometric mesoporous particles (as building blocks). We have selected a bimodal porous silica, denoted as UVM-7 (a nanometric version of the well-known MCM-41 materials), consisting of small aggregates of nanometric surfactant-assisted mesoporous particles. A colloidal suspension of this material in water is used to coat through successive impregnation cycles the CF surface. The small intraparticle mesopore system (with pore diameters around 2−3 nm) is due to the supramolecular templating effect of the surfactant. Textural large-mesopores/macropores (in the 20−70 nm range) have their origin in the interparticle UVM-7 voids. The large macrocellular macropores are due to the CF support. The resulting monoliths present a good and homogeneous coverage level. Moreover, these composites display better mechanic properties than those of related silica self-supported monoliths.