Synthesis and characterization of SiC materials with hierarchical porosity obtained by replication techniques

Porous silicon carbide monoliths were obtained using the infiltration of preformed SiO₂ frameworks with appropriate carbon precursors such as mesophase pitch. The initial SiO₂ monoliths possessed a hierarchical pore system, composed of an interpenetrating bicontinuous macropore structure and 13 nm mesopores confined in the macropore walls. After carbonization, further heat treatment at ca. 1400 °C resulted in the formation of a SiC–SiO₂ composite, which was converted into a porous SiC monolith by post-treatment with ammonium fluoride solution. The resulting porous SiC featured high crystallinity, high chemical purity and showed a surface area of 280 m² g⁻¹ and a pore volume of 0.8 ml g⁻¹.