Tubular and Rodlike Ordered Mesoporous Silicon (Oxy)carbide Ceramics and their Structural Transformations

• Published in: Chemistry of materials Vol. 20; no. 16; pp. 5421 - 5433
• Main Authors: Krawiec, Piotr, Schrage, Christian, Kockrick, Emanuel, Kaskel, Stefan
• Format: Journal Article
• Language: English
• Published: American Chemical Society 26.08.2008
• Subjects: Nanomaterials (Nanops, Nanotubes, etc.); Porous Materials (including Meso- and Micro-Porous Materials); Templated and Nanoimprinted Materials
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm801035g

Ordered mesoporous silicon carbide ceramics with hexagonal p6mm (OM-SiC-3, OM-SiC-5), cubic Ia3d (OM-SiC-8) and cubic I41/a or lower (OM-SiC-8) pore arrangement symmetries were prepared via nanocasting of SBA-15 and KIT-6 ordered mesoporous silica templates with polycarbosilane (PCS) precursor (numbering of the OM-SiC materials corresponds to their CMK ordered mesoporous carbon analogues). Four different PCS were used for the OM-SiC preparation (liquid SMP-10, low-molecular-weight PCS with M W = 800 melted at 320 °C and PCS with M W = 800, 1400, 3500 dissolved in heptane/butanol). Infiltration of liquid vinyl functionalized SMP-10 precursor, and subsequent pyrolysis in vacuum resulted in OM-SiC-5 materials with tubular structure similar to that of the CMK-5 carbons (according to the TEM, low angle X-ray diffraction and nitrogen physisorption measurements). No significant differences were observed between the direct melt (PCS-800 at 320 °C) and wet impregnation procedure (PCS-800 in heptane/butanol) for OM-SiC-3, whereas significant differences were measured for materials prepared using different molecular weights of the PCS precursors. The influence of different precursor loadings and final pyrolysis temperature was also investigated. In the case of materials prepared from cubic KIT-6, transformation of the OM-SiC-8 symmetry could be observed by small-angle X-ray diffraction.