Preparation of large-sized C/SiO₂ macroporous conducting materials

Polyacrylonitrile(PAN)/SiO₂ composites were prepared by using large-sized macroporous silica as template, in which acrylonitrile solution was filled to perform in-situ polymerization followed by solvent evaporation. The PAN/SiO₂ composites were carbonized in vacuum at 800 ℃ to obtain C/SiO₂ composites. The samples were characterized by SEM, FTIR, XPS and XRD. The results show that the silica template has a strong capillarity effect, which makes PAN coated on the 3D silica layer as thin films. The thickness of the PAN film can be adjusted by changing the concentration of acrylonitrile in the polymerizing solution or the repeating times of the coating. The dependence of conductivity on the thickness of carbon film has also been observed. When the silica template is coated twice by a solution containing 33% mass fraction of acrylonitrile, the obtained C/SiO₂ composites exhibit the volume resistance of 16 Ω·cm, and the average thickness of carbon film is 16 nm, while the BET surface area is 93 m²·g^-1.