Synthesis of a conducting SiO2-carbon composite from commercial silicone grease and its conversion to paramagnetic SiO2 particles

The thermal decomposition of commercial silicone grease was carried out in a closed reactor (Swagelok) that was heated at 800 degrees C for 3 h, yielding a SiO2-carbon composite with a BET surface area of 369 m(2)/g. The bulk conductivity (5.72 x 10(-6) S center dot cm(-2)) of the SiO2-carbon composite was determined by impedance measurements. The as-prepared SiO2-carbon composite was further annealed at 500 C in air for 2 h, which led to the formation of white paramagnetic silica particles ( confirmed by ESR), possessing a surface area of 111 m(2)/g. The present synthetic technique requires unsophisticated equipment and a low-cost commercial precursor, and the reaction is carried out without a solvent, surfactant, or catalyst. The mechanism for the formation of a porous SiO2-carbon composite from the silicone grease is also presented.