Stoichiometry of the C + SiO ₂ Reaction

The reaction of one‐to‐one molar carbon/silica powder mixtures was studied using simultaneous thermogravimetric analysis and mass spectroscopy with crystalline and amorphous silica. Reaction proceeded via a two‐stage path in which there are at least three identifiable competing global reactions. During the first stage, silicon carbide is formed along with small amounts of silicon monoxide. The most likely reaction path during this stage is the following: SiO 2 ( s ) + C( s ) → SiO( g ) + CO( g ); SiO( g ) + 2C( s ) → SiC( s ) + CO( g ). The second stage consists of reactions between silica with silicon carbide which form silicon monoxide and, where conditions permit, may also form silicon metal. The major reaction during this stage is 2SiO 2 ( g ) + SiC( s ) → 3SiO( g ) + CO( g ).