The following statements are incorrect: (a) Ceramics, glass and cement are all silicate products; (b) It can be produced from soda ash, limestone and in time.

A. Ceramics, glass and cement are all traditional silicate products, and their main components all contain silicate, so A is correct;

B.CaCO3+SiO2？ High temperature? . ? CaSiO3+CO2↑、Na2CO3+SiO2？ High temperature? . ? Na2SiO3+CO2↑ =, the main raw materials of glass are soda ash, limestone and timely, and the main components of glass are sodium silicate, calcium silicate and silicon dioxide, so B is correct;

C. Silicon is located at the junction of metal and nonmetal, which is a good semiconductor material, and silicon dioxide is the main raw material of optical fiber, so C is wrong;

D. Sodium silicate is a kind of mineral glue, which does not burn, but coating sodium silicate on the surface of wood blocks the direct contact between wood and oxygen in the air, and can be used as a raw material for preparing wood flame retardant, so D is correct;

So choose C.