申論題

6. Both kaolinite and mullite are Al-Si-O compounds. The chemical formula of kaolinite is Al₂(Si₂O₅)(OH)₄, of mullite is 3Al₂O₃ 2SiO₂. Can we use kaolinite as the refractory for a 1600℃ furnace ? Explain brietly using the phase diagram for SiO₂-A1₂O₃ in the following (10%).
Note: the atomic weight of Al is 27, of Si is 14, of O is 8.