Synthesis of mullite from technogenic materials and pyrophyllite

Pyrophyllite introduced into a ceramic batch prepared from the gravity tailings of zircon-ilmenite ore raises the mullite formation temperature by 50–80°C and increases the mullite content of the resulting material. The first stage of the synthesis yields non-acid-resistant mullite. The early formation and rapid buildup of mullite are due to the formation of small amounts of a liquid phase. Large amounts of the liquid phase (>50%) do not favor mullite buildup because they heal lattice defects and thus hamper sintering.