Polycrystalline mullite fiber is used as the lining of high-temperature kilns because its service temperature is greater than 1250 ℃. In the high-temperature flame furnace, radiation heat transfer is dominant, and convection heat transfer generally accounts for only 10%.

Therefore, improving the blackness of furnace lining materials is an effective way to improve the heat transfer capacity in the furnace.

Polycrystalline mullite refractory fiber has a large absorption capacity, which is close to blackbody, according to its material and structural properties.