China's Refractories

Abstract: In order to improve the high-temperature performance of mullite ceramic materials, mullite ceramic bodies were placed in closed containers with AlF₃ · 3H₂O powder and kept at 1 600 ℃ for 6 h. AlF₃ · 3H₂O reacts with O₂ to produce gaseous compounds AlOF and F, which penetrate into the bodies, promote Al₂O₃ and SiO₂ to form mullite whiskers, and strengthen the mullite ceramic materials. The results show that the mullite ceramics have enhanced hot strength, increased bulk density and declined apparent porosity by adding a certain amount of AlF₃ · 3H₂O in a closed container. When the addition of AlF₃ · 3H₂O is 6%, the bulk density of the ceramic material reaches the maximum and the apparent porosity is the lowest; and when the addition of AlF₃ · 3H₂O is 8%, the hot strength of the material is the highest.

Key words: mullite whiskers, ceramic materials, gas infiltration, high temperature performance