Preparation of mullite whiskers and their enhancement effect on ceramic matrix composites

Mullite whiskers were facilely prepared by sintering kyanite at high temperature, with the addition of AlF₃·3H₂O. The as-prepared whiskers have been characterized systematically in terms of phase composition, morphology, and structure. Results showed that the morphology and size of mullite whiskers were strongly depended on the content of AlF₃·3H₂O and sintering temperature. At temperatures in the range of 1 100 to 1 500°C with 4 wt% addition of AlF₃·3H₂O, the well-shaped mullite whiskers were obtained. For an instance, the mullite whiskers with 5–10 μm in length and 0.1–0.2 μm in cross-section could be formed at 1 400°C, with 4 wt% addition of AlF₃·3H₂O. Moreover, results showed that the addition of mullite whiskers into ceramic matrix enhanced its fracture toughness significantly.