Synthesis of mullite whiskers using salt flux method

Using SiO₂ and Al₂O₃ as raw materials, mullite whiskers were prepared by heating at 1 200°C for 4 h in potassium sulfate flux. The morphology, crystalline characteristics, compositions and growth direction of whiskers were investigated by means of XRD, SEM, EDS and TEM. The results indicate that the as-synthesized whiskers are about 4 μm in length and 0.5-1 μm in diameter, and mullite whiskers grow along c-axis direction ([001] direction). The formation of mullite whiskers is controlled by dissolution-precipitation reactions, and the salt flux method is a good way to grow mullite whiskers.