Research Of Preparing Superfine Fibrous Sillimanite Powder

This article used 0.074mm sillimanite powders as raw material to prepare fibrous superfine sillimanite powders by vibrating mill, planetary ball mill, stired mill and spiral jet mill. Meanwhile, the broken behavior of sillimanite crystal and the mechanism of the breaking plants used in the experiment was analysed. Besides, the fiber reinforced experiment of the clay light-weight refractory material was researched.The obtained result indicated that the spiral jet mill compare to the vibrating mill, planetary ball mill and stirred mill is more suitable to prepare the fibrous superfine sillimanite powders. Under the following condition of spiral jet mill: grinding pressure of 0.7MPa, feeding pressure of 0.3MPa and the feeding rate of 3.65g/s, the fibrous superfine sillimanite powders with length/diameter （L/D） ratio of 9.3 and particle size d₉₀ of 20.09μm was prepared. This kind sillimanite powders is superior to the raw material obviously.Calculate the bond energy of chemical bond in the sillimanite crystal. It is found that the Al-O connected double chains formed by alternate AlO4 and SiO4 tetrahedra in sillimanite crystal is more likely to be broken under strong force. Then it may make the sillimanite crystal occur the fracture parallel to c-axis which correspond with the cleavage on the （010） plane, and form the fibrous shape.Through the calculation of the bond energy of chemical bond, the difference between the electrostatic force needed to break the sillimanite crystal perpendicular to c-axis and that parallel to c-axis is small. The ratio of the two is about 1/3（6.44 ke²/19.02 ke²）. It explain the reason why it is difficult to prepare the fibrous superfine sillimanite powders.The fiber reinforced experiment of the clay light-weight refractory material was engaged with as-prepared fibrous superfine sillimanite powders. The results indicated that the volume density of the clay light-weight refractory material is 0.49g/cm³ which is hardly changed, however, the compressive strength and the rupture strength is 1.16MPa, 0.78MPa which increased by 28% and 30% respectively, when the addition of fibrous sillimanite superfine powders was 12% in total.