Sillimanite

We deal with high quality Sillimanite, with the lowest percentage of impurities. Sillimanite or Aluminium Silicate is used as a raw material for high alumina refractories, which are extensively used in Iron and Steel, petrochemicals, Electrical, Cement, Zinc and Glass Industries.

The overall use and demand for Sillimanite group minerals has increased steadily throughout the world over the past few decades.

SILLIMANITE APPLICATIONS

Sillimanite is used In:

Refractory products: It is stable in all temperatures up to 1550^oC after which it gets converted to mullite.

• High melting point and low coefficient of thermal expansion.
• Low expansion in conversion to mullite: Between the temperatures of 1545^oC to 1550^oC, as it changes over to mullite there is a permanent expansion of 2-3%. The maximum expansion (rarely observed) by volume noted in sillimanite is 4%, while the linear expansion is less than 1%. As it shows negligible expansion while changing over to mullite, the mineral can be used without pre-calcination.
• There is minimal increase in porosity upon heating, as the volume porosity of grains hardly exceeds 6% after heating. If heating is prolonged, it tends to decrease due to vitrification, and this is a great advantage in all applications in which problems of corrosion and abrasion arise.
• Mechanical strength and toughness, resistance to mechanical shock
• Low electrical conductivity
• It gives a neutral reaction and is resistive to corrosive slags and to oxidizing and reducing conditions. As it is very resistant to glass slag, it has wide application as lining material in glass melting furnace. It is not suitable in iron smelting, however, as iron corrodes it rapidly. As it is also not highly resistant to molten metallic oxides, it is not suitable for metallurgical operations.

Sillimanite in Electrical Components: Sillimanite powder mixed with high-grade china-clay is commonly used in the manufacture of spark plugs and other insulating materials required at high voltages. This combination works well due to its low electrical conductivity and high thermal stability.

Maxworth Minerals produces high purity sillimanite powder containing minimum quantities of iron oxide, which would otherwise alter the electrical conductivity of the product.

Sillimanite in Ceramics: Sillimanite gets calcined into mullite during the firing and this is used in ceramic products. Mullite has two common forms of morphology which are significant for its application. The first is a platelet shape with low aspect ratio and the second form is a needle shape with high aspect ratio. The needle shape mullite can form in the ceramic body during sintering and offers tremendous benefits as the mullite needles interlock to increase the mechanical strength and thermal shock resistance of the ceramic product.

Maxworth Minerals offers high purity sillimanite powder, with minimum basic impurities like sodium and calcium that cause the formation of this needle shape mullite in ceramic manufacture.