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Application of silica micropowder in unshaped refractory materials

[11/04/2021]



Silica micropowder is a more commonly used micropowder in refractory castables. The silica powder has a small particle size, which can fill the pores between the particles in the castable and reduce the water consumption of the castable; the silica powder has a standard spherical structure and has a "ball effect". When it is filled between the particles, the relative sliding friction between the particles is converted into rolling friction, thereby reducing the friction between the particles, causing the viscosity of the castable to decrease and the fluidity to be improved.

Due to its special production process, silica micropowder has an amorphous crystal structure, and it is easy to form bond breaks on the surface of the particles. Due to the existence of broken bonds, the silica powder can easily absorb OH- in water to form Si-OH in the aqueous solution, and dissociate into Si-O- and H+ in the aqueous solution. Due to its relatively small particle size (micron level), silica micropowder can easily form a micelle structure with an electric double layer in an aqueous solution. Silica powder with higher activity can adsorb OH- in the aqueous solution, forming a large number of hydroxyl groups on the surface of its particles. During low-temperature curing, the silica powder can undergo a dehydration reaction to form a -Si-O-Si- bond between the particles, thereby improving the mold release strength of the castable. Silica powder can become a liquid phase at high temperatures, reducing the viscosity of mass transfer between particles, thereby enhancing the rate of mass transfer and promoting sintering between particles. Therefore, the castable mixed with silica micropowder can promote the sintering of the matrix in the castable at 800°C, enhance the interlocking and interlocking ability of particles, and improve the mid-temperature strength of the castable.
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