Sol is a colloidal solution composed of silicic acid multimolecular polymers, also known as silicic acid solution, which is odorless and its molecular formula is SiO2?nH2O. The particles of polymers are usually at 7~20nm, and there are different ways to prepare silica sol, and the common methods are ion exchange method, silicon powder one-step hydrolysis method, silane hydrolysis method, etc.

When the water of silica sol evaporates, the colloidal particles are firmly attached to the surface of the object, and the silicon-oxygen combination is formed between the particles, making its three-dimensional structure more stable and the binding strength higher.

  Application diagram of colloidal silica in amorphous refractories. Due to the strong adsorption capacity and large specific surface area of silica sol, the silica sol is distributed on the surface of the refractory particles, forming a gel around the particles, and at the same time, the hydroxyl group on the surface of the particles solidifies and removes the water, forming a spatial network structure of Si-O-Si combination, which greatly improves the strength of the refractory in the process of construction and curing. After the construction body is dry, the gel binds the aggregates together to form a skeleton, which greatly improves the strength.

?The addition of silica sol to the aluminum silicon carbide castable can significantly improve the slag erosion resistance of the refractory. As a binding agent, colloidal silica can be used as a substitute for pure aluminate cement in corundum castables to significantly extend the service life, shorten the construction time, and improve the thermal strength.  Colloidal Silica can be used as a binder to replace tar and organic resin in the press-in mud, which can improve the construction performance and use performance of the press-in mud and greatly reduce environmental pollution.

  The refractory material used as a binding agent has the advantages of good high temperature stability, high strength and good thermal shock resistance, so the service life and construction performance of the material are improved, so the application of colloidal silica in amorphous refractories is more and more extensive.

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