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Silicon Powder In Castable Refractory

July 05, 2018

There are two main types of SiO2 powder used in castables: one is made of high pure silica, the other is a by-product of the producing silicon or metallic silicon or ferrosilicon, both of them are amorphous. The former is granular and inactive.The latter is hollow spherical, active, unreunited and well-filled. After being mixed with the castable refractory, the surface of the silica forms a siloxane network structure by drying and dehydrated. The temperature increased and is not easily broken, and the medium temperature strength is increased, and the mullite was formed with Al2O3 at high temperature, and the strength of the material was also improved. Therefore, silicon micropowder is widely used in low cement, ultra low cement and no cement castable.

SiO2 is used together with a suitable dispersing agent and added to the castable refractory. Since the silicon micropowder is a very distinct spherical particle, it is easy to enter tiny void in the castable and the particle size is small. So that not only the water reducing effect is good, but also the density of the refractory castable is improved, after dryed, the porosity rated is reduced. The performance of strength and high temperature is improved. At the same time, the activated silicon micropowder forms a colloidal particles adsorb a dispersant around it to form a solvent layer, thus increasing the fluidity of the castable refractory and improving its molding performance. In addition,due to the fine particle size, large surface free energy, large lattice defect and high activity, the silicon micropowder is more likely to undergo solid phase sintering reaction at medium and high temperatures and mullite reaction with AL2O3 in high alumina refractory materials. Thereby improving the post-buring strength and high temperature performance of the low cement refractory castable.