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Study on Deflocculation of SiO2 Sol Combined with Mullite Castable

wallpapers Industry 2020-07-14

Due to its unique properties, castables prepared with mullite as aggregate have an essential role in the industrial metallurgy process. The best way to use the potential of mullite refractories is to form a large amount of mullite phase in the matrix material. A feasible method for synthesizing mullite matrix is ​​to add highly dispersible alumina and silica to the ingredients to make them react in situ during high-temperature firing to form mullite. Among them, as the highly dispersible silica, it is most suitable to use industrially produced stable water-dispersed silica (SiO2 sol). The SiO2 particles in the SiO2 sol are nano-sized and can be more evenly distributed in the castable mixture; at the same time, the SiO2 sol is also a ready-made binder.

In the ingredients of composite materials containing highly dispersed components, active anti-flocculation agents must be added to prevent the agglomeration of small particles and ensure their uniform distribution in the castable mixture. The research proves that for the cement-free refractory castable combined with the low water content of SiO2 sol, the anti-flocculation effect of traditional anti-flocculation agents such as polycarbonate, citric acid and sodium tripolyphosphate is not ideal; In a material system close to refractories, catechol shows excellent deflocculation performance, and its amount can produce a significant deflocculation effect when it accounts for a few ten-thousandths of the total mass of the ingredients.

In this experiment, Russian researchers studied catechol as an anti-flocculation agent containing mullite aggregate (≤3 mm), corundum powder (≤0.063 mm), active Al2O3 powder, SiO2 fine powder, NH4+ ions The role of stable SiO2 sol (binder) in cementless castables. For comparison, the traditional deflocculating agent sodium tripolyphosphate was also used. During the test, the initial flow value and vibration flow value of the castable were measured at room temperature compressive strength, room temperature flexural strength and phase composition after firing at 1 400 ℃.

The results of the study prove that the initial flow value of the castable with 0.005% (w) catechol added to the mullite cementless castable is 133 mm, and the flow value after 30 vibrations is 175 mm; The initial flow value of the castable of sodium tripolyphosphate (addition amount is 20 times of catechol) is 122 mm, and the flow value of 30 vibrations is 160 mm. After firing at 1 400 ℃, the two castable samples have little difference in normal temperature strength; the phase composition of the matrix is ​​also the same, both are composed of mullite and corundum; SiO2 in SiO2 sol and SiO2 fine powder all participate in Mo Come to the petrochemical reaction.

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Tag: SiO2