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Fumed Silica-The Main Component Is SiO2, Why Is Fumed Silica The Most Popular?

wallpapers Industry 2020-07-14

We know that the content of silicon dioxide (SiO2) in nature is vibrant. Sand, crystal, quartz sand, silicon powder, diatomaceous earth, etc., the main components are SiO2; in synthetic silica, precipitation method white carbon black, gas-phase method white carbon black, etc., the main ingredients are also SiO2. These are natural products such as sand grains, silica powder and diatomaceous earth. Some of them are applied directly without processing, and some enter the market after processing, but the application fields of the products are minimal. Fumed silica is the most widely used chemically prepared silica product. Although the amount of precipitated silica is relatively large, the application area of ​​fumed silica is full. On the market, fumed silica products also have the highest selling prices (except for jewellery and collectable crystals), and involve the broadest range of applications. Why is the price of fumed silica so high, but it still becomes the darling of the market? This is mainly related to the unique synthesis process of fumed silica and the excellent performance of the product.

How is fumed silica synthesized? Why do they have so many unique properties?

In terms of the production process of the whole gas-phase method of white carbon black, it has the following characteristics:

(1) In terms of raw materials, the raw materials for the synthesis of fumed silica are elementary. One type is halogenated silanes (SiCl4 and CH3SiCl3) and combustible gases (hydrogen and oxygen (air)), which can effectively prevent other substances from being brought into the product.

(2) In terms of process, the halosilane is vaporized before entering the reactor, the temperature of the hydrolysis reaction is also around 2000°C, and then the aggregation, separation, deacidification and other processes are completed at high temperature, the entire process is in a continuous, sealed The system is completed to ensure that the product is not affected and polluted by the outside world.

(3) All the critical links of the entire production device are made of high temperature resistant, acid and alkali resistant materials, which can avoid other pollution sources from entering the product during the production process.

Due to the characteristics of raw materials and production processes for the production of fumed silica, the fumed silica products have a small particle size (primary particle size 7-40nm), large specific surface area (100-400m2/g), and high surface activity ( The surface contains highly active Si-OH groups); the gas-phase white carbon black product prepared under this particular process also has a unique three-position branch structure, and the product has a high porosity. In appearance, the fumed white carbon black appears as a "smog" fluffy white ultra-fine powder, so it has the English name fumed silica.

Besides, gas-phase silica is amorphous, and the product has high purity (SiO2%≥99.8%); moreover, due to the presence of surface-active silicon hydroxyl groups and the low bulk density of the gas-phase silica, its good fluidity is It is possible to achieve dry surface modification by gas-phase silica, which can be produced without destroying the particular structure of gas-phase silica, by modifying the surface modifiers with different structures and functions, Obtain different functional products to realize the functionalization of fumed silica. It is precisely because of the unique architecture and performance of the gas-phase silica that it shows excellent reinforcement, thickening, thixotropy, anti-settling, anti-sagging, adsorption, heat insulation and other functions in practical applications. Dozens of fields such as rubber, plastics, gumming, adhesives, industrial catalysis, food, medicine, CMP, thermal insulation materials, etc., have a wide range of applications, making the gas-phase method silica become "white fumei" in silica and The "darling" of the market. At present, domestic enterprises continue to absorb and digest technology, such as Yichang Huifu Silicon Material Co., Ltd. has been able to produce high-quality hydrophilic fumed silica and hydrophobic fumed silica with independent intellectual property rights.


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Tag: Silica