What is fumed silica?
Fumed silica is one of the extremely important high-tech ultra-fine inorganic new materials, with porous, non-toxic, tasteless, and non-polluting, the average primary particle size of about 7-40 nanometers, a specific surface area of 50-380m2/g, the product has high purity, the content of SiO22is not less than 99.8%, it's a kind of multi-functional additives.
Silicon dioxide (SiO2) is very abundant in nature. Sand, crystal, quartz sand, silica micro powder, diatomaceous earth, etc., the main component is SiO2 synthetic silica, precipitated silica, fumed silica, etc., its main component is also SiO2. like sand, silica micro powder diatomaceous earth, etc., these are natural products, some of which are directly applied without processing, and some of them are processed and enter the market, but the products have a very limited field of application. Precipitated silica (silicon dioxide) and fumed silica (silicon dioxide) are the most widely used chemically prepared silica products. Although the amount of precipitated silica is relatively large, fumed silica has a wider range of applications. In the market, fumed silica products are also the most expensive (except for crystals as jewelry and collections), and have the widest range of applications.
The production process for fumed silica
Fumed silica is an ultrafine powder material obtained by high-temperature hydrolysis and condensation of halosilanes in a hydroxide flame. Due to its unique preparation process, it has a different structure and unique properties from other silica products.
Production process of fumed silica
1) in terms of raw materials, the synthesis of fumed silica raw materials is very simple, a class of halosilanes (SiCI and CHSiCl;) and combustible gases (hydrogen and oxygen (air)), effectively preventing the introduction of other substances into the product.
2) In terms of process, halosilanes are vaporized first and then enter into the reactor, the temperature of the hydrolysis reaction is also around 2000°C, and then aggregation, separation, deacidification, and other processes are completed at high temperatures, the whole process is completed in a continuous, sealed system, to ensure that the product is not subject to external influences and contamination
3) Each key link of the whole production device adopts high temperature resistant, acid and alkali corrosion-resistant materials, which can prevent other pollutants from entering the products during the production process.
The characteristics of raw materials and production process of fumed silica production make the fumed silica products have small particle size (primary particle size 7-40nm), large specific surface area (100-400m2/g), high surface activity (the surface contains highly active Si-OH groups), and the fumed silica products prepared under this special process also have a special three-positioned dendritic structure, and the products have high porosity. In appearance, fumed silica is shown as "smoke" fluffy white superfine powder, so it has the English name of fumed silica.
The structure and properties of fumed silica
So what are the unique structures and properties of fumed silica?
1) Unique "three-dimensional branch" structure
In the production process of pyrogenic silica, the first halosilane hydrolysis and condensation of a single silica particle, and then gradually grow into 7-40nm spherical particles, the particles are called silica "primary particles" (Primary Particle).
"Primary particles" in the reactor with the direction of the flame continues to move forward, the particles collide with each other, at this time because the temperature in the reactor is still relatively high, the particles are still close to the molten state, the particles are fused after the collision, the formation of several spherical particles fused by the three-dimensional dendritic structure of the particles, known as the silicon dioxide "Aggregate Particle. Since the particles in an aggregate are fused, it is a stable structure that is almost impossible to separate.
Silicon dioxide "aggregates" continue to move forward with the airflow in the pipe, collide, and then connect, forming a flocculent, fluffy powder, called silicon dioxide "Agglomerate Particle" (Agglomerate Particle). Due to the low temperature in the pipeline at this time, the connection between the "aggregates" is only connected by physical adsorption, which is a kind of unstable structure, and can be separated (dispersible) under the fixed mechanical force.
2) High surface activity
In pyrogenic silica in the high-temperature hydrolysis condensation process, the surface also has part of the residual silica (Si-OH), the existence of surface silicon light base, making the surface of pyrogenic silica polarity stronger, higher surface activity!
Fumed silica surface existence of "siloxy" and "silica", of which the silicon light group has a high activity, can form hydrogen bonds, or react with other groups, which also ensures that the silica particles can form a stable network, and at the same time, with other media, have a good interaction with each other, so that the silica particles can form a stable network, and at the same time, with other media. This also ensures the formation of a stable network between silica particles and good interaction with other media, which makes silica show good properties such as strengthening, toughening, thickening, thixotropy, and anti-settling.
In addition, the existence of silica light base, also for the surface modification of fumed silica to provide the possibility of selecting different structures of surface modifiers and silica light base reaction, some functional groups grafted to the surface of fumed silica, to make the function of fumed silica more diversified.
3) Small particle size, large specific surface area
The "native particle size" of fumed silica is 7-40nm, what is the concept? We can compare the data from the following table to understand. If we magnify a fumed silica particle to a standard soccer ball so big, needs to enlarge about 30 million times; If the proportion, of the soccer ball is about 30 million times, it will become almost as big as Mars.
Application of fumed silica
Fumed silica is in amorphous form, high purity (SiO2,99.8%), the existence of surface active silicon light group, as well as fumed silica low stacking density, good mobility characteristics for fumed silica to realize the dry surface modification has become a possibility, can be realized without destroying the special structure of the fumed silica surface modification, by selecting the different structure and functionality of the surface modifiers for its modification, can obtain different functional products, to achieve a dry surface modification, and thus achieve the goal of the fumed silica. By choosing different structural and functional surface modifiers for its modification, different functional products can be obtained, thus realizing the functionalization of fumed silica.
Fumed silica Supplier
Luoyang Trunnano Tech Co., Ltd (TRUNNANO) is a professional fumed silica powder supplier with over 12 years experience in chemical products research and development.
We accept payment via Credit Card, T/T, West Union and Paypal. Trunnano will ship the goods to customers overseas through FedEx, DHL, by air, or by sea.
