Since fumed silica is produced in the process, firstly, the halosilane is hydrolyzed and condensed into individual silica particles, and then gradually grown into spherical particles of 7-40 nm, which are called "primary particles" of silica (Primary) Particle).

The "primary particles" continue to move forward in the direction of the flame in the reaction furnace, and the particles collide with each other. At this time, since the temperature in the reaction furnace is still relatively high, the particles are close to the molten state, and the particles are welded together after the collision, forming A particle of a three-dimensional dendritic structure in which a plurality of spherical particles are welded together is called an "Aggregate Particle" of silica. Since the particles in the aggregate are welded to each other, they are stable structures and are almost impossible to separate.

The silica "aggregates" continue to move forward and collide with the gas flow in the pipe and then join together to form a flocculent fluffy powder called Agglomerate Particle. . Since the temperature inside the pipe is low at this time, the connection between the "aggregates" is only connected by physical adsorption, and is an unstable structure which is separable (dispersible) under a certain mechanical force. .

2 is a transmission electron micrograph of fumed silica; and FIG. 3 is a transmission electron micrograph of precipitated silica. It can be seen from the photos that there is a clear difference between the dispersion states of the two. It is precisely because the fumed silica is dispersed in the system to form a "near-perfect" three-dimensional network structure of nanoparticles, which makes it excellent. Reinforce, thicken, thixotropic, anti-settling, discharge and other properties.