Chemical vapor deposition is also known as dry or pyrolysis. Its primary particle size is between 7 and 40 nm. The specific surface area is generally greater than 100 m 2 /g, and the silica content is not less than 99.8%. Generally, silicon tetrachloride gas is used for high-temperature hydrolysis in a mixed gas stream of hydrogen and air to synthesize silica aerosol, followed by aggregation, cyclone separation, deacidification and the like.

The preparation of silica by gas phase method is currently the main method for preparing nano-scale silica. The white carbon black product prepared by the method has high purity, large specific surface area, good dispersion, and fine particles and spherical shape. The disadvantages are high requirements on equipment, complicated technology, high raw materials and large investment scale.