Fumed silica
（重定向自Pyrogenic silica）
![Fumed silica with surface area of 130 m2/g](/Images/godic/202502/05/Sio2_130m2_per_gram_under_blue_book_1600dpi3114.jpg")
![](/Images/godic/202502/05/Fumed_silica_process.svg3114.png")
Fumed silica (CAS number 112945-52-5), also known as pyrogenic silica because it is produced in a flame, consists of microscopic droplets of amorphous silica fused into branched, chainlike, three-dimensional secondary particles which then agglomerate into tertiary particles. The resulting powder has an extremely low bulk density and high surface area. Its three-dimensional structure results in viscosity-increasing, thixotropic behavior when used as a thickener or reinforcing filler.