| abstract |
An aqueous suspension containing 20-60% SiO2 is spray dried to give aggregates 5-500 microns in diameter. The SiO2 may be produced by vapour phase hydrolysis of chlorides or fluorides, or by reaction of SiO2 and carbon in an electric arc. The aggregates may be heated at 800-1200 DEG C. to reduce surface area, and may be coated, e.g. with metal from vapour phase, or hydrophobized. They are said to be spherical or hollow-spherical. Examples give product surface areas of 150 and 45 m2/gm., densities of 470 and 650 g/l., and specific particle size distributions. |