Effect of ultrasound on synthesis of spherical silica

Spherical particles of silica were prepared in the presence of ultrasound at various frequencies (20, 1740, 4000 kHz) and intensities (<25.4 W/cm(2)). It was found that the sphere size increased with increasing ultrasonic intensity and that the 20 kHz sonication induced agglomeration among the spheres. It was inferred that such agglomeration is dominated by a silanol group (-OH) at the surface of silica spheres. Size parameters, such as sphere size, agglomeration size, and ultrasonic vibration amplitude-are discussed.