A06 リン酸カルシウム粒子の凝集促進に及ぼす超音波の作用

抄録

To enhance the particle agglomeration in a precipitation process, 2.0 MHz ultrasound was irradiated to suspension of calcium phosphate. Only with 1 minute irradiation, the ultrasound triggered particle growth, and enhanced sedimentation. During the ultrasonic irradiation, floe of particles grew progressively. The flocculated particles rapidly settled down under gravity after stopping the irradiation and the suspension separated into layers such as clear, cloudy and dense. Progress of the separation with time was expressed by the normalized height of the boundaries. Effects of ultrasonic power on the particles agglomeration were examined. The irradiation with high power was found to be effective. There was a threshold power for the agglomeration. Appearance of the surface and inside the suspension changed significantly depending on the power below and above the threshold. Visually observable bubbles appeared and moved around at the power above the threshold. Ultrasonic particle agglomeration is relating with physical effects of ultrasound and the possible mechanisms are particle acceleration by vibration, radiation force under standing wave, acoustic streaming, jet flow induced by the bubble collapse and microstreaming around vibrating bubbles. The investigation suggested that microstreaming and acoustic streaming probably contribute to the agglomeration.