Ultrasonics
From Wikipedia, the free encyclopedia
Ultrasonics is a trade term coined by the Ultrasonic Manufacturers Association and used by its successor, the Ultrasonic Industry Association, to refer to the use of high-intensity acoustic energy to change materials. This usage is contrasted to ultrasound, which is generally reserved for imaging, as in sonar, materials examination (NDI), and diagnostics (mammography, doppler bloodflow, etc.). However, in spite of this distinction, much technical material on ultrasound imaging actually uses the term ultrasonics, for example
- Ultrasonic Flaw Detection for Technicians, 3rd ed., 2004 by J. C. Drury
- Ultrasonic nondestructive evaluation : engineering and biological material characterization, Boca Raton, FL : CRC Press, c2004, by Tribikram Kundu
Ultrasonication offers great potential in the processing of liquids and slurries, by improving the mixing and chemical reactions in various applications and industries. Ultrasonication generates alternating low-pressure and high-pressure waves in liquids, leading to the formation and violent collapse of small vacuum bubbles. This phenomenon is termed cavitation and causes high speed impinging liquid jets and strong hydrodynamic shear-forces. These effects are used for the deagglomeration and milling of micron-size and nano-size materials as well as for the disintegration of cells or the mixing of reactants. In this aspect, ultrasonication is an alternative to high-speed mixers and agitator bead mills. Furthermore, chemical reactions benefit from the free radicals created by the cavitation as well as from the energy input and the material transfer through boundary layers. For many processes, this sonochemical (see sonochemistry) effect leads to a substantial reduction the reaction time, like in the transesterification of oil into biodiesel. Ultrasonication can easily be tested in lab scale for its effect on various liquid formulations. Within the past five years equipment manufacturers like Hielscher developed a number of larger ultrasonic processors of up to 16kW power. Therefore volumes from 1mL up to several hundred gallons per minute can be sonicated, today in order to achieve all kind of results.
