METHOD AND APPARATUS FOR THE CONTROL OF SOLIDIFICATION IN LIQUIDS

摘要

The invention provides a method of solidifying a liquid including the steps of reducing the temperature of the liquid below its melting point and subjecting the liquid to a physical disturbance, preferably irradiating the undercooled or partially solidified liquid with ultrasound to control nucleation and/or crystal growth. The preferred frequency of ultrasound is in the range 16-100 kHz, most preferably 20-40 kHz. In an embodiment of the invention undercooled liquids are irradiated at up to 1 DEG C below their melting point to induce formation of large crystals (500 microns) in the solidified product. In another embodiment partially solidified liquids are irradiated below their melting point so as to induce formation of many small crystals (50 microns) in the solidified product. Apparatus for carrying out the methods are described.