Suppression or control of liquid convection in float zones in a zero-gravity environment by viscous gas shear

Abstract

In the float-zone processing of materials in a zero-gravity environment, such as outer space or in orbital flight, the Marangoni flow at the free surface of the float zone is stopped by directing streams of heated, non-reactive gas(es) tangentially to the surface and in a direction and with a velocity such that counterbalancing shear forces are produced. The total resultant shear forces at the surface are therefore zero, and all Marangoni convection throughout the float zone is virtually eliminated. Alternatively, changes in the gas streams can produce any specified non-zero convection velocity in a critical region when desired. Also useful and beneficial in reducing or controlling or modifying the resultant velocity of the combined convections for float-zone processes carried out on earth. Particularly useful in the growing of improved doped semiconductor crystals, and also useful in improving the controlled solidification in float zones for the fabrication of improved glasses and metal alloys in zero gravity or on earth.

Dependencies are inferred from the claim text.