Use of Terrestrial Methods for Advanced Monocrystals Growth in Zero Gravity and the Solution of the Arising in these Conditions Problems

Abstract

Mono-crystal growth with a uniform distribution of internal components under terrestrial conditions is difficult because of strong thermo gravitational convection. Thermo gravitational convection leads to instability of crystal growth, which limits the possibility of obtaining mono-crystal with a high degree of homogeneity of its structure. The results of the first experiments on crystals growth in microgravity carried out in space confirmed the possibility of obtaining more perfect crystals due to the absence of thermo gravitational convection. However, despite the fact that under zero gravity there is no thermo gravitational convection to replace it in crystallization solutions and melts, new convective processes of a non-gravitational type arise- Marangoni convection, associated with a change in the surface tension at the fluid-gas interface, as well as small thermo gravitational processes caused by weak residual gravitational force, leading to the complication of obtaining homogeneous mono-crystals. Another problem is the presence, in contrast to terrestrial conditions because of the absence of the Archimedes force, of gas inclusions in melts and crystalline solutions, which also leads to the impossibility of obtaining improved homogeneous mono-crystals. Along with the description of existing methods for homogeneous mono-crystals growth in terrestrial conditions, the article presents ways of solving the problems of degassing crystalline solutions and melts, and the uniform distribution of their internal components in them for homogeneous mono-crystals growth in space flight using the process of vibro-turbulization.