The influence of vibration on crystallization processes in microgravity
- Paper number
IAC-08.A2.2.5
- Author
Mr. Peter Rabochiy, Space Research Institute of NAS and NSA of Ukraine, Ukraine
- Year
2008
- Abstract
Numerical modeling of influence of vibration on convective processes in the melt and the distribution of a dopant in a crystal is carried out for cylindrical domain in axisymmetric approximation. It is shown that vibrating influence along the direction of crystal growth causes a periodic convective flow in the melt, which result in occurrence of periodic spatial concentration inhomogeneity in a crystal. It is also shown that fast rotation of the melt can be used to control concentration inhomogeneity in a crystal. The problem of influence of a translational vibration along the direction of crystal growth on the stability of a solid–liquid interface is considered for microgravity conditions. It is assumed that period of vibration is much smaller than characteristic hydrodynamical time, and Prandtl number of the system is small. The multiscale approach and linear stability analysis are used. It is shown that vibration leads to the same effect as the gravity in terrestrial conditions, resulting in occurrence of the long–wave instability (vibrational mode) caused by hydrodynamical effects in the melt. The increase in concentration of a dopant promotes development of both morphological and vibrational instabilities. The increase in the velocity of crystal growth stabilizes vibrational mode and destabilizes morphological mode. As a result, stability of crystallization front is possible only in a narrow interval of growth velocity values between the maximal critical velocity for a vibrational mode and the minimal critical velocity for a morphological mode.
- Abstract document
- Manuscript document
(absent)