Abstract
An experimetal study of quasi-two-dimensional growth of a liquid-crystal material is presented under normal and microgravity. The rate of solidification is mainly limited by the heat transfer of latent heat, which is generated at the solid-liquid interface along the temperature gradient. The rate of heat transfer is governed by both molecular diffusion and thermal convection. To clarify the effect of these mechanism of transport on solidification is the subject of this work. Zero-gravity experiment was executed usin Laser Interferometric Observation System (LOIS) launched by MASER IV in March, 1990. Liquid crystal, 4-cyano-4' -5-alkoxy-biphenyl (Merck) was used as a test material. Two transitions were observed in the same run under the conditions of nornal and microgravity. Micro-convection at the solid-nematic interface was observed only on the ground. Although interface convection was disappeared in space, oscillation of the growth rate was confirmed as the additional phenomena. It is concluded that the micro-convection diminishes the undercooling and the subsequent growth rate of the solid phase on the ground.
