The Experiment On Detached Solidification In Gravity Condition And Numerical Simulation

At present, the popular methods for large crystal growth in gravity condition are Czochralski and Bridgman. But it's difficult for the materials growth with sensitive characters for hot stresses. Duffar and Regel put forward detached solidification which combines the advantages of Czochralski and Bridgman. This method can improve the quality of crystal dramatically. At present the experiment research have been done in space, and there is no breakthrough in gravity condition.In this paper, for exploring how to achieve detached solidification and the relative mechanism, the experiment research was done in gravity condition, and the speed and temperature fields during detached solidification were researched with simulation method.For achieving detached solidification in the gravity condition, the water filled with CO2 gas and the oil with higher solidification temperature than water were used as the experimental materials. The translation controller moved the test tube with the experimental materials from hot region to cold region, and the CO2 bubbles overflowed from the water to oil during the process of water solidification as the result of the different solubility in water and ice. At the same time the oil on the water solidified and stopped the CO2 bubbles escaping from the oil. In this circumstance, CO2 gap was formed around the oil, detached solidification was conducted. Many factors have great influences on detached solidification, for example translation speed, cold bath temperature and so on. During the overflows of bubbles, a part of ice was achieved detached solidification. From this experiment, it can be known it was feasible that the gas gap needed by detached solidification was provided by the CO2 filled in water when water went into ice.The simulation on fluid during detached solidification was done by FLUENT. The influences of gravity, temperature differences, width of gas gap were analyzed. When gravity got bigger, the flow in fluid got complicated; when temperature differences and width of gap got bigger, the flow became stronger, and there are critical numbers, when the condition gets this critical numbers, the flow would get un symmetrical.