Study On Process And Theory Of Gallium Crystallization

Since the 21st century,the rapid development of semiconductor lighting,LED field,mobile phones and other tech industries has been witnessed.Gallium,as a raw material,is in great demand,and the required purity is increasingly high.Many methods have been used to produce high purity gallium.The crystallization draws people's attention due to energy saving.So it is particularly important to investigate the crystallization behavior of gallium.This thesis mainly focuses on the influence factors of undercoolings such as cold junction temperature,holding time after heating,holding time after cooling,heating temperature and crystal shape.The experiment shows that the undercooling of gallium nucleation increases with the decrease of cold junction temperature,increases with the increase of holding time after heated and increases with the increase of temperature,However,decreases with the increasing of holding time after cooled.The shape of mold performs a great influence on the undercooling,and the conical mold can greatly reduce the undercooling.This thesis mainly studies the so lid-liquid interface temperature gradient changes when the liquid solidified.The influence of undercooling on the crystal morphology and the quality trends have been studied as well.It can be seen from the crystal growth experiment that in the crystallization process,a positive temperature gradient and a negative temperature gradient are existed.In the Teflon mold,the undercooling has a great impact on the existence time of the positive temperature gradient.The greater the undercooling is,the shorter the existence time of the positive temperature gradient will be.The initial morphology of crystals is mainly under the influence of undercooling.When the undercooling is more than 12 ?,the morphology is needle-like or feathery form.When the undercooling is less than 8?,a single regular crystal will be appeared.In the macroscopic morphology,many step beams which consist of a large number of steps can be seen when the undercooling is small.