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Computer simulations were performed on the spontaneous solidification and artificial intervention solidification processes of liquid gallium (Ga) by using molecular dynamics. The formation and evolution mechanism of the microstructure of liquid Ga under different solidification conditions were systematically studied using a combination of microstructural methods including the pair distribution function, bond-type index, and cluster-type index. The simulation results revealed that spontaneous homogeneous nucleation started from icosahedrons and defective icosahedrons. Artificial intervention can effectively control the thermostatic crystallization processes of liquid Ga, favoring crystal formation with large grains. The simulation results explain important experimental phenomena and the solidification theory of Ga smelting by the crystallization method from the microscopical point of view. We tested experimentally the process conditions for high-purity Ga smelting by the crystallization method as obtained from our simulations, resulting in successful preparation of metallic Ga with purity of 99.99999%. [ABSTRACT FROM AUTHOR]

In this study, radial crystallization purification method under induction was proposed for preparing 6N,7N ultra-high purity gallium crystal seed. The effect of cooling temperature on the morphology of the crystal seed, as well as the cooling water temperature, flow rate, and the addition amount of crystal seed on the crystallization process was explored, and the best purification process parameters were obtained as follows: temperature of the crystal seed preparation, 278 K; temperature and flow rate of the cooling water, 293 K and 40 L·h−1, respectively; and number of added crystal seed, six. The effects of temperature and flow rate of the cooling water on the crystallization rate were investigated. The crystallization rate decreased linearly with increasing cooling water temperature, but increased exponentially with increasing cooling water flow. The governing equation of the crystallization rate was experimentally determined, and three purification schemes were proposed. When 4N crude gallium was purified by Scheme I, 6N high-purity gallium was obtained, and 7N high-purity gallium was obtained by Schemes II and III. The purity of high-purity gallium prepared by the three Schemes I, II, and III was 99.999987%, 99.9999958%, and 99.9999958%, respectively. [ABSTRACT FROM AUTHOR]

As one of the critical raw materials, very pure gallium is important for the semiconductor and photoelectric industry. Unfortunately, refining gallium to obtain a purity that exceeds 99.99999% is very difficult. In this paper, a new, facile and efficient continuous partial recrystallization method to prepare gallium of high purity is investigated. Impurity concentrations, segregation coefficients, and the purification effect were measured. The results indicated that the contaminating elements accumulated in the liquid phase along the crystal direction. The order of the removal ratio was Cu > Mg > Pb > Cr > Zn > Fe. This corresponded to the order of the experimentally obtained segregation coefficients for each impurity: Cu < Mg < Pb < Cr < Zn < Fe. The segregation coefficient of the impurities depended strongly on the crystallization rate. All observed impurity concentrations were substantially reduced, and the purity of the gallium obtained after our refinement exceeded 99.99999%. [ABSTRACT FROM AUTHOR]