Theoretical Study Of Structure Evolution About Heterogeneous Solidifying Process In Nano-scale

Most of materials, especially metal materials, in their preparation and molding process must experience the transformation from the liquid state to the solid state. Therefore, no matter the development of new materials or improvement traditional materials, solidification theory and technology always have important significance of science and engineering. Especially, heterogeneous solidifying behavior of multiple complex metal melt with solid particles involved in, will have important scientific significance on enriching the solidification theory of enhance metal-based materials, and toughening theory, as well as the essential basic theory in coagulator books, and will bring the new breakthrough on particles strengthen the metal-based Compound materials.Nucleation is the first step of a first order phase transition. A new phase is always sprung up in nucleation phenomena. The two main types of nucleation are homogeneous nucleation, where the new phase is formed in a uniform substance, and heterogeneous nucleation, when nucleation occurs on a pre-existing surface, and its solidifying mode is heterogeneous solidification of multiple complex metal melt with solid phrase participated. However, the growth of heterogeneous solidifying mechanism is not very understood, need us to study profoundly. So, this paper focused on the heterogeneous solidification and growth of the melt with existence of foreign particles.Recently years, the study of carbon nanotubes enhance the metal-based compound materials has aroused the peoples attention. We used molecular dynamics simulation studied Si melt heterogeneous solidifying on surfaces of carbon nanotubes. We found beside the atoms confined in carbon nanotubes can form helical multishell nanowires, the atoms solidifying on the surfaces of carbon nanotubes can also form perfect helical mutishell hierarchical nanowire structures under the effect of uniform potential field outside the carbon nanotubes, and each shell is composed by rows of atoms wound helically upwards in same direction, side by side. And, we also discussed the heredity effect of carbon nanotubes during the Si melt heterogeneous solidification and growth. We think it is the potential field uniformly radiated around the carbon nanotubes caused the heredity effect and formation of the multi-layered annual ring structures during the nucleation. Then we used molecular dynamics simulation studied the Si melt heterogeneous solidifying and growing on surfaces of carbon nanocones, which have the same carbon network structures with carbon nanotubes. Si atoms outside the carbon nanocones are concentrated to form magic multishell structures composed of coaxial and equidistant conical shells, and sometimes the atom chain is helix along the carbon nanocones helical direction, which displays the strictly structure matching and the intense structure relevance. We also study the heredity effect of carbon nanocones during the Si melt heterogeneous solidification and growth. We think it is the potential field uniformly radiated around the carbon nanocones caused the heredity effect and formation of the Si atoms multi-layered conical structures. We also used the molecular dynamics simulation studied the Al melt heterogeneous solidifying and growing on surfaces of boron-nitrogen nanotubes. On boron-nitrogen nanotube surfaces, we also found perfect Al coaxial, helical, multishell and equal distance cylindrical structures and heredity effect. These study results are favor of observing the heredity effect in cast industry, and better understanding on the heredity effect in crystal growing and the manufacturing process of materialsUsed molecular dynamics simulation, we studied multiple heterogeneous. We studied Si melt heterogeneous solidifying on the multiple surfaces of nanorope. Perfect helical and multishell structures composed of coaxial semicylinders around the nanorope are obtained. Due to the equal potential energies, the competitions of silicon atoms between CNTs are present and an interface formed. From the pair correlation function curves during the solidifying process, non-crystal structure formed, and at last, the system emerge the characteristic of ordered crystal. The carbon nanotubes in nanorope have great effect on the melt solidification, which displays the intense structure relevance. The defects, such as vacancy and Stone-Wales defects, on CNT surfaces have no effect on forming perfect hierarchical structures. These results have great advantages on strengthening the performances of the metal-based or non-crystal compound materials in case industry.