Theoretical study of hierarchical structures and heredity effect of silicon solidifying on carbon nanotube

Liquid-Liquid Phase Transition in Metallic Droplets

We report theoretical evidence of the substrate-induced liquid-liquid phase transition (LLPT) behaviors in a single Al droplet and Ti-Al droplets. The Al droplet can produce an LLPT induced by substrates in part, forming a special three-layer structure. However, the introduction of a Ti droplet can promote the LLPT in an Al droplet. Al and Ti droplets do not coalesce into a homogeneously mixed droplet but produce the ordered liquid films. The substrate-induced LLPT in the Al droplet is characterized by the transition from the disordered to ordered structure. Results indicate that the substrate and the Ti droplet are the driving forces to promote the LLPT. The LLPT of the Ti-Al droplets in the wedge-shaped substrate is also observed, indicating that the confined Ti-Al droplets are more likely to undergo an LLPT.

Molecular dynamics study on the heterogeneous nucleation of liquid Al-Cu alloys on different kinds of copper substrates

Al-Cu alloys are widely used in aeronautics and aerospace engineering because they exhibit outstanding performance. However, their casting characteristics are poor. Heterogeneous nucleation plays a significant role in controlling crystal growth. MD simulations are performed to explore the heterogeneous nucleation of liquid Al-Cu on a copper substrate including the heat-up process, preservation process, and freezing process. The simulation results show that the Al-Cu melt becomes layered at the liquid-solid interface and tends to be ordered in the structure because of the induced effect from the substrate. The crystal structure information is found to be gradually delivered from the substrate to the liquid, and this transmission capacity of information decays with increasing distance from the substrate. The liquid Al-Cu alloy with high copper content frozen on the single substrate tends to form a perfect crystal structure more easily, but the Al-Cu melt with low copper content between two copper substrates tends to form an arch-shaped structure, which can disappear when the copper content reaches a specific proportion. Moreover, different angles of the grooved substrates also affect the heterogeneous nucleation of the Al-Cu melt and its solidified structure. Our findings provide new insights into the defect and structural changes during heterogeneous nucleation, and our findings also promote leading-edge studies, which can provide new ideas to mechanical research.

Abnormal separation of the silicon–oxygen bond in the liquid layering transition of silicon dioxide in a nanoslit

Layering transition and separation of silicon and oxygen in liquid SiO₂ become obvious due to the strengthening of the nanoconfined effect.

Heterogeneous nucleation of Al melt in symmetrical or asymmetrical confined nanoslits

MD simulations are performed to study the solidification of Al melt in confined nanoslits (NSs) constructed by identical or different substrates, as well as on Fe substrates. Compared to the single substrate, the confined NS could promote the crystallization of Al melt, and its size has a significant impact on the solidified structure. In symmetrical NSs, liquid Al atoms would stack based on the atomic arrangement mode of the substrate, however in asymmetrical confined NSs, the atomic arrangement mode of liquid Al is governed by the constitution of asymmetrical substrates. Specifically, for the NS formed by Fe(110) and Fe(111) substrates, the induced region from the Fe(110) substrate is much bigger than that from Fe(111). Moreover, the freezing of liquid Al in asymmetrical NSs constructed from copper and iron has also been studied. These results throw light on heterogeneous nucleation in confined space.

Theoretical study of the pathway to heterogeneous nucleation of liquid copper on the groove substrate with different wedge angles

The induced effect from the substrate decays with the increasing distance from the substrate, then the final structure gradually recovers its inherent structure.

How does carbon nanoring deform to spiral induced by carbon nanotube?

Molecular dynamics (MD) simulations have been performed on the interaction between carbon nanoring (CNR) and single-wall carbon nanotube (SWCNT). The results show that, the CNR can spontaneously insert into the hollow interior of the SWCNTs to form a DNA-like double-helix, or collapse to a linked double graphitic nanoribbon and wrap in a helical manner around a tube. Further analyses of energy components show that this unique phenomenon is the result of the Van der Waals interaction. The spiral configuration of the CNR takes the least amount of energy and achieves the maximum occupancy. The sizes of CNR and SWCNT should meet the required conditions to guarantee the spiral form in the insertion and wrapping processes. Two CNRs can also be encapsulated in the SWCNT to form a helix at the same time. Furthermore, we also studied the encapsulation process of CNRs modified with –OH and –H functional groups.