Semicrystalline polymers under nanoconfinement show distinct structural and thermomechanical properties compared to their bulk counterparts. Despite extensive research on semicrystalline polymers under nanoconfinement, the nanoconfinement effect on the local crystallization process and the unique structural evolution of such polymers have not been fully understood. In this study, we unveil such effects by using coarse-grained molecular dynamics simulations to study the crystallization process of a model semicrystalline polymer—polyvinyl alcohol (PVA)—under different levels of nanoconfinement induced by nanoparticles that are represented implicitly. We quantify in detail the evolution of the degree of crystallinity ($X_C$) of PVA and examine distinct crystalline regions from simulation results. The results show that nanoconfinement can promote the crystallization process, especially at the early stage, and the interfaces between nanoparticles and polymer can function as crystallite nucleation sites. In general, the final $X_C$ of PVA increases with the levels of nanoconfinement. Further, nanoconfined cases show region-dependent $X_C$ with higher and earlier increase of $X_C$ in regions closer to the interfaces. By tracking region-dependent $X_C$ evolution, our results indicate that nanoconfinement can lead to a heterogenous crystallization process with a second-stage crystallite nucleation in regions further away from the interfaces. In addition, our results show that even under very high cooling rates, the nanoconfinement still promotes the crystallization of PVA. This study provides important insights into the underlying mechanisms for the intricate interplay between nanoconfinement and the crystallization behaviors of semicrystalline polymer, with the potential to guide the design and characterization of semicrystalline polymer-based nanocomposites.

Epitaxially c-axis oriented thin films of La_0.7Ca_0.3MnO₃ (LCMO) have been fabricated on (001) SrTiO₃ and (001) LaAlO₃ substrates by pulsed laser-ablated deposition technique. The physical properties of as-grown films are correlated with the structural nature of the substrate. The O₂-annealed films grown on both substrates exhibit higher metal-insulator (M-I) transition temperatures (T_MI) and larger magnetoresistance (MR) ratios than the corresponding as-grown films. On the other hand, the Ar-annealed films display enhanced MR without any noticeable change in T_MI. We suggest that increase in T_MI is mainly ascribed to oxygen incorporation whereas enhancement of MR is largely associated with microstructural change induced by thermal annealing. Structural and transport data reveal that post-annealing with O₂ not only saturates the anion defect sites but also relieves structural strain, resulting in the enhancement of T_MI and large MR.

This study sought to characterize aluminum nanocomposite wires that were fabricated through a cold-rolling process, having potential applications in TIG (tungsten inert gas) welding of aluminum. A206 (Al-4.5Cu-0.25Mg) master nanocomposites with 5 wt % γAl₂O₃ nanoparticles were first manufactured through a hybrid process combining semi-solid mixing and ultrasonic processing. A206/1 wt % γAl₂O₃ nanocomposites were fabricated by diluting the prepared master nanocomposites with a monolithic A206 alloy, which was then added to a pure aluminum melt. The fabricated Al–γAl₂O₃ nanocomposite billet was cold-rolled to produce an Al nanocomposite wire with a 1 mm diameter and a transverse area reduction of 96%. Containing different levels of nanocomposites, the fabricated samples were mechanically and electrically characterized. The results demonstrate a significantly higher strength of the aluminum wires with the nanocomposite addition. Further, the addition of alumina nanoparticles affected the wires’ electrical conductivity compared with that of pure aluminum and aluminum–copper alloys. The overall properties of the new material demonstrate that these wires could be an appealing alternative for fillers intended for aluminum welding.