The ability to control the organization of anisotropic nanoparticles, such as nanorods, with high precision would greatly facilitate the fabrication of functional materials. Using a hybrid computational model, we systematically investigate the directed self-assembly of Janus nanorods, with two chemically different surface compartments, in binary polymer mixtures. Our simulations demonstrate that the energetic contributions from the surface chemistry of the Janus nanorods, the rod-rod interaction, and the spatial confinement from the polymer phases can be tailored to tune the orientation angle of the nanorods with respect to phase interface, leading to the formation of ''lying'', tilt, and ''standing'' interfacial superstructures. A detailed insight into the mechanism regarding this precise control of nanorod orientation at the interface is obtained by evaluating the rod-phase interaction energy and the entropic energy of the tethered ligands on the rods. Furthermore, since the Janus rods are localized at the interface between two polymer phases, the structural evolution of the polymer nanocomposites is dramatically curtailed. This kinetic arrest is found to depend on the surface chemistry and the aspect ratio of Janus rods. The results demonstrated in this paper offer a novel approach to achieve morphological and kinetic control in nanoscopic composites towards unique photovoltaic and mechanical properties.

We perform computer simulations to explore the suprastructures and their formation mechanism in the length-dependent assembly of a stiff polymer chain on the carbon nanotube surface. Three types of local conformations, that is, helical wrapping along the nanotube threadline, nonhelical loop, and straight extension along the nanotube, are identified in the very stiff polymer, depending on its length. It is revealed that the high elastic energy penalty and the large length of a long stiff polymer hinder its conformation transition on the nanotube, which impairs the match between the polymer beads and the structural details of the underlying nanotube surface and thereby weakens the polymer-nanotube interaction. A preferred chain length with an energy minimum is documented for the first time in the self-assemble of a stiff polymer at the nanotube interface. These data significantly advance our understanding of the superstructure formation by self-assembly of various chain-like molecules (e.g., polymer, surfactants, DNA, peptides, etc.) on carbon nanotube.

No abstract

No abstract

Anti-vibration bars (AVBs) are essential components of a steam generator (SG) and are used to prevent steam generator tubes (SGTs) from vibrating intensely because of flow-induced vibration. However, the contact force generated at contact surfaces between AVBs and tubes can change the natural frequency and wear behavior of the tube. Contact force is represented by clamping force in this study. Considering the effect of the clamping force on the natural frequency and sliding distance of SGT, dynamic wear behavior under different clamping forces was analyzed based on the finite element method, and the natural frequency of the tube was measured in the present work. Moreover, the wear experiment was conducted at room temperature to verify the conclusions of dynamic behavior analysis. The increase in clamping force reduces the sliding distance of SGT, and wear depth affected by both clamping force and sliding distance also decreases.