Graphene, the thinnest, strongest, and stiffest material with exceptional thermal conductivity and electron mobility, has increasingly received world-wide attention in the past few years. These unique properties may lead to novel or improved technologies to address the pressing global challenges in many applications including transparent conducting electrodes, field effect transistors, flexible touch screen, single-molecule gas detection, desalination, DNA sequencing, osmotic energy production, etc. To realize these applications, it is necessary to transfer graphene films from growth substrate to target substrate with large-area, clean, and low defect surface, which are crucial to the performances of large-area graphene devices. This critical review assesses the recent development in transferring large-area graphene grown on Fe, Ru, Co, Ir, Ni, Pt, Au, Cu, and some nonmetal substrates by using various synthesized methods. Among them, the transfers of the most attention kinds of graphene synthesized on Cu and SiC substrates are discussed emphatically. The advances and the main challenges of each wet and dry transfer method for obtaining the transferred graphene film with large-area, clean, and low defect surface are also reviewed. Finally, the article concludes the most promising methods and the further prospects of graphene transfer.

Understanding the mechanism of ion rejection in the separation process remains a major hurdle in designing new membrane materials for seawater desalination. Here, we investigate the effects of water and aromatic polyamide (PA) membrane on the rejection of salt ions, such as Fe²⁺, Na⁺, and Cl⁻, by molecular dynamic simulations. Results demonstrate that water plays a key role in salt ion rejection because salt ions preferentially interact with water molecules to form hydrates with multishell structures, which aids the rejection of various salt ions. For FeCl₂ aqueous solution, the innermost shell water molecules of a Fe²⁺ hydrate can hardly be replaced by other substances in their molecular dynamics simulations, so ions would be highly rejected if the effective diameter of a water channel (EDC) in the membrane is smaller than that of the innermost shell of a hydrate. However, the water molecules in the second water shell can be replaced by the atoms of the membrane when the EDC is smaller than the size of the second shell (about 9 Å). Besides, although the sizes of these ions approximate to those of water molecules, the rejection level of PA membrane to salt ions is higher than that to water, which is accounted for by the formation of hydrate. POLYM. ENG. SCI., 55:466–473, 2015. © 2014 Society of Plastics Engineers

Temperature window effect has been used to extrude polyethylene blends 5000s/TR-571 and bimodal polyethylene GC100s with low extrusion temperatures and pressures. Rheological results indicate that the temperature window effect occurs during the extrusions of the GC100s and blends 5000s/TR-571. For the blends 5000s/TR-571, both the temperature window and the minimum extrusion pressure dramatically decreases with increasing content of 5000s. For bimodal polyethylene GC100s, successive self-nucleation and annealing (SSA) fractionation results suggest that the pick at high temperature on the SSA curve of the extrudates obtained inside the temperature window is remarkably lower than those of the extrudates obtained outside the temperature window. This indicates that the lamellae of the extrudates obtained in the window are thinner than those obtained outside the window, which is attributed to the fact that the well-aligned chains as the result of structure memory effect can act as nucleating agent in the crystallization process. POLYM. ENG. SCI., 54:303–309, 2014. © 2013 Society of Plastics Engineers

In this work, both hexene copolymerized polyethylene of TR-571 and homopolymerized polyethylene of 5000s were ram extruded using a temperature window effect. The rheological results show that the extrusion pressures abruptly drops at very narrow extrusion temperature windows for the two types of polyethylenes, but the window range (150–155°C) of TR-571 are higher about 6°C than that of 5000s, and the threshold melt velocity value (where the window effect set in) for TR-571 is remarkably lower than that of 5000s. Besides, the differential scanning calorimeter experiments indicate that the melting points (T_m) of the extrudates obtained inside the temperature window are lower 3.74–4.56°C than those obtained outside, whereas the crystallization peak temperatures (T_c) of the former are higher 3.29–3.57°C than those of the later. The crystal orientation, shown in the photographs of wide-angle x-ray diffraction and scanning electron microscope, indicates that the chain alignment induced by elongational flow in the temperature window can at least be partially maintained and leave a structure memory in the melt state. Successive self-nucleation and annealing fractionation results suggest that these well-aligned chains as the result of structure memory effect can act as a nucleating agent in the crystallization process. Thus, the number of the lamellae increases and the thickness decrease, which finally leading to higher T_c and lower T_m of extrudates obtained inside a temperature window. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013