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Flexible transparent conductive films or substrates prepared from plastics or cellulose are widely used in optoelectronic devices. However, all of these films or substrates are fabricated by complex and expensive methods, which consume much energy and time. In this work, we report for the first time a remarkably facile and effective approach for fabricating flexible transparent films directly from wood. The resulting films exhibit an array of exceptional optical and mechanical properties. The well-aligned cell structures in natural wood are maintained during delignification, leading to anisotropic films with high transparency (≈90% transmittance). These anisotropic films with well-aligned cell structures show mechanical tensile strengths higher than those of the original wood, and can be used as screen protection films for cellphones. Furthermore, ultrathin, highly transparent, and outstandingly conductive films have been prepared from such films and silver nanowires (AgNWs) using the Meyer technique. A conductive film with an optimal area density (341 mg m) of AgNWs showed outstanding synergistic properties, with a transmittance of 80% and a sheet resistance of 11 Ω sq, equal to the conductivity of ITO. Of importance here is that the low-cost anisotropic transparent wood film shows promising potential for electronics applications in solar cells, flexible displays, and other products.

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In conventional foams, electrical properties often play a secondary role. However, this scenario becomes different for 3D graphene foams (GrFs). In fact, one of the motivations for synthesizing 3D GrFs is to inherit the remarkable electrical properties of individual graphene sheets. Despite immense experimental efforts to study and improve the electrical properties of 3D GrFs, lack of theoretical studies and understanding limits further progress. The causes to this embarrassing situation are identified as the multiple freedoms introduced by graphene sheets and multiscale nature of this problem. In this article, combined with transport modeling and coarse-grained molecular dynamic (MD) simulations, a theoretical framework is established to systematically study the electrical conducting properties of 3D GrFs with or without deformation. In particular, through large-scale and massive calculations, a general relation between contact area and conductance for two van der Waals bonded graphene sheets is demonstrated, in terms of which the conductivity maximum phenomenon in GrFs is first theoretically proposed and its competition mechanism is explained. Moreover, the theoretical prediction is consistent with previous experimental observations.

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Author: A series of novel intrinsically flame-retardant thermoplastic poly(imide-urethanes) (TPIUs) has been synthesized by 4,4′-diphenylmethane diisocyanate (MDI), poly(tetrahydrofuran) (PTMG), pyromellitic anhydride (PMDA), and hydroxyl-terminated poly(dimethylsiloxane) (PDMS) used as flame retardants. The obtained TPIU/PDMS exhibited good tensile strength and elongation at break. TPIU/PDMS has a higher thermal decomposition temperature than that of commercial PTMG−MDI−1,4-butanediol-based thermoplastic polyurethane (TPU) according to thermal gravimetric analysis. The total heat released and peak heat release rate of TPIU/12.4%PDMS were found to be lower than those of the pure TPIU by 8.0% and 26.3%, respectively, based on cone calorimeter testing. The condensed phase of TPIU/PDMS has been investigated by scanning electron microscopy, Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy. The results indicate that the good flame retardancy of TPIU/PDMS can be attributed to thermally stable compounds with Si−O structures on the surface of its char layers.

A three-dimensional molecular dynamics simulation is performed to study atomic force microscopy cutting on silicon monocrystal surface. The displacive phase transformation from the four-coordinated diamond cubic phase to the six-coordinated β-silicon phase is observed due to localized high pressure. During phase transformation, atoms are of high potential and temperature, and the values of pressure and temperature are in good agreement with those according to the phase diagram.

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