Here we quantify the electron transport properties of aligned carbon nanotube (CNT) networks as a function of the CNT length, where the electrical conductivities may be tuned by up to 10× with anisotropies exceeding 40%. Testing at elevated temperatures demonstrates that the aligned CNT networks have a negative temperature coefficient of resistance, and application of the fluctuation induced tunneling model leads to an activation energy of ≈ 14 meV for electron tunneling at the CNT-CNT junctions. Since the tunneling activation energy is shown to be independent of both CNT length and orientation, the variation in electron transport is attributed to the number of CNT-CNT junctions an electron must tunnel through during its percolated path, which is proportional to the morphology of the aligned CNT network.The quantum confinement mediated landmark properties of one dimensional materials, such as nanowires, nanofibers, and nanotubes, makes them attractive to a number of high value applications. Recently, carbon nanotubes (CNTs) were extensively studied in scalable aligned architectures, commonly known as forests, which promise the design and facile manufacture of multifunctional material architectures with tunable properties.
The energy losses and geometric constraints associated with conventional curing techniques of polymeric systems motivate the study of a highly scalable out-of-oven curing method using a nanostructured resistive heater comprised of aligned carbon nanotubes (A-CNT). The experimental results indicate that, when compared to conventional oven based techniques, the use of an "out-of-oven" A-CNT integrated heater leads to orders of magnitude reductions in the energy required to process polymeric layered structures such as composites. Integration of this technology into structural systems enables the in situ curing of large-scale polymeric systems at high efficiencies, while adding sensing and control capabilities.
Here, a nanomaterial with morphology‐controlled nanoscale capillaries is utilized to overcome manufacturing challenges in layered polymeric architectures. It is demonstrated that the capillary pressure from a nanoporous film replaces the need for applied pressure to manufacture void‐free layered polymeric architectures. Manufacturing of aerospace‐grade advanced carbon fiber composites is performed for the first time without utilizing pressure from an autoclave. Combined with a conductive curing approach, this work allows advanced composites to be manufactured without costly oven or pressure vessel infrastructure. The nanomaterial‐enabled capillary pressure is quantified as 50% greater than typical pressures used in such processing, and is anticipated to overcome the limitations imposed by the requirement of high applied pressure in many other applications such as adhesive joining of various bulk materials including metals, press forming, and closed‐mold infusion processing of layered composites and polymers.
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