The effects of polymer structures on the thermoelectric properties of polymer-wrapped semiconducting carbon nanotubes have yet to be clarified for elucidating intrinsic transport properties. We systematically investigate thickness dependence of thermoelectric transport in thin films containing networks of conjugated polymer-wrapped semiconducting carbon nanotubes. Well-controlled doping experiments suggest that the doping homogeneity and then in-plane electrical conductivity significantly depend on film thickness and polymer species. This understanding leads to achieving thermoelectric power factors as high as 412 μW m−1 K−2 in thin carbon nanotube films. This work presents a standard platform for investigating the thermoelectric properties of nanotubes.
We examine the effect of UV/O3 oxidation on the thermoelectric properties of semiconducting carbon nanotube films. The oxidative UV/O3 treatment leads to the introduction of epoxy and carbonyl groups and a significant increase in the thermoelectric power factor up to 140 μW m−1 K−2. This power factor is three times larger than that of chemically-doped films because of the enhanced Seebeck coefficient. Characterization with Raman and mid-IR absorption/extinction spectroscopy reveals that the UV/ozone treatment results in simultaneous charge carrier doping and defect formation. This simple way of enhancing thermoelectric properties is suitable for the production of large-area, flexible thermoelectric devices based on semiconducting carbon nanotubes.
The effects of fiber orientation and stress ratio on the crack propagation behavior were studied with single edge-notched specimens which were cut from an injection-molded plate (IMP) of short carbon-fiber reinforced polyphenylene sulphide, at five fiber angles relative to the loading axis, i.e. θ = 0° (MD), 22.5°, 45°, 67.5°, 90° (TD).Macroscopic crack propagation path was nearly perpendicular to the loading axis for the cases of MD and TD. For the other fiber angles, the crack path was inclined because the crack tended to propagate along inclined fibers. In the relation between the crack propagation rate, da/dN, and the stress intensity factor range, ∆K, the propagation rate of fatigue cracks was slowest for MD, and increased with increasing fiber angle. When da/dN was correlated to ∆K/E (E = Young's modulus), the relations for different orientations merged into a single relation. The core layer existing in IMP accelerated crack propagation in MD direction, and decelerated in TD direction. The da/dN vs ∆K/E relation of skin-layer plates is close to that for IMP. The effect of stress ratio becomes minimal when da/dN is correlated to the range of the energy release rate, ∆G = G max -G min (G max , G min = maximum, minimum energy release rates). The relation between da/dN and ∆G/E shows the least scatter for SFRP with different fiber orientations under different stress ratios.
Key words:Fatigue crack propagation, Short-fiber reinforced plastics, Material orientation, Stress ratio, Fracture mechanics, Injection molding
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.