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Type: Text × Subject: Carbon × Subject: Nanocomposites ×

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    Effect of synthesis catalyst on structure of nitrogen-doped carbon nanotubes and electrical conductivity and electromagnetic interference shielding of their polymeric nanocomposites
    (New York, NY [u.a.] : Pergamon Press, 2016) Arjmand, Mohammad; Chizari, Kambiz; Krause, Beate; Pötschke, Petra; Sundararaj, Uttandaraman
    Different catalysts including Co, Fe, and Ni were used to synthesize nitrogen-doped carbon nanotubes (N-CNTs) by chemical vapor deposition technique. Synthesized N-CNTs were melt mixed with a polyvinylidene fluoride (PVDF) matrix using a small scale mixer at different concentrations ranging from 0.3 to 3.5 wt%, and then compression molded. The characterization techniques revealed significant differences in the synthesis yield and the morphological and electrical properties of both N-CNTs and nanocomposites depending on the catalyst type. Whereas Co and Fe resulted in yields comparable to industrial multiwalled CNTs, Ni was much less effective. The N-CNT aspect ratio was the highest for Co catalyst, followed by Ni and Fe, whereas nitrogen content was the highest for Ni. Raman spectroscopy revealed lowest defect number and highest N-CNT crystallinity for Fe catalyst. Characterization of N-CNT/PVDF nanocomposites showed better dispersion for N-CNTs based on Co and Fe as compared to Ni, and the following order of electrical conductivity and electromagnetic interference shielding (from high to low): Co > Fe > Ni. The superior electrical properties of (N-CNT)Co nanocomposites were ascribed to a combination of high synthesis yield, high aspect ratio, low nitrogen content and high crystallinity of N-CNTs combined with a good state of N-CNT dispersion.
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    Electrospinning of ultrafine metal oxide/carbon and metal carbide/carbon nanocomposite fibers
    (London : RSC Publishing, 2015) Atchison, Jennifer S.; Zeiger, Marco; Tolosa, Aura; Funke, Lena M.; Jäckel, Nicolas; Presser, Volker
    Electrospinning has emerged as a facile technology for the synthesis of ultrafine fibers and even nanofibers of various materials. While carbon nanofibers have been extensively investigated, there have also been studies reported on metal oxide and metal carbide fibers. Yet, comparative studies, especially following the same general synthesis approach, are lacking. In our comprehensive study, we use a sol gel process by which a carrier polymer (cellulose acetate or polyvinylpyrrolidone) is mixed with titanium butoxide, zirconium(IV) acetylacetonate, or niobium n-butoxide to yield nanotextured titania/carbon, zirconia/carbon, or niobia/carbon nonwoven textiles. Carbothermal reduction between 1300 °C and 1700 °C effectively transforms the metal oxide/carbon fibers to metal carbide/carbon nanocomposite while preserving the fiber integrity. As a beneficial effect, the fiber diameter decreases compared to the as-spun state and we obtained ultrafine fibers: 294 ± 108 nm for ZrC/C, 122 ± 28 nm for TiC/C, and 65 ± 36 nm for NbC/C. The highly disordered and porous nature of the carbon matrix engulfing the metal carbide nanocrystals enables a high specific surface area of up to 450 m2 g−1 (TiC/C) after carbothermal reduction.