ИСТИНА

Carbon nanotube-based materials exhibit properties far below theoretical predictions and even much lower than those for some conventional carbon materials [1, 2]. So it is one of the most challenging targets of carbon materials science to translate outstanding properties of carbon nanotubes into macroscopic composite or fiber features. One can suggest rather obvious idea that the synthesi of longer nanotubes helps. Recently, some works like [3, 4] showed that it works and brings higher electric conductivity and better mechanical strength. Although there are several methods discovered for synthesizing millimeter- and centimeter-long nanotubes including our own technique [5], the macroscopic material requires the nanotubes in quantities, which are difficult or impossible to produce in laboratory bench scale. So it is necessary to scale up, which is a difficult chemical engineering problem for any process, and is especially difficult for such a delicate topochemical reaction. This work reports a scaled up process of the longer carbon nanotube synthesis. A suspended-bed synthesis rig is reported capable of producing carbon nanotube cotton in spools or piles in kilogram amounts. A possibility to produce free-standing non-woven nanotube thin films is demonstrated. The embryonation and initial growth periods are recorded. The carbon nanotube cotton was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, thermal analysis (TGA/TSC) and X-ray photoelectron spectroscopy (XPS). It was shown that the material is dominated by double- and triple-walled carbon nanotubes. Various methods of final treatment/purification from residual catalyst were investigated, the residual catalyst level of less than 0.2 % weight are reachable. It was also shown that the carbon nanotube cotton is electrically conductive and shows more that 1 kS/cm even in loose form with multiplication if densified. Opportunities of combing, roving and spinning the carbon nanotube cotton are discussed. In conclusion this successful scale-up development paves the way for intensification of research and development in macroscopic carbon nanotube-based fubers and composite materials. References 1. V.Z. Mordkovich, S.A. Urvanov, V.D. Kravchenko, N.V. Kazennov, E.A. Zhukova and A.R. Karaeva, Materials Research Innovations (2016) 20, 14 2. M. Zhang, K.R. Atkinson, and R.H. Baughman, Science (2004) 306, 1358. 3. J. N. Wang, X. G. Luo, T. Wu & Y. Chen, Nature Communications (2014) 5, Article number: 3848. 4. L. Liu, W. Ma and Z. Zhang, Small (2011) 7, 1504. 5. A.R. Karaeva, M.A. Khaskov, E.B. Mitberg, B.A.Kulnitskiy, I.A.Perezhogin, L.A. Ivanov, V.N. Denisov, A.N. Kirichenko and V.Z. Mordkovich, Fullerenes, Nanotubes and Carbon Nanostructures (2012) 20, 411.