Introduction of CO_(2)is a facile way to tune the growth of vertically aligned double-or single-walled carbon nanotube(CNT)forests on wafers.In the absence of CO_(2),a double-walled CNT convexity was obtained.With increasing concentration of CO_(2),the morphologies of the forests transformed first into radial blocks,and finally into bowl-shaped forests.Furthermore,the wall number and diameter distribution of the CNTs were also modulated by varying the amount of CO_(2).With increasing CO_(2)concentration,CNTs with fewer wall number and smaller diameter were obtained.The addition of CO_(2)is speculated to generate water and serve as a weak oxidant for high quality CNT growth.It can tune the growth rate and the morphologies of the forests,prevent the formation of amorphous carbon,and reduce the wall number of the CNTs.
We report a novel method to prepare nanohybnd shish-kebab （NHSK） structure of polyethylene （PE）and carbon nanotube （CNT）. Pristine CNTs without surface modification with high concentration was effectively dispersed in xylene solution by a simple shearing method, which induces the quick crystallization of PE in xylene to form a novel NHSK structure with more dense and smaller PE kebab on CNT axis. The flocculated NHSK productwas transferred quickly from the xylene solution to the ethanol solution, in order to shorten the preparation time. The freeze-drying method was used in vacuum instead of high-temperature drying to avoid the aggregation of NHSK product. These improvements allow the formation of NHSK with an absolute yield of 200 mg.h-1, which is 2000 folds of that reported previously. It is favorable to apply this structured material in high performance nano- composite, by improving the compatibility of CNTs in p polymer and the interfacial force between CNTs and polymer.
Novel inexpensive, light, flexible, and even rollup or wearable devices are required for multi-functional portable electronics and developing new versatile and flexible electrode materials as alternatives to the materials used in contemporary batteries and supercapacitors is a key challenge. Here, binder-free activated carbon （AC）/carbon nanotube （CNT） paper electrodes for use in advanced supercapacitors have been fabricated based on low-cost, industrial-grade aligned CNTs. By a two-step shearing strategy, aligned CNTs were dispersed into individual long CNTs, and then 90 wt%-99 wt% of AC powder was incorporated into the CNT pulp and the AC/CNT paper electrode was fabricated by deposition on a filter. The specific capacity, rate performance, and power density of the AC/CNT paper electrode were better than the corresponding values for an AC/acetylene black electrode. The capacity reached a maximum value of 267.6 F/g with a CNT loading of 5 wt%, and the energy density and power density were 22.5 W.h/kg and 7.3 kW/kg at a high current density of 20 A/g. The AC/CNT paper electrode also showed a good cycle performance, with 97.5% of the original capacity retained after 5000 cycles at a scan rate of 200 mV/s. This method affords not only a promising paper-like nanocomposite for use in low-cost and flexible supercapacitors, but also a general way of fabricating multi-functional paper-like CNT-based nanocomposites for use in devices such as flexible lithium ion batteries and solar cells.
