Strong and Ductile Colossal Carbon Tubes with Walls of Rectangular Macropores

We report a new type of carbon material—porous colossal carbon tubes. Compared with carbon nanotubes, colossal carbon tubes have a much bigger size, with a diameter of between 40 and $100\mu \mathrm{m}$ and a length in the range of centimeters. Significantly, the walls of the colossal tubes are composed of macroscopic rectangular columnar pores and exhibit an ultralow density comparable to that of carbon nanofoams. The porous walls of colossal tubes also show a highly ordered lamellar structure similar to that of graphite. Furthermore, colossal tubes possess excellent mechanical and electrical properties.

Figure 1

(a) Scanning electron microscopy (SEM) image of colossal carbon tubes (CCTs) grown for 30 min. (b) SEM image of CCTs grown for 3 h. (c) Raman spectra of CCTs. Lines 1 and 2 correspond to the tubes in (a) and (b), respectively.

Figure 2

(a) Schematic illustration and SEM images corresponding to the specific positions in the scheme by the top view of a tube. Precipitates are observed on the outer surface of the tube wall, shown by the arrow. (b) Schematic illustration and a corresponding SEM image by the side view of the tube wall. Schemes in (a) and (b) are drawn by the AutoCAD Software based on experimental results.

Figure 3

(a) Layered structure of the tube wall, observed by a high resolution transmission electron microscopy. (b) A typical x-ray diffraction pattern.

Figure 4

Mechanical properties of the CCT. (a) Curves of engineering and true stresses vs engineering strain, showing a high tensile strength of 6.9 GPa. The engineering stress and strain are defined as the load divided by the original cross-sectional area and the elongation divided by the original length of the sample, respectively [26]. The true stress is defined as the load divided by the in situ cross-sectional area. The cross-sectional area of the CCT was calculated as the area between the inner and outer walls. (b) SEM image of the breaking part under tensile stress.

Figure 5

Temperature dependence of the electrical conductivity in a CCT.

Figure 6

Schematic illustration of the formation of a CCT scrolled from a macroporous graphite sheet.