Double-walled CNTs

Figure 1. CNTs and other nano-sized carbon particles (a) scrolling a graphene sheet (b) closed and opened single-walled CNT (c) double-walled CNT (d) CNT sites doped with boron and nitrogen (e) nanopipettes (f) nanocones and (g) nanorings.

A multi-walled CNT is a coaxial assembly of single-walled CNTs, normally encased by 10 to 30 consecutive layers of carbon atoms. Multi-walled CNTs are more synthesized than single-walled CNTs. In most cases multi-walled CNT contain many structural defects. Recently the synthesis of double-walled CNTs has been reported7 (Figure lc). 

Figure 19.2 shows a typical TEM image of SWNTs made by Professor Xie. The purity of SWNTs is more than 80% with some thin-wall (double-wall) CNTs. The concentration of amorphous carbon is <5% and ash is <2%. The price for these CNTs is around 20 per gram. In the future, the price may be even lower if the process and facility can be further improved. A more reasonable price for carbon nanotubes will make it possible to pursue projects in which large quantities of nanotubes are needed. 

Li and Chou [54] 2004 Molecular structural mechanics with 3D space frame-like structures with beams (3,3X8,8) (5,0X14,0) — 0.4-1.2 Buckling behaviors under either compression or bending for both single-and double-walled CNTs... 

Nonlinear free vibration of embedded double-walled CNTs at different boundary condition... 

By contrast, single-walled CNTs (SWCNTs) are a cylindrical tube formed by wrapping a single-layer graphene sheet. According to the wall number of a CNT, it can be classified as a SWCNT, double-walled CNT (DWCNT), triple-walled CNT (TWCNT), or multi-walled CNT (MW-CNT). 

Stable aerogels based on single- or double-walled CNTs and ferrocene-grafted poly(p-phenyleneethynylene) (Fc-PPE) copolymers were produced by forming a three-dimensional assembly in solution, followed by CO2 supercritical drying (Kohlmeyer et al., 2011). The method is based on the fact that at sufficient copolymer concentration, the ferrocenyl groups act as anchoring units and the... 

To confirm the wirelike structure to be CNTs, higher-resolution observation via HRTEM was used to investigate the compound morphology. Because CNTs can exist in many forms like SWCNTs, double-walled CNTs, or MWCNTs, it is important to distinguish their forms. HRTEM provides a useful visual method to analyze the... 

Influence of Interphase properties on the macroscopic response of single- and double-walled CNT/epoxy nanocomposites ... 

According to Cui et al. [82], the stress transfer in double-walled CNTs from the outer to the iimer walls within polymer composites is poor, such that the inner walls are virtually unstressed during the tensile and compressive deformation. The implication of this finding is that a significant reduction in the effective modulus of the reinforcement in MWCNTs composites is expected. 

This paper reports a modeling method for calculating the in-plane stiffness and shear modulus of double-walled CNTs (DWNTs) via molecular simulations. The strain energy and the corresponding second derivative with respect to displacanent subjected to CNTs are used to evaluate the material properties via an elastic rod theory. Length dependence of the mechanical properties is explored for DWNTs. In addition, van der Waals effect on difference of the material properties between DWNTs and SWNTs is investigated. 

---