**9. Applications**

In our previous works, we demonstrated that MWCNT having shorter SBPL have a certain merit in a polymer composite for electrical conductive application. When MWCNTs are nee‐ dle-like, polymer composites comprised of them exhibit higher electrical conductivity com‐ pared to those comprised of tortuous MWCNTs. The situation changed drastically when the composites were molded into a specimen by injection molding machine. The needle like CNTs aligned to the flow direction, which broke the electrical conductive networks, then the composites lose the electrical conductivity. However, this problem was not observed when the composites contained tortuous MWCNTs which have a short SBPL. We also showed that the electrical percolation threshold depends on the length of MWCNT when MWCNT are needle-like. But, the electrical percolation threshold depends on the SBPL for a tortuous MWCNT. Thermal conductivity and linear thermal expansivity are also strongly dependant properties on the SBPL of MWCNT. Especially, thermal shrinkable material can be fabricat‐ ed as well as thermal expansive material by controlling SBPL of MWCNT.

### **Author details**

Heon Sang Lee

Address all correspondence to: heonlee@dau.ac.kr

Dong-A University, Department of Chemical Engineering, Sahagu, Busan, South Korea

### **References**

[1] Lee, H. S.; Yun, C. H.; Kim, S. K.; Choi, J. H.; Lee, C. J.; Jin, H. J.; Lee, H.; Park, S. J.; Park, M. Appl. Phys. Lett. 2009, 95, 134104.


*N o*

52 Syntheses and Applications of Carbon Nanotubes and Their Composites

the faster thermal motion of nanoparticle compared to a larger particles.

ed as well as thermal expansive material by controlling SBPL of MWCNT.

Dong-A University, Department of Chemical Engineering, Sahagu, Busan, South Korea

[1] Lee, H. S.; Yun, C. H.; Kim, S. K.; Choi, J. H.; Lee, C. J.; Jin, H. J.; Lee, H.; Park, S. J.;

Address all correspondence to: heonlee@dau.ac.kr

Park, M. Appl. Phys. Lett. 2009, 95, 134104.

**9. Applications**

**Author details**

Heon Sang Lee

**References**

*RT <sup>G</sup> M* r

*e*

The plateau modulus of polymer is usually reported in the order of 10 6~7Pa. Entanglement molecular weight of polymer is about 1000~2000 g/mole. The entanglement length is about 10~100 nm.The particles having comparable size to the entanglement length of a polymer would feel less frictional force than expected from the melt viscosity in macrorheology. Therefore, viscosity of polymer melt is much lower for the nanoparticles. This may lead to

In our previous works, we demonstrated that MWCNT having shorter SBPL have a certain merit in a polymer composite for electrical conductive application. When MWCNTs are nee‐ dle-like, polymer composites comprised of them exhibit higher electrical conductivity com‐ pared to those comprised of tortuous MWCNTs. The situation changed drastically when the composites were molded into a specimen by injection molding machine. The needle like CNTs aligned to the flow direction, which broke the electrical conductive networks, then the composites lose the electrical conductivity. However, this problem was not observed when the composites contained tortuous MWCNTs which have a short SBPL. We also showed that the electrical percolation threshold depends on the length of MWCNT when MWCNT are needle-like. But, the electrical percolation threshold depends on the SBPL for a tortuous MWCNT. Thermal conductivity and linear thermal expansivity are also strongly dependant properties on the SBPL of MWCNT. Especially, thermal shrinkable material can be fabricat‐

= (35)


**Chapter 4**

**Fabrication, Purification and Characterization of**

Mohsen Jahanshahi and Asieh Dehghani Kiadehi

based on number of walls, the single-walled and multi-walled.

chemical/biochemical sensors [15-18], hydrogen storage [19].

does not require expensive apparatus [25,26].

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/51116

**1. Introduction**

**(ADLM)**

**Carbon Nanotubes: Arc-Discharge in Liquid Media**

Carbon nanotubes (CNTs) were first discovered by Iijima in 1991 [1]. CNTs have sparked great interest in many scientific fields such as physics, chemistry, and electrical engineering [2, 3]. CNTs are composed of graphene sheets rolled into closed concentric cylinders with diameter of the order of nanometers and length of micrometers. CNTs are in two kinds,

The diameter of single walled carbon nanotubes (SWNTs) ranges from 0.4 nm to 3nm and the length can be more than 10 mm that makes SWNTs good experimental templates to study one-dimensional mesoscopic physics system [3]. These unique properties have been the engines of the rapid development in scientific studies in carbon based mesoscopic phys‐ ics and numerous applications such as high performance field effect transistors [4-9], singleelectron transistors [10, 11], atomic force microscope tips [12], field emitters [13, 14],

There are three important methods to produce high quality CNT namely laser [20], arc dis‐ charge [21, 22], and Chemical Vapor Deposition (CVD) [23, 24]. Recently, arc discharge in liquid media has been developed to synthesize several types of nano-carbon structures such as: carbon onions, carbon nanohorns and carbon nanotubes. This is a low cost technique as it

However, several techniques such as oxidation, nitric acid reflux, HCl reflux, organic func‐ tionalization, filtration, mechanical purification and chromatographic purification have been developed that separate the amorphous carbons and catalyst nanoparticles from the CNTs while a significant amount of CNTs are also destroyed during these purification processes [27].

> © 2013 Jahanshahi and Kiadehi; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2013 Jahanshahi and Kiadehi; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.
