NCO CONH CHa OCN HaC NHOC NCO CONH FIGURE 8.7 Schematic of a functionalized SWNT. refluxing is that it also tends to cut the nanotubes to shorter lengths,thus reducing the fiber aspect ratio.Other milder treatments have also been devel- oped;one of them is the ozone treatment.The ozonized surface can be reacted with several types of reagents,such as hydrogen peroxide,to create the acidic group attachments.In the second step of this process,the carbon nanotubes containing the acidic groups are subjected to amidation reaction either in a mixture of thionyl chloride(SOCl2)and dimethyl formamide or directly in presence of an amine.The second step produces amide functionality on carbon nanotubes that are more reactive than the acid groups. 8.3.4 MECHANICAL PROPERTIES OF CARBON NANOTUBES Theoretical calculations for defect-free carbon nanotubes show that the Young's modulus of 1-2 nm diameter SWNT is ~1 TPa and that of MWNT is between 1.1 and 1.3 TPa (Table 8.3).The Young's modulus of SWNT is inde- pendent of tube chirality,but it decreases with increasing diameter.The Young's TABLE 8.3 Properties of Carbon Nanotubes Young's Tensile Density Modulus(GPa) Strength(GPa) (g/cm) SWNT 1054 75 1.3 SWNT Bundle 563 1.3 MWNT 12002 2.6 Graphite (in-plane) 350 2.5 2.6 P-100 Carbon fiber 758 2.41 2.15 Note:1 TPa 103 GPa. Theoretical values. 2007 by Taylor Francis Group,LLC.refluxing is that it also tends to cut the nanotubes to shorter lengths, thus reducing the fiber aspect ratio. Other milder treatments have also been devel￾oped; one of them is the ozone treatment. The ozonized surface can be reacted with several types of reagents, such as hydrogen peroxide, to create the acidic group attachments. In the second step of this process, the carbon nanotubes containing the acidic groups are subjected to amidation reaction either in a mixture of thionyl chloride (SOCl2) and dimethyl formamide or directly in presence of an amine. The second step produces amide functionality on carbon nanotubes that are more reactive than the acid groups. 8.3.4 MECHANICAL PROPERTIES OF CARBON NANOTUBES Theoretical calculations for defect-free carbon nanotubes show that the Young’s modulus of 1–2 nm diameter SWNT is ~1 TPa and that of MWNT is between 1.1 and 1.3 TPa (Table 8.3). The Young’s modulus of SWNT is inde￾pendent of tube chirality, but it decreases with increasing diameter. The Young’s CONH NCO CH3 CONH CH3 H NHOC NCO 3C OCN FIGURE 8.7 Schematic of a functionalized SWNT. TABLE 8.3 Properties of Carbon Nanotubes Young’s Modulus (GPa) Tensile Strength (GPa) Density (g=cm3 ) SWNT 1054a 75a 1.3 SWNT Bundle 563 1.3 MWNT 1200a 2.6 Graphite (in-plane) 350 2.5 2.6 P-100 Carbon fiber 758 2.41 2.15 Note: 1 TPa ¼ 103 GPa. a Theoretical values.
2007 by Taylor & Francis Group, LLC