Contents

#### **Preface XI**


#### **Section 2 State-of-the-Art Physical 9**


#### **X** Contents

#### **Section 3 State-of-the-Art Nanocomposites 125**

Chapter 8 **Highly Anisotropic Polymer Composites Based on Carbon Nanotubes 127** Geoffrey R. Mitchell, Fred J. Davis, Saeed Mohan and Meruyert Nazhipkyzy

Preface

at least at nano-level.

It gives us immense pleasure in introducing a book titled *Carbon Nanotubes - Recent Progress* based on state of the art of physical, state of the art of nanocomposites, state of the art of elec‐ trochemical, as well as state of the art of energy with their outstanding and potential applica‐ tions. These deal with advanced nanotechnological aspects of the synthesis, growth, development, and potential applications of carbon or hybrid materials such as CNTs. The dis‐ cussion of these aspects develops through the fundamentals and applied experimental routes in conventional methods via the interaction of carbon nanotubes to finally comprise the inter‐ facing of the science and technological worlds. Today, CNT has undoubtedly accomplished its conventional essence and has taken new directions from preparation to applications in re‐ search and development (R&D) areas of science. The new paths and emerging frontiers are branching out from time to time around this advanced nanotechnology stage on nanotubes. Advances in carbon materials with instrumentation for evaluating the structural model mate‐ rials now enable us to understand quite broadly almost all the events that take place for CNTs

Authors Y. Hayashi et al. introduce the rapid growth of dense and long carbon nanotube ar‐ rays that have succeeded in surpassing their challenges by synthesizing dense and long CNT arrays. In this contribution, they conclude in their chapter the aids in unveiling the current achievements in the growth of dense and long CNT arrays and their application in spinning

Shimoi's efforts to construct a field emission cathode with SWCNTs have so far only helped average out a nonhomogeneous electron emitter plane with large FE current fluctuations and a short emission lifetime. The utilization of CNTs to obtain an effective cathode, one with a stable emission and low FE current fluctuation, relies on the ability to disperse CNTs uniform‐ ly in liquid media. Highly crystalline SWCNT-based FE lighting elements that exhibit stable electron emission, a long emission lifetime, and low-power consumption for electron emitters are successfully manufactured. This FE device employing highly crystalline SWCNTs has the potential for conserving energy through low-power consumption in our habitats. Additional‐ ly, the attempt to apply highly crystalline SWCNTs as electron emission source was success‐ fully achieved to obtain a planar light-emission device with low-power consumption. Highly crystalline SWCNTs are an electrical element that can make a significant improvement in FE characteristics. A thin cathodic electrode film assembled via a wet process employing a highly crystalline SWCNT is expected to provide energy conservation as an FE electron emission source. By combining such elemental technologies, both of the control the on-and-off switch‐ ing of electron emissions in an arbitrary manner and the amplification of the luminance output with the persistence characteristics of a fluorescent screen, a flat-panel light-emission device with high brightness efficiency with an energy conserve driving method, was assembled for

threads or CNT yarns with numerous other possible applications.


## Preface

**Section 3 State-of-the-Art Nanocomposites 125**

**Carbon Nanotubes 147**

**Section 4 State-of-the-Art Electrochemical 207**

**Conductive Electrodes 209** Bu-Jong Kim and Jin-Seok Park

**Section 5 State-of-the-Art Energy 261**

Li and Wei Chen

**Nanotubes 127**

Nazhipkyzy

**VI** Contents

Chapter 8 **Highly Anisotropic Polymer Composites Based on Carbon**

Chapter 9 **Recent Progress on Electrochemical Capacitors Based on**

Chapter 10 **Studies of Nanocomposites of Carbon Nanotubes and a**

Chapter 11 **Applications of Carbon Nanotubes to Flexible Transparent**

Chapter 12 **Production of Water Dispersible Carbon Nanotubes and Nanotube/Cellulose Composite 235** Kazi Hanium Maria and Tetsu Mieno

Chapter 13 **The Porous Carbon Nanotube-Cellulose Papers as Current Collector and Electrode for Lithium Ion Battery and**

Chapter 14 **Potential Application of Photo-thermal Volumetric Ignition of**

**Carbon Nanotubes in Internal Combustion Engines 307** Antonio Paolo Carlucci, Bruce Chehroudi, Antonio Ficarella,

**Walled Carbon Nanotubes Functionalized with Borane 331** Duraisamy Silambarasan, Velappa Jayaraman Surya, Veerapandy

Xiaogang Sun, Manyuan Cai, Long Chen, Zhiwen Qiu, Jie Wang, Xu

**Supercapacitor Applications 263**

Domenico Laforgia and Luciano Strafella

Vasu and Kombiah Iyakutti

Chapter 15 **Reversible and Reproducible Hydrogen Storage in Single-**

**Negative Dielectric Anisotropy Liquid Crystal 189** Parvathalu Kalakonda and Germano S Iannacchione

Emilia Grądzka and Krzysztof Winkler

Geoffrey R. Mitchell, Fred J. Davis, Saeed Mohan and Meruyert

It gives us immense pleasure in introducing a book titled *Carbon Nanotubes - Recent Progress* based on state of the art of physical, state of the art of nanocomposites, state of the art of elec‐ trochemical, as well as state of the art of energy with their outstanding and potential applica‐ tions. These deal with advanced nanotechnological aspects of the synthesis, growth, development, and potential applications of carbon or hybrid materials such as CNTs. The dis‐ cussion of these aspects develops through the fundamentals and applied experimental routes in conventional methods via the interaction of carbon nanotubes to finally comprise the inter‐ facing of the science and technological worlds. Today, CNT has undoubtedly accomplished its conventional essence and has taken new directions from preparation to applications in re‐ search and development (R&D) areas of science. The new paths and emerging frontiers are branching out from time to time around this advanced nanotechnology stage on nanotubes. Advances in carbon materials with instrumentation for evaluating the structural model mate‐ rials now enable us to understand quite broadly almost all the events that take place for CNTs at least at nano-level.

Authors Y. Hayashi et al. introduce the rapid growth of dense and long carbon nanotube ar‐ rays that have succeeded in surpassing their challenges by synthesizing dense and long CNT arrays. In this contribution, they conclude in their chapter the aids in unveiling the current achievements in the growth of dense and long CNT arrays and their application in spinning threads or CNT yarns with numerous other possible applications.

Shimoi's efforts to construct a field emission cathode with SWCNTs have so far only helped average out a nonhomogeneous electron emitter plane with large FE current fluctuations and a short emission lifetime. The utilization of CNTs to obtain an effective cathode, one with a stable emission and low FE current fluctuation, relies on the ability to disperse CNTs uniform‐ ly in liquid media. Highly crystalline SWCNT-based FE lighting elements that exhibit stable electron emission, a long emission lifetime, and low-power consumption for electron emitters are successfully manufactured. This FE device employing highly crystalline SWCNTs has the potential for conserving energy through low-power consumption in our habitats. Additional‐ ly, the attempt to apply highly crystalline SWCNTs as electron emission source was success‐ fully achieved to obtain a planar light-emission device with low-power consumption. Highly crystalline SWCNTs are an electrical element that can make a significant improvement in FE characteristics. A thin cathodic electrode film assembled via a wet process employing a highly crystalline SWCNT is expected to provide energy conservation as an FE electron emission source. By combining such elemental technologies, both of the control the on-and-off switch‐ ing of electron emissions in an arbitrary manner and the amplification of the luminance output with the persistence characteristics of a fluorescent screen, a flat-panel light-emission device with high brightness efficiency with an energy conserve driving method, was assembled for the first time in the world. Finally, the application of FE electron sources employing highly crystalline SWCNTs was determined to be effective for conserving energy based on such re‐ sults and is expected to establish other devices that are driven with low-power consumption in the future.

effect. Especially, in the short emission electronic pulses, pulse broadening limits the possibili‐

Preface IX

Shirasu et al. review the general and recent studies, in which they investigate the nominal ten‐ sile strength and strength distribution of MWCNTs synthesized by the CVD method, followed by a series of high-temperature annealing steps that culminate with annealing at 2900 °C. The structural-mechanical relationships of such MWCNTs are investigated through tensile-loading experiments with individual MWCNTs, Weibull-Poisson statistics TEM observation, and Ram‐ an spectroscopy analysis. They also reviewed the nominal tensile strength and Weibull scale and shape parameters of the nominal tensile strength distribution of MWCNTs based on our recent studies. The comparatively low value of the shape parameter for MWCNTs resulted from the irregular nanotube structure, which reflects a larger tube defect density relative to conventional fiber materials. Nonetheless, the MWCNTs with an intermediate level of crystal‐ linity produced complete fracture of nanotube walls and exhibited higher nominal tensile strength, suggesting that there is an optimal nanotube defect density for increasing the nomi‐ nal tensile strength, not too low but also not too high, so as to permit an adequate load transfer between the nanotube walls. To improve the properties of macroscopic CNT composite per‐ formance, the structure and properties of MWCNT yarns and sheets must be optimized at all hierarchical levels: from individual MWCNTs to MWCNT bundles, MWCNT networks, and MWCNT yarns and sheets. Future research efforts aimed at each of the following levels should be pursued to improve mechanical properties, particularly the nominal tensile strength of CVD-grown MWCNTs: (1) improved synthesis methods should be developed to reduce structural defects such as *discontinuous flaws* and *kinks and bends*, and (2) the degree of interwall crosslinking and load transfer between adjacent nanotube walls should be optimized by posttreatments, such as thermal annealing and electron irradiation. We believe that the above improvements might enable the realization of higher nominal tensile strength. More well-de‐ fined CNT architectures should contribute to enhanced mechanical properties as well as im‐

ty of the high frequency and short pulse because of the thermal effect.

proved electrical and thermal properties of MWCNT yarns and composites.

Bu-Jong Kim et al. focus on the properties of CNTs, and their applications especially for flexi‐ ble TCEs are presented, including the preparation details of CNTs based on solution process‐ es, the surface modification of flexible substrates, and the various types of hybrid TCEs based on CNTs. Here, transparent conductive electrodes (TCEs) have attracted great interest because of their wide applications in solar cells, liquid crystal displays (LCDs), organic light-emitting diodes (OLEDs), and touch screen panels (TSPs). Indium-tin-oxide (ITO) thin films as TCEs possess exceptional optoelectronic properties, but they have several disadvantages, such as a brittle nature due to their low fracture strain and lack of flexibility, a high processing tempera‐ ture—which damages the flexible substrates—low adhesion to polymeric materials, and rela‐ tive rarity on Earth, which makes their price unstable. This has motivated several research studies lately for developing alternative materials to replace ITO, such as metal meshes, metal nanowires, conductive polymers, graphene, and carbon nanotubes (CNTs). Out of the above candidates, CNTs have advantages in chemical stability, thermal conductivity, mechanical strength, and flexibility. CNTs have excellent chemical stability, thermal and electrical conduc‐ tivity (high intrinsic conductivity), mechanical strength, flexibility, solution processability, and potential for production at a low cost. Based on these advantages, the CNT-based TCEs are presented. Here, it was illustrated that the adhesion of the CNTs was remarkably improved after the surface modification via corona pretreatment of the PET substrates. Then, in this con‐ tribution, the hybrid-type TCEs, which can be commercialized in various applications, were

Authors P. Kalakonda et al. interpret that these results arising from the LC-CNT surface inter‐ action lead to pinning orientational order uniformly along the CNT, without pinning the posi‐ tion of the 9OO4 molecule. These effects of incorporating CNTs with LC are likely due to elastic coupling between CNT and LC. This changes the elastic properties of composites and thermal anisotropic properties of CNT. Here, the complex-specific heat is reported over a wide temperature range for a negative dielectric anisotropy alkoxyphenylbenzoate liquid crystal (9OO4) and CNT composites as a function of carbon nanotube concentration. It has been ob‐ served that the combination of CNT and LC provides a very useful way to align CNTs and also dramatically increases the order in the liquid crystal performance, which is useful in LCD. They have presented a detailed calorimetric study on the effect of carbon nanotubes on phase transitions of the 9OO4/CNT nanocomposites as a function of CNT concentration. The com‐ plex-specific heat was measured over a wide range of temperature for negative dielectric ani‐ sotropy alkoxyphenylbenzoate-9OO4)/CNT composites as a function of CNT concentration.

In this contribution, S.A. Hashemi et al. introduce aligned CNT network within the matrix via various kinds of electric fields (AC and DC) that were evaluated. In this case, alignment mech‐ anism of CNTs within the matrix and two useful techniques for justification of CNT alignment throughout the matrix were examined and presented, respectively. Afterward, effective fac‐ tors in the matter of CNT alignment and applicable procedures for fabrication of nanocompo‐ sites containing aligned CNTs were studied and presented, respectively. At the end, significant effects of CNT alignment on overall properties of nanocomposites that include elec‐ trical and mechanical properties were evaluated. Achieved results revealed that alignment of CNTs within the matrix can lead to significant improvement in the electrical and mechanical properties of nanocomposites at same filler loading compared with random distribution of CNTs within the matrix, while production steps and conditions can also highly affect the out‐ come data. In fact, CNTs act as path for transferring current from negative to positive elec‐ trode. This phenomenon can boost both electrical and mechanical properties of developed nanocomposites at same filler content. On the other hand, achieved results revealed that the overall properties of nanocomposites that include mechanical and electrical properties are higher for parallel direction than perpendicular direction and random distribution of CNTs within the matrix, which is due to the desire of CNTs in the formation of longitudinal connec‐ tions than transverse connections. Finally, by aligning CNTs within the matrix, significant im‐ provement in overall properties of nanocomposites at same filler loadings compared with random distribution can be achieved, which is very essential for aerospace and aviation indus‐ tries that encounter with serious limits in the matter of structures' weight.

Author X. Wei focuses on the field emission of CNT cold cathodes as an electron source, in‐ cluding how to synthesize it by CVD method and how to realize its electron emission. In addi‐ tion, they report pulsed electron emission of CNT cathodes. The combination of the laser pulse and the cold cathode will offer the possibility of pulsed field emission. Our approach demon‐ strates the growth mechanism and the emission mechanism of CNTs, which are beneficial for controlling performance of its fascinating application on emerging fields. Generally, the ther‐ mal effect will lead to a response time, but the field emission is instantaneous. For the pulsed field emission, the response time and pulse broadening are the weaknesses caused by thermal effect. Especially, in the short emission electronic pulses, pulse broadening limits the possibili‐ ty of the high frequency and short pulse because of the thermal effect.

the first time in the world. Finally, the application of FE electron sources employing highly crystalline SWCNTs was determined to be effective for conserving energy based on such re‐ sults and is expected to establish other devices that are driven with low-power consumption

Authors P. Kalakonda et al. interpret that these results arising from the LC-CNT surface inter‐ action lead to pinning orientational order uniformly along the CNT, without pinning the posi‐ tion of the 9OO4 molecule. These effects of incorporating CNTs with LC are likely due to elastic coupling between CNT and LC. This changes the elastic properties of composites and thermal anisotropic properties of CNT. Here, the complex-specific heat is reported over a wide temperature range for a negative dielectric anisotropy alkoxyphenylbenzoate liquid crystal (9OO4) and CNT composites as a function of carbon nanotube concentration. It has been ob‐ served that the combination of CNT and LC provides a very useful way to align CNTs and also dramatically increases the order in the liquid crystal performance, which is useful in LCD. They have presented a detailed calorimetric study on the effect of carbon nanotubes on phase transitions of the 9OO4/CNT nanocomposites as a function of CNT concentration. The com‐ plex-specific heat was measured over a wide range of temperature for negative dielectric ani‐ sotropy alkoxyphenylbenzoate-9OO4)/CNT composites as a function of CNT concentration. In this contribution, S.A. Hashemi et al. introduce aligned CNT network within the matrix via various kinds of electric fields (AC and DC) that were evaluated. In this case, alignment mech‐ anism of CNTs within the matrix and two useful techniques for justification of CNT alignment throughout the matrix were examined and presented, respectively. Afterward, effective fac‐ tors in the matter of CNT alignment and applicable procedures for fabrication of nanocompo‐ sites containing aligned CNTs were studied and presented, respectively. At the end, significant effects of CNT alignment on overall properties of nanocomposites that include elec‐ trical and mechanical properties were evaluated. Achieved results revealed that alignment of CNTs within the matrix can lead to significant improvement in the electrical and mechanical properties of nanocomposites at same filler loading compared with random distribution of CNTs within the matrix, while production steps and conditions can also highly affect the out‐ come data. In fact, CNTs act as path for transferring current from negative to positive elec‐ trode. This phenomenon can boost both electrical and mechanical properties of developed nanocomposites at same filler content. On the other hand, achieved results revealed that the overall properties of nanocomposites that include mechanical and electrical properties are higher for parallel direction than perpendicular direction and random distribution of CNTs within the matrix, which is due to the desire of CNTs in the formation of longitudinal connec‐ tions than transverse connections. Finally, by aligning CNTs within the matrix, significant im‐ provement in overall properties of nanocomposites at same filler loadings compared with random distribution can be achieved, which is very essential for aerospace and aviation indus‐

tries that encounter with serious limits in the matter of structures' weight.

Author X. Wei focuses on the field emission of CNT cold cathodes as an electron source, in‐ cluding how to synthesize it by CVD method and how to realize its electron emission. In addi‐ tion, they report pulsed electron emission of CNT cathodes. The combination of the laser pulse and the cold cathode will offer the possibility of pulsed field emission. Our approach demon‐ strates the growth mechanism and the emission mechanism of CNTs, which are beneficial for controlling performance of its fascinating application on emerging fields. Generally, the ther‐ mal effect will lead to a response time, but the field emission is instantaneous. For the pulsed field emission, the response time and pulse broadening are the weaknesses caused by thermal

in the future.

VIII Preface

Shirasu et al. review the general and recent studies, in which they investigate the nominal ten‐ sile strength and strength distribution of MWCNTs synthesized by the CVD method, followed by a series of high-temperature annealing steps that culminate with annealing at 2900 °C. The structural-mechanical relationships of such MWCNTs are investigated through tensile-loading experiments with individual MWCNTs, Weibull-Poisson statistics TEM observation, and Ram‐ an spectroscopy analysis. They also reviewed the nominal tensile strength and Weibull scale and shape parameters of the nominal tensile strength distribution of MWCNTs based on our recent studies. The comparatively low value of the shape parameter for MWCNTs resulted from the irregular nanotube structure, which reflects a larger tube defect density relative to conventional fiber materials. Nonetheless, the MWCNTs with an intermediate level of crystal‐ linity produced complete fracture of nanotube walls and exhibited higher nominal tensile strength, suggesting that there is an optimal nanotube defect density for increasing the nomi‐ nal tensile strength, not too low but also not too high, so as to permit an adequate load transfer between the nanotube walls. To improve the properties of macroscopic CNT composite per‐ formance, the structure and properties of MWCNT yarns and sheets must be optimized at all hierarchical levels: from individual MWCNTs to MWCNT bundles, MWCNT networks, and MWCNT yarns and sheets. Future research efforts aimed at each of the following levels should be pursued to improve mechanical properties, particularly the nominal tensile strength of CVD-grown MWCNTs: (1) improved synthesis methods should be developed to reduce structural defects such as *discontinuous flaws* and *kinks and bends*, and (2) the degree of interwall crosslinking and load transfer between adjacent nanotube walls should be optimized by posttreatments, such as thermal annealing and electron irradiation. We believe that the above improvements might enable the realization of higher nominal tensile strength. More well-de‐ fined CNT architectures should contribute to enhanced mechanical properties as well as im‐ proved electrical and thermal properties of MWCNT yarns and composites.

Bu-Jong Kim et al. focus on the properties of CNTs, and their applications especially for flexi‐ ble TCEs are presented, including the preparation details of CNTs based on solution process‐ es, the surface modification of flexible substrates, and the various types of hybrid TCEs based on CNTs. Here, transparent conductive electrodes (TCEs) have attracted great interest because of their wide applications in solar cells, liquid crystal displays (LCDs), organic light-emitting diodes (OLEDs), and touch screen panels (TSPs). Indium-tin-oxide (ITO) thin films as TCEs possess exceptional optoelectronic properties, but they have several disadvantages, such as a brittle nature due to their low fracture strain and lack of flexibility, a high processing tempera‐ ture—which damages the flexible substrates—low adhesion to polymeric materials, and rela‐ tive rarity on Earth, which makes their price unstable. This has motivated several research studies lately for developing alternative materials to replace ITO, such as metal meshes, metal nanowires, conductive polymers, graphene, and carbon nanotubes (CNTs). Out of the above candidates, CNTs have advantages in chemical stability, thermal conductivity, mechanical strength, and flexibility. CNTs have excellent chemical stability, thermal and electrical conduc‐ tivity (high intrinsic conductivity), mechanical strength, flexibility, solution processability, and potential for production at a low cost. Based on these advantages, the CNT-based TCEs are presented. Here, it was illustrated that the adhesion of the CNTs was remarkably improved after the surface modification via corona pretreatment of the PET substrates. Then, in this con‐ tribution, the hybrid-type TCEs, which can be commercialized in various applications, were fabricated, and their characteristics were demonstrated. In particular, the studies about im‐ proving the electrical conductivity and transmittance of CNTs-TCEs may warrant increased interest. Finally, in authors' chapter, the metal-based TCEs coated with CNTs were considered as an effective structure to resolve the high reflectance generated by the intrinsic properties of metals. Until now, the TCEs fabricated using only CNTs had insufficient properties for appli‐ cations to electronic devices. Various hybrid types of CNT-based TCEs, however, could have potential in the application to next-generation flexible and stretchable electronics to overcome various issues.

tion of methane, hydrogen, LPG, and gasoline applying this novel approach to initiate combustion are shown. In particular, the abovementioned fuels have been mixed with air in a constant-volume vessel and ignited with nano-powder or a conventional spark ignition sys‐ tem. In fact, the new light-activated distributed ignition demonstrates superior performance, which includes a shorter combustion duration, a shorter ignition delay period, and an in‐ creased pressure peak and improved combustion efficiency. A direct observation of the com‐ bustion process has established that benefits shown here are due to the fact that photothermal ignition system establishes a spatially distributed ignition, which consequently leads to a fast‐ er consumption of the air/fuel mixture in the test vessel. Higher pressure peaks and shorter rapid rising period are achieved by the fact that the new ignition system leads to more ignition nuclei that burn near-simultaneously, hence contributing to a volumetrically distributed com‐ bustion process in the combustion chamber, drastically different from the flame front propa‐ gation observed with the spark ignition. Moreover, it was demonstrated for the first time that the proposed ignition system is able to ignite air/gasoline mixtures when liquid gasoline fuel is injected into chamber, without isolating/encapsulating the nano-energetic material. Highspeed camera images acquired during combustion process indicate that photothermal ignition resulted in volumetrically distributed quasi-homogeneous ignition followed by a better and faster consumption of the air/fuel mixture with no discernible flame front. This behavior is in contrast to what was observed with the spark ignition, namely, a single ignition point fol‐ lowed by a flame propagation across the combustion chamber. Finally, these results are con‐ sidered to be of scientific and practical importance, because the combustion process, initiated in mixtures with extremely lean air/fuel ratios of interest in lean-burn HCCI engines, would

Preface XI

allow substantial reductions of fuel consumption, nitrogen oxides, and soot emissions.

In E. Gradzka et al.'s reviews on the theoretical and practical aspects of electrochemical capaci‐ tors based on carbon nanotubes, in particular, recent improvements in the capacitance proper‐ ties of the systems are discussed. In the first part, the charge storage mechanisms of the electrochemical capacitors are briefly described. The next part of the review is devoted to the capacitance properties of pristine single- and multiwalled carbon nanotubes. The major por‐ tion of the review is focused on the capacitance properties of modified carbon nanotubes. The electrochemical properties of nanotubes with boron, nitrogen, and other atoms incorporated into the carbon network structure as well as nanotubes modified with different functional groups are discussed. Special attention is paid to the composites of carbon nanotubes and con‐ ducting polymers, transition metal oxides, carbon nanostructures, and carbon gels. In all cases, the influences of different parameters such as porosity, structure of the electroactive layer, conductivity of the layer, nature of the heteroatoms, solvent, and supporting electrolyte on the capacitance performance of hybrid materials are discussed. Finally, the capacitance properties of different systems containing carbon nanotubes are compared and summarized. In the de‐ velopment of electrochemical capacitors, carbon nanotubes and their composites have been widely used as electrode materials. The specific capacitance of pristine carbon nanotubes is relatively low and depends on many factors such as the kind of carbon nanotubular material, i.e., single- or multiwalled; its orientation, i.e., open or closed tips; surface area; synthesis method; solvent; and supporting electrolyte. Compared with pristine carbon nanotubes, func‐ tionalized carbon nanotubes by heteroatoms or functional groups attached to nanotube walls are expected to display improved capacitance performance. The formation of composites based on carbon nanotubes provides especially high surface area due to the presence of CNTs, which is very important in the case of storage systems. Moreover, it enhances the properties of both the carbon nanotubes and the second component. Apart from the improvement in capaci‐

Authors K.H. Maria et al. describe the polymer wrapping methods, which used to disperse CNT by using gelatin, an environmentally friendly and easily decomposable biopolymer. The amino acid chain of gelatin becomes immobilized by the physical adsorption in the side wall of the CNTs through hydrophobic-hydrophobic interaction and results in the untangling of the CNT bundles. The dispersed solution remains stable for more than a month. Furthermore, this technique does not affect the physical properties of CNTs while enabling their dispersion in aqueous solutions. In addition, gelatin can be easily removed from the nanotubes after the dispersion of nanotubes by heating in water and filtration. Gelatin-dispersed CNTs are homo‐ geneously mixed with the cellulose suspension and dried at room temperature to produce CNT/cellulose composite paper sheet. Adding MWNTs in composite improves the mechani‐ cal, thermal, and electrical properties of cellulose. SEM investigation confirms the homogene‐ ous distribution of MWNTs in the cellulose, which can be attributed to the improvement of its characteristics. Both sides of the CNT/cellulose sheet show the uniform electrical conductivity, which is enhanced by increasing the MWNT content. IR image of the sheet clearly shows the temperature homogeneity of the surface. Thermal stability and the flame retardancy of the sheet are also found to be improved. The sheet has also strong absorbing of electromagnetic waves, which makes them important for microwave technology applications. The potential applications of CNTs as composites offer new opportunities to produce cost-effective electron‐ ics. CNT-based sheet has been prepared by using a papermaking process. MWNTs improve the mechanical, thermal, and electrical properties of cellulose. SEM investigation confirms the homogeneous distribution of MWNTs in the cellulose, which can be attributed to the improve‐ ment of its characteristics. These electrically conductive and electromagnetic-wave-absorption properties can be useful in radar wave absorbing, electrothermal heating elements, 2D electric circuit applications, electromagnetic shields, etc.

Authors A.P. Carlucci et al. describe that to improve performance and lower pollutant levels, researchers have proposed alternatives to conventional ignition or combustion processes, such as HCCI combustion, whose critical requirement for proper operation is the precise control of the autoignition timing within the engine operating cycle. Here, an innovative volumetrically distributed ignition approach is proposed to control the onset of the autoignition process, tak‐ ing advantage of the optical ignition properties of carbon nanotubes when exposed to lowconsumption light source. It is shown that this ignition method enhanced the combustion of methane, hydrogen, LPG, and gasoline (injected in liquid phase). Results for this new ignition method show that pressure gradient and combustion efficiency are increased, while combus‐ tion duration and ignition delay decreased. A direct observation of the combustion process indicates that these benefits are due to the spatially distributed ignition followed by a faster consumption of the air/fuel mixture. The use of this ignition system is therefore proposed as a promising technology for the combustion management in internal combustion engines, specif‐ ically for HCCI engines. In this contribution, the promising results in enhancing the combus‐

tion of methane, hydrogen, LPG, and gasoline applying this novel approach to initiate combustion are shown. In particular, the abovementioned fuels have been mixed with air in a constant-volume vessel and ignited with nano-powder or a conventional spark ignition sys‐ tem. In fact, the new light-activated distributed ignition demonstrates superior performance, which includes a shorter combustion duration, a shorter ignition delay period, and an in‐ creased pressure peak and improved combustion efficiency. A direct observation of the com‐ bustion process has established that benefits shown here are due to the fact that photothermal ignition system establishes a spatially distributed ignition, which consequently leads to a fast‐ er consumption of the air/fuel mixture in the test vessel. Higher pressure peaks and shorter rapid rising period are achieved by the fact that the new ignition system leads to more ignition nuclei that burn near-simultaneously, hence contributing to a volumetrically distributed com‐ bustion process in the combustion chamber, drastically different from the flame front propa‐ gation observed with the spark ignition. Moreover, it was demonstrated for the first time that the proposed ignition system is able to ignite air/gasoline mixtures when liquid gasoline fuel is injected into chamber, without isolating/encapsulating the nano-energetic material. Highspeed camera images acquired during combustion process indicate that photothermal ignition resulted in volumetrically distributed quasi-homogeneous ignition followed by a better and faster consumption of the air/fuel mixture with no discernible flame front. This behavior is in contrast to what was observed with the spark ignition, namely, a single ignition point fol‐ lowed by a flame propagation across the combustion chamber. Finally, these results are con‐ sidered to be of scientific and practical importance, because the combustion process, initiated in mixtures with extremely lean air/fuel ratios of interest in lean-burn HCCI engines, would allow substantial reductions of fuel consumption, nitrogen oxides, and soot emissions.

fabricated, and their characteristics were demonstrated. In particular, the studies about im‐ proving the electrical conductivity and transmittance of CNTs-TCEs may warrant increased interest. Finally, in authors' chapter, the metal-based TCEs coated with CNTs were considered as an effective structure to resolve the high reflectance generated by the intrinsic properties of metals. Until now, the TCEs fabricated using only CNTs had insufficient properties for appli‐ cations to electronic devices. Various hybrid types of CNT-based TCEs, however, could have potential in the application to next-generation flexible and stretchable electronics to overcome

Authors K.H. Maria et al. describe the polymer wrapping methods, which used to disperse CNT by using gelatin, an environmentally friendly and easily decomposable biopolymer. The amino acid chain of gelatin becomes immobilized by the physical adsorption in the side wall of the CNTs through hydrophobic-hydrophobic interaction and results in the untangling of the CNT bundles. The dispersed solution remains stable for more than a month. Furthermore, this technique does not affect the physical properties of CNTs while enabling their dispersion in aqueous solutions. In addition, gelatin can be easily removed from the nanotubes after the dispersion of nanotubes by heating in water and filtration. Gelatin-dispersed CNTs are homo‐ geneously mixed with the cellulose suspension and dried at room temperature to produce CNT/cellulose composite paper sheet. Adding MWNTs in composite improves the mechani‐ cal, thermal, and electrical properties of cellulose. SEM investigation confirms the homogene‐ ous distribution of MWNTs in the cellulose, which can be attributed to the improvement of its characteristics. Both sides of the CNT/cellulose sheet show the uniform electrical conductivity, which is enhanced by increasing the MWNT content. IR image of the sheet clearly shows the temperature homogeneity of the surface. Thermal stability and the flame retardancy of the sheet are also found to be improved. The sheet has also strong absorbing of electromagnetic waves, which makes them important for microwave technology applications. The potential applications of CNTs as composites offer new opportunities to produce cost-effective electron‐ ics. CNT-based sheet has been prepared by using a papermaking process. MWNTs improve the mechanical, thermal, and electrical properties of cellulose. SEM investigation confirms the homogeneous distribution of MWNTs in the cellulose, which can be attributed to the improve‐ ment of its characteristics. These electrically conductive and electromagnetic-wave-absorption properties can be useful in radar wave absorbing, electrothermal heating elements, 2D electric

Authors A.P. Carlucci et al. describe that to improve performance and lower pollutant levels, researchers have proposed alternatives to conventional ignition or combustion processes, such as HCCI combustion, whose critical requirement for proper operation is the precise control of the autoignition timing within the engine operating cycle. Here, an innovative volumetrically distributed ignition approach is proposed to control the onset of the autoignition process, tak‐ ing advantage of the optical ignition properties of carbon nanotubes when exposed to lowconsumption light source. It is shown that this ignition method enhanced the combustion of methane, hydrogen, LPG, and gasoline (injected in liquid phase). Results for this new ignition method show that pressure gradient and combustion efficiency are increased, while combus‐ tion duration and ignition delay decreased. A direct observation of the combustion process indicates that these benefits are due to the spatially distributed ignition followed by a faster consumption of the air/fuel mixture. The use of this ignition system is therefore proposed as a promising technology for the combustion management in internal combustion engines, specif‐ ically for HCCI engines. In this contribution, the promising results in enhancing the combus‐

various issues.

X Preface

circuit applications, electromagnetic shields, etc.

In E. Gradzka et al.'s reviews on the theoretical and practical aspects of electrochemical capaci‐ tors based on carbon nanotubes, in particular, recent improvements in the capacitance proper‐ ties of the systems are discussed. In the first part, the charge storage mechanisms of the electrochemical capacitors are briefly described. The next part of the review is devoted to the capacitance properties of pristine single- and multiwalled carbon nanotubes. The major por‐ tion of the review is focused on the capacitance properties of modified carbon nanotubes. The electrochemical properties of nanotubes with boron, nitrogen, and other atoms incorporated into the carbon network structure as well as nanotubes modified with different functional groups are discussed. Special attention is paid to the composites of carbon nanotubes and con‐ ducting polymers, transition metal oxides, carbon nanostructures, and carbon gels. In all cases, the influences of different parameters such as porosity, structure of the electroactive layer, conductivity of the layer, nature of the heteroatoms, solvent, and supporting electrolyte on the capacitance performance of hybrid materials are discussed. Finally, the capacitance properties of different systems containing carbon nanotubes are compared and summarized. In the de‐ velopment of electrochemical capacitors, carbon nanotubes and their composites have been widely used as electrode materials. The specific capacitance of pristine carbon nanotubes is relatively low and depends on many factors such as the kind of carbon nanotubular material, i.e., single- or multiwalled; its orientation, i.e., open or closed tips; surface area; synthesis method; solvent; and supporting electrolyte. Compared with pristine carbon nanotubes, func‐ tionalized carbon nanotubes by heteroatoms or functional groups attached to nanotube walls are expected to display improved capacitance performance. The formation of composites based on carbon nanotubes provides especially high surface area due to the presence of CNTs, which is very important in the case of storage systems. Moreover, it enhances the properties of both the carbon nanotubes and the second component. Apart from the improvement in capaci‐

tance performance, the addition of CNTs reduces cost compared to metal oxide; improves sta‐ bility compared to conducting polymers, which exhibit rapid degradation in performance after repetitive cycles because of their swelling and shrinking; and improves the poor volu‐ metric performance of supercapacitors based on other carbon nanomaterials. The capacitance properties strongly depend on the localization of the redox system. It was found that encapsu‐ lation of the redox phase inside a nanotubular material provides higher specific capacitance than a redox system situated outside of carbon nanotubes. Recently, a new generation of cheap storage systems based on mesoporous carbon aerogels was discovered. However, in this case, there is a problem with the nonhomogeneous spread of carbon nanotubes within the whole network of carbon aerogel. Hence, increasing attention is needed to solve this problem because this system could be the future for storage devices. A very promising system seems to be the attachment of redox-active nanoparticles to carbon nanotubes. Compared to bulk mate‐ rials, they exhibit unique properties arising from their nanoscale sizes, such as high electrical conductivity, large surface area, short path lengths for the transport of ions, and high electro‐ chemical activity. Ultrafast compact capacitors based on 3D hybrid structures that increase the accessible surface area and allow fast ion diffusion are introducing a new class of electrode materials for storage devices.

face of CNTs results in hydrophobic to hydrophilic transitions, which increase their occupancy of the water molecules, thereby breaking down 1D water wires, as seen in pristine CNTs. Finally, charged or functionalized carbon nanotubes behave quite differently compared to pristine CNTs. Functionalization not only affects properties like band gap, conductivity, and metallic nature of CNTs, but it also greatly affects the properties of confined fluids. The functionalization of CNTs changes the overall nature of the CNTs and increases the hydrophilicity, which varies almost linearly with the degree of functionalization. As the degree of functionalization provides us with a handle on the properties of confined water, it might be interesting to see if we can use carbon

In this book, X. Sun et al. focused on a new type of carbon nanotube-cellulose composite mate‐ rials as current collector of LIBs and as electrodes of SCs to improve and enhance their energy/ power density and cyclic performance. CNTs have been widely used as conductive agent for both anodes and cathodes to replace super carbon black to satisfy the multifunctional require‐ ments for LIBs. Generally, LIB and supercapacitors (EDLCs and LIC) are the most commonly used energy storage services for mobile application. Lithium ion batteries are currently the most popular type of battery for powering portable electronic devices and are growing in pop‐ ularity for defense, automotive, and aerospace applications. Here, CNTs and CNTCP for pri‐ mary/second batteries and supercapacitor applications were reported. It has a great potential application value for the porous carbon nanotube-cellulose papers as current collectors and electrodes in lithium ion battery and supercapacitors. However, there are still some problems to be solved. The pore size and porosity and carbonization process of CNTCPs need to be in‐ novated to improve the strength and electrical conductivity. New high flexibility and strength of nanofibers need to be developed to adapt to electrolytes due to the cellulose papers, which are easily destroyed in liquid. Further investigations need to be done to overcome technologi‐

This work aims to bridge the gap between undergraduates, graduates, and scientists in ap‐ plied carbon material as well as composite sciences, in order to initiate researchers into CNT study in a straightforward way as possible and to introduce the researchers to the opportuni‐ ties offered by the applied science and technological fields. I worked unswervingly to com‐ plete this work on *Carbon Nanotubes - Recent Progress* under InTechOpen publisher. I hope that this contribution would further enhance the applied carbon materials in nano- and bioscience, especially in bringing new entrants into the applied and hybrid CNT science and technology

Center of Excellence for Advanced Materials Research (CEAMR) and Chemistry department

Center of Excellence for Advanced Materials Research (CEAMR) and Chemistry department

**Mohammed Muzibur Rahman**

Preface XIII

**Abdullah Mohamed Asiri**

Faculty of Science, King Abdulaziz University, Saudi Arabia

Faculty of Science, King Abdulaziz University, Saudi Arabia

fields, and help scientists to forward and develop their own field of specialization.

nanotubes as a prototype for studying complex biological system like aquaporins.

cal barriers for industrial applications of CNTCP in LIBs and SCs.

Authors G.R. Mitchell et al. describe in their chapter that CNTs have some exceptional proper‐ ties for the design of multiscale nanocomposite materials. Due to the unique properties of nanotubes, they offer promise in composite materials with a large portion of current research on these materials dedicated to embedding them in a polymer matrix. They first consider re‐ cent developments in the synthesis of carbon nanotubes and their properties such as stiffness and trajectory. Next they detail the challenges of dispersion and alignment that are presented in the preparation of polymer/CNT composites. Finally, they review the existing literature to identify the progress made in preparing high-performance polymer/CNT composites and their properties and present one particular solution. Finally, there are great opportunities for the inclusion of CNTs in the emerging technology of additive or direct digital manufacturing. The future is especially promising in this area.

In the chapter by authors D. Silambarasan et al., they describe the hydrogenation and dehy‐ drogenation studies of SWCNTs functionalized with BH3. The SWCNTs are successfully func‐ tionalized with BH3 using LiBH4 as the precursor. The deposition process involves a simple drop casting method. The presence of BH3 in the functionalized sample is confirmed using IR study. From XPS study, apart from C, the presence of Li, B, and O is also observed in the func‐ tionalized sample. Then, the functionalized samples are hydrogenated for different time dura‐ tion. A maximum storage capacity is achieved at 50ºC, which is close to the US DOE target for a HSM to be used for on-board applications. Based on thermal annealing, a systematic investi‐ gation on desorption of hydrogen is carried out. The evidences for desorption are provided by Raman, CHNS-elemental, and TG/TDS measurements. The results show that thermal anneal‐ ing treatment induces desorption of hydrogen from the hydrogenated functionalized SWCNTs. The deterioration level of the sample is also checked using Raman analysis. Overall, this investigation shows that the SWCNTs functionalized with BH3 may be a suitable hydro‐ gen storage system that is capable of storing and releasing hydrogen under optimum condi‐ tions suitable for hydrogen-based fuel cells used in vehicular applications.

Authors D. Atre et al. describe the degree of functionalization on CNTs greatly, which affects their properties; the structure and dynamics of water confined inside pristine and functionalized/ charged carbon nanotubes (CNTs) are of prime importance. The presence of charges on the sur‐

face of CNTs results in hydrophobic to hydrophilic transitions, which increase their occupancy of the water molecules, thereby breaking down 1D water wires, as seen in pristine CNTs. Finally, charged or functionalized carbon nanotubes behave quite differently compared to pristine CNTs. Functionalization not only affects properties like band gap, conductivity, and metallic nature of CNTs, but it also greatly affects the properties of confined fluids. The functionalization of CNTs changes the overall nature of the CNTs and increases the hydrophilicity, which varies almost linearly with the degree of functionalization. As the degree of functionalization provides us with a handle on the properties of confined water, it might be interesting to see if we can use carbon nanotubes as a prototype for studying complex biological system like aquaporins.

tance performance, the addition of CNTs reduces cost compared to metal oxide; improves sta‐ bility compared to conducting polymers, which exhibit rapid degradation in performance after repetitive cycles because of their swelling and shrinking; and improves the poor volu‐ metric performance of supercapacitors based on other carbon nanomaterials. The capacitance properties strongly depend on the localization of the redox system. It was found that encapsu‐ lation of the redox phase inside a nanotubular material provides higher specific capacitance than a redox system situated outside of carbon nanotubes. Recently, a new generation of cheap storage systems based on mesoporous carbon aerogels was discovered. However, in this case, there is a problem with the nonhomogeneous spread of carbon nanotubes within the whole network of carbon aerogel. Hence, increasing attention is needed to solve this problem because this system could be the future for storage devices. A very promising system seems to be the attachment of redox-active nanoparticles to carbon nanotubes. Compared to bulk mate‐ rials, they exhibit unique properties arising from their nanoscale sizes, such as high electrical conductivity, large surface area, short path lengths for the transport of ions, and high electro‐ chemical activity. Ultrafast compact capacitors based on 3D hybrid structures that increase the accessible surface area and allow fast ion diffusion are introducing a new class of electrode

Authors G.R. Mitchell et al. describe in their chapter that CNTs have some exceptional proper‐ ties for the design of multiscale nanocomposite materials. Due to the unique properties of nanotubes, they offer promise in composite materials with a large portion of current research on these materials dedicated to embedding them in a polymer matrix. They first consider re‐ cent developments in the synthesis of carbon nanotubes and their properties such as stiffness and trajectory. Next they detail the challenges of dispersion and alignment that are presented in the preparation of polymer/CNT composites. Finally, they review the existing literature to identify the progress made in preparing high-performance polymer/CNT composites and their properties and present one particular solution. Finally, there are great opportunities for the inclusion of CNTs in the emerging technology of additive or direct digital manufacturing. The

In the chapter by authors D. Silambarasan et al., they describe the hydrogenation and dehy‐ drogenation studies of SWCNTs functionalized with BH3. The SWCNTs are successfully func‐ tionalized with BH3 using LiBH4 as the precursor. The deposition process involves a simple drop casting method. The presence of BH3 in the functionalized sample is confirmed using IR study. From XPS study, apart from C, the presence of Li, B, and O is also observed in the func‐ tionalized sample. Then, the functionalized samples are hydrogenated for different time dura‐ tion. A maximum storage capacity is achieved at 50ºC, which is close to the US DOE target for a HSM to be used for on-board applications. Based on thermal annealing, a systematic investi‐ gation on desorption of hydrogen is carried out. The evidences for desorption are provided by Raman, CHNS-elemental, and TG/TDS measurements. The results show that thermal anneal‐ ing treatment induces desorption of hydrogen from the hydrogenated functionalized SWCNTs. The deterioration level of the sample is also checked using Raman analysis. Overall, this investigation shows that the SWCNTs functionalized with BH3 may be a suitable hydro‐ gen storage system that is capable of storing and releasing hydrogen under optimum condi‐

Authors D. Atre et al. describe the degree of functionalization on CNTs greatly, which affects their properties; the structure and dynamics of water confined inside pristine and functionalized/ charged carbon nanotubes (CNTs) are of prime importance. The presence of charges on the sur‐

tions suitable for hydrogen-based fuel cells used in vehicular applications.

materials for storage devices.

XII Preface

future is especially promising in this area.

In this book, X. Sun et al. focused on a new type of carbon nanotube-cellulose composite mate‐ rials as current collector of LIBs and as electrodes of SCs to improve and enhance their energy/ power density and cyclic performance. CNTs have been widely used as conductive agent for both anodes and cathodes to replace super carbon black to satisfy the multifunctional require‐ ments for LIBs. Generally, LIB and supercapacitors (EDLCs and LIC) are the most commonly used energy storage services for mobile application. Lithium ion batteries are currently the most popular type of battery for powering portable electronic devices and are growing in pop‐ ularity for defense, automotive, and aerospace applications. Here, CNTs and CNTCP for pri‐ mary/second batteries and supercapacitor applications were reported. It has a great potential application value for the porous carbon nanotube-cellulose papers as current collectors and electrodes in lithium ion battery and supercapacitors. However, there are still some problems to be solved. The pore size and porosity and carbonization process of CNTCPs need to be in‐ novated to improve the strength and electrical conductivity. New high flexibility and strength of nanofibers need to be developed to adapt to electrolytes due to the cellulose papers, which are easily destroyed in liquid. Further investigations need to be done to overcome technologi‐ cal barriers for industrial applications of CNTCP in LIBs and SCs.

This work aims to bridge the gap between undergraduates, graduates, and scientists in ap‐ plied carbon material as well as composite sciences, in order to initiate researchers into CNT study in a straightforward way as possible and to introduce the researchers to the opportuni‐ ties offered by the applied science and technological fields. I worked unswervingly to com‐ plete this work on *Carbon Nanotubes - Recent Progress* under InTechOpen publisher. I hope that this contribution would further enhance the applied carbon materials in nano- and bioscience, especially in bringing new entrants into the applied and hybrid CNT science and technology fields, and help scientists to forward and develop their own field of specialization.

#### **Mohammed Muzibur Rahman**

Center of Excellence for Advanced Materials Research (CEAMR) and Chemistry department Faculty of Science, King Abdulaziz University, Saudi Arabia

#### **Abdullah Mohamed Asiri**

Center of Excellence for Advanced Materials Research (CEAMR) and Chemistry department Faculty of Science, King Abdulaziz University, Saudi Arabia

**Section 1**

**Introduction**

**Section 1**
