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Synthesis of carbon microfibers by chemical vapor deposition during the catalytic decomposition of turpentine oil
NEW CARBON MATERIALS Volume 26, Issue 5, Aug 2011 Online English edition of the Chinese language journal Cite this article as: New Carbon Materials, 2011, 26(5):356–360.
RESEARCH PAPER
Synthesis of carbon microfibers by chemical vapor deposition during the catalytic decomposition of turpentine oil Kanchan Saxena*, Pramod Kumar, V. K. Jain Amity Institute of Advanced Research and Studies (Materials and Devices), Amity University, Noida, U.P., India
Abstract: Carbon microfibers were synthesized by chemical vapor deposition during the decomposition of turpentine oil in the presence of nickel sulfate as a catalyst precursor on a graphite host. The fibers were separated from graphite and metal impurities by acid treatment, followed by several washes with deionized water. These fibers have a diameter of approximately 3-5 µm and they were studied by optical and scanning electron microscopy. A sponge-like morphology of the microfibers due to self-assembly was observed. Key Words: Carbon microfiber; Turpentine oil; Nickel sulfate; Graphite; Chemical vapor deposition
1
Introduction
Chemical vapor deposition (CVD) is a well-known technique for growing thin films of various materials. Particularly, it has attracted enormous interest in the development of nanomaterials under the hot topic of nanotechnology. In a CVD process, the chemical compounds introduced into a furnace are first vaporized, which then diffuse over an inert surface accompanied by chemical reactions between the precursor molecules. For instance, carbon nanomaterials have been synthesized using precursors such as methane, acetylene, toluene, xylene, benzene, or any type of hydrocarbon or carbonaceous materials. Attempts have also been made to synthesize carbon nanotubes (CNTs) from regenerative precursors, such as camphor[1-2] and turpentine oil[3-4]. Further, a catalyst is the main constituent responsible for the nucleation of CNTs. Transition metals, such as Co, Fe, and Ni, and their mixtures have been widely used as catalysts[5-8] on different supports for the decomposition of hydrocarbons. Because of the outstanding electronic, thermal, and mechanical properties of CNTs and nanofibers, they are being developed and extensively studied for a large number of applications in nanoelectronics, biosensors, or reinforcing agents in composite materials. However, in the context of nanoreinforcements (for instance, nanoparticles, nanowires, and nanotubes), it is difficult to develop lightweight, high-strength, and high-toughness polymer composites because of their agglomeration in the matrix-one of the major drawbacks limiting their reinforcing effect[9]. Radially aligned carbide nanowires on carbon microfibers used as hybrid reinforcements are reported to effectively prevent agglomeration of the nanowires in the matrix, thereby achieving an outstanding dispersion in the manufactured composites[9].
A large volume of research on the synthesis of CNTs[1-8] and carbon microfibers[9-12], their properties, and applications has been carried out during recent years. Carbon microfibers show astounding properties, including high mechanical strength and good electron transport, and are of great interest for industrial applications[10]. The high strength, exceptional elasticity (elastic modulus ~39.43-1.66 GPa), high aspect ratio, and low density of carbon nanowires have made them ideal mechanical reinforcements for lightweight composites. Gao and Kwai[11] have also shown that B4C nanowire/carbon microfiber hybrid is able to block 99.8% of ultraviolet irradiation. Carbon fibers with diameters of approximately 1-2 µm have been synthesized by thermal CVD with a mixture of nitrogen and acetylene on nickel-coated silicon substrates in a furnace[9]. Shi et al.[13] prepared carbon microfibers from short carbon fibers through shear pulverization using a self-designed pan-mill type equipment at ambient temperature. Recently, we synthesized carbon microfibers using graphite powder as the supporting material, with turpentine oil as the carbon source and nickel as the catalyst in a CVD furnace with dual temperature zones. The details of the synthesis procedure and the microscopic studies conducted on the procured carbon fibers are reported here.
2 2.1
Experimental Synthesis of carbon microfibers
Fig.1 shows the CVD setup used in the synthesis of carbon microfibers. It consists of a horizontal tube furnace, which has two temperature zones-1 and 2, as shown in the figure. The preparation of the fibers was conducted in a quartz flow reactor (40 mm inner diameter and 90 cm length) located
Received date: 1 December 2010; Revised date: 5 October 2011 *Corresponding author. E-mail: [email protected] Copyright©2011, Institute of Coal Chemistry, Chinese Academy of Sciences. Published by Elsevier Limited. All rights reserved. DOI: 10.1016/S1872-5805(11)60088-7
Kanchan Saxena et al. / New Carbon Materials, 2011, 26(5): 356–360
at 150 °C for 24 h. 2.3
Fig.1 Experimental setup for the synthesis of carbon microfibers
inside the furnace. Graphite powder, obtained from Aldrich Co., USA, was used as the supporting material. Nickel sulfate (100 mg) was thoroughly wet-mixed with 400 mg graphite powder and dried in oven at 100 °C for one hour before transporting to the CVD furnace in an alumina boat inside the quartz tube. The boat was placed in the second zone of the CVD furnace. After placing the boat in the furnace, the temperatures of both the zones were maintained at 400 °C. One end of the furnace near the first zone was connected to an argon gas supply, and the flow rate of the gas was controlled with a needle valve and monitored by counting the number of air bubbles in water from the other end of the furnace through a Teflon pipe of 1-mm diameter. The flow rate of the gas was fixed at 10 bubbles per minute. After controlling the flow of the gas, the temperature of the second zone was raised to 850 °C and maintained at this level for 10-15 min. Turpentine oil was then introduced using a syringe from a Teflon pipe into the first zone of the CVD furnace. The decomposed gases from the turpentine oil were carried to the graphite powder by the carrier gas at a slow rate. Turpentine oil (10 mL) was then sprayed into the first zone along with the carrier gas each time. The entire process was completed in about 40 min, and thereafter, the temperatures of both the zones were brought down to room temperature. Argon gas was allowed to flow until the temperature of both zones was below 100 °C. The alumina boat containing the graphite powder and deposits from the decomposition of turpentine oil was taken out for purification and isolation of carbon microfibers. 2.2
Purification
Step I: The material recovered from the alumina crucible was taken in a beaker and stirred in a mixture of nitric acid and deionized water in a weight ratio of 1:9 for 1 h. The stirred mixture was then boiled to evaporate the liquid. The material obtained was washed with deionized water until the pH of the mixture was 5. Step II: A mixture of nitric acid and water in a weight ratio of 9:1 was added to the material obtained and stirred for 30 min. The mixture was boiled to evaporate the liquid and then washed with deionized water until the pH of the mixture was 6. Step III: The material obtained was further boiled in a mixture of sulfuric acid and nitric acid in a weight ratio of 1:4 and again boiled to evaporate the liquid. The resulting material was washed with deionized water until the pH of the material was 7. The material recovered was then dried in an oven
Characterization
Fourier transform infrared (FTIR) spectroscopic studies were carried out using a Nicolet 5DX spectrometer (Thermo Nicolet Corporation, USA) with pressed KBr pellets. A high-resolution optical microscope (Metzer Biomedical And Electronics PVT. Ltd, India), coupled with a charge-coupled device camera and interfaced to a computer, was used to study a thin film of the carbon fibers. Scanning electron microscopy (SEM) studies of the same films were also carried out using a Carl Zeiss EVO50 SEM instrument (Carl Zeiss AG, Deutschland) for determining the size of the carbon fibers.
3
Results and discussion
FTIR was first carried out on the black powder that was recovered after the purification steps. The FTIR spectrum of the material obtained was compared with that of multiwalled carbon nanotubes (MWCNTs) obtained from Aldrich Co. (USA), as shown in Fig.2. The FTIR spectrum of the material (Fig. 2a) obtained was found to be similar to that of MWCNTs (Fig. 2b), because all the prominent peaks were at the same position indicating that the obtained powder comprised carbon fibers. The material obtained was sonicated in an ultrasonic bath in deionized water for one hour. A small amount of the sonicated carbon fibers was spread on a slide with the help of a spatula and dried in an oven at 100 °C for 10 min. The prepared film was observed under an optical microscope (Metzer Biomedical And Electronics PVT. Ltd, India) at 400× magnification. Fig.3 shows micrographs of the thin film as observed under the optical microscope. Fig. 3(a-b) are micrographs of the thin films obtained after steps I and III, respectively. A network of fibrous structure was clearly observed, as depicted in Fig. 3. Some black spots were also observed due to the presence of impurities (Fig. 3a), which were reduced in size and number after Step III, as shown in Fig. 3b. Fig.4(a-c) shows the SEM images of the films of the purified sample at three different magnifications. The estimated diameter of the fibers was in the range of 3-5 µm. The various morphologies of the carbon microfibers that were observed are depicted in Fig.5. A single straight fiber (a), a twisted fiber (b), and a twisted structure with a folded loop of carbon fiber (c) are shown in Fig. 5. Fibers with lengths as long as 5 mm were observed. The carbon microfibers obtained after sonication in deionized water were poured in a Petri dish, left to dry in ambient conditions for three to four days, and then studied under the optical microscope. Fig. 5d shows the micrograph of the observed texture of carbon microfibers. A sponge-like structure (Fig. 5d) was observed quite similar to the formation of the honeycomb morphology of carbon microfibers due to the self-assembly of fibers through intermolecular interactions[14]. Formation of such a quasi-periodic microporous structure of carbon microfibers is important for many applications. Further, quasi-periodic microporous structure
Kanchan Saxena et al. / New Carbon Materials, 2011, 26(5): 356–360
Fig.2 FTIR spectra of (a) carbon microfibers and (b) multiwalled CNTs
Fig.3 Optical micrographs of the thin films obtained after(a) Step I and (b) Step III
Fig.4
SEM images of carbon microfibers at three different magnifications
Kanchan Saxena et al. / New Carbon Materials, 2011, 26(5): 356–360
Fig.5 Various morphologies of carbon microfibers (a) a single straight fiber, (b) a twisted fiber, (c) a twisted structure with a folded loop of carbon fiber, and (d) sponge-like structure
was obtained without using any sophisticated technique or without using a periodic substrate template. Similar results were obtained when the synthesis procedure was repeated a number of times and studied after purification using optical microscopy and SEM. This indicates that carbon microfibers of sizes in the range 3-5 µm can be prepared using the simple procedure reported herein. Synthesis of carbon microfiber composites with polymers, which may also find applications in the areas of organic optoelectronics and photovoltaic devices, is under way.
4
Conclusion
[2] Kumar M, Ando Y. Controlling the diameter distribution of carbon nanotubes grown from camphor on a zeolite support[J]. Carbon, 2005, 43: 533-540. [3] Chatterjee A K, Sharon M, Banerjee R, et al. CVD synthesis of carbon nanotubes using a finely dispersed cobalt catalyst and their use in double layer electrochemical capacitors[J]. Electrochim Acta, 2003, 48: 3439-3446. [4] Afre R A, Soga T, Jimbo T, et al. Growth of vertically aligned carbon nanotubes on silicon and quartz substrate by spray pyrolysis of a natural precursor: Turpentine oil[J]. Chem Phys Lett , 2005, 414: 6-10. [5] Fonseca A, Harnadi K, Nagy J B, et al. Optimization of catalytic production and purification of Buckytubes[J]. J Mol Cat A:
Carbon microfibers with diameters approximately in the range of 3-5 µm and lengths of about 5 mm have been synthesized by thermal CVD using a mixture of argon and turpentine oil vapors on nickel-graphite surface.
[6] Okazaki T, Shinohara H. Synthesis and characterization of sin-
Acknowledgment
[7] Maruyama S, Kojima R, Miyauchi Y, et al. Low-temperature
Chem, 1996, 107: 159-168. gle-wall carbon nanotubes by hot-filament assisted chemical vapor deposition[J]. Chem Phys Lett, 2003, 376: 606-611. synthesis of high-purity single-walled carbon nanotubes from
The authors are thankful to Dr. Ashok K. Chauhan, Founder Chairman of Amity University (Noida, U. P., India) for his continuous encouragement during the course of this work.
References [1] Kumar M, Ando Y. Single-wall and multi-wall carbon nanotubes from camphor—a botanical hydrocarbon[J]. Chem Phys Lett, 2000, 374: 521-526.
alcohol[J]. Chem Phys Lett, 2002 , 360: 229-234. [8] Journet C, Maser W K, Bernier P, et al. Large-scale production of single-walled carbon nanotubes by the electric-arc technique[J]. Nature, 1997, 388: 756-758. [9] Coleman J N, Dalton A B, Curran S, et al. Phase separation of carbon nanotubes and turbostratic graphite using a functional organic polymer[J]. Adv Mater, 2000, 12: 213-216. [10] Tao
B
X,
Dong
L,
Wang
X,
et
al.
B4C-nanowires/carbon-microfiber hybrid structures and com-
Kanchan Saxena et al. / New Carbon Materials, 2011, 26(5): 356–360
posites from cotton T-shirts[J]. Adv Mat, 2010, 22: 2055-2059.
878-882.
[11] Gao L Z, Kwai S. The production of straight carbon microfibers
[13] Shi F, Lu C, Liang M. Preparation and characterization of car-
by the cracking of methane over Co-SBA-15 catalysts[J].
bon microfiber through shear pulverization using Pan-Mill
Catalysis Letters, 2007, 118: 211-218. [12] Li Y J, Lau S P, Tay B K. Oriented carbon microfibers grown by
equipment[J].
J of Mat
Engin Perform, 2010, 19: 643-649.
[14] Liu H, Li S, Zhai J, et al. Self-assembly of large-scale mi-
catalytic decomposition of acetylene and their field emission
cro-patterns on aligned carbon nanotube films[J].
properties[J]. Diamond and Related Materials, 2001, 10:
Chem Int Ed, 2004, 43: 1146-1146.
Angew
RESEARCH PAPER
Synthesis of carbon microfibers by chemical vapor deposition during the catalytic decomposition of turpentine oil Kanchan Saxena*, Pramod Kumar, V. K. Jain Amity Institute of Advanced Research and Studies (Materials and Devices), Amity University, Noida, U.P., India
Abstract: Carbon microfibers were synthesized by chemical vapor deposition during the decomposition of turpentine oil in the presence of nickel sulfate as a catalyst precursor on a graphite host. The fibers were separated from graphite and metal impurities by acid treatment, followed by several washes with deionized water. These fibers have a diameter of approximately 3-5 µm and they were studied by optical and scanning electron microscopy. A sponge-like morphology of the microfibers due to self-assembly was observed. Key Words: Carbon microfiber; Turpentine oil; Nickel sulfate; Graphite; Chemical vapor deposition
1
Introduction
Chemical vapor deposition (CVD) is a well-known technique for growing thin films of various materials. Particularly, it has attracted enormous interest in the development of nanomaterials under the hot topic of nanotechnology. In a CVD process, the chemical compounds introduced into a furnace are first vaporized, which then diffuse over an inert surface accompanied by chemical reactions between the precursor molecules. For instance, carbon nanomaterials have been synthesized using precursors such as methane, acetylene, toluene, xylene, benzene, or any type of hydrocarbon or carbonaceous materials. Attempts have also been made to synthesize carbon nanotubes (CNTs) from regenerative precursors, such as camphor[1-2] and turpentine oil[3-4]. Further, a catalyst is the main constituent responsible for the nucleation of CNTs. Transition metals, such as Co, Fe, and Ni, and their mixtures have been widely used as catalysts[5-8] on different supports for the decomposition of hydrocarbons. Because of the outstanding electronic, thermal, and mechanical properties of CNTs and nanofibers, they are being developed and extensively studied for a large number of applications in nanoelectronics, biosensors, or reinforcing agents in composite materials. However, in the context of nanoreinforcements (for instance, nanoparticles, nanowires, and nanotubes), it is difficult to develop lightweight, high-strength, and high-toughness polymer composites because of their agglomeration in the matrix-one of the major drawbacks limiting their reinforcing effect[9]. Radially aligned carbide nanowires on carbon microfibers used as hybrid reinforcements are reported to effectively prevent agglomeration of the nanowires in the matrix, thereby achieving an outstanding dispersion in the manufactured composites[9].
A large volume of research on the synthesis of CNTs[1-8] and carbon microfibers[9-12], their properties, and applications has been carried out during recent years. Carbon microfibers show astounding properties, including high mechanical strength and good electron transport, and are of great interest for industrial applications[10]. The high strength, exceptional elasticity (elastic modulus ~39.43-1.66 GPa), high aspect ratio, and low density of carbon nanowires have made them ideal mechanical reinforcements for lightweight composites. Gao and Kwai[11] have also shown that B4C nanowire/carbon microfiber hybrid is able to block 99.8% of ultraviolet irradiation. Carbon fibers with diameters of approximately 1-2 µm have been synthesized by thermal CVD with a mixture of nitrogen and acetylene on nickel-coated silicon substrates in a furnace[9]. Shi et al.[13] prepared carbon microfibers from short carbon fibers through shear pulverization using a self-designed pan-mill type equipment at ambient temperature. Recently, we synthesized carbon microfibers using graphite powder as the supporting material, with turpentine oil as the carbon source and nickel as the catalyst in a CVD furnace with dual temperature zones. The details of the synthesis procedure and the microscopic studies conducted on the procured carbon fibers are reported here.
2 2.1
Experimental Synthesis of carbon microfibers
Fig.1 shows the CVD setup used in the synthesis of carbon microfibers. It consists of a horizontal tube furnace, which has two temperature zones-1 and 2, as shown in the figure. The preparation of the fibers was conducted in a quartz flow reactor (40 mm inner diameter and 90 cm length) located
Received date: 1 December 2010; Revised date: 5 October 2011 *Corresponding author. E-mail: [email protected] Copyright©2011, Institute of Coal Chemistry, Chinese Academy of Sciences. Published by Elsevier Limited. All rights reserved. DOI: 10.1016/S1872-5805(11)60088-7
Kanchan Saxena et al. / New Carbon Materials, 2011, 26(5): 356–360
at 150 °C for 24 h. 2.3
Fig.1 Experimental setup for the synthesis of carbon microfibers
inside the furnace. Graphite powder, obtained from Aldrich Co., USA, was used as the supporting material. Nickel sulfate (100 mg) was thoroughly wet-mixed with 400 mg graphite powder and dried in oven at 100 °C for one hour before transporting to the CVD furnace in an alumina boat inside the quartz tube. The boat was placed in the second zone of the CVD furnace. After placing the boat in the furnace, the temperatures of both the zones were maintained at 400 °C. One end of the furnace near the first zone was connected to an argon gas supply, and the flow rate of the gas was controlled with a needle valve and monitored by counting the number of air bubbles in water from the other end of the furnace through a Teflon pipe of 1-mm diameter. The flow rate of the gas was fixed at 10 bubbles per minute. After controlling the flow of the gas, the temperature of the second zone was raised to 850 °C and maintained at this level for 10-15 min. Turpentine oil was then introduced using a syringe from a Teflon pipe into the first zone of the CVD furnace. The decomposed gases from the turpentine oil were carried to the graphite powder by the carrier gas at a slow rate. Turpentine oil (10 mL) was then sprayed into the first zone along with the carrier gas each time. The entire process was completed in about 40 min, and thereafter, the temperatures of both the zones were brought down to room temperature. Argon gas was allowed to flow until the temperature of both zones was below 100 °C. The alumina boat containing the graphite powder and deposits from the decomposition of turpentine oil was taken out for purification and isolation of carbon microfibers. 2.2
Purification
Step I: The material recovered from the alumina crucible was taken in a beaker and stirred in a mixture of nitric acid and deionized water in a weight ratio of 1:9 for 1 h. The stirred mixture was then boiled to evaporate the liquid. The material obtained was washed with deionized water until the pH of the mixture was 5. Step II: A mixture of nitric acid and water in a weight ratio of 9:1 was added to the material obtained and stirred for 30 min. The mixture was boiled to evaporate the liquid and then washed with deionized water until the pH of the mixture was 6. Step III: The material obtained was further boiled in a mixture of sulfuric acid and nitric acid in a weight ratio of 1:4 and again boiled to evaporate the liquid. The resulting material was washed with deionized water until the pH of the material was 7. The material recovered was then dried in an oven
Characterization
Fourier transform infrared (FTIR) spectroscopic studies were carried out using a Nicolet 5DX spectrometer (Thermo Nicolet Corporation, USA) with pressed KBr pellets. A high-resolution optical microscope (Metzer Biomedical And Electronics PVT. Ltd, India), coupled with a charge-coupled device camera and interfaced to a computer, was used to study a thin film of the carbon fibers. Scanning electron microscopy (SEM) studies of the same films were also carried out using a Carl Zeiss EVO50 SEM instrument (Carl Zeiss AG, Deutschland) for determining the size of the carbon fibers.
3
Results and discussion
FTIR was first carried out on the black powder that was recovered after the purification steps. The FTIR spectrum of the material obtained was compared with that of multiwalled carbon nanotubes (MWCNTs) obtained from Aldrich Co. (USA), as shown in Fig.2. The FTIR spectrum of the material (Fig. 2a) obtained was found to be similar to that of MWCNTs (Fig. 2b), because all the prominent peaks were at the same position indicating that the obtained powder comprised carbon fibers. The material obtained was sonicated in an ultrasonic bath in deionized water for one hour. A small amount of the sonicated carbon fibers was spread on a slide with the help of a spatula and dried in an oven at 100 °C for 10 min. The prepared film was observed under an optical microscope (Metzer Biomedical And Electronics PVT. Ltd, India) at 400× magnification. Fig.3 shows micrographs of the thin film as observed under the optical microscope. Fig. 3(a-b) are micrographs of the thin films obtained after steps I and III, respectively. A network of fibrous structure was clearly observed, as depicted in Fig. 3. Some black spots were also observed due to the presence of impurities (Fig. 3a), which were reduced in size and number after Step III, as shown in Fig. 3b. Fig.4(a-c) shows the SEM images of the films of the purified sample at three different magnifications. The estimated diameter of the fibers was in the range of 3-5 µm. The various morphologies of the carbon microfibers that were observed are depicted in Fig.5. A single straight fiber (a), a twisted fiber (b), and a twisted structure with a folded loop of carbon fiber (c) are shown in Fig. 5. Fibers with lengths as long as 5 mm were observed. The carbon microfibers obtained after sonication in deionized water were poured in a Petri dish, left to dry in ambient conditions for three to four days, and then studied under the optical microscope. Fig. 5d shows the micrograph of the observed texture of carbon microfibers. A sponge-like structure (Fig. 5d) was observed quite similar to the formation of the honeycomb morphology of carbon microfibers due to the self-assembly of fibers through intermolecular interactions[14]. Formation of such a quasi-periodic microporous structure of carbon microfibers is important for many applications. Further, quasi-periodic microporous structure
Kanchan Saxena et al. / New Carbon Materials, 2011, 26(5): 356–360
Fig.2 FTIR spectra of (a) carbon microfibers and (b) multiwalled CNTs
Fig.3 Optical micrographs of the thin films obtained after(a) Step I and (b) Step III
Fig.4
SEM images of carbon microfibers at three different magnifications
Kanchan Saxena et al. / New Carbon Materials, 2011, 26(5): 356–360
Fig.5 Various morphologies of carbon microfibers (a) a single straight fiber, (b) a twisted fiber, (c) a twisted structure with a folded loop of carbon fiber, and (d) sponge-like structure
was obtained without using any sophisticated technique or without using a periodic substrate template. Similar results were obtained when the synthesis procedure was repeated a number of times and studied after purification using optical microscopy and SEM. This indicates that carbon microfibers of sizes in the range 3-5 µm can be prepared using the simple procedure reported herein. Synthesis of carbon microfiber composites with polymers, which may also find applications in the areas of organic optoelectronics and photovoltaic devices, is under way.
4
Conclusion
[2] Kumar M, Ando Y. Controlling the diameter distribution of carbon nanotubes grown from camphor on a zeolite support[J]. Carbon, 2005, 43: 533-540. [3] Chatterjee A K, Sharon M, Banerjee R, et al. CVD synthesis of carbon nanotubes using a finely dispersed cobalt catalyst and their use in double layer electrochemical capacitors[J]. Electrochim Acta, 2003, 48: 3439-3446. [4] Afre R A, Soga T, Jimbo T, et al. Growth of vertically aligned carbon nanotubes on silicon and quartz substrate by spray pyrolysis of a natural precursor: Turpentine oil[J]. Chem Phys Lett , 2005, 414: 6-10. [5] Fonseca A, Harnadi K, Nagy J B, et al. Optimization of catalytic production and purification of Buckytubes[J]. J Mol Cat A:
Carbon microfibers with diameters approximately in the range of 3-5 µm and lengths of about 5 mm have been synthesized by thermal CVD using a mixture of argon and turpentine oil vapors on nickel-graphite surface.
[6] Okazaki T, Shinohara H. Synthesis and characterization of sin-
Acknowledgment
[7] Maruyama S, Kojima R, Miyauchi Y, et al. Low-temperature
Chem, 1996, 107: 159-168. gle-wall carbon nanotubes by hot-filament assisted chemical vapor deposition[J]. Chem Phys Lett, 2003, 376: 606-611. synthesis of high-purity single-walled carbon nanotubes from
The authors are thankful to Dr. Ashok K. Chauhan, Founder Chairman of Amity University (Noida, U. P., India) for his continuous encouragement during the course of this work.
References [1] Kumar M, Ando Y. Single-wall and multi-wall carbon nanotubes from camphor—a botanical hydrocarbon[J]. Chem Phys Lett, 2000, 374: 521-526.
alcohol[J]. Chem Phys Lett, 2002 , 360: 229-234. [8] Journet C, Maser W K, Bernier P, et al. Large-scale production of single-walled carbon nanotubes by the electric-arc technique[J]. Nature, 1997, 388: 756-758. [9] Coleman J N, Dalton A B, Curran S, et al. Phase separation of carbon nanotubes and turbostratic graphite using a functional organic polymer[J]. Adv Mater, 2000, 12: 213-216. [10] Tao
B
X,
Dong
L,
Wang
X,
et
al.
B4C-nanowires/carbon-microfiber hybrid structures and com-
Kanchan Saxena et al. / New Carbon Materials, 2011, 26(5): 356–360
posites from cotton T-shirts[J]. Adv Mat, 2010, 22: 2055-2059.
878-882.
[11] Gao L Z, Kwai S. The production of straight carbon microfibers
[13] Shi F, Lu C, Liang M. Preparation and characterization of car-
by the cracking of methane over Co-SBA-15 catalysts[J].
bon microfiber through shear pulverization using Pan-Mill
Catalysis Letters, 2007, 118: 211-218. [12] Li Y J, Lau S P, Tay B K. Oriented carbon microfibers grown by
equipment[J].
J of Mat
Engin Perform, 2010, 19: 643-649.
[14] Liu H, Li S, Zhai J, et al. Self-assembly of large-scale mi-
catalytic decomposition of acetylene and their field emission
cro-patterns on aligned carbon nanotube films[J].
properties[J]. Diamond and Related Materials, 2001, 10:
Chem Int Ed, 2004, 43: 1146-1146.
Angew