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Synthesis of carbon nanofibers using C60, graphite and boron
Materials Letters 64 (2010) 1243–1246
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
Synthesis of carbon nanofibers using C60, graphite and boron Jianhui Zhang ⁎, Ishwor Khatri, Naoki Kishi, Tetsuo Soga, Takashi Jimbo Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555, Japan
a r t i c l e
i n f o
Article history: Received 12 February 2010 Accepted 28 February 2010 Available online 4 March 2010 Keywords: Chemical vapor deposition Fullerene Nanomaterials
a b s t r a c t The growth of carbon nanofibers (CNFs) using C60, graphite-carbon and boron powders via the ultrasonic spray pyrolysis method of ethanol is reported. CNFs of various morphologies were observed with different powders. Kinked CNFs of about 100 nm were produced while using a mixture of C60 particles and ethanol as precursors, whereas straight CNFs were obtained using graphite-carbon and boron powders as catalysts. Element analysis measurement of the as-produced CNFs shows that the CNFs synthesized using C60 and graphite powder have the carbon particles on the tip. When boron powders were added in ethanol, boron related materials were examined at the tip of the CNFs. The present study indicates that the clusters composed of carbon and boron related materials act as nucleating sites for CNF formation. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Carbon nanofibers have been used for filaments and these are composed of graphene layers which are stacked at an angle to the fiber axis (such as herringbone, cup-stacked, or stacked type filaments). They are of different types ranging from amorphous to well graphitized carbon. CNFs of amorphous type with diameters ranging from several tens to 500 nm [1] are also present. They have good mechanical, chemical, electronic chemical and physical properties [2], with a high aspect ratio and a high specific surface area. CNFs have been extensively applied in hydrogen storage [3] and field emission [4]. There are several methods to produce CNFs. Some of the popular methods are arc discharge [5] and chemical vapor deposition (CVD) [6]. The CVD method is carried out using a small quartz tube under atmospheric pressure and a high carbon source flow rate using a horizontal furnace. The metal catalysts (Fe, Ni, and Co) [7] and carbon sources are used as precursors. It is a reliable method which can produce dense CNFs. Recently, we reported that CNFs can be synthesized without using a metal catalyst in the ultrasonic spray pyrolysis method. CNFs with several tens of nanometers have been obtained at 750 °C from carbon particles which are produced using C60 as starting materials. [8]. To realize such a high yield synthesis of CNFs without using metal catalysts, further study on growth using other carbon materials and other elements are needed. In the present study, we report that CNFs can be synthesized not only using C60, but also using graphite powder. We also found that boron related materials can act as catalyst for synthesis of CNFs. The
⁎ Corresponding author. Tel.: + 81 52 735 5532; fax: + 81 52 735 7120. E-mail address: [email protected] (J. Zhang). 0167-577X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2010.02.059
element analysis measurement indicates that the CNFs synthesized using carbon materials and boron powder has the small particles composed of carbon and boron related materials at the tip. 2. Experimental details Details of the present method have been reported previously [8]. Briefly, Si wafer was used as a substrate and ethanol as a carbon source. The reactor furnace was heated to 850 °C under N2 flow. All types of carbon particles (C60 and graphite) and boron were mixed in the ethanol and placed inside the atomization chamber of ultrasonic spray pyrolysis method. The deposition was performed for 1 h. After the deposition, the reactor furnace was cooled down to room temperature in N2 atmosphere. In the present study, graphite powder (Kojundo Chemical Laboratory; 99.7%), C60 (Frontier Carbon Corporation; 99%) and boron powder (Kojundo Chemical Laboratory; 99%) were used. Produced samples were analyzed using a scanning electron microscope (SEM), a transmission electron microscope (TEM), as well as an energy dispersive spectrum (EDS), a Raman spectroscopy and a thermo-gravimetric analysis (TGA). The excitation wavelength according to the Raman measurement was 532 nm. 3. Results and discussion Fig. 1(a) shows CNFs synthesized from C60 and ethanol. Diameters of the CNFs are about 100–200 nm. Fig. 1(b) shows the SEM image of the CNFs synthesized from graphite powders and ethanol. It indicated that dense CNFs were obtained not only from C60 but also from graphite-carbon powder with ethanol. CNFs with a diameter of about 100–500 nm were observed in the sample. We noticed the formation of larger diameter CNFs in graphite-carbon/ethanol case whereas it is smaller in C60/ethanol case. After finding, such differences in diameter distribution and morphologies of CNFs with C60 and graphite-carbon,
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J. Zhang et al. / Materials Letters 64 (2010) 1243–1246
Fig. 1. SEM images of CNFs synthesized using (a) C60, (b) graphite, (c) boron powders.
we examined further by adding boron onto the ethanol. Interestingly, the morphology was totally changed and straight CNFs of about 100– 200 nm were formed as shown in Fig. 1(c). Fig. 2 shows the TEM images and their EDS of CNFs using C60 and graphite as catalysts. In Fig. 2(a) TEM images of CNF shows a diameter of about 100 nm. It indicates that the present CNF has an amorphous structure. We also observed a black spot at the tip of the CNF. Fig. 2(b) shows the EDS of the tip (spot (i)) of the CNF, in Fig. 2(a). There are two strong peaks, which correspond to carbon and copper, respectively. The Cu peak results from the Cu parts of the measurement chamber and the carbon peak comes from the tip of the CNF. This indicates that the black spot at the tip of the CNF is composed of carbon. Fig. 2(c) shows a TEM image of an individual CNF synthesized using graphite powders with ethanol. This CNF also has a black spot at the bottom. Fig. 2(d) shows the EDS measurement at the tip (spot (ii)) in Fig. 2(c). Two strong peaks which correspond to carbon and copper were also observed. This indicates that the CVD using graphitic carbon also forms CNFs.
Fig. 2. TEM images and EDS of CNFs synthesized using carbon powders. (a) TEM image of a CNF using C60, (b) EDS spectrum of the spot (i) in (a), (c) TEM image of a CNF using graphite and (d) EDS spectrum of the spot (ii) in (a).
J. Zhang et al. / Materials Letters 64 (2010) 1243–1246
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Fig. 4. Raman spectra of CNF synthesized using (a) C60, (b) graphite and (c) boron powders.
Fig. 5. TGA curves of the samples synthesized using (a) C60 and (b) graphite powder.
Fig. 3. TEM images and EDS spectra of a CNF synthesized using boron particles. (a) TEM image of the CNF. EDS spectra of (b) the tip and (c) the body of the CNF marked (iii) and (iv), respectively.
Fig. 3(a) shows the TEM image of an individual CNF using boron powders with a carbon precursor. The CNF has an amorphous structure. Fig. 3(b) shows the EDS spectrum at the tip of the CNF with four strong peaks, which are of boron, carbon, oxygen and copper. This EDS indicates that the tip of the CNF (iii) is composed of boron oxide and boron carbide. Fig. 3(c), which is the EDS spectrum of the body of CNF (iv), shows that the body of the CNFs is composed of carbon only. The present study shows that the clusters composed of carbon or boron related materials act as nucleating sites for CNFs formation. Fig. 4 shows the Raman spectra of CNFs prepared using three different sources. Fig. 4(a) is Raman of CNFs using C60. Spectra marked with (b) and (c) are of CNFs synthesized using graphite and boron with an ethanol precursor. All spectra have distinctive D and G peaks located at around 1350 cm− 1 and 1600 cm− 1 [9], respectively. The ID/IG ratio of these samples was almost same.
TGA measurements were performed to clarify thermal stability in the air. Thermal stability of the samples can be analyzed by comparing the weight loss temperature of the samples. In the CNFs sample from boron, the initial temperature of the carbon weight loss of the sample could not be clearly known, because the weight of the sample increases due to the oxidation of a residual boron catalyst into massive solid oxides (not shown). Fig. 5 shows the TGA of samples prepared using C60 (marked with (a)) and graphite (marked with (b)). As shown in Fig. 5 the samples prepared using graphite decompose faster than those using C60. It is observed that samples prepared using C60 are more stable than that using graphite.
4. Conclusion We have successfully synthesized CNFs with a diameter of about 100 ∼ 500 nm using ultrasonic spray pyrolysis without using metal catalysts. CNFs can be synthesized not only from C60 but also from graphite-carbon. CNFs can also be produced using boron power with a carbon precursor. We found that the clusters composed of carbon or boron related materials exist at the tip of the CNFs, which may act as a nucleating site for the formation of CNFs. The results show that the carbon and boron related materials can also be used for producing CNFs.
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J. Zhang et al. / Materials Letters 64 (2010) 1243–1246
References [1] [2] [3] [4] [5]
Baker RTK, Barber MA, Harris PS, Feats FS, Waite RJ. J Catal 1972;26:51–62. Nanni F, Travaglia P, Valentini M. Comp Sci and Technol 2009;69:485–90. Blackman JM, Patrick JW, Arenillas A, Shi W, Snape CE. Carbon 2006;44:1376–85. Ahmed SF, Das S, Mitra MK, Chattopadhyay KK. Appl Sur Sci 2007;254:610–5. Zhao X, Qiu J, Sun Y, Hao C, Sun T, Cui L. Carbon 2009;47:2940.
[6] Yap HY, Ramaker B, Sumant AV, Carpick RW. Diam and Rel Mater 2006;15:1622–8. [7] Romero A, Garrido A, Nieto-Márquez A, Sánchez P, Lucas Ad, Valverde JL. Micro and Meso Mater 2008;110:318–29. [8] Zhang J, Khatri I, Kishi N, Soga T, Jimbo T. IEICE Trans Electron 2009;E92-C:1432–7. [9] Dresselhaus MS, Dresselhaus G, Jorio A, Souza Filho AG, Saito R. Carbon 2002;40: 2043–61.
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
Synthesis of carbon nanofibers using C60, graphite and boron Jianhui Zhang ⁎, Ishwor Khatri, Naoki Kishi, Tetsuo Soga, Takashi Jimbo Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555, Japan
a r t i c l e
i n f o
Article history: Received 12 February 2010 Accepted 28 February 2010 Available online 4 March 2010 Keywords: Chemical vapor deposition Fullerene Nanomaterials
a b s t r a c t The growth of carbon nanofibers (CNFs) using C60, graphite-carbon and boron powders via the ultrasonic spray pyrolysis method of ethanol is reported. CNFs of various morphologies were observed with different powders. Kinked CNFs of about 100 nm were produced while using a mixture of C60 particles and ethanol as precursors, whereas straight CNFs were obtained using graphite-carbon and boron powders as catalysts. Element analysis measurement of the as-produced CNFs shows that the CNFs synthesized using C60 and graphite powder have the carbon particles on the tip. When boron powders were added in ethanol, boron related materials were examined at the tip of the CNFs. The present study indicates that the clusters composed of carbon and boron related materials act as nucleating sites for CNF formation. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Carbon nanofibers have been used for filaments and these are composed of graphene layers which are stacked at an angle to the fiber axis (such as herringbone, cup-stacked, or stacked type filaments). They are of different types ranging from amorphous to well graphitized carbon. CNFs of amorphous type with diameters ranging from several tens to 500 nm [1] are also present. They have good mechanical, chemical, electronic chemical and physical properties [2], with a high aspect ratio and a high specific surface area. CNFs have been extensively applied in hydrogen storage [3] and field emission [4]. There are several methods to produce CNFs. Some of the popular methods are arc discharge [5] and chemical vapor deposition (CVD) [6]. The CVD method is carried out using a small quartz tube under atmospheric pressure and a high carbon source flow rate using a horizontal furnace. The metal catalysts (Fe, Ni, and Co) [7] and carbon sources are used as precursors. It is a reliable method which can produce dense CNFs. Recently, we reported that CNFs can be synthesized without using a metal catalyst in the ultrasonic spray pyrolysis method. CNFs with several tens of nanometers have been obtained at 750 °C from carbon particles which are produced using C60 as starting materials. [8]. To realize such a high yield synthesis of CNFs without using metal catalysts, further study on growth using other carbon materials and other elements are needed. In the present study, we report that CNFs can be synthesized not only using C60, but also using graphite powder. We also found that boron related materials can act as catalyst for synthesis of CNFs. The
⁎ Corresponding author. Tel.: + 81 52 735 5532; fax: + 81 52 735 7120. E-mail address: [email protected] (J. Zhang). 0167-577X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2010.02.059
element analysis measurement indicates that the CNFs synthesized using carbon materials and boron powder has the small particles composed of carbon and boron related materials at the tip. 2. Experimental details Details of the present method have been reported previously [8]. Briefly, Si wafer was used as a substrate and ethanol as a carbon source. The reactor furnace was heated to 850 °C under N2 flow. All types of carbon particles (C60 and graphite) and boron were mixed in the ethanol and placed inside the atomization chamber of ultrasonic spray pyrolysis method. The deposition was performed for 1 h. After the deposition, the reactor furnace was cooled down to room temperature in N2 atmosphere. In the present study, graphite powder (Kojundo Chemical Laboratory; 99.7%), C60 (Frontier Carbon Corporation; 99%) and boron powder (Kojundo Chemical Laboratory; 99%) were used. Produced samples were analyzed using a scanning electron microscope (SEM), a transmission electron microscope (TEM), as well as an energy dispersive spectrum (EDS), a Raman spectroscopy and a thermo-gravimetric analysis (TGA). The excitation wavelength according to the Raman measurement was 532 nm. 3. Results and discussion Fig. 1(a) shows CNFs synthesized from C60 and ethanol. Diameters of the CNFs are about 100–200 nm. Fig. 1(b) shows the SEM image of the CNFs synthesized from graphite powders and ethanol. It indicated that dense CNFs were obtained not only from C60 but also from graphite-carbon powder with ethanol. CNFs with a diameter of about 100–500 nm were observed in the sample. We noticed the formation of larger diameter CNFs in graphite-carbon/ethanol case whereas it is smaller in C60/ethanol case. After finding, such differences in diameter distribution and morphologies of CNFs with C60 and graphite-carbon,
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J. Zhang et al. / Materials Letters 64 (2010) 1243–1246
Fig. 1. SEM images of CNFs synthesized using (a) C60, (b) graphite, (c) boron powders.
we examined further by adding boron onto the ethanol. Interestingly, the morphology was totally changed and straight CNFs of about 100– 200 nm were formed as shown in Fig. 1(c). Fig. 2 shows the TEM images and their EDS of CNFs using C60 and graphite as catalysts. In Fig. 2(a) TEM images of CNF shows a diameter of about 100 nm. It indicates that the present CNF has an amorphous structure. We also observed a black spot at the tip of the CNF. Fig. 2(b) shows the EDS of the tip (spot (i)) of the CNF, in Fig. 2(a). There are two strong peaks, which correspond to carbon and copper, respectively. The Cu peak results from the Cu parts of the measurement chamber and the carbon peak comes from the tip of the CNF. This indicates that the black spot at the tip of the CNF is composed of carbon. Fig. 2(c) shows a TEM image of an individual CNF synthesized using graphite powders with ethanol. This CNF also has a black spot at the bottom. Fig. 2(d) shows the EDS measurement at the tip (spot (ii)) in Fig. 2(c). Two strong peaks which correspond to carbon and copper were also observed. This indicates that the CVD using graphitic carbon also forms CNFs.
Fig. 2. TEM images and EDS of CNFs synthesized using carbon powders. (a) TEM image of a CNF using C60, (b) EDS spectrum of the spot (i) in (a), (c) TEM image of a CNF using graphite and (d) EDS spectrum of the spot (ii) in (a).
J. Zhang et al. / Materials Letters 64 (2010) 1243–1246
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Fig. 4. Raman spectra of CNF synthesized using (a) C60, (b) graphite and (c) boron powders.
Fig. 5. TGA curves of the samples synthesized using (a) C60 and (b) graphite powder.
Fig. 3. TEM images and EDS spectra of a CNF synthesized using boron particles. (a) TEM image of the CNF. EDS spectra of (b) the tip and (c) the body of the CNF marked (iii) and (iv), respectively.
Fig. 3(a) shows the TEM image of an individual CNF using boron powders with a carbon precursor. The CNF has an amorphous structure. Fig. 3(b) shows the EDS spectrum at the tip of the CNF with four strong peaks, which are of boron, carbon, oxygen and copper. This EDS indicates that the tip of the CNF (iii) is composed of boron oxide and boron carbide. Fig. 3(c), which is the EDS spectrum of the body of CNF (iv), shows that the body of the CNFs is composed of carbon only. The present study shows that the clusters composed of carbon or boron related materials act as nucleating sites for CNFs formation. Fig. 4 shows the Raman spectra of CNFs prepared using three different sources. Fig. 4(a) is Raman of CNFs using C60. Spectra marked with (b) and (c) are of CNFs synthesized using graphite and boron with an ethanol precursor. All spectra have distinctive D and G peaks located at around 1350 cm− 1 and 1600 cm− 1 [9], respectively. The ID/IG ratio of these samples was almost same.
TGA measurements were performed to clarify thermal stability in the air. Thermal stability of the samples can be analyzed by comparing the weight loss temperature of the samples. In the CNFs sample from boron, the initial temperature of the carbon weight loss of the sample could not be clearly known, because the weight of the sample increases due to the oxidation of a residual boron catalyst into massive solid oxides (not shown). Fig. 5 shows the TGA of samples prepared using C60 (marked with (a)) and graphite (marked with (b)). As shown in Fig. 5 the samples prepared using graphite decompose faster than those using C60. It is observed that samples prepared using C60 are more stable than that using graphite.
4. Conclusion We have successfully synthesized CNFs with a diameter of about 100 ∼ 500 nm using ultrasonic spray pyrolysis without using metal catalysts. CNFs can be synthesized not only from C60 but also from graphite-carbon. CNFs can also be produced using boron power with a carbon precursor. We found that the clusters composed of carbon or boron related materials exist at the tip of the CNFs, which may act as a nucleating site for the formation of CNFs. The results show that the carbon and boron related materials can also be used for producing CNFs.
1246
J. Zhang et al. / Materials Letters 64 (2010) 1243–1246
References [1] [2] [3] [4] [5]
Baker RTK, Barber MA, Harris PS, Feats FS, Waite RJ. J Catal 1972;26:51–62. Nanni F, Travaglia P, Valentini M. Comp Sci and Technol 2009;69:485–90. Blackman JM, Patrick JW, Arenillas A, Shi W, Snape CE. Carbon 2006;44:1376–85. Ahmed SF, Das S, Mitra MK, Chattopadhyay KK. Appl Sur Sci 2007;254:610–5. Zhao X, Qiu J, Sun Y, Hao C, Sun T, Cui L. Carbon 2009;47:2940.
[6] Yap HY, Ramaker B, Sumant AV, Carpick RW. Diam and Rel Mater 2006;15:1622–8. [7] Romero A, Garrido A, Nieto-Márquez A, Sánchez P, Lucas Ad, Valverde JL. Micro and Meso Mater 2008;110:318–29. [8] Zhang J, Khatri I, Kishi N, Soga T, Jimbo T. IEICE Trans Electron 2009;E92-C:1432–7. [9] Dresselhaus MS, Dresselhaus G, Jorio A, Souza Filho AG, Saito R. Carbon 2002;40: 2043–61.