- Email: [email protected]
Joining glass fiber layers using a functionalized carbon nanofiber entangled network
CARBON
5 4 ( 2 0 1 3 ) 4 8 9 –5 0 0
Available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/carbon
Letters to the Editor
Joining glass fiber layers using a functionalized carbon nanofiber entangled network Chee-Sern Lim, Mauricio E. Guzman, Bob Minaie
*
Department of Mechanical Engineering, Wichita State University, 1845 Fairmount St. Wichita, KS 67260, USA
A R T I C L E I N F O
A B S T R A C T
Article history:
As-received glass fiber layers are joined using a carboxylic acid-functionalized carbon
Received 5 August 2012
nanofiber (OCNF) entangled network utilizing a solution filtering process. Optical and
Accepted 22 November 2012
SEM images of the OCNF/glass fiber assembly reveal fiber-bridging effect and show that
Available online 5 December 2012
the OCNF entangled network continuously covers the glass fiber layers. In the absence of polymer matrix, test result shows that a significant amount of peeling force is required to separate the OCNF/glass fiber assembly. Furthermore, fracture analysis indicates evidence of OCNF pull-out and alignment perpendicular to the glass fiber layer along the crack. 2012 Elsevier Ltd. All rights reserved.
Fiber-reinforced polymer composites (FRPC) are well known for their excellent in-plane strength and stiffness but suffer from poor interlaminar fracture toughness due to matrix-dominated properties. One of the solutions to this shortcoming is the use of 3D braided fibers and throughthe-thickness stitching [1]. These approaches, however, yield composite parts exhibiting weaker in-plane strength and stiffness. In the past two decades, carbon nanotubes (CNTs) [2] and carbon nanofibers (CNFs) [3] have been demonstrated as better candidates to improve the mechanical properties of the FRPC. Traditionally, the CNTs/CNFs are dispersed in the resin and then infused into a preform to fabricate hierarchical composites [4,5]. However, this method is limited by the dispersion quality of the CNT/CNF and high viscosity of the resin, hindering scalable manufacturing of large hierarchical composite parts. Other methodologies involving growth [6], direct placement [7], or deposition [8] of CNT/CNF have been developed to create CNT-/CNF-fiber hybrid layers for fabricating hierarchical composites. Even though an increase in surface roughness of the hybrid layers was achieved using the aforementioned methods, the layers could not be joined without a polymer matrix.
In the present study, the use of carboxylic-acid functionalized CNFs (OCNFs) to join two glass fiber layers is demonstrated. The resulting OCNF/glass fiber assembly was tested in order to determine the peeling force needed for separating the glass fiber layers, as described below. As-received CNFs (PR-24-XT-PS, Applied Science, Inc.) were functionalized according to procedure previously reported [9] but with a treatment time of 2 h to obtain the OCNFs. A solution filtration setup was used to join two as-received plainweave glass fiber layers (5.08 cm · 5.08 cm) with the OCNFs, as illustrated in Fig. 1. The OCNF aqueous solution (0.35 mg/ mL) was prepared by tip-sonicating the OCNFs with ultrapure deionized water at medium power for 10 min. To prepare the OCNF/glass fiber assembly, a nylon membrane was first coated with 50 mL of OCNF solution (over an area equivalent to the glass fiber layers). Afterward, the first glass fiber layer was placed on the OCNF-coated area and half of the layer was covered with aluminum foil to prevent OCNF coating. Then, additional 250 mL of OCNF solution was slowly added to the first glass fiber layer. Subsequently, the second glass fiber layer was placed on top of the first glass fiber layer and filtered with additional 300 mL of the OCNF solution. Note that
* Corresponding author: Fax: +1 316 978 3236. E-mail address: [email protected] (B. Minaie). 0008-6223/$ - see front matter 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.carbon.2012.11.050
490
CARBON
5 4 ( 2 0 1 3 ) 4 8 9 –5 0 0
Fig. 1 – Experimental setup for sample preparation (top) and actual picture (bottom) of OCNF/glass fiber assembly.
the OCNF solution was added to the membrane and glass fiber layers drop-wise using a pipette. Upon completing the filtration, the OCNF/glass fiber assembly was rinsed with acetone and dried with vacuum applied overnight. The amount of the OCNFs added to the OCNF/glass fiber assembly was approximately 154 mg. After removing the aluminum foil, the OCNF/glass fiber assembly was cut to obtain a thin strip of approximately 9 mm · 50.8 mm. The specimen was then tested using a tensile test instrument. Characterization of the OCNF/glass fiber assembly was performed using optical and SEM imaging prior to the peel test. Fig. 2(a) depicts the optical cross-sectional image of the OCNF/glass fiber assembly. It is clear that the OCNFs were successfully incorporated into the glass fiber layers that seemed to be joined by the OCNF entangled network. The SEM image shown in Fig. 2(b) reveals that the OCNFs were tightly packed and interconnected with each other at the region between the glass fiber layers. Moreover, Fig. 2(c) shows that the OCNFs penetrated between the fiber tows and the connected individual filaments (indicated by the small yellow arrows), resulting in a fiber-bridging effect that could benefit the load transfer. Another interesting finding (Fig. 2(d)) that can be drawn from the cross-section of the OCNF/glass fiber assembly is the continuity of the OCNF network at the interface (defined by the yellow curve) between the glass fiber layer and the OCNF entangled network. Combining these observations, it can be clearly seen that the OCNFs continuously extended from the first glass fiber layer to the second glass fiber layer, creating a joined architecture based solely on the OCNFs without the presence of a polymer matrix. These findings suggest that a significant amount of peeling force is required to separate the OCNF/glass fiber assembly, noting that the two as-received glass fiber layers practically need zero force to be separated since nothing holds the as-received glass fiber layers together.
To validate the above statement drawn based on the findings in Fig. 2, a peel test was conducted (illustrated in the inset of Fig. 3) at 20 lm/min. The peeling force was recorded with respect to the crosshead displacement during the test, as shown in Fig. 3. As the test progressed, the test specimen underwent repetitive loading and unloading behavior. The initial and maximum peeling force for causing the separation of the OCNF/glass fiber assembly were approximately 170 mN and 250 mN, respectively. These findings could be attributed to the sequential detachment of the OCNF entangled network as possible reinforcement mechanism. To investigate this, the crack cross-section of the test specimen was examined using SEM. As shown in Fig. 4, significant OCNF pull-out effect at the interface between the glass fiber layer and the OCNF entangled network was identified. The pull-out effect can be explained by the interlocking mechanism within the OCNF entangled network, which is directly responsible for the elevated peeling force to separate the OCNF/glass fiber assembly. In addition, evidence of OCNF alignment perpendicular to the glass fiber layer was observed after the test, suggesting that the pronounced pull-out effect could promote alignment as the OCNFs slide with respect to each other during the test. In summary, joining of two glass fiber layers using an OCNF entangled network through a solution filtering process was demonstrated. Optical and SEM images of the OCNF/glass fiber assembly showed evidence of fiber-bridging effect as well as a OCNF entangled network continuously extending from the first glass fiber layer to the second glass fiber layer. As a result of the filtering process, the peeling force required to separate the OCNF/glass fiber assembly was significant due to the OCNF entangled network. Failure analysis revealed significant OCNF pull-out effect and alignment perpendicular to the glass fiber layer along the crack, which could be explained by the sequential detachment of the OCNF entangled network as reinforcement mechanism. Based on the results presented,
CARBON
5 4 (2 0 1 3) 4 8 9–50 0
491
Fig. 2 – (a) Optical image of the cross-section of OCNF/glass fiber assembly and SEM images of (b) OCNF entangled network between the glass fiber layers, (c) OCNFs bridging individual filaments, and (d) the interface between the glass fiber layer (above the yellow curve) and OCNF entangled network (below the yellow curve). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 4 – SEM image of the crack cross-section indicating OCNF pull-out effect and alignment perpendicular to the glass fiber layer.
Fig. 3 – Peeling force of OCNF/glass fiber assembly as a function of crosshead displacement. The inset illustrates the schematic of the peel test.
it is suggested that the mechanical properties of the FRPC can be effectively improved if OCNF/glass fiber assembly is used.
Acknowledgements This research is funded by the Office of Naval Research (Grant No. N000140810893) and the National Aeronautics and Space Administration (Grant No. NNX07A027A). The authors would like to thank Mr. Joseph Daniel Schaefer from Northwestern University for his active discussion.
492
CARBON
5 4 ( 2 0 1 3 ) 4 8 9 –5 0 0
R E F E R E N C E S
[1] Marvin B, Dow H, Benson Dexter. Development of stitched, braided and woven composite structures in the ACT program and at Langley Research Center. Hampton, Virginia; NASA/TP97-206234; 1997. [2] Rachmadini Y, Tan VBC, Tay TE. Enhancement of mechanical properties of composites through incorporation of CNT in VARTM – a review. J Reinf Plast Compos 2010;29(18):2782–807. [3] Tibbetts GG, Lake ML, Strong KL, Rice BP. A review of the fabrication and properties of vapor-grown carbon nanofiber/ polymer composites. Compos Sci Technol 2007;67(7– 8):1709–18. [4] Fan Z, Santare MH, Advani SG. Interlaminar shear strength of glass fiber reinforced epoxy composites enhanced with multiwalled carbon nanotubes. Compos A 2008;39(3):540–54. [5] Kuang-Ting H, Sadeghian R, Gangireddy S, Minaie B. Manufacturing carbon nanofibers toughened polyester/glass
[6]
[7]
[8]
[9]
fiber composites using vacuum assisted resin transfer molding for enhancing the mode-I delamination resistance. Compos A 2006;37(10):1787–95. Garcia EJ, Wardle BL, John Hart A, Yamamoto N. Fabrication and multifunctional properties of a hybrid laminate with aligned carbon nanotubes grown In Situ. Compos Sci Technol 2008;68(9):2034–41. Li Y, Hori N, Arai M, Hu N, Liu Y, Fukunaga H. Improvement of interlaminar mechanical properties of CFRP laminates using VGCF. Compos A 2009;40(12):2004–12. Rodriguez AJ, Guzman ME, Lim C-S, Minaie B. Mechanical properties of carbon nanofiber/fiber-reinforced hierarchical composites manufactured with multiscale-reinforcement fabrics. Carbon 2011;49(3):937–48. Lim C-S, Rodriguez AJ, Guzman ME, Schaefer JD, Minaie B. Processing and properties of polymer composites containing aligned functionalized carbon nanofibers. Carbon 2011;49(6):1873–83.
Synthesis of carbon nanohorn–carbon nanotube hybrids using palm olein as a precursor S.A.M. Zobir a b c
a,b,*
, Z. Zainal c, C.S. Keng c, S.H. Sarijo b, M. Yusop
a
NANO-SciTech Centre, Institute of Science, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia Faculty of Applied Science, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia Faculty of Science, Universiti Putra Malaysia (UPM), 43400 UPM Serdang, Selangor, Malaysia
A R T I C L E I N F O
A B S T R A C T
Article history:
The formation of carbon nanohorn (CNH)–multi walled carbon nanotube (MWCNT) hybrids
Received 1 August 2012
was accomplished using chemical vapour deposition at 950 C. A bio-renewable resource,
Accepted 26 November 2012
palm olein, and a mixture of zinc nitrate and ferrocene were used as the carbon precursor
Available online 5 December 2012
and catalyst, respectively. The hybrid shows good graphitic quality and a high aspect ratio of the aligned MWCNT. The estimated lengths and diameters of CNH are about 100–400 and 50–100 nm, respectively. It is believed that the surface of the ZnO particles was impregnated by the metal irons from ferrocene and grouped them together, which then served as a base for the formation of bundles of aligned MCWNTs. 2012 Elsevier Ltd. All rights reserved.
Lately, intense research has been conducted to utilise green, renewable bioresource as an alternative way to produce nanomaterials, especially carbon nanostructures. Previous studies showed that palm olein, the main products from palm trees (Elaeis guineesis) can be used for the synthesis of carbon micro- and nanospheres [1] and carbon nanotubes [2]. It was found that carbon nanostructures are useful for various applications from electronics to medical applications
and from simple to complex applications. This is due to their superior properties compared with their counterpart in the bulk form [3,4]. CNH is carbon nanostructure with a horn-shaped sheath aggregate of graphene sheets with approximately 40–50 nm in tubule length and approximately 2 and 3 nm in diameter. The structure is derived from a single walled carbon nanotube (SWCNT) and ended by a five-pentagon conical cap with a
* Corresponding author at: NANO-SciTech Centre, Institute of Science, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia. Fax: +60 355443870. E-mail address: [email protected] (S.A.M. Zobir). 0008-6223/$ - see front matter 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.carbon.2012.11.056
5 4 ( 2 0 1 3 ) 4 8 9 –5 0 0
Available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/carbon
Letters to the Editor
Joining glass fiber layers using a functionalized carbon nanofiber entangled network Chee-Sern Lim, Mauricio E. Guzman, Bob Minaie
*
Department of Mechanical Engineering, Wichita State University, 1845 Fairmount St. Wichita, KS 67260, USA
A R T I C L E I N F O
A B S T R A C T
Article history:
As-received glass fiber layers are joined using a carboxylic acid-functionalized carbon
Received 5 August 2012
nanofiber (OCNF) entangled network utilizing a solution filtering process. Optical and
Accepted 22 November 2012
SEM images of the OCNF/glass fiber assembly reveal fiber-bridging effect and show that
Available online 5 December 2012
the OCNF entangled network continuously covers the glass fiber layers. In the absence of polymer matrix, test result shows that a significant amount of peeling force is required to separate the OCNF/glass fiber assembly. Furthermore, fracture analysis indicates evidence of OCNF pull-out and alignment perpendicular to the glass fiber layer along the crack. 2012 Elsevier Ltd. All rights reserved.
Fiber-reinforced polymer composites (FRPC) are well known for their excellent in-plane strength and stiffness but suffer from poor interlaminar fracture toughness due to matrix-dominated properties. One of the solutions to this shortcoming is the use of 3D braided fibers and throughthe-thickness stitching [1]. These approaches, however, yield composite parts exhibiting weaker in-plane strength and stiffness. In the past two decades, carbon nanotubes (CNTs) [2] and carbon nanofibers (CNFs) [3] have been demonstrated as better candidates to improve the mechanical properties of the FRPC. Traditionally, the CNTs/CNFs are dispersed in the resin and then infused into a preform to fabricate hierarchical composites [4,5]. However, this method is limited by the dispersion quality of the CNT/CNF and high viscosity of the resin, hindering scalable manufacturing of large hierarchical composite parts. Other methodologies involving growth [6], direct placement [7], or deposition [8] of CNT/CNF have been developed to create CNT-/CNF-fiber hybrid layers for fabricating hierarchical composites. Even though an increase in surface roughness of the hybrid layers was achieved using the aforementioned methods, the layers could not be joined without a polymer matrix.
In the present study, the use of carboxylic-acid functionalized CNFs (OCNFs) to join two glass fiber layers is demonstrated. The resulting OCNF/glass fiber assembly was tested in order to determine the peeling force needed for separating the glass fiber layers, as described below. As-received CNFs (PR-24-XT-PS, Applied Science, Inc.) were functionalized according to procedure previously reported [9] but with a treatment time of 2 h to obtain the OCNFs. A solution filtration setup was used to join two as-received plainweave glass fiber layers (5.08 cm · 5.08 cm) with the OCNFs, as illustrated in Fig. 1. The OCNF aqueous solution (0.35 mg/ mL) was prepared by tip-sonicating the OCNFs with ultrapure deionized water at medium power for 10 min. To prepare the OCNF/glass fiber assembly, a nylon membrane was first coated with 50 mL of OCNF solution (over an area equivalent to the glass fiber layers). Afterward, the first glass fiber layer was placed on the OCNF-coated area and half of the layer was covered with aluminum foil to prevent OCNF coating. Then, additional 250 mL of OCNF solution was slowly added to the first glass fiber layer. Subsequently, the second glass fiber layer was placed on top of the first glass fiber layer and filtered with additional 300 mL of the OCNF solution. Note that
* Corresponding author: Fax: +1 316 978 3236. E-mail address: [email protected] (B. Minaie). 0008-6223/$ - see front matter 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.carbon.2012.11.050
490
CARBON
5 4 ( 2 0 1 3 ) 4 8 9 –5 0 0
Fig. 1 – Experimental setup for sample preparation (top) and actual picture (bottom) of OCNF/glass fiber assembly.
the OCNF solution was added to the membrane and glass fiber layers drop-wise using a pipette. Upon completing the filtration, the OCNF/glass fiber assembly was rinsed with acetone and dried with vacuum applied overnight. The amount of the OCNFs added to the OCNF/glass fiber assembly was approximately 154 mg. After removing the aluminum foil, the OCNF/glass fiber assembly was cut to obtain a thin strip of approximately 9 mm · 50.8 mm. The specimen was then tested using a tensile test instrument. Characterization of the OCNF/glass fiber assembly was performed using optical and SEM imaging prior to the peel test. Fig. 2(a) depicts the optical cross-sectional image of the OCNF/glass fiber assembly. It is clear that the OCNFs were successfully incorporated into the glass fiber layers that seemed to be joined by the OCNF entangled network. The SEM image shown in Fig. 2(b) reveals that the OCNFs were tightly packed and interconnected with each other at the region between the glass fiber layers. Moreover, Fig. 2(c) shows that the OCNFs penetrated between the fiber tows and the connected individual filaments (indicated by the small yellow arrows), resulting in a fiber-bridging effect that could benefit the load transfer. Another interesting finding (Fig. 2(d)) that can be drawn from the cross-section of the OCNF/glass fiber assembly is the continuity of the OCNF network at the interface (defined by the yellow curve) between the glass fiber layer and the OCNF entangled network. Combining these observations, it can be clearly seen that the OCNFs continuously extended from the first glass fiber layer to the second glass fiber layer, creating a joined architecture based solely on the OCNFs without the presence of a polymer matrix. These findings suggest that a significant amount of peeling force is required to separate the OCNF/glass fiber assembly, noting that the two as-received glass fiber layers practically need zero force to be separated since nothing holds the as-received glass fiber layers together.
To validate the above statement drawn based on the findings in Fig. 2, a peel test was conducted (illustrated in the inset of Fig. 3) at 20 lm/min. The peeling force was recorded with respect to the crosshead displacement during the test, as shown in Fig. 3. As the test progressed, the test specimen underwent repetitive loading and unloading behavior. The initial and maximum peeling force for causing the separation of the OCNF/glass fiber assembly were approximately 170 mN and 250 mN, respectively. These findings could be attributed to the sequential detachment of the OCNF entangled network as possible reinforcement mechanism. To investigate this, the crack cross-section of the test specimen was examined using SEM. As shown in Fig. 4, significant OCNF pull-out effect at the interface between the glass fiber layer and the OCNF entangled network was identified. The pull-out effect can be explained by the interlocking mechanism within the OCNF entangled network, which is directly responsible for the elevated peeling force to separate the OCNF/glass fiber assembly. In addition, evidence of OCNF alignment perpendicular to the glass fiber layer was observed after the test, suggesting that the pronounced pull-out effect could promote alignment as the OCNFs slide with respect to each other during the test. In summary, joining of two glass fiber layers using an OCNF entangled network through a solution filtering process was demonstrated. Optical and SEM images of the OCNF/glass fiber assembly showed evidence of fiber-bridging effect as well as a OCNF entangled network continuously extending from the first glass fiber layer to the second glass fiber layer. As a result of the filtering process, the peeling force required to separate the OCNF/glass fiber assembly was significant due to the OCNF entangled network. Failure analysis revealed significant OCNF pull-out effect and alignment perpendicular to the glass fiber layer along the crack, which could be explained by the sequential detachment of the OCNF entangled network as reinforcement mechanism. Based on the results presented,
CARBON
5 4 (2 0 1 3) 4 8 9–50 0
491
Fig. 2 – (a) Optical image of the cross-section of OCNF/glass fiber assembly and SEM images of (b) OCNF entangled network between the glass fiber layers, (c) OCNFs bridging individual filaments, and (d) the interface between the glass fiber layer (above the yellow curve) and OCNF entangled network (below the yellow curve). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 4 – SEM image of the crack cross-section indicating OCNF pull-out effect and alignment perpendicular to the glass fiber layer.
Fig. 3 – Peeling force of OCNF/glass fiber assembly as a function of crosshead displacement. The inset illustrates the schematic of the peel test.
it is suggested that the mechanical properties of the FRPC can be effectively improved if OCNF/glass fiber assembly is used.
Acknowledgements This research is funded by the Office of Naval Research (Grant No. N000140810893) and the National Aeronautics and Space Administration (Grant No. NNX07A027A). The authors would like to thank Mr. Joseph Daniel Schaefer from Northwestern University for his active discussion.
492
CARBON
5 4 ( 2 0 1 3 ) 4 8 9 –5 0 0
R E F E R E N C E S
[1] Marvin B, Dow H, Benson Dexter. Development of stitched, braided and woven composite structures in the ACT program and at Langley Research Center. Hampton, Virginia; NASA/TP97-206234; 1997. [2] Rachmadini Y, Tan VBC, Tay TE. Enhancement of mechanical properties of composites through incorporation of CNT in VARTM – a review. J Reinf Plast Compos 2010;29(18):2782–807. [3] Tibbetts GG, Lake ML, Strong KL, Rice BP. A review of the fabrication and properties of vapor-grown carbon nanofiber/ polymer composites. Compos Sci Technol 2007;67(7– 8):1709–18. [4] Fan Z, Santare MH, Advani SG. Interlaminar shear strength of glass fiber reinforced epoxy composites enhanced with multiwalled carbon nanotubes. Compos A 2008;39(3):540–54. [5] Kuang-Ting H, Sadeghian R, Gangireddy S, Minaie B. Manufacturing carbon nanofibers toughened polyester/glass
[6]
[7]
[8]
[9]
fiber composites using vacuum assisted resin transfer molding for enhancing the mode-I delamination resistance. Compos A 2006;37(10):1787–95. Garcia EJ, Wardle BL, John Hart A, Yamamoto N. Fabrication and multifunctional properties of a hybrid laminate with aligned carbon nanotubes grown In Situ. Compos Sci Technol 2008;68(9):2034–41. Li Y, Hori N, Arai M, Hu N, Liu Y, Fukunaga H. Improvement of interlaminar mechanical properties of CFRP laminates using VGCF. Compos A 2009;40(12):2004–12. Rodriguez AJ, Guzman ME, Lim C-S, Minaie B. Mechanical properties of carbon nanofiber/fiber-reinforced hierarchical composites manufactured with multiscale-reinforcement fabrics. Carbon 2011;49(3):937–48. Lim C-S, Rodriguez AJ, Guzman ME, Schaefer JD, Minaie B. Processing and properties of polymer composites containing aligned functionalized carbon nanofibers. Carbon 2011;49(6):1873–83.
Synthesis of carbon nanohorn–carbon nanotube hybrids using palm olein as a precursor S.A.M. Zobir a b c
a,b,*
, Z. Zainal c, C.S. Keng c, S.H. Sarijo b, M. Yusop
a
NANO-SciTech Centre, Institute of Science, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia Faculty of Applied Science, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia Faculty of Science, Universiti Putra Malaysia (UPM), 43400 UPM Serdang, Selangor, Malaysia
A R T I C L E I N F O
A B S T R A C T
Article history:
The formation of carbon nanohorn (CNH)–multi walled carbon nanotube (MWCNT) hybrids
Received 1 August 2012
was accomplished using chemical vapour deposition at 950 C. A bio-renewable resource,
Accepted 26 November 2012
palm olein, and a mixture of zinc nitrate and ferrocene were used as the carbon precursor
Available online 5 December 2012
and catalyst, respectively. The hybrid shows good graphitic quality and a high aspect ratio of the aligned MWCNT. The estimated lengths and diameters of CNH are about 100–400 and 50–100 nm, respectively. It is believed that the surface of the ZnO particles was impregnated by the metal irons from ferrocene and grouped them together, which then served as a base for the formation of bundles of aligned MCWNTs. 2012 Elsevier Ltd. All rights reserved.
Lately, intense research has been conducted to utilise green, renewable bioresource as an alternative way to produce nanomaterials, especially carbon nanostructures. Previous studies showed that palm olein, the main products from palm trees (Elaeis guineesis) can be used for the synthesis of carbon micro- and nanospheres [1] and carbon nanotubes [2]. It was found that carbon nanostructures are useful for various applications from electronics to medical applications
and from simple to complex applications. This is due to their superior properties compared with their counterpart in the bulk form [3,4]. CNH is carbon nanostructure with a horn-shaped sheath aggregate of graphene sheets with approximately 40–50 nm in tubule length and approximately 2 and 3 nm in diameter. The structure is derived from a single walled carbon nanotube (SWCNT) and ended by a five-pentagon conical cap with a
* Corresponding author at: NANO-SciTech Centre, Institute of Science, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia. Fax: +60 355443870. E-mail address: [email protected] (S.A.M. Zobir). 0008-6223/$ - see front matter 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.carbon.2012.11.056